利用可再生能源发电,并通过低温电解水技术生产氢气,被认为是一种环保且可持续的制氢途径,是未来氢能发展的重要方向之一.采用该方法生产的氢气因其环保特性而被称为“绿氢”.然而,目前绿氢高昂的生产成本限制了电解水制氢技术的大规模...利用可再生能源发电,并通过低温电解水技术生产氢气,被认为是一种环保且可持续的制氢途径,是未来氢能发展的重要方向之一.采用该方法生产的氢气因其环保特性而被称为“绿氢”.然而,目前绿氢高昂的生产成本限制了电解水制氢技术的大规模应用.因此,开发先进的非贵金属催化剂和电催化体系以降低电解水制氢成本具有重要意义.界面工程是一种提升非贵金属催化剂电解水性能的有效策略,但目前对其催化活性位点的识别及活性提升机制的研究仍然不足.本文采用简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF催化剂,并研究了其在电解水过程中的催化活性位点及这些位点在提升催化能力方面的协同作用.采用扫描电镜(SEM)证明了Ni_(2)P/CoP/FeP_(4)/IF催化剂呈现纳米线网络结构,这种结构不仅有利于增加催化剂的电化学活性位点和加速反应动力学,而且促进了连续产生的气泡从活性位点逃逸,从而提高了催化剂的机械稳定性.电化学研究结果表明,所制备Ni_(2)P/CoP/FeP_(4)/IF催化剂在1.0 mol L^(‒1)KOH溶液中表现出较好的析氧反应(OER)和析氢反应(HER)活性,分别仅需218和127 mV的过电位,即可达到100 mA cm^(‒2)的电流密度.将Ni_(2)P/CoP/FeP_(4)/IF分别作为阴极和阳极构建双电极电解槽,该装置产生100和500 mA cm^(‒2)的电流密度分别仅需1.68和2.05 V的电压,这一性能优于大多数已报道的自支撑过渡金属磷化物催化剂.多步计时电位测试结果进一步证实了Ni_(2)P/CoP/FeP_(4)/IF作为阳极和阴极材料在水分解过程中具有较好的长期耐久性.X射线光电子能谱和差分电荷分析表明,电子从富电子的FeP_(4)向缺电子的Ni_(2)P和CoP转移,这促使Ni_(2)P和CoP上的电子积累和FeP_(4)上的空穴积累,有利于优化反应中间体的吸附和脱附自由能,提升OER和HER催化性能.结合X射线衍射、扫描电镜、透射电镜、X射线光电子能谱和原位拉曼光谱结果发现,催化剂重构后形成的特定(氧)氢氧化物结构,是OER反应真正的关键活性位点.原位拉曼光谱进一步证实了异质界面促进了OER过程中Ni_(2)P/CoP/FeP_(4)/IF的快速重构.此外,利用密度泛函理论分析了催化剂的HER反应机理.计算结果表明,H2O优先吸附在Fe位点并发生水解,随后产生的H*吸附在Ni位点上并发生解吸,从而促进了催化剂中Fe和Ni活性位点的高效利用.同时,CoP的引入提高了Ni_(2)P/CoP/FeP_(4)/IF催化剂的水吸附和解离能力,进一步提升了其HER活性.综上所述,本文通过简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF过渡金属磷化物纳米线网络催化剂,并将其用于碱性水分解.通过多种表征技术及理论计算结果分析,识别了电解水过程中的关键催化活性位点,即催化剂重构后形成的特定(氧)氢氧化物结构,并揭示了其在OER和HER反应中的催化机制.本研究可为高性能碱性电解水催化剂的理性设计和开发提供参考.展开更多
In an attempt to develop low-cost,non-noble-metal bifunctional electrocatalysts for water electrolysis in alkaline media,cobalt-doped molybdenum carbide@N-doped carbon nanosheets/nanotubes were fabricated by using C3N...In an attempt to develop low-cost,non-noble-metal bifunctional electrocatalysts for water electrolysis in alkaline media,cobalt-doped molybdenum carbide@N-doped carbon nanosheets/nanotubes were fabricated by using C3N4 as the carbon source on a 3D porous nickel foam substrate.Benefiting from the optimized electronic structure and enhanced mass and charge transport,as well as the 3D conducting pathway,MoxCoy@N-CNSs/CNTs shows superior performance towards both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in an alkaline medium.The optimal electrocatalyst is Mo2Co1@N-CNSs/CNTs,which reveals a current density of 10 mA cm^-2 at the low overpotentials of 99 mV and 300 mV for the HER and OER,respectively,and a relatively low cell voltage(1.63 V)for the overall water electrolysis.The method of optimizing the composition and nanostructure of a material provides a new avenue for the development and utilization of high-performance electrocatalysts.展开更多
Catalysts play decisive roles in determining the energy conversion efficiencies of energy devices.Up to now,various types of nanostructured materials have been studied as advanced electrocatalysts.This review highligh...Catalysts play decisive roles in determining the energy conversion efficiencies of energy devices.Up to now,various types of nanostructured materials have been studied as advanced electrocatalysts.This review highlights the application of one‐dimensional(1D)metal electrocatalysts in energy conversion,focusing on two important reaction systems-direct methanol fuel cells and water splitting.In this review,we first give a broad introduction of electrochemical energy conversion.In the second section,we summarize the recent significant advances in the area of 1D metal nanostructured electrocatalysts for the electrochemical reactions involved in fuel cells and water splitting systems,including the oxygen reduction reaction,methanol oxidation reaction,hydrogen evolution reaction,and oxygen evolution reaction.Finally,based on the current studies on 1D nanostructures for energy electrocatalysis,we present a brief outlook on the research trend in 1D nanoelectrocatalysts for the two clean electrochemical energy conversion systems mentioned above.展开更多
Efficient,stable,and noble‐metal‐free electrocatalysts for both the oxygen evolution reaction and the hydrogen evolution reaction are highly imperative for the realization of low‐cost commercial water‐splitting el...Efficient,stable,and noble‐metal‐free electrocatalysts for both the oxygen evolution reaction and the hydrogen evolution reaction are highly imperative for the realization of low‐cost commercial water‐splitting electrolyzers.Herein,a cost‐effective and ecofriendly strategy is reported to fabricate coral‐like FeNi(OH)x/Ni as a bifunctional electrocatalyst for overall water splitting in alkaline media.With the assistance of mild corrosion of Ni by Fe(NO3)3,in situ generated FeNi(OH)x nanosheets are intimately attached on metallic coral‐like Ni.Integration of these nanosheets with the electrodeposited coral‐like Ni skeleton and the supermacroporous Ni foam substrate forms a binder‐free hierarchical electrode,which is beneficial for exposing catalytic active sites,accelerating mass transport,and facilitating the release of gaseous species.In 1.0 mol L^-1 KOH solution,a symmetric electrolyzer constructed with FeNi(OH)x/Ni as both the anode and the cathode exhibits an excellent activity with an applied potential difference of 1.52 V at 10 mA cm^-2,which is superior to that of an asymmetric electrolyzer constructed with the state‐of‐the‐art RuO2‐PtC couple(applied potential difference of 1.55 V at 10 mA cm^-2).This work contributes a facile and reliable strategy for manufacturing affordable,practical,and promising water‐splitting devices.展开更多
Step-scheme(S-scheme)heterojunctions in photocatalysts can provide novel and practical insight on promoting photogenerated carrier separation.The latter is critical in controlling the overall efficiency in one-step ph...Step-scheme(S-scheme)heterojunctions in photocatalysts can provide novel and practical insight on promoting photogenerated carrier separation.The latter is critical in controlling the overall efficiency in one-step photoexcitation systems.In this study,a nanosized BiVO4/Bi0.6Y0.4VO4 solid solution was prepared by a coprecipitation method following with hydrothermal or calcination processes.The S-scheme heterojunction was fabricated by in-situ pressure-induced transformations of bismuth vanadate from the tetragonal zircon phase to the monoclinic scheelite phase,which led to the formation of BiVO4 nanoparticles with a diameter of approximately 5 nm on the surface of BiVO_(4)/Bi_(0.6)Y_(0.4)VO_(4)/Bi_(0.6)Y_(0.4)VO_(4) with S-scheme heterojunctions showed significantly enhanced photocatalytic overall water splitting activity compared with using bare BiVO_(4)/Bi_(0.6)Y_(0.4)VO_(4).Characterization of the carrier dynamics demonstrated that a superior carrier separation through S-type heterojunctions might have caused the enhanced overall water splitting(OWS)activity.Surface photovoltage spectra and the results of selective photodeposition experiments indicated that the photogenerated holes mainly migrated to the BiVO4 nanoparticles in the heterojunction.This confirmed that the charge transfer route corresponds to an S-scheme rather than a type-II heterojunction mechanism under light illumination.This study presents a facile and efficient strategy to construct S-scheme heterojunctions through a pressure-induced phase transition.The results demonstrated that S-scheme junctions composed of different crystalline phases can boost the carrier separation capacity and eventually improve the photocatalytic OWS activity.展开更多
When a proton reduction cocatalyst is loaded on an n-type semiconductor for photocatalytic overall water splitting(POWS),the location of water oxidation sites is generally considered at the surface of the semiconducto...When a proton reduction cocatalyst is loaded on an n-type semiconductor for photocatalytic overall water splitting(POWS),the location of water oxidation sites is generally considered at the surface of the semiconductor due to upward band-bending of n-type semiconductor which may ease the transfer of the photogenerated holes to the surface.However,this is not the case for Pt/SrTiO_(3),a model semiconductor based photocatalyst for POWS.It was found that the photogenerated holes are more readily accumulated at the interface between Pt cocatalyst and SrTiO_(3) photocatalyst as probed by photo-oxidative deposition of PbO_(2),indicating that the water oxidation sites are located at the interface between Pt and SrTiO_(3).Electron paramagnetic resonance and scanning transmission electron microscope studies suggest that the interfacial oxygen atoms between Pt and SrTiO_(3) in Pt/SrTiO_(3) after POWS are more readily lost to form oxygen vacancies upon vacuum heat treatment,regardless of Pt loading by photodeposition or impregnation methods,which may serve as additional support for the location of the active sites for water oxidation at the interface.Density functional theory calculations also suggest that the oxygen evolution reaction more readily occurs at the interfacial sites with the lowest overpotential.These experimental and theoretical studies reveal that the more active sites for water oxidation are located at the interface between Pt and SrTiO_(3),rather than on the surface of SrTiO_(3).Hence,the tailor design and control of the interfacial properties are extremely important for the achievement or improvement of the POWS on cocatalyst loaded semiconductor photocatalyst.展开更多
Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated ele...Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated electrons in Ga_(2)O_(3) loaded with Cr_(2)O_(3)-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy.The structure of these Cr_(2)O_(3)-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy,as Rh particles partly covered with Cr_(2)O_(3).The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction.The loaded Cr_(2)O_(3) promotes electron transfer from Ga_(2)O_(3) to Rh,which accelerates the electron-consuming reaction for H2 evolution.Based on these observations,a photocatalytic water-splitting mechanism for Cr_(2)O_(3)-Rh/Ga_(2)O_(3) photocatalysts has been proposed.The elucidation of the roles of the Cr_(2)O_(3)-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.展开更多
Two-dimensional(2D)carbon nitride(CN)photocatalysts are attracting extensive attention owing to their excellent photocatalytic properties.In this study,we successfully prepared CN materials with heterogeneous structur...Two-dimensional(2D)carbon nitride(CN)photocatalysts are attracting extensive attention owing to their excellent photocatalytic properties.In this study,we successfully prepared CN materials with heterogeneous structures via hydrothermal treatment,high-temperature roasting,ball milling,sintering,and other processes.Benefitting from interface interactions in hybrid architectures,the CN photocatalysts exhibited high photocatalytic activity.The rate of hydrogen production using these CN photocatalysts reached 17028.82μmol h^(−1)g^(−1),and the apparent quantum efficiency was 11.2%at 420 nm.The ns-level time-resolved photoluminescence(PL)spectra provided information about the time-averaged lifetime of fluorescence charge carriers;the lifetime of the charge carriers causing the fluorescence of CN reached 9.99 ns.Significantly,the CN photocatalysts displayed satisfactory results in overall water splitting without the addition of sacrificial agents.The average hydrogen and oxygen production rates were 270.95μmol h^(−1)g^(−1)and 115.21μmol h^(−1)g^(−1)in 7 h,respectively,which were promising results for the applications of the catalysts in overall water splitting processes.We investigated the high efficiency of the prepared CN photocatalysts via a series of tests(UV-vis diffuse reflectance spectroscopy,photocurrent response measurements,PL emission spectroscopy,time-resolved PL spectroscopy,and Brunauer-Emmett-Teller analysis).Furthermore,the Mott-Schottky plot and current-voltage curve were acquired via electrochemical tests.The fabricated CN photocatalyst had a small p-n junction in its heterogeneous structure,which further enhanced its photocatalytic efficiency.Therefore,this work can promote the development of CN photocatalysts.展开更多
文摘利用可再生能源发电,并通过低温电解水技术生产氢气,被认为是一种环保且可持续的制氢途径,是未来氢能发展的重要方向之一.采用该方法生产的氢气因其环保特性而被称为“绿氢”.然而,目前绿氢高昂的生产成本限制了电解水制氢技术的大规模应用.因此,开发先进的非贵金属催化剂和电催化体系以降低电解水制氢成本具有重要意义.界面工程是一种提升非贵金属催化剂电解水性能的有效策略,但目前对其催化活性位点的识别及活性提升机制的研究仍然不足.本文采用简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF催化剂,并研究了其在电解水过程中的催化活性位点及这些位点在提升催化能力方面的协同作用.采用扫描电镜(SEM)证明了Ni_(2)P/CoP/FeP_(4)/IF催化剂呈现纳米线网络结构,这种结构不仅有利于增加催化剂的电化学活性位点和加速反应动力学,而且促进了连续产生的气泡从活性位点逃逸,从而提高了催化剂的机械稳定性.电化学研究结果表明,所制备Ni_(2)P/CoP/FeP_(4)/IF催化剂在1.0 mol L^(‒1)KOH溶液中表现出较好的析氧反应(OER)和析氢反应(HER)活性,分别仅需218和127 mV的过电位,即可达到100 mA cm^(‒2)的电流密度.将Ni_(2)P/CoP/FeP_(4)/IF分别作为阴极和阳极构建双电极电解槽,该装置产生100和500 mA cm^(‒2)的电流密度分别仅需1.68和2.05 V的电压,这一性能优于大多数已报道的自支撑过渡金属磷化物催化剂.多步计时电位测试结果进一步证实了Ni_(2)P/CoP/FeP_(4)/IF作为阳极和阴极材料在水分解过程中具有较好的长期耐久性.X射线光电子能谱和差分电荷分析表明,电子从富电子的FeP_(4)向缺电子的Ni_(2)P和CoP转移,这促使Ni_(2)P和CoP上的电子积累和FeP_(4)上的空穴积累,有利于优化反应中间体的吸附和脱附自由能,提升OER和HER催化性能.结合X射线衍射、扫描电镜、透射电镜、X射线光电子能谱和原位拉曼光谱结果发现,催化剂重构后形成的特定(氧)氢氧化物结构,是OER反应真正的关键活性位点.原位拉曼光谱进一步证实了异质界面促进了OER过程中Ni_(2)P/CoP/FeP_(4)/IF的快速重构.此外,利用密度泛函理论分析了催化剂的HER反应机理.计算结果表明,H2O优先吸附在Fe位点并发生水解,随后产生的H*吸附在Ni位点上并发生解吸,从而促进了催化剂中Fe和Ni活性位点的高效利用.同时,CoP的引入提高了Ni_(2)P/CoP/FeP_(4)/IF催化剂的水吸附和解离能力,进一步提升了其HER活性.综上所述,本文通过简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF过渡金属磷化物纳米线网络催化剂,并将其用于碱性水分解.通过多种表征技术及理论计算结果分析,识别了电解水过程中的关键催化活性位点,即催化剂重构后形成的特定(氧)氢氧化物结构,并揭示了其在OER和HER反应中的催化机制.本研究可为高性能碱性电解水催化剂的理性设计和开发提供参考.
基金supported by the National Natural Science Foundation of China(51622102,51571124,21421001)the 111 Project(B12015)+1 种基金the Natural Science Foundation of Tianjin(18ZXJMTG00040,16PTSYJC00030)the Fundamental Research Funds for the Central Universities~~
文摘In an attempt to develop low-cost,non-noble-metal bifunctional electrocatalysts for water electrolysis in alkaline media,cobalt-doped molybdenum carbide@N-doped carbon nanosheets/nanotubes were fabricated by using C3N4 as the carbon source on a 3D porous nickel foam substrate.Benefiting from the optimized electronic structure and enhanced mass and charge transport,as well as the 3D conducting pathway,MoxCoy@N-CNSs/CNTs shows superior performance towards both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in an alkaline medium.The optimal electrocatalyst is Mo2Co1@N-CNSs/CNTs,which reveals a current density of 10 mA cm^-2 at the low overpotentials of 99 mV and 300 mV for the HER and OER,respectively,and a relatively low cell voltage(1.63 V)for the overall water electrolysis.The method of optimizing the composition and nanostructure of a material provides a new avenue for the development and utilization of high-performance electrocatalysts.
基金supported by the National Natural Science Foundation of China(21575134,21633008,21773224)National Key R&D Program of China(2016YFA0203200)K.C.Wong Education Foundation~~
文摘Catalysts play decisive roles in determining the energy conversion efficiencies of energy devices.Up to now,various types of nanostructured materials have been studied as advanced electrocatalysts.This review highlights the application of one‐dimensional(1D)metal electrocatalysts in energy conversion,focusing on two important reaction systems-direct methanol fuel cells and water splitting.In this review,we first give a broad introduction of electrochemical energy conversion.In the second section,we summarize the recent significant advances in the area of 1D metal nanostructured electrocatalysts for the electrochemical reactions involved in fuel cells and water splitting systems,including the oxygen reduction reaction,methanol oxidation reaction,hydrogen evolution reaction,and oxygen evolution reaction.Finally,based on the current studies on 1D nanostructures for energy electrocatalysis,we present a brief outlook on the research trend in 1D nanoelectrocatalysts for the two clean electrochemical energy conversion systems mentioned above.
文摘Efficient,stable,and noble‐metal‐free electrocatalysts for both the oxygen evolution reaction and the hydrogen evolution reaction are highly imperative for the realization of low‐cost commercial water‐splitting electrolyzers.Herein,a cost‐effective and ecofriendly strategy is reported to fabricate coral‐like FeNi(OH)x/Ni as a bifunctional electrocatalyst for overall water splitting in alkaline media.With the assistance of mild corrosion of Ni by Fe(NO3)3,in situ generated FeNi(OH)x nanosheets are intimately attached on metallic coral‐like Ni.Integration of these nanosheets with the electrodeposited coral‐like Ni skeleton and the supermacroporous Ni foam substrate forms a binder‐free hierarchical electrode,which is beneficial for exposing catalytic active sites,accelerating mass transport,and facilitating the release of gaseous species.In 1.0 mol L^-1 KOH solution,a symmetric electrolyzer constructed with FeNi(OH)x/Ni as both the anode and the cathode exhibits an excellent activity with an applied potential difference of 1.52 V at 10 mA cm^-2,which is superior to that of an asymmetric electrolyzer constructed with the state‐of‐the‐art RuO2‐PtC couple(applied potential difference of 1.55 V at 10 mA cm^-2).This work contributes a facile and reliable strategy for manufacturing affordable,practical,and promising water‐splitting devices.
文摘Step-scheme(S-scheme)heterojunctions in photocatalysts can provide novel and practical insight on promoting photogenerated carrier separation.The latter is critical in controlling the overall efficiency in one-step photoexcitation systems.In this study,a nanosized BiVO4/Bi0.6Y0.4VO4 solid solution was prepared by a coprecipitation method following with hydrothermal or calcination processes.The S-scheme heterojunction was fabricated by in-situ pressure-induced transformations of bismuth vanadate from the tetragonal zircon phase to the monoclinic scheelite phase,which led to the formation of BiVO4 nanoparticles with a diameter of approximately 5 nm on the surface of BiVO_(4)/Bi_(0.6)Y_(0.4)VO_(4)/Bi_(0.6)Y_(0.4)VO_(4) with S-scheme heterojunctions showed significantly enhanced photocatalytic overall water splitting activity compared with using bare BiVO_(4)/Bi_(0.6)Y_(0.4)VO_(4).Characterization of the carrier dynamics demonstrated that a superior carrier separation through S-type heterojunctions might have caused the enhanced overall water splitting(OWS)activity.Surface photovoltage spectra and the results of selective photodeposition experiments indicated that the photogenerated holes mainly migrated to the BiVO4 nanoparticles in the heterojunction.This confirmed that the charge transfer route corresponds to an S-scheme rather than a type-II heterojunction mechanism under light illumination.This study presents a facile and efficient strategy to construct S-scheme heterojunctions through a pressure-induced phase transition.The results demonstrated that S-scheme junctions composed of different crystalline phases can boost the carrier separation capacity and eventually improve the photocatalytic OWS activity.
文摘When a proton reduction cocatalyst is loaded on an n-type semiconductor for photocatalytic overall water splitting(POWS),the location of water oxidation sites is generally considered at the surface of the semiconductor due to upward band-bending of n-type semiconductor which may ease the transfer of the photogenerated holes to the surface.However,this is not the case for Pt/SrTiO_(3),a model semiconductor based photocatalyst for POWS.It was found that the photogenerated holes are more readily accumulated at the interface between Pt cocatalyst and SrTiO_(3) photocatalyst as probed by photo-oxidative deposition of PbO_(2),indicating that the water oxidation sites are located at the interface between Pt and SrTiO_(3).Electron paramagnetic resonance and scanning transmission electron microscope studies suggest that the interfacial oxygen atoms between Pt and SrTiO_(3) in Pt/SrTiO_(3) after POWS are more readily lost to form oxygen vacancies upon vacuum heat treatment,regardless of Pt loading by photodeposition or impregnation methods,which may serve as additional support for the location of the active sites for water oxidation at the interface.Density functional theory calculations also suggest that the oxygen evolution reaction more readily occurs at the interfacial sites with the lowest overpotential.These experimental and theoretical studies reveal that the more active sites for water oxidation are located at the interface between Pt and SrTiO_(3),rather than on the surface of SrTiO_(3).Hence,the tailor design and control of the interfacial properties are extremely important for the achievement or improvement of the POWS on cocatalyst loaded semiconductor photocatalyst.
文摘Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated electrons in Ga_(2)O_(3) loaded with Cr_(2)O_(3)-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy.The structure of these Cr_(2)O_(3)-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy,as Rh particles partly covered with Cr_(2)O_(3).The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction.The loaded Cr_(2)O_(3) promotes electron transfer from Ga_(2)O_(3) to Rh,which accelerates the electron-consuming reaction for H2 evolution.Based on these observations,a photocatalytic water-splitting mechanism for Cr_(2)O_(3)-Rh/Ga_(2)O_(3) photocatalysts has been proposed.The elucidation of the roles of the Cr_(2)O_(3)-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.
文摘Two-dimensional(2D)carbon nitride(CN)photocatalysts are attracting extensive attention owing to their excellent photocatalytic properties.In this study,we successfully prepared CN materials with heterogeneous structures via hydrothermal treatment,high-temperature roasting,ball milling,sintering,and other processes.Benefitting from interface interactions in hybrid architectures,the CN photocatalysts exhibited high photocatalytic activity.The rate of hydrogen production using these CN photocatalysts reached 17028.82μmol h^(−1)g^(−1),and the apparent quantum efficiency was 11.2%at 420 nm.The ns-level time-resolved photoluminescence(PL)spectra provided information about the time-averaged lifetime of fluorescence charge carriers;the lifetime of the charge carriers causing the fluorescence of CN reached 9.99 ns.Significantly,the CN photocatalysts displayed satisfactory results in overall water splitting without the addition of sacrificial agents.The average hydrogen and oxygen production rates were 270.95μmol h^(−1)g^(−1)and 115.21μmol h^(−1)g^(−1)in 7 h,respectively,which were promising results for the applications of the catalysts in overall water splitting processes.We investigated the high efficiency of the prepared CN photocatalysts via a series of tests(UV-vis diffuse reflectance spectroscopy,photocurrent response measurements,PL emission spectroscopy,time-resolved PL spectroscopy,and Brunauer-Emmett-Teller analysis).Furthermore,the Mott-Schottky plot and current-voltage curve were acquired via electrochemical tests.The fabricated CN photocatalyst had a small p-n junction in its heterogeneous structure,which further enhanced its photocatalytic efficiency.Therefore,this work can promote the development of CN photocatalysts.
