Hydrothermal synthesis and photocatalytic properties of layered La2Ti2O7 nanosheets

摘要糖尿病因能引起身体多系统的损害而成为威胁全球人类健康的疾病之一。

糖尿病患者在日常生活中，需要长期规律地监控血糖浓度从而降低持续高血糖引起的并发症发病几率，因此研发高效、可靠的葡萄糖传感器非常重要。

目前，市售的血糖仪为酶基葡萄糖电化学传感器，该类传感器所使用试纸的活性物质为葡萄糖氧化酶，酶作为价格昂贵的生物活性分子且固定化过程复杂使得该类传感器的成本颇高，因此人们尝试用各种金属及碳材料等构建价格低廉、稳定性好的无酶葡萄糖电化学传感器，以期替代酶基葡萄糖电化学传感器。

近些年，有部分研究工作致力于将金属有机骨架化合物（MOFs）用作硬模板或前驱体，以制备具有优异电催化氧化葡萄糖活性的MOFs衍生材料。

但此类材料大多为粉体，需采用粘结剂将其涂覆于传统电极上制备成工作电极，导致制备复杂、电活性材料易脱落、稳定性也较差。

鉴于此，本论文以泡沫镍为基材，利用水热合成法，在其上原位生长了Ni-MOF，并以此为模板制备出自支撑的Ni@C纳米片电极及CuNi@C电极，将其用于构建无酶葡萄糖传感器并对其性质进行研究。

以下为本论文的主要研究结果：（1）通过水热合成、热解两个步骤制备了自支撑Ni@C纳米片电极，该电极具有三维多级孔道结构，在葡萄糖的无酶检测方面表现出优异的电催化活性。

研究结果显示，该电极检测葡萄糖的灵敏度高达32.7944 mA·mM−1·cm−2，明显优于某些镍基材料电极，线性范围为0.15 μmol·L−1~ 1.475 mmol·L−1，检出限低至50 nmol·L−1，并且该电极对葡萄糖表现出良好的选择性，且具有较好的重现性、长期稳定性及抗氯离子毒化性能。

此外，研究结果显示自支撑Ni@C纳米片电极可用于人体血清样品的实际检测，并且测定结果具有较高的准确度和精密度。

（2）在自支撑Ni@C纳米片电极的基础上，通过恒电位电沉积的方法制备了自支撑CuNi@C电极，Cu纳米颗粒均匀生长于电极表面，由于Cu与Ni之间的协同催化作用，该电极具有优异的无酶葡萄糖传感性能。

Journal of Hazardous Materials 176 (2010) 139–145Contents lists available at ScienceDirectJournal of HazardousMaterialsj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /j h a z m atSynthesis of nanocrystalline anatase TiO 2by one-pot two-phase separated hydrolysis-solvothermal processes and its high activity for photocatalytic degradation of rhodamine BMingzheng Xie,Liqiang Jing ∗,Jia Zhou,Jingsheng Lin,Honggang Fu ∗Key Laboratory of Functional Inorganic Materials Chemistry (Heilongjiang University),Ministry of Education,School of Chemistry and Materials Science,Harbin 150080,PR Chinaa r t i c l e i n f o Article history:Received 7August 2009Received in revised form 6October 2009Accepted 2November 2009Available online 10 November 2009Keywords:Hydrolysis-solvothermal method Nanocrystalline TiO 2Anatase thermal stability Charge separationPhotocatalytic activitya b s t r a c tSi-doped and un-doped nanocrystalline TiO 2samples have been synthesized by simple one-pot water-organic two-phase separated hydrolysis-solvothermal (HST)processes,and characterized by XRD,BET,TEM,FT-IR,DRS and surface photovoltage techniques.The effects of the solvothermal temperature and Si doping on the anatase thermal stability,and on the photocatalytic activity for degrading rhodamine B were investigated in detail.The results show that,as the solvothermal temperature rises,the crystallinity and thermal stability of the resulting nano-sized anatase TiO 2gradually increase.Noticeably,the as-prepared TiO 2obtained at appropriate solvothermal temperature (160◦C)exhibits high photocatalytic activity.Moreover,although Si doping does not improve the photocatalytic activity of the as-prepared anatase TiO 2,it greatly enhances the anatase thermal stability and inhibits crystallite growth during the process of post-thermal treatment.Interestingly,the Si-doped TiO 2post-treated at high temperature displays much higher photocatalytic activity than commercial P25TiO 2.It is clearly demonstrated that the joint effects of high anatase crystallinity and large surface area lead to high photocatalytic activity.This work provides a simple and effective strategy for the synthesis of high-performance TiO 2-based functional nanomaterials.© 2009 Published by Elsevier B.V.1.IntroductionSemiconductor photocatalysis has attracted much attention in the past two decades owing to their applications to environmen-tal purification [1–6].It has been shown to be especially interesting for the treatment of dye compounds usually present in wastewaters from textile industries,because of the possibility of utilizing solar light as the energy source for the decontamination of these efflu-ents [7–12].Among several oxide semiconducting photocatalysts used often,TiO 2is taken as one of the ideal photocatalysts,because of its outstanding photocatalytic activity,chemical stability,low cost and non toxicity [4–6].It usually has two crystalline phases,anatase (Eg =3.2eV)and rutile (Eg =3.0eV),and the anatase phase frequently exhibits higher photocatalytic activity than the rutile one [6,13].Until now,the most popular commercial TiO 2named by Degussa P25,containing around 85%anatase and 15%rutile,usually possessed excellent photocatalytic activity [4–6].Its high activity is mainly attributed to its mixed phase composition and high anatase crystallinity,which would favor photoinduced charge separation,as well as to large surface area (about 55m 2g −1).∗Corresponding authors.Tel.:+8645186608616;fax:+8645186673647.E-mail addresses:Jinglq@ (L.Jing),Fuhg@ (H.Fu).In addition to the phase composition,surface area and anatase crystallinity are two important factors influencing photocatalytic performance of TiO 2.It is widely accepted that photocatalytic reactions mainly take place on the surfaces of photocatalysts.Expectedly,the adsorption of pollutants in advance is one of the most important steps in photocatalytic reactions [4–6].Thus,large surface area is generally favorable to enhance photocatalytic activ-ity of TiO 2.High anatase crystallinity usually means few defects,which easily act as the recombination centers for photogenerated electrons and holes [14,15].Thus,high crystallinity would promote photocatalytic reactions.It has been demonstated that the increase in the anatase crystallinity could usually lead to the enhancement in the photocatalytic activity [16,17].However,there is an obvi-ous inconsistency between large surface area and high anatase crystallinity,since large surface area,often resulting from porous structure and very small particle size,usually corresponds to low anatase crystallinity of TiO 2.Therefore,the solution to the above inconsistency is the crucial to fabricate high activity TiO 2-based photocatalysts.Thermal treatment at high temperature is generally adopted to improve anatase crystallinity of nano-sized TiO 2.However,the anatase-to-rutile transformation will happen if the treatment tem-perature is too high (over 600◦C).On the basis of the phase transformation mechanism that the rutile phase starts to occur at0304-3894/$–see front matter © 2009 Published by Elsevier B.V.doi:10.1016/j.jhazmat.2009.11.008140M.Xie et al./Journal of Hazardous Materials176 (2010) 139–145the interfaces between the anatase particles in the agglomerated TiO2particles[18],it is expected that the phase transformation usually leads to the remarkable increase in the particle size and consequently make surface area greatly decrease.Therefore,it is predicted that the increase in the anatase thermal stability might be a feasible strategy to solve the inconsistent issue mentioned above.The sol–gel technique based on the hydrolysis of titanium alkoxide is widely developed to synthesize nano-sized TiO2 [19].However,this technique usually has marked shortcomings, such as weak anatase crystallinity,complicated synthesis and post-treatment procedures,poor monodispersity,and possibly accompanied by too much of waste liquids.Those shortcomings would greatly influence the performance and large-scale pro-duction and successful applications in industry of the resulting TiO2nanomaterials.Thus,simple methods that are easily oper-ated to obtain monodispersed nanocrystalline TiO2simultaneously with high anatase crystallinity are still desired.Very recently, Tang et al.developed a one-step synthesis method to prepare high-quality ultrafine inorganic semiconductor nanocrystals via a two-phase interface hydrolysis reaction under hydrothermal conditions[20],which is named by the two-phase separated hydrolysis-solvothermal(HST)process in our work,and mainly demonstrated that the prepared ZrO2nanocrystals have good monodispersity and high crystallinity.This newly developed method spurs us to carry out this work,in which we aim to design and synthesize high active nano-sized TiO2-based photocatalysts.Herein,we synthesize Si-doped and un-doped nanocrystalline TiO2by the simple one-pot phase separated HST processes.It is found that the un-doped TiO2obtained at160◦C exhibits higher photocatalytic activity than that prepared by the traditional sol-hydrothermal method at the same temperature.Moreover,the resulting Si-doped TiO2post-treated at high temperature exhibits much higher photocatalytic activity than well-known P25TiO2. Thesefindings are in good agreement with our expectations. It should be suggested that the joint effects of high anatase crystallinity and large surface area are responsible for the high pho-tocatalytic activity.This work would provide an effective strategy to design and fabricate high-performance TiO2-based functional materials with high anatase thermal stability,and further expand the application areas due to high anatase thermal stability.2.Experimental sectionAll used chemicals are of the analytical grade and are used as received without further purification,and doubly deionized water is employed throughout.2.1.Synthesis of materialsNano-sized TiO2is synthesized by the HST process[20].The key point to the synthetic reaction is to combine the hydroly-sis and nucleation process at the confined water/toluene interface with the subsequent crystallization process in the toluene under solvothermal condition.A30mL of Teflon lined stainless-steel ves-sel,in which a10mL of weight bottle is installed to contain the organic toluene,is used as the reaction device to carry out the HST experiment.In a typical process,10mL of water phase and8mL of toluene phase,which contains a desired amount of Ti(OBu)4, was placed in the device separately.Then,the sealed device is kept at certain temperature(120–200◦C)for2h,followed by naturally cooling to room temperature.Under the solvothermal conditions, both the water and toluene are evaporated to diffuse gradually to the other side to form an interface.It is expected that the inter-face may locate near the organic phase side since the toluene has a higher boiling point than the water.When the water steam and toluene steam containing a certain amount of Ti(OBu)4molecules meet,the hydrolysis reaction between Ti(OBu)4and water will occur immediately,simultaneously leading to the crystal nucleus of TiO2.Then,the formed crystal nucleus is further crystallized in the organic phase.Thus,the resulting nanocrystalline TiO2is col-lected in the toluene,and subsequently the dried TiO2nanopowder is obtained by distilling the toluene system at120◦C.At last,dif-ferent TiO2samples are produced by further calcining dried TiO2at different temperature for2h.T X-Y,in which X is the solvothermal temperature and Y is the calcination temperature,is used to repre-sent the specific TiO2sample.In addition,to obtain Si-doped TiO2 by the HST process,a desired amount of(C2H4O)4Si and Ti(OBu)4 are added together to the organic phase,and ST X-Y indicates the3 in mole%Si-doped TiO2sample.2.2.Characterization of materialsThe samples are characterized by X-ray powder diffraction (XRD)with a Rigaku D/MAX-rA powder diffractometer(Japan), using Cu K␣radiation( =0.15418nm),and an accelerating volt-age of30kV and emission current of20mA are employed;The specific surface areas of the samples are measured by BET instru-ment(Micromeritics automatic surface area analyzer Gemini2360, Shimadzu),with nitrogen adsorption at77K;Transmission elec-tron microscopy(TEM)observation was completed on a JEOL JEM-2010EX instrument operated at200kV accelerating voltage; The Fourier transform infrared spectra(FT-IR)of the samples are collected with a Bruker Equinox55Spectrometer,using KBr as diluents;The ultraviolet–visible diffuse reflectance spectra(UV–vis DRS)of the samples are recorded with a Model Shimadzu UV2550 spectrophotometer;The SPS measurements of the samples are car-ried out with a home-built apparatus that had been described in detail elsewhere[21–23].2.3.Evaluation of photocatalytic activityRhodamine B(RhB)is commonly used as a dye,and it has been found to be potentially toxic and carcinogenic[24].Thus, RhB is chosen as the representative organic dye pollutant to evalu-ate photocatalytic activity of the as-prepared TiO2.Photocatalytic experiments are carried out in a100mL of photochemical glass reactor,and the similar solar light is provided from a side of the reactor by a150W GYZ220high-pressure Xenon lamp made in china without anyfilter,which is placed at about10cm from the reactor.During the measurements of photocatalytic degradation rate of RhB,0.05g of the TiO2sample and60mL of50mg/L RhB solu-tion are mixed by a magnetic stirrer for30min in the darkfirst,in order to make the reactive system uniform and the adsorption equi-librium,then begin to illuminate.After photocatalytic reaction for 1h,the RhB concentration is analyzed by means of the optical char-acteristic absorption at553nm after centrifugation with a Model Shimadzu UV2550spectrophotometer[24].To obtain the evolu-tion curves of photocatalytic degradation of RhB,0.1g of the TiO2 sample and60mL of50mg/L RhB(15mg/L phenol)solution are employed and the RhB concentrations after photocatalytic reaction for different time are measured.3.Results and discussion3.1.Measurements of XRD and BETThe XRD peaks at2Â=25.28◦and2Â=27.40◦are often taken as the characteristic peaks of anatase(101)and rutile(110)crystal phase,respectively[25,26].The mass percentage of anatase phase in the TiO2samples can be estimated from the respective inte-grated characteristic XRD peak intensities using the quality factorM.Xie et al./Journal of Hazardous Materials176 (2010) 139–145141Fig.1.XRD patterns of different TiO2samples.ratio of anatase-to-rutile(1.265),and the crystallite size can also be determined from the broadening of corresponding X-ray spec-tral peak by Scherrer formula[26].Fig.1shows the XRD patterns of different TiO2samples,including home-made un-doped and Si-doped TiO2and commercial P25TiO2.It is seen from the Fig.1 that the T160-120sample has a pure anatase phase,and its crystal-lite size is6.6nm.As the thermal treatment temperature increases, the anatase XRD peaks gradually become strong,indicating that the anatase crystallinity increases,meanwhile the correspond-ing crystallite size gradually becomes large(Table1).When the temperature increases to750◦C,however,the rutile phase(17%) appears,indicating that the phase transformation begins to take place.In general,the beginning temperature of phase transfor-mation of nano-sized anatase TiO2prepared by the sol process is generally at about600◦C[5,14].It should be pointed that the T160-Table1Phase composition,crystallite size and surface area of different TiO2samples.Sample Phase composition(%)Crystallitesize(nm)Surface area (m2g−1)Anatase RutileT160-120100– 6.6131.9 T160-500100–20.756.4 T160-700100–25.341.6 T160-750831728.126.2 ST160-120100–7.4152.3 ST160-600100–8.1128.9 ST160-700100–9.489.5 ST160-800100–11.563.4 P2*******.558.2120sample exhibits high anatase crystallinity and large crystallite size compared with that obtained by the sol-hydrothermal process at the same temperature based on the XRD patterns,shown in the supporting information(SI-I).High anatase crystallinity and large crystallite size mean low surface energy,and the low surface energy is unfavorable to the phase transformation process,consequently leading to the enhancement in the beginning phase transforma-tion temperature.This is also further supported by the results that the XRD intensity of the resulting TiO2gradually increases and the corresponding beginning phase transformation temperature also rises as the solvothermal temperature is enhanced supporting information(SI-I).Moreover,it is expected that the high dispersity of the original anatase nanocrystals obtained by the HST process, which had been well demonstrated[20],also should play an impor-tant role in the inhibition phase transformation process based on the mechanism mentioned above[18].Therefore,it can be deduced that the enhanced beginning phase transformation temperature is attributed to the high crystallinity,large crystallite size and high dispersity of the as-prepared anatase crystallites.As the thermal treatment temperature increases,the anatase XRD peaks of the Si-doped TiO2gradually increase,demonstrating that the corresponding anatase crystallinity becomes high.Inter-estingly,compared with the un-doped TiO2,the Si-doped TiO2 exhibits high anatase thermal stability since no rutile appears in the Si-doped TiO2by the thermal treatment at800◦C.This demon-strates that the introduction of Si inhibits the phase change,which is in good agreement with the literatures[27,28].In addition,the phases related to Si are not detected from XRD patterns.For the un-doped TiO2,the T160-120has a large BET surface area (131.9m2g−1)(Table1),and the surface area obviously decreases as the thermal treatment temperature increases.Noticeably,Si doping effectively maintains the large surface area of nano-sized TiO2.After thermal treatment at the temperature as high as800◦C, the ST800still has larger surface area than P25TiO2.3.2.Measurements of TEM and FT-IRThe TEM photographs of different TiO2samples are shown in Fig.2.It can be seen that all the samples have similar spherical form.The T160-120has an about7nm average particle size with narrow size distribution(Fig.2A),which is in accordance with the crystallite size evaluated by the Scherrer formula,indicating that the obtained TiO2crystallites are easily separated.After the thermal treatment at750◦C,the average particle size of the un-doped TiO2 has increased to about30nm,with wide size distribution(Fig.2B), which is attributed to the occurrence of rutile based on the XRD patterns,accompanied by the particle agglomeration[18].By com-parison,it can be noticed that Si doping effectively inhibits the growth of nanocrystalline TiO2,since the ST160-120and ST160-800 exhibit about6.0and12nm particle sizes,respectively,both with narrow size distribution(Fig.2C and D).Thus,these TEM observa-tions are well responsible for the corresponding surface areas listed in the Table1.Fig.3shows the FT-IR spectra of different TiO2samples.The IR peaks at about1630and3400cm−1are ascribed to surface hydroxyl and adsorbed water molecules[29,30].The IR band at 400–850cm−1corresponds to the Ti–O–Ti stretching vibration mode in crystal TiO2[29].The IR peaks at about3000and1497cm−1 are ascribed to the C–H and C C stretching vibration mode in aro-matic ring[31].As the thermal treatment temperature increases,the intensity of IR band related to Ti–O–Ti vibration mode also increases,indicating that the corresponding TiO2crystallinity becomes high,which is in accordance with the XRD results.Moreover,the surface hydroxyl amount of the Si-doped TiO2sample gradually decreases.However, the ST160-800still displays a larger amount of surface hydroxyl142M.Xie et al./Journal of Hazardous Materials176 (2010) 139–145Fig.2.TEM images of different TiO 2samples (A)T160-120,(B)T160-750,(C)ST160-120,(D)ST160-800.than the T160-700.In addition,all the Si-doped TiO 2samples have a IR peak at about 1050cm −1,which results from Si–O–Si mode in SiO 2[32].Based on the above analyses of XRD,TEM and IR,it can be deduced that Si doping inhibits the anatase-to-rutile phasetrans-Fig.3.IR spectra of different TiO 2samples.formation and simultaneous particle growth of nanocrystalline TiO 2,which is attributed to the existence of amorphous SiO 2.The SiO 2would hold back the contacts between the anatase nanocrys-tals,the diffusions between anatase crystallites,and the surface ionic mobilities [27,32–35].3.3.Measurements of DRS and SPSThe UV–vis DRS spectra of different TiO 2are shown in Fig.4.According to the energy band structure of TiO 2,it can be con-firmed that the strong optical absorption below 390nm is mainly attributed to the electron transitions from the valence band to con-duction band [21,29].It can be noticed that the DRS spectrum of the doped TiO 2shifts slightly to the red with increasing the treatment temperature from 120to 800◦C,which strongly demonstrates that the crystallite size and the phase transformation are effectively sup-pressed.This is in good agreement with the above XRD and TEM results.The surface photovoltage generation mainly arises from the cre-ation of electron-hole pairs,followed by the separation under a built-in electric field,also called space-charge layer.Thus,it can be expected that the stronger is the surface photovoltage spec-troscopy (SPS)response,the higher is the photoinduced charge carrier [36,21].Fig.5shows the SPS responses of different TiO 2sam-M.Xie et al./Journal of Hazardous Materials 176 (2010) 139–145143Fig.4.DRS spectra of different TiO 2samples.ples.For all the samples,an obvious SPS response can be found at the wavelength range from 300to 375nm,which is attributed to the electron transitions from the valence band to conduction band (O 2p →Ti 3d )on the basis of the DRS spectra and TiO 2band structure [21,29].For the Si-doped TiO 2sample with anatase phase compo-sition,the SPS response gradually becomes strong with increasing the treatment temperature,which is mainly because of the increase in the antatase crystallinity.The high crystallinity makes electronic band perfect so as to enhance the built-in field strength,which can promote charge separation [22],meanwhile leads to the decrease in the defect amounts,which is also favorable for charge sepa-ration [37,14].This is also supported by the point that the SPS response of un-doped TiO 2increases as the solvothermal temper-ature or the post-treatment temperature is enhanced supporting information (SI-II).However,compared with the un-doped TiO 2,all the Si-doped TiO 2samples exhibit low SPS responses,which are possibly ascribed to the SiO 2as the nonconductor.In addition to the band-to-band SPS response,a weak SPS response related to surface states,located at the wavelength range from 375to 420nm,is found in the ST160-800sample.This surface state-related SPS response might result from the electronic transitions from the anatase sur-face states to the rutile conduction band in the phase-mixed TiO 2[38].According to the above XRD results,there is not rutile phase in the ST800.Actually,there might be a small amount of rutile since the XRD detection is very limited.3.4.Photocatalytic activityGenerally speaking,the high photocatalytic degradation rate corresponds to the high photocatalytic activity.In thephotocat-Fig.5.SPS responses of different TiO 2samples.Fig.6.Photocatalytic degradation rates (A)and evolution curves (B)of RhB solution on different TiO 2samples (the corresponding degradation rate constants are listed in the parentheses).alytic experiment,The 150W Xenon lamp,with similar emitting spectrum to the sun,is used as light pared with the photocatalytic degradation,the direct photolysis (1%)is so small that the corresponding degradation is neglectable.The photocat-alytic degradation rates of RhB,which equal to the differences between the total degradation rates in the presence of light and the adsorption degradation rates in the absence of light,on the different TiO 2samples,are shown in the Fig.6.It can be seen from Fig.6A that,for the un-doped TiO 2,the pho-tocatalytic activity gradually decreases as the thermal treatment temperature increases.This seems un-imaginable since the pho-toinduced charge separation situation should be improved with increasing the treatment temperature on the basis of SPS responses supporting information (SI-II).Thus,it is deduced that the decrease in the activity is mainly attributed to the great decrease in the sur-face area shown in Table 1.However,it should be pointed that,among the as-prepared three TiO 2samples at the solvothermal temperatures of 120,160and 200◦C,the TiO 2obtained at 160◦C displays the highest activity,and also it is superior to the TiO 2obtained by the traditional sol-hydrothermal process at the same temperature supporting information (SI-III).It is expected that the high activity of the T160-120is attributed to the high anatase crys-tallinity and the high crystallite monodispersity [20].As expected,it can be confirmed from the photocatalytic degra-dation rates of RhB (Fig.6B)that the Si-doped TiO 2gradually exhibits much high photocatalytic activity as the thermal treat-ment temperature is enhanced.Noticeably,the TiO 2sample by thermal treatment over 600◦C possesses high activity compared with the P25TiO 2,which is also proved by the photocatalytic degra-dation of phenol Appendix B (SI-III).Based on the above SPS,TEM144M.Xie et al./Journal of Hazardous Materials176 (2010) 139–145and BET measurements,it is concluded that the high photoindued charge separation rate,small particle size and large surface area are responsible for the high photocatalytic activity of Si-doped TiO2treated at high temperature.Moreover,a certain amount of surface hydroxyl and rutile phase are also favorable for photocat-alytic reactions[17].In addition,it is also confirmed that the RhB photocatalytic degradation processes in our experiments follow one-order reactions,which is accordance with the literature[39].4.ConclusionsOn the basis of the above systematic investigation,mainly by means of XRD,BET,TEM,IR and SPS measurements,the follow-ing conclusions can be drawn:(i)Nanocrystalline TiO2with high anatase crystallinity and high crystallite monodispersity is success-fully synthesized by the HST processes,and its anatase thermal stability is enhanced with increasing the solvothermal tempera-ture.(ii)The as-prepared nanocrystalline TiO2obtained at160◦C exhibits higher photocatalytic activity than that prepared by the transitional sol-thermal method at the same hydrothermal temper-ature,demonstrating that the HST route is an extremely effective synthetic approach.(iii)As expected,Si doping greatly enhances the anatase thermal stability,meanwhile effectively inhibiting the growth of the TiO2crystallites,resulting in high photocatalytic activity,superior to that of P25TiO2.It is suggested that the photocatalytic activity of nano-sized TiO2 is jointly determined by the photoinduced charge separation ability and the surface area.Based on the SPS responses,high anatase crys-tallinity,which can be produced by enhancing the anatase thermal stability,greatly favors photoinduced charge separation.The phase separated SHT synthesis overcomes the difficulty of producing high anatase crystallinity and also with large surface area,resulting in highly active nanostructured TiO2-based functional materials with high thermal stability.AcknowledgementsThis work isfinancially supported from the National Nature Sci-ence Foundation of China(No.20501007),the programme for New Century Excellent Talents in universities(NCET-07-0259),the Key Project of Science&Technology Research of Ministry of Educa-tion of China(No.207027)and the Science Foundation of Excellent Youth of Heilongjiang Province of China(JC200701),for which we are very grateful.Appendix A.Supplementary dataSupplementary data associated with this article can be found,in the online version,at doi:10.1016/j.jhazmat.2009.11.008. 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Material Sciences 材料科学, 2019, 9(6), 549-557Published Online June 2019 in Hans. /journal/mshttps:///10.12677/ms.2019.96070One-Step Hydrothermal Synthesis of ChiralCarbon Quantum DotsYao Wang, Yupeng Lu, Yuanzhe Li, Lumeng Wang, Fan ZhangCollege of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan ShanxiReceived: May 21st, 2019; accepted: Jun. 4th, 2019; published: Jun. 11th, 2019AbstractCarbon Quantum Dots (CQDs) have many excellent properties, such as low toxicity, biocompatibil-ity, photoluminescence, etc., which play an important role in many fields such as photocatalytic electrocatalytic chemical sensing in biological imaging and endowing CQDs with chiral proper-tiesto broaden its applications in chiral recognition and separation and asymmetric catalysis and chiral detection. Chiral carbon quantum dots (L-CQDs and D-CQDs) were synthesized by one-step hydrothermal method using tryptophan (L-Trp and D-Trp) as carbon source and chiral source and sodium hydroxide as reaction regulator. The optical properties and surface structures of L-CQDs and D-CQDs were characterized by high resolution lens electron microscopy, elemental analyzer, ultraviolet-visible absorption spectrometer, steady-state fluorescence spectrometer and circu-lar dichroism (CD). The results show that the prepared L-CQDs and D-CQDs with particle size less than 10 nm presented similar characteristics and optical properties, with strong fluores-cence characteristics and the property of stimulating independence, whose the maximum emis-sion wavelength is 476 nm as well as the optimal excitation wavelength is 360 nm. CD signals taking on mirror symmetry feature near 223 and 290 nm indicate that L-CQDs and D-CQDs are enantiomers.KeywordsHydrothermal Method, Chirality, Carbon Quantum Dots, Circular Dichroism一步水热法制备手性碳量子点王耀，鲁羽鹏，李远哲，王璐梦，张帆太原理工大学材料学院，山西太原收稿日期：2019年5月21日；录用日期：2019年6月4日；发布日期：2019年6月11日王耀 等摘要碳量子点(Carbon Quantum Dots, CQDs)有着很多优良的特性，如：低毒性、生物相容性、光致发光等特性，在生物成像、光催化、电催化、化学传感等许多领域起着重要的作用，赋予CQDs 手性特性。

当代化工研究Modem Chemical Research35 2021・05基础研究氮掺杂花状黑色二氧化钛(TQ)的制备及光催化性能研究*秦莲郭紫露刘娜马海燕王强段志英(西北民族大学化工学院甘肃730000)摘耍：本论文以金属钛粉和尿素为原料，利用水热法制备出氮掺杂黑色二氧化钛(Ti()2)光催化剂，并对其光催化性能进行了红外光谱、紫外光谱和SEM等表征实验，探讨了氮掺杂花状黑色二氧化钛(Tit)2)光催化剂的光催化性能.将甲基橙溶液作为目标降解染料，在模拟太阳光条件下照射含有不同氮掺杂含量的光催化剂的甲基橙溶液，紫外一可见分光光度计测试不同光催化剂的光催化性能.通过对不同形貌，不同掺杂量的催化剂比较研究，探讨结构与光催化性能之间丝关系.实验结果表明：以尿素:黑色花状二氧化钛=2:1餉比例制备的氮掺杂花状黑色二氧化钛催化剂对甲基橙溶液的催化降解效果最好，提高了对染料的降解作用°关键词：水热法；氮掺杂；花状黑色二氧化钛；可见光催化中图55•类号：0文献标识码：AStudy on Preparation of Nitrogen Doped Flower Black Titanium Dioxide(TiO2)and ItsPhotocatalytic PerformanceQin Lian,Guo Zilu,Liu Na,Ma Haiyan,Wang Qiang,Duan Zhiying(School of Chemical Engineering,Northwest University for Nationalities,Gansu,730000) Abstract:In this paper,the nitrogen-doped black titanium dioxide(RO)photocatalyst was prepared by hydrothermal method using titanium powder and urea as raw materials.The photocatalytic performance of the nitrogen-doped f lower black titanium dioxide(TiO^photocatalyst was studied by infrared spectroscopy,ultraviolet spectroscopy and SEM.Methyl orange solution was used as the target dye for degradation.Methyl orange solution containing different nitrogen doping content was irradiated under simulated sunlight conditions.The photocatalytic performance of different p hotocatalysts was tested by UV-Vis spectrophotometer.The relationship between the structure and p hotocatalytic p erformance was studied by comparing the catalysts with different morphologies and doping amounts.The experimental results showed that the nitrogen-doped f lowery black titanium dioxide catalyst prepared yvith the ratio of u rea to black f lowery titanium dioxide=2:l had the best catalytic degradation effect on methyl orange solution,which improved the degradation effect of d ye.Key words：hydrothermal method^N-doped\floral black titanium dioxide^visible light catalysis随着人类生活方式的改变和工业化的持续发展，如危险响口甸。

OriginalarticleHydrothermal synthesis of single-crystal CeCO3OH and their thermal conversion to CeO2Kun Gao a,Yi-Yang Zhu a,Da-Qing Tong a,Li Tian a,Zhao-Hui Wang a,b,Xiao-Zu Wang a,*a College of Chemistry and Chemical Engineering,Nanjing University of Technology,Nanjing210009,Chinab State Key Laboratory of Materials-Oriented Chemical Engineering,Nanjing University of Technology,Nanjing210009,China1.IntroductionIn recent years,cerium compounds have been widely used incatalysis[1–4],fuel cells[5]and chemical materials[6–8]due totheir specific4f energy levels of the Ce-element[9,10].Among allthe cerium compounds,cerium carbonate hydroxide,as animportant functional material,has been attracted much attentionbecause of its novel electronic properties,optical properties andchemical characteristics arising from their4f electrons[9–12].Recently,cerium carbonate hydroxide with different morphol-ogies was synthesized by different methods,such as self-assembly,sonochemical[13,14],hydrothermal[15–18],and microwave-assisted hydrothermal route[19].Among all the preparationmethods,the hydrothermal process is considered to be an effectiveand economical route due to its merits of low synthesistemperature,high powder reactivity and versatile shape control[20–23].In a hydrothermal system,CeCO3OH with differentstructures corresponding to distinct morphologies have beensynthesized[18,24,25].There have been sufficient studies report-ing on the synthesis of different morphologies,for example,Guoet al.reported the synthesis of triangular micro-plate,bundle-like,shuttle-like andflower-like structures of CeCO3OH by hydrother-mal method[15,16,18].Li and Zhao synthesized single-crystallineCeCO3OH with dendrite-like structures through a facile hydro-thermal method and obtained CeO2by heating CeCO3OH at5008Cfor6h[26].Zhang et al.synthesized CeCO3OH rhombic micro-plates by the precipitation method in the presence of3-aminopropyltriethoxysilane[28].However,most of these reportson the synthesis of CeCO3OH micro/nanoparticles were preparedusing CO(NH2)2or HMT as the alkaline and carbon resource[13–18]and added surfactant or template to adjust the nucleation andcrystal growth of CeCO3OH particles[13,15–18,28],which makesthe process complex and raw materials more costly.So it isimportant to explore a facile method to synthesize morphology-controlled CeCO3OH micro/nanomaterials.In this paper,we report a simple method to synthesize dendrite-like CeCO3OH crystallites using CeCl3Á7H2O as the cerium source,triethylenetetramine as both an alkaline and carbon source.Thepolycrystalline CeO2was obtained by calcination of the precursor at5008C for4h,partly maintaining the dendrite-like morphology.Theoptical absorption properties of CeO2were also investigated.2.ExperimentalAll chemical reagents were of analytical grade without furtherpurification.In a typical synthesis,0.001mol of CeCl3Á7H2O wasdissolved in60mL deionized water to form a clear solution,andthen0.30mL triethylenetetramine was added to the transparentsolution in order to completely react with Ce3+at258C for about0.5h with continued stirring.The resulting homogenous solutionChinese Chemical Letters25(2014)383–386A R T I C L E I N F OArticle history:Received10August2013Received in revised form8September2013Accepted26September2013Available online1December2013Keywords:CeCO3OHHydrothermalCerium carbonate hydroxideNanostructuresA B S T R A C THexagonal single-crystalline cerium carbonate hydroxide(CeCO3OH)precursors with dendritemorphologies have been synthesized by a facile hydrothermal method at1808C using CeCl3Á7H2O asthe cerium source,triethylenetetramine as both an alkaline and carbon source,with triethylenete-tramine also playing an important role in the formation of the dendrite structure.Polycrystalline ceria(CeO2)have been obtained by calcining the precursor at5008C for4h.The morphology of the precursorwas partly maintained during the heating process.The optical absorption spectra indicate the CeO2nano/microstructures have a direct band gap of2.92eV,which is lower than values of the bulk powderdue to the quantum size effect.The high absorption in the UV region for CeO2nano/microstructureindicated that this material was expected to be used as UV-blocking materials.ß2013Xiao-Zu Wang.Published by Elsevier B.V.on behalf of Chinese Chemical Society.All rightsreserved.*Corresponding author.E-mail address:wangxiaozu@(X.-Z.Wang).Contents lists available at ScienceDirectChinese Chemical Lettersj o u rn a l h om e p a g e:w w w.e l s e v i e r.c o m/l o c a t e/c c l e t1001-8417/$–see front matterß2013Xiao-Zu Wang.Published by Elsevier B.V.on behalf of Chinese Chemical Society.All rights reserved./10.1016/let.2013.11.047was transferred to a 100mL Teflon-line stainless steel autoclave,which was sealed and maintained at 1808C for 24h,and cooled to room temperature naturally.The white precipitate was collected by centrifugation,washed several times with distilled water and ethanol,and dried at 708C for 6h.The as-synthesized CeCO 3OH was calcined to produce straw-yellow CeO 2in air at 5008C for 4h.The XRD measurements were performed on a Bruker-D8Advanced X-ray diffractometer,equipped with graphite-monochromatizedhigh-intensity Cu K a radiation (l =1.5418A˚).The morphologies and sizes of the resulting products were examined by field-emission scanning electron microscopy (FESEM,Hitachi S-4800)and transmission electron microscopy (TEM,JEM2000EX),respec-tively.The thermal behavior of the resulting products was carried out by differential scanning calorimetric analysis (DSC)and thermogravimetric analysis (TG)with a Netzsch-449C simulta-neous TG/DSC apparatus heating from room temperature to 6008C (108C/min)in flowing air.UV/vis absorption spectra were acquired on a spectrophotometer (Shimadzu)and the analyzed range was 200–800nm.3.Results and discussionFig.1presents the typical XRD pattern of the as-synthesized CeCO 3OH products.All of the diffraction peaks in Fig.1can be exactly indexed to the pure hexagonal crystalline phase ofCeCO 3OH with lattice constants a =7.2382A˚,c =9.9596A ˚,which are in good agreements with the literature values (JCPDS 32-0189).No impurity peaks are detected,indicating the high purity of the final product.The strong and sharp diffraction peaks suggest that the products are highly crystallined.Fig.2shows a typical SEM image of the CeCO 3OH dendrite structure synthesized at 1808C for 24h.As shown in Fig.2,it reveals most of the as-prepared CeCO 3OH products display twofold-symmetric structures with a length of 1–2m m along the trunk.The detailed morphology of the structures of CeCO 3OH dendrites is further studied using TEM and SAED (Select-area electron diffraction).A typical high magnification TEM image of the structure of CeCO 3OH dendrites is shown in Fig.3.It reveals that the product is composed of a long central trunk with secondary and tertiary sharp branches,which are parallel to each other and emerge at 608angles with respect to the central trunk.The SAED pattern in the inset of Fig.3taken from an individual dendrite-like nanostructure is indexed to hexagonal CeCO 3OH,indicating that the individual is a single crystal.The diffraction pattern indicates the individual dendrite-like CeCO 3OH is well crystallized.The typical TG pattern of the as-prepared CeCO 3OH dendrite structure is shown in Fig.4a.The TG curve shows that CeCO 3OH begins to decompose at about 2808C and finishes at 6008C.Thetotal weight loss between 2808C and 6008C is measured at about 21.70%,which is close to the results in the theoretical value calculated from following reaction:4CeCO 3OH þO 2!4CeO 2þ2H 2O þ4CO 2(1)The DSC curve (Fig.4b)shows one endothermic peak with a maximum at 300.08C.The temperature range of the endothermic peak in the DSC curve agrees well with the weight loss in the TG curve,corresponding to endothermic behavior during the thermal decomposition/oxidation of CeCO 3OH to CeO 2.Fig.5shows the XRD pattern of CeO 2obtained by calcinations of as-prepared CeCO 3OH.All of the peaks are well assigned to pure face-centered cubic (fcc)structure of CeO 2with lattice constantsa =5.412A˚,which is in good agreement with the JCPDS card (No.43-1002).No obvious peaks for other elements or impurities were observed.The strong and sharp reflection peaks suggest that the as-prepared products are well crystallized.After the CeCO 3OH dendrites are calcined in air at 5008C for 4h,CeO 2dendrites are formed.As shown in Fig.6a,SEM image of CeO 2reveals that the dendrite morphology was partly sustained after thermal decomposition/oxidation to CeO 2.Fig.6b presents a typical TEM image of CeO 2dendrite and its corresponding ED pattern (Fig.6b inset).The discontinuous rings in ED pattern indicate that it could consist of CeO 2polycrystals with an oriented crystallographic axis.In our experiment,since triethylenetetramine was not used,noting products were obtained.Fig.7shows the SEM image of raw material (CeCl 3Á7H 2O),only erose particles were observed,indicating the triethylenetetramine plays an important role in the formation of CeCO 3OH dendrite structures.As is well known,triethylenetetramine at the room tempera-ture will release OH Àin the aqueous solution.Meanwhile,triethylenetetramine has large average capacities for the absorp-tion CO 2[27].So the CO 32Àanions in the solution may result from1020304050602θ (° )(002)(110)(112)(004)(300)(114)(302)(220)(222)(304)Fig.1.XRD patternof the CeCO 3OH dendrite-like nanostructure.Fig.2.SEM image of the as-synthesized CeCO 3OH.Fig.3.TEM image of the as-synthesized CeCO 3OH.K.Gao et al./Chinese Chemical Letters 25(2014)383–386384the possible oxidation of triethylenetetramine,the absorption andslight dissolution of CO 2from air.In the hydrothermal process,the C—N bond in triethylenete-tramine is the easiest bond to break,so upon heating to a certain temperature,triethylenetetramine hydrolyzes to form NH 4+and CO 32À.The cerium ions can exist in the form of [Ce(H 2O)n ]3+in aqueous solution,and then [Ce(H 2O)n ]3+is changed into [Ce(OH)(H 2O)n +]2+,and finally CeCO 3OH is obtained by the reaction between [Ce(OH)(H 2O)n À1]2+and CO 32À.It is proposed that dendrite structures are obtained through a seed-mediated growth in the presence of micelles of triethylenetetramine.The CeCO 3OH nuclei were created and used as seed center,these random moving nuclei in the environment can aggregate with each other to form anisotropic morphology.In our experiment,we consider that triethylenetetramine used as the alkaline and surfactant in the hydrothermal process.Therefore,existing triethylenetetramine,as a capping agent in the reaction system,is absorbed selectively on the different planes of CeCO 3OH seeds,helps to lower the surface energy and results in the different growth rate of different planes to form the dendrite structures.The real formation mechanism of CeCO 3OH dendrite structure needs further investigation.Fig.8shows the UV/vis diffuse absorption spectra of CeCO 3OH and CeO 2.Fig.8a shows the UV/vis absorption spectra for CeCO 3OH.The spectra displayed a strong absorption band below 400nm in the spectra.As seen in Fig.8b and 8c,when the synthesized particles were calcined to produce straw yellow CeO 2by heating at 5008C for 4h,the CeO 2has a stronger absorption band below 480nm in the spectra,which is originated from change-transfer transition between O 2p and Ce 4f bonds [28–30].The optional band gap E g can be determined based on the absorbance spectrum of the powders by the following equation:E g =1240/l AE ,where l AE is the edge wavelength of absorbance.The onset of absorption for CeO 2is at 425.3nm,which corresponds to the band gap energy (E g )of 2.92eV,lower than the values of bulk100200300400500600700800024681012←b. DSC cur veH e a t f l o w (m W /m g )Temerature (oC)← a . TG curve80859095100W e i g h t l o s s(%)Fig.4.TG-DSC pattern of the as-synthesized CeCO 3OH.10203040506070802θ (° )(111)(200)(220)(311)(222)(400)(311)(420)Fig.5.XRD pattern of the CeO 2sample.Fig.6.The typical SEM and TEM images of CeO 2obtained from thermal decomposition/oxidation of CeCO 3OH dendrite structure.Fig.7.SEM image of CeCl 3Á7H 2O powders.800700600500400300200b A b s o r b a n c e (a .u )Wavelength (nm)a800700600500400300200A b s o r b a n c e (a .u )Wavelength (nm)cFig.8.UV/vis absorption spectra of CeCO 3OH (a)and CeO 2(b),(c).K.Gao et al./Chinese Chemical Letters 25(2014)383–386385powders(3.19eV).In general,reduction in crystal size would increase the band gap width because of the quantum size effect [31].Hence,the high absorption in the UV region for CeO2show that the materials can be used as UV-blocking,shielding materials to avoid damage from ultraviolet rays and optical devices.4.ConclusionIn summary,we have successfully synthesized CeCO3OH dendrite structures by a facile hydrothermal method in the presence of triethylenetetramine.After annealing the CeCO3OH precursor powders at5008C for4h,CeO2nano/microstructures with dendrite morphology could be obtained with the morphology partly kept.It is believed that triethylenetetramine plays an important role in the growth of CeCO3OH dendrite structures.The optical absorption spectra indicate that the CeO2nano/microstruc-ture have a direct band gap of2.92eV,which is lower than the values of bulk powders.It is expected that these materials canfind potential application in catalysis and UV-blocking material. 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铁酸铋的制备及其在光催化领域的研究进展卢鹏;胡雪利;赖昕;刘小平;芦婉婷;王晓雪;邱建【摘要】不同的制备方法,可以得到不同形貌的BiFeO3晶体,从而使其具备不同的性能.该材料的制备方法主要有固相反应法、共沉淀法、水热法、溶胶-凝胶法等.旨在对目前已见报道的BiFeO3的制备方法进行比较,并对该材料在水处理方面的光催化应用进行了综述.集光催化性及铁电磁性于一身的BiFeO3,将在光催化领域有着广阔的应用前景.【期刊名称】《应用化工》【年(卷),期】2018(047)006【总页数】4页(P1270-1273)【关键词】铁酸铋;制备;光催化;研究进展【作者】卢鹏;胡雪利;赖昕;刘小平;芦婉婷;王晓雪;邱建【作者单位】重庆工商大学环境与资源学院,重庆 400067;重庆工商大学环境保护研究所,重庆 400067;重庆工商大学环境与资源学院,重庆 400067;重庆工商大学环境与资源学院,重庆 400067;重庆工商大学环境与资源学院,重庆 400067;西华大学食品与生物工程学院,四川成都 610039;重庆市南岸区生态环境监测站,重庆400067;重庆工商大学环境保护研究所,重庆 400067【正文语种】中文【中图分类】TQ135.3+2;Q643.36光催化技术因其具有反应速度快、处理对象无差别、对污染物降解完全等优点，使该技术成为在污染物处理、空气净化等领域被广泛应用的新技术[1-2]。

目前，TiO2因具有氧化能力强、催化活性高、性质稳定、价廉无毒等特点，被广泛应用于废水处理、空气净化、杀菌自洁等方面。

但是，由于TiO2的禁带宽度为3.2 eV，对可见光的利用效率低，且目前多为粉末状形态，极难回收。

这些劣势极大地限制了TiO2光催化材料在现实工程中的应用。

因此，开发新型且便于回收的光催化材料，已成为目前研究的热点[3-5]。

BiFeO3是一种新型的铁电磁材料，该材料具有三方扭曲的钙钛矿结构，在室温下同时具有铁电有序和G型反铁磁有序两种结构。

第42卷第10期2023年10月硅㊀酸㊀盐㊀通㊀报BULLETIN OF THE CHINESE CERAMIC SOCIETY Vol.42㊀No.10October,2023g-C 3N 4/Ag 基二元复合光催化剂降解环境污染物的研究进展柏林洋1,蔡照胜2(1.江苏旅游职业学院,扬州㊀225000;2.盐城工学院化学化工学院,盐城㊀224051)摘要:光催化技术在太阳能资源利用方面呈现出良好的应用前景,已受到世界各国的广泛关注㊂g-C 3N 4是一种二维结构的非金属聚合物型半导体材料,具有合成简单㊁成本低㊁化学性质稳定㊁无毒等特点,在环境修复和能量转化方面应用潜力较大㊂但g-C 3N 4存在对可见光吸收能力差㊁比表面积小和光生载流子复合速率高等缺点,限制了其实际应用㊂构筑异质结光催化剂是提高光催化效率的有效途径之一㊂基于Ag 基材料的特点,前人对g-C 3N 4/Ag 基二元复合光催化剂进行了大量研究,并取得显著成果㊂本文总结了近年来AgX(X =Cl,Br,I)/g-C 3N 4㊁Ag 3PO 4/g-C 3N 4㊁Ag 2CO 3/g-C 3N 4㊁Ag 3VO 4/g-C 3N 4㊁Ag 2CrO 4/g-C 3N 4㊁Ag 2O /g-C 3N 4和Ag 2MoO 4/g-C 3N 4复合光催化剂降解环境污染物的研究进展,并评述了g-C 3N 4/Ag 基二元复合光催化剂目前面临的主要挑战,展望了其未来发展趋势㊂关键词:g-C 3N 4;Ag 基材料;二元复合光催化剂;光催化性能;环境污染物中图分类号:TQ426㊀㊀文献标志码:A ㊀㊀文章编号:1001-1625(2023)10-3755-09Research Progress on g-C 3N 4/Ag-Based Binary Composite Photocatalysts for Degradation of Environmental PollutantsBAI Linyang 1,CAI Zhaosheng 2(1.Jiangsu Institute of Tourism,Yangzhou 225000,China;2.School of Chemistry and Chemical Engineering,Yancheng Institute of Technology,Yancheng 224051,China)Abstract :Photocatalysis technology shows a good application prospect in the utilization of solar energy resource and has attracted worldwide attention.g-C 3N 4is a two-dimensional polymeric metal-free semiconductor material with the characteristics of facile synthesis,low cost,high chemical stability and non-toxicity,which has great potential in environmental remediation and energy conversion.However,g-C 3N 4has the drawbacks of poor visible light absorption capacity,low specific surface area and high recombination rate of photogenerated charge carriers,which limits its practical application.Constructing heterojunction photocatalyst has become one of effective pathways for boosting photocatalytic efficiency.Based on the inherent merits of Ag-based materials,a lot of researches have been carried out on g-C 3N 4/Ag-based binary photocatalysts and prominent results have been achieved.Recent advances on AgX (X =Cl,Br,I)/g-C 3N 4,Ag 3PO 4/g-C 3N 4,Ag 2CO 3/g-C 3N 4,Ag 3VO 4/g-C 3N 4,Ag 2CrO 4/g-C 3N 4,Ag 2O /g-C 3N 4and Ag 2MoO 4/g-C 3N 4composite photocatalysts for the degradation of environmental pollutants were summarized.The major challenges of g-C 3N 4/Ag-based binary composite photocatalysts were reviewed and the future development trends were also forecast.Key words :g-C 3N 4;Ag-based material;binary composite photocatalyst;photocatalytic performance;environmental pollutant㊀收稿日期:2023-05-15;修订日期:2023-06-12基金项目:江苏省高等学校自然科学研究面上项目(19KJD530002)作者简介:柏林洋(1967 ),男,博士,副教授㊂主要从事光催化材料方面的研究㊂E-mail:linybai@通信作者:蔡照胜,博士,教授㊂E-mail:jsyc_czs@0㊀引㊀言随着全球经济的快速增长和工业化进程的加快,皮革㊁印染㊁制药和化工等行业排放的环境污染物总量3756㊀陶㊀瓷硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷也不断增长㊂这些环境污染物存在成分复杂㊁毒性大㊁难以降解等特点,对人们的身体健康和生态环境产生严重威胁,已成为制约经济和社会发展的突出问题㊂如何实现环境污染物的高效降解是目前亟待解决的重要问题㊂效率低㊁能耗高及存在二次污染是利用传统处理方法处置环境污染物的主要缺陷[1]㊂光催化技术作为一种新型的绿色技术,具有环境友好㊁成本低㊁反应效率高和无二次污染等优点,在解决环境污染问题方面具有很大的发展潜力,深受人们的关注[2-4]㊂g-C3N4属于一种非金属聚合物型半导体材料,具有二维分子结构,即C原子和N原子通过sp2杂化形成的共轭石墨烯平面结构,具有适宜的禁带宽度(2.7eV)和对460nm以下可见光良好的响应能力㊂g-C3N4具有合成原料成本低㊁制备工艺简单㊁耐酸耐碱和稳定性好等特点,在催化[5]㊁生物[6]和材料[7]等领域应用广泛㊂然而,g-C3N4较小的比表面积㊁较弱的可见光吸收能力和较快的光生载流子复合率等不足导致其光量子利用率不高,给实际应用带来较大困难[8]㊂为了克服上述问题,前人提出了对g-C3N4进行形貌调控[9]㊁元素掺杂[10-11]和与其他半导体耦合[12-13]等方法㊂其中,将g-C3N4与其他半导体耦合形成异质结光催化剂最为常见㊂Ag基半导体材料因具有成本合理㊁光电性能好和光催化活性高等特点而深受青睐,但仍存在光生载流子快速复合和光腐蚀等缺陷㊂近年来,人们将Ag基材料与g-C3N4进行复合,整体提高了复合光催化剂的催化性能,并由此取得了大量极有价值的科研成果㊂本文综述了近年来g-C3N4/Ag银基二元复合光催化剂的制备方法㊁性能和应用等方面的研究现状,同时展望了未来的发展趋势,期望能为该领域的研究人员提供新的思路㊂1㊀g-C3N4/Ag基二元复合光催化剂近年来,基于Ag基半导体材料能与g-C3N4能带结构匹配的特点,构筑g-C3N4/Ag基异质结型复合光催化体系已成为国内外的研究热点㊂这类催化剂通常采用沉淀法在g-C3N4表面负载Ag基半导体材料㊂其中,Ag基体的成核和生长是关键问题㊂通过对Ag基材料成核和生长工艺的控制,实现了Ag基材料在g-C3N4上的均匀分布㊂此外,通过对g-C3N4微观结构进行调控,使其具有较大的比表面积和较高的结晶度,从而进一步提高复合光催化剂的催化性能㊂相对于纯g-C3N4和Ag基光催化剂,g-C3N4/Ag基二元复合光催化剂通过两组分的协同效应和界面作用,不仅能提高对可见光的吸收利用率,而且能有效抑制g-C3N4和Ag基材料中光生e-/h+对的重组,从而提高复合光催化剂的活性和稳定性㊂在g-C3N4/Ag基二元复合光催化材料中,以AgX(X=Cl,Br,I)/g-C3N4㊁Ag3PO4/g-C3N4㊁Ag2CO3/g-C3N4㊁Ag3VO4/g-C3N4㊁Ag2CrO4/g-C3N4㊁Ag2O/g-C3N4和Ag2MoO4/g-C3N4为典型代表㊂1.1㊀AgX(X=Cl,Br,I)/g-C3N4二元复合光催化剂AgX(X=Cl,Br,I)在杀菌㊁有机污染物降解和光催化水解产氢等方面展现出优异的性能㊂但AgX (X=Cl,Br,I)是一种光敏材料,在可见光下容易发生分解,形成Ag0,从而影响其催化活性及稳定性㊂将AgX(X=Cl,Br,I)与g-C3N4复合是提升AgX(X=Cl,Br,I)使用寿命㊁改善光催化性能最有效的方法之一㊂Li等[14]采用硬模板法制备出一种具有空心和多孔结构的高比表面积g-C3N4纳米球,并以其为载体,通过沉积-沉淀法得到AgBr/g-C3N4光催化材料㊂XRD分析显示AgBr的加入并没有改变g-C3N4的晶体结构,瞬态光电流试验表明AgBr/g-C3N4光电流密度高于g-C3N4,橙黄G(OG)染料经10min可见光照射后的降解率达到97%㊂Shi等[15]报道了利用沉淀回流法制备AgCl/g-C3N4光催化剂,研究了AgCl的量对催化剂结构及光催化降解草酸性能的影响,确定了最佳修饰量,分析了催化剂用量㊁草酸起始浓度㊁酸度和其他有机成分对光催化活性影响,通过自由基捕获试验揭示了光降解反应中起主要作用的活性物质为光生电子(e-)㊁羟基自由基(㊃OH)㊁超氧自由基(㊃O-2)和空穴(h+)㊂彭慧等[16]采用化学沉淀法制备具有不同含量AgI的AgI/g-C3N4光催化剂,SEM测试表明AgI纳米颗粒分布在层状结构g-C3N4薄片的表面,为催化反应提供了更多的活性位㊂该系列催化剂应用于光催化氧化降解孔雀石绿(melachite green,MG)的结果显示,AgI/g-C3N4(20%,质量分数,下同)的光催化性能最好,MG经2h可见光辐照后去除率达到99.8%㊂部分AgX(X=Cl,Br,I)/g-C3N4二元复合光催化剂的研究现状如表1所示㊂第10期柏林洋等:g-C 3N 4/Ag 基二元复合光催化剂降解环境污染物的研究进展3757㊀表1㊀AgX (X =Cl ,Br ,I )/g-C 3N 4二元复合光催化剂光降解环境污染物的研究现状Table 1㊀Research status of AgX (X =Cl ,Br ,I )/g-C 3N 4binary composite photocatalysts forphotodegradation of enviromental pollutantsPhotocatalytst Synthesis method TypePotential application Photocatalytic activity Reference AgBr /g-C 3N 4Sonication-assisted deposition-precipitation II-schemeDegradation of RhB,MB and MO 100%degradation for RhB,95%degradation for MB and 90%degradation for MO in 10min [17]AgCl /g-C 3N 4Precipitation Z-schemeDegradation of RhB and TC 96.1%degradation for RhB and 77.8%degradation for TC in 120min [18]AgCl /g-C 3N 4Solvothermal +in situ ultrasonic precipitation Z-scheme Degradation of RhB 92.2%degradation in 80min [19]AgBr /g-C 3N 4Deposition-precipitation II-schemeDegradation of MO 90%degradation in 30min [20]AgI /g-C 3N 4In-situ growth II-scheme Degradation of RhB 100%degradation in 60min [21]㊀㊀Note:MO-methyl orange,RhB-rhodamine B,TC-tetracycline hydrochloride,MB-methyl blue.1.2㊀Ag 3PO 4/g-C 3N 4二元复合光催化剂纳米Ag 3PO 4禁带宽度为2.5eV 左右,对可见光有很好的吸收作用,且光激发后具有很强的氧化性,在污染物降解和光解水制氢等领域有良好的应用前景[22]㊂但是,纳米Ag 3PO 4易团聚,光生载流子的快速重组使光催化活性大大降低,此外,Ag 3PO 4还易受光生e -的腐蚀,从而影响稳定性㊂Ag 3PO 4与g-C 3N 4复合可显著降低e -/h +对的重组,有效提高光催化性能㊂Wang 等[23]采用原位沉淀法获得Z-型异质结构g-C 3N 4/Ag 3PO 4复合光催化剂,并有效地提高了e -/h +对的分离效率㊂TEM 结果显示,Ag 3PO 4粒子被g-C 3N 4纳米片所覆盖,UV-DRS 结果表明,Ag 3PO 4的添加使g-C 3N 4吸收边发生红移,且吸收光强度显著增强,光降解实验结果显示,30%g-C 3N 4/Ag 3PO 4光催化剂在40min 内能去除约90%的RhB㊂胡俊俊等[24]利用了原位沉淀法合成了一系列Ag 3PO 4/g-C 3N 4复合光催化剂,研究了Ag 3PO 4和g-C 3N 4的物质的量比对催化剂在可见光下催化降解MB 性能的影响,发现在最优组分下,MB 经可见光辐照30min 后可以被完全降解㊂Mei 等[25]采用焙烧-沉淀法制备了一系列Ag 3PO 4/g-C 3N 4复合光催化剂,并用于可见光条件下降解双酚A(bisphenol A,BPA),发现Ag 3PO 4质量分数为25%时,光催化降解BPA 的性能最好,3h 能降解92.8%的BPA㊂潘良峰等[26]采用化学沉淀法制备出一种具有空心管状的Ag 3PO 4/g-C 3N 4光催化剂,SEM 结果表明,Ag 3PO 4颗粒均匀分布于空心管状结构g-C 3N 4的表面,两者形成一个较强异质结构,将其用于盐酸四环素(tetracycline hydrochloride,TC)光催化降解,80min 能降解98%的TC㊂Deonikar 等[27]研究了采用原位湿化学法合成催化剂过程中使用不同溶剂(去离子水㊁四氢呋喃和乙二醇)对Ag 3PO 4/g-C 3N 4的结构和光降解MB㊁RhB 及4-硝基苯酚性能的影响,发现不同溶剂对复合光催化剂的形貌有着重要影响,从而影响光催化性能,其中以四氢呋喃合成的复合光催化剂的催化降解性能最佳,这是由于g-C 3N 4纳米片均匀包裹在Ag 3PO 4的表面,从而促使两者界面形成较为密切的相互作用,有利于e -/h +对的分离㊂部分Ag 3PO 4/g-C 3N 4二元复合光催化剂的研究进展见表2㊂表2㊀Ag 3PO 4/g-C 3N 4二元复合光催化剂光降解环境污染物的研究现状Table 2㊀Research status of Ag 3PO 4/g-C 3N 4binary composite photocatalysts for photodegradation of environmental pollutantsPhotocatalyst Synthesis method Type Potential application Photocatalytic activity Reference g-C 3N 4/Ag 3PO 4In situ precipitation Z-scheme Degradation of BPA 100%degradation in 180min [28]g-C 3N 4/Ag 3PO 4Hydrothermal Z-schemeDecolorization of MB Almost 93.2%degradation in 25min [29]g-C 3N 4/Ag 3PO 4In situ prepcipitation II-scheme Reduction of Cr(VI)94.1%Cr(VI)removal efficiency in 120min [30]g-C 3N 4/Ag 3PO 4Chemical precipitation Z-scheme Degradation of RhB 90%degradation in 40min [31]g-C 3N 4/Ag 3PO 4In situ precipitation Z-scheme Degradation of levofloxacin 90.3%degradation in 30min [32]Ag 3PO 4/g-C 3N 4Chemical precipitation Z-schemeDegradation of gaseous toluene 87.52%removal in 100min [33]Ag 3PO 4/g-C 3N 4Calcination +precipitation Z-scheme Degradation of diclofenac (DCF)100%degradation in 12min [34]Ag 3PO 4/g-C 3N 4In situ deposition Z-scheme Degradation of RhB and phenol 99.4%degradation in 9min for RhB;97.3%degradation in 30min for phenol [35]3758㊀陶㊀瓷硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷续表Photocatalyst Synthesis method Type Potential application Photocatalytic activity Reference Ag3PO4/g-C3N4In situ hydrothermal II-scheme Degradation of sulfapyridine(SP)94.1%degradation in120min[36] Ag3PO4/g-C3N4In situ growth Z-scheme Degradation of berberine100%degradation in15min[37] g-C3N4/Ag3PO4In situ deposition Z-scheme Degradation of ofloxacin71.9%degradation in10min[38] Ag3PO4/g-C3N4Co-precipitation Z-scheme Degradation of MO98%degradation in10min[39]g-C3N4/Ag3PO4Calcination+precipitation Z-scheme Degradation of MO,RhB and TC95%degradation for MO in30min;[40]96%degradation for RhB in15min;80%degradation for TC in30min1.3㊀Ag2CO3/g-C3N4二元复合光催化剂Ag4d轨道和O2p轨道杂化,形成Ag2CO3的价带(valence band,VB);Ag5s轨道和Ag4d轨道进行杂化,形成Ag2CO3导带(conduction band,CB),而CB中原子轨道杂化会降低Ag2CO3带隙能,从而提高光催化活性[41]㊂纳米Ag2CO3带隙能约为2.5eV,可见光响应性好,在可见光作用下表现出良好的光催化降解有机污染物特性[42-43]㊂然而,经长时间光照后,Ag2CO3晶粒中Ag+会被光生e-还原成Ag0,导致其光腐蚀,引起光催化性能下降[44]㊂Ag2CO3与g-C3N4耦合,能够有效地抑制光腐蚀,促进e-/h+对的分离,进而改善光催化性能㊂An等[45]通过构筑Z型核壳结构的Ag2CO3@g-C3N4材料来增强Ag2CO3和g-C3N4界面间的相互作用,从而有效防止光腐蚀发生,加速光生e-/h+对的分离,实现了催化剂在可见光辐照下高效降解MO㊂Yin等[46]通过水热法制备Ag2CO3/g-C3N4光催化剂,探讨了g-C3N4的含量㊁合成温度对催化剂结构和光降解草酸(oxalic acid,OA)性能的影响,获得最优条件下合成的催化剂能在45min光照时间内使OA去除率达到99.99%㊂Pan等[41]采用煅烧和化学沉淀两步法,制备了一系列Ag2CO3/g-C3N4光催化剂,TEM结果显示,Ag2CO3纳米粒子均匀分布在g-C3N4纳米片表面,且形貌规整㊁粒径均一,光催化性能测试结果表明,60% Ag2CO3/g-C3N4光催化活性最高,MO和MB分别经120和240min可见光光照后,其降解率分别为93.5%和62.8%㊂Xiu等[47]使用原位水热法构筑了Ag2CO3/g-C3N4光催化剂,光降解试验结果表明,MO经可见光辐照1h的去除率为87%㊂1.4㊀Ag3VO4/g-C3N4二元复合光催化剂纳米Ag3VO4带隙能约为2.2eV,可用于催化可见光降解环境污染物,是一种具有应用前景的新型半导体材料㊂然而,如何提高Ag3VO4光催化性能,仍然是学者研究的重点㊂构建Ag3VO4/g-C3N4异质结催化剂是提高Ag3VO4的催化性能的一种有效方法㊂该方法能够降低Ag3VO4光生载流子的复合率,拓宽可见光的吸收范围㊂Hind等[48]通过溶胶凝胶法制备出一种具有介孔结构的Ag3VO4/g-C3N4复合光催化剂,该复合催化剂经60min可见光照射能将Hg(II)全部还原,其光催化活性分别是Ag3VO4和g-C3N4的4.3倍和5.4倍,主要是由于异质结界面处各组分间紧密结合以及催化剂具有较高的比表面积和体积比,从而促进光生载流子的分离㊂蒋善庆等[49]利用化学沉淀法制备了系列Ag3VO4/g-C3N4催化剂,催化性能研究结果表明,Ag3VO4负载量为20%(质量分数)时,其光催化降解微囊藻毒素的效果最好,可见光辐照100min后降解率为85.43%,而g-C3N4在相同条件下的降解率仅为18.76%㊂1.5㊀Ag2CrO4/g-C3N4二元复合光催化剂纳米Ag2CrO4具有特殊的晶格和能带结构,其带隙能为1.8eV,可见光响应良好,是一种非常理想的可见光区半导体材料㊂然而,Ag2CrO4存在自身的电子结构和晶体的缺陷,导致其光催化效率性能较差,严重影响了实际应用[50-52]㊂将Ag2CrO4与g-C3N4复合形成异质结光催化剂是提高其光催化效率和稳定性的一种有效途径,因为Ag2CrO4在光照下产生的光生e-快速地迁移到g-C3N4表面,可避免光生e-在Ag2CrO4表面聚集而引起光腐蚀㊂Ren等[53]利用SiO2为硬模板,以氰胺为原料,合成出具有中空介孔结构的g-C3N4,再通过化学沉淀法制备了系列g-C3N4/Ag2CrO4光催化剂,并将其用于RhB和TC的可见光降解,研究发现g-C3N4/Ag2CrO4催化剂具有较高比表面积和丰富的孔道结构,在可见光辐射下表现出较高的光催化活性㊂Rajalakshmi等[54]利用水热方法合成了一系列Ag2CrO4/g-C3N4光催化剂,并将其用于对硝基苯酚的光催化降解,结果表明,Ag2CrO4质量分数为10%时,其降解率达到97%,高于单组分g-C3N4或Ag2CrO4,原因是与第10期柏林洋等:g-C 3N 4/Ag 基二元复合光催化剂降解环境污染物的研究进展3759㊀Ag 2CrO 4和g-C 3N 4界面间形成了S-型异质结,能提高e -/h +对的分离效率㊂1.6㊀Ag 2O /g-C 3N 4二元复合光催化剂纳米Ag 2O 是一种理想的可见光半导体材料,在受到光辐照后,其电子发生跃迁,CB 上光生e -能够将Ag 2O 晶粒中Ag +还原成Ag 0,而VB 上h +能够使Ag 2O 的晶格氧氧化为O 2,导致其结构不稳定㊂然而,纳米Ag 2O 在有机物污染物降解方面表现出良好的稳定性[55],这是因为Ag 2O 的表面会随着光化学反应的进行被一定数量的Ag 0纳米粒子所覆盖,而Ag 0纳米粒子作为光生e -陷阱,能够降低e -在Ag 2O 表面的富集,同时,由于光生h +具有较强的氧化性能力,既能实现对有机污染物的直接氧化,又能避免其对晶格氧的氧化,从而提高了纳米Ag 2O 光催化活性和稳定性㊂Liang 等[56]在常温下采用简易化学沉淀法制备了p-n 结Ag 2O /g-C 3N 4复合光催化剂,研究发现,起分散作用的g-C 3N 4为Ag 2O 纳米颗粒的生长提供了大量成核位点并限制了Ag 2O 纳米颗粒聚集,p-n 结的形成以及在光化学反应过程中生成的Ag 纳米粒子,加速了光生载流子的分离和迁移,拓宽了光的吸收范围,在可见光和红外光照下降解RhB 溶液过程中表现出良好的催化活性,其在可见光和红外光照下反应速率分别是g-C 3N 4的26倍和343倍㊂Jiang 等[57]通过液相法制备了一系列介孔结构的g-C 3N 4/Ag 2O 光催化剂,试验结果表明,Ag 2O 的添加显著提高了g-C 3N 4/Ag 2O 光催化剂的吸光性能和比表面积,因此对光催化性能的提升有促进作用,当Ag 2O 含量为50%时,光催化分解MB 的效果最好,经120min 可见光光照后,MB 的脱除率达到90.8%,高于g-C 3N 4和Ag 2O㊂Kadi 等[58]以Pluronic 31R 1表面活性剂为软模板,以MCM-41为硬模板,合成出具有多孔结构的Ag 2O /g-C 3N 4光催化剂,TEM 结果显示,球形Ag 2O 的纳米颗粒均匀地分布于g-C 3N 4的表面,催化性能评价表明0.9%Ag 2O /g-C 3N 4复合光催化剂光催化效果最佳,60min 能完全氧化降解环丙沙星,其降解效率分别是Ag 2O 和g-C 3N 4的4倍和10倍㊂1.7㊀Ag 2MoO 4/g-C 3N 4二元复合光催化剂Ag 2MoO 4具有良好的导电性㊁抗菌性㊁环保性,以及优良的光催化活性,在荧光材料㊁导电玻璃㊁杀菌剂和催化剂等方面有着广阔的应用前景[59]㊂但Ag 2MoO 4带隙大(3.1eV),仅能对紫外波段光进行响应,限制了其对太阳光的利用㊂当Ag 2MoO 4与g-C 3N 4进行耦合时,可以将其对太阳光的吸收范围由紫外拓展到可见光区,从而提高太阳光的利用率㊂Pandiri 等[60]通过水热合成的方法,制备出β-Ag 2MoO 4/g-C 3N 4异质结光催化剂,SEM 结果显示该催化剂中β-Ag 2MoO 4纳米颗粒均匀地分布在g-C 3N 4纳米片的表面,光催化性能测试结果表明在3h 的可见光照射下,其降解能力是β-Ag 2MoO 4和g-C 3N 4机械混合物的2.6倍,主要原因在于β-Ag 2MoO 4和g-C 3N 4两者界面间形成更为紧密的异质结,使得e -/h +对被快速分离㊂Wu 等[61]采用简单的原位沉淀方法成功构建了Ag 2MoO 4/g-C 3N 4光催化剂,并将其应用于MO㊁BPA 和阿昔洛韦的降解,结果表明该催化剂显示出良好的太阳光催化活性,这主要是因为Ag 2MoO 4和g-C 3N 4界面间存在着一定的协同效应,可有效地提高对太阳光的利用率,降低载流子的复合概率㊂2㊀g-C 3N 4/Ag 基二元复合光催化剂电荷转移机理模型研究g-C 3N 4/Ag 基二元复合光催化剂在可见光的辐照下,价带电子发生跃迁,产生e -/h +对㊂e -被催化剂表面吸附的O 2捕获产生㊃O -2,并进一步与水反应生成㊃OH,形成的三种活性自由基(h +㊁㊃O -2和㊃OH),实现水中有机污染物的高效降解(见图1)㊂而光催化反应机理与载流子的迁移机制密切相关㊂目前,g-C 3N 4/Ag 基二元复合光催化剂体系中主要存在三种不同的光生载流子的转移机制,分别为I 型㊁II 型和Z 型㊂图1㊀g-C 3N 4/Ag 基二元复合光催化剂降解有机污染物的光催化反应机理Fig.1㊀Photocatalytic reaction mechanism of g-C 3N 4/Ag-based binary composite photocatalyst for degradation of organic pollutants3760㊀陶㊀瓷硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷2.1㊀I 型异质结载流子转移机理模型图2(a)为I 型异质结构中的光生e -/h +对转移示意图㊂半导体A 和半导体B 均对可见光有响应,其中,半导体A 的带隙较宽,半导体B 的带隙较窄,并且半导体B 的VB 和CB 均位于半导体A 之间,在可见光的照射下,e -发生跃迁,从CB 到VB,半导体A 的CB 上的e -和VB 上的h +分别向半导体B 的CB 和VB 转移,从而实现了e -/h +对的分离㊂以Ag 2O /g-C 3N 4复合催化剂为例[58],当Ag 2O 和g-C 3N 4相耦合时,因为g-C 3N 4的VB 具有更正的电势,h +被转移到Ag 2O 的VB 上,同时,光激发e -在g-C 3N 4的CB 上,其电势较负,e -便传输到Ag 2O 的CB 上,CB 上e -与O 2结合形成㊃O -2,并进一步与H +结合生成了㊃OH,而有机物污染物被Ag 2O 的价带上h +氧化分解生成CO 2和H 2O㊂2.2㊀II 型异质结载流子转移机理模型II 型异质结是一种能级交错带隙型结构,如图2(b)所示,其中半导体A 的CB 电位较负,在可见光照射下,e -从CB 上转移到半导体B 的CB 上,h +从半导体B 的VB 转移到半导体A 的VB 上,从而使e -/h +对得以分离㊂以Ag 3PO 4@g-C 3N 4为例[62],由于g-C 3N 4的CB 的电势较Ag 3PO 4低,光生e -从g-C 3N 4迁移到Ag 3PO 4的CB 上,而Ag 3PO 4的CB 电势较g-C 3N 4高,h +从Ag 3PO 4的VB 迁移到g-C 3N 4的VB 上,从而实现e -/h +对的分离,g-C 3N 4表面的h +可直接氧化降解MB,而Ag 3PO 4表面积聚的电子又会被氧捕获,产生H 2O 2,并进一步分解成㊃OH,从而加快MB 的降解㊂上述I 型和II 型结构CB 的氧化能力和VB 还原能力低于单一组分,造成复合半导体的氧化还原能力降低[63]㊂2.3㊀Z 型异质结载流子转移机理模型构建Z 型异质结光光催化剂使得e -和h +沿着特有的方向迁移,有效解决复合催化剂氧化还原能力降低问题[64]㊂Z 型异质结催化剂e -/h +对的迁移方向如图2(c)所示,e -从半导体B 的电势较高的CB 转移到半导体A 的电势较低的VB 进行复合,从而实现半导体A 的e -和半导体B 的h +发生分离㊂h +在半导体B 表面氧化性能更强,在半导体A 上e -具有较高还原特性,两者共同作用使环境污染物得以顺利降解㊂为了更好地解释Z 型异质结h +和e -迁移机理,以Ag 3VO 4/g-C 3N 4复合光催化剂为例[48],复合光催化剂经可见光激发后,Ag 3VO 4和g-C 3N 4都发生了e -跃迁,在Ag 3VO 4的CB 上e -与g-C 3N 4的VB 上h +进行复合时,e -对Ag 3VO 4的腐蚀作用被削弱,同时,也实现了g-C 3N 4的CB 上e -和Ag 3PO 4的价带上h +发生分离,g-C 3N 4的CB 上e -具有较强的还原性,将Hg 2+还原成Hg 0,而Ag 3PO 4的VB 上h +具有较强的氧化性,可将HOOH氧化生成CO 2和H 2O㊂图2㊀电子-空穴对转移机理示意图Fig.2㊀Schematic diagrams of electron-hole pairs transfer mechanism 3㊀结语和展望g-C 3N 4/Ag 基二元复合光催化剂因其较强的可见光响应和优异的光催化性能,在环境污染物的降解方面具有广阔的发展空间㊂近年来,国内外研究人员在理论研究㊁制备方法和光催化性能等多个领域取得了重要进展,为光催化理论的发展奠定了坚实的基础㊂然而,g-C 3N 4/Ag 基二元复合光催化剂在实际应用中还面临诸多问题,如制备工艺复杂㊁光腐蚀㊁光催化剂回收利用困难㊁光催化降解污染物的反应机理尚不明确等,第10期柏林洋等:g-C3N4/Ag基二元复合光催化剂降解环境污染物的研究进展3761㊀现有的光催化降解模型仍有较大的分歧,亟待深入研究㊂为了获得性能优良的g-C3N4/Ag基复合光催化剂,实现产业化应用,应进行以下几方面的研究:1)在g-C3N4/Ag基二元光催化剂的基础上,构建多元复合光催化剂,是进一步提升光生载流子分离效率的有效㊁可靠手段,也是当今和今后光催化剂的研究重点㊂2)对g-C3N4/Ag基二元光催化剂体系中e-/h+对的转移㊁分离和复合等过程进行系统研究,并阐明其光催化反应机制㊂3)针对当前合成的g-C3N4材料多为体相,存在着颗粒大㊁比表面积小㊁活性位少等缺陷,应通过对g-C3N4材料的形状㊁形貌及尺寸的调控,来实现Ag 基材料在g-C3N4材料表面的均匀分布,降低e-/h+对的重组概率,从而大幅度提高复合光催化剂的性能㊂4)Ag基材料的光腐蚀是导致光催化活性和稳定性下降的重要因素,探索一种更为有效的光腐蚀抑制机制,是将其推广应用的关键㊂5)当前合成的g-C3N4/Ag基二元复合光催化剂多为粉末状,存在着易团聚㊁难回收等问题,从而限制了其循环利用㊂因此,需要开展g-C3N4/Ag基二元复合光催化剂回收和再利用的研究,这将有利于社会效益和经济效益的提高㊂参考文献[1]㊀LIN Z S,DONG C C,MU W,et al.Degradation of Rhodamine B in the photocatalytic reactor containing TiO2nanotube arrays coupled withnanobubbles[J].Advanced Sensor and Energy Materials,2023,2(2):100054.[2]㊀DIAO Z H,JIN J C,ZOU M Y,et al.Simultaneous degradation of amoxicillin and norfloxacin by TiO2@nZVI composites coupling withpersulfate:synergistic effect,products and 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