Rapid carrier recombination and slow charge transfer dynamics have significantly reduced the performance of photocatalytic hydrogen production.Construction of heterojunctions via utilizing the sulfur-edge and metal-ed...Rapid carrier recombination and slow charge transfer dynamics have significantly reduced the performance of photocatalytic hydrogen production.Construction of heterojunctions via utilizing the sulfur-edge and metal-edge sites of metal sulfide semiconductor for improving photocatalytic activity remains a significant challenge.Herein,a novel ZnIn_(2)S_(4)/MnS S-scheme heterojunction was prepared by hydrothermal synthesis to accelerate charge carrier transfer for efficient photocatalysis.Notably,ZnIn_(2)S_(4)/MnS exhibited excellent photocatalytic hydrogen evolution activity(7.95 mmol g^(-1)h^(-1))under visible light irradiation(≥420 nm),up to 4.7 times higher than that of pure ZnIn_(2)S_(4).Additionally,cycling experiments showed that ZM-2 remained high stability after four cycles.Density-functional theory(DFT)calculations and in situ XPS results confirm the formation of S-scheme heterojunction,indicating that the tight interfacial contact between ZnIn_(2)S_(4)and Mn S with the presence of Mn-S bonds(the unsaturated Mn edges of MnS and the uncoordinated S atoms in the edge of ZnIn_(2)S_(4))promoted faster charge transfer.Besides,the unsaturated S atom on the surface of Mn S is an active site with strong H+binding ability,which can effectively reduce the overpotential or activation barrier for hydrogen evolution.This study illustrates the critical influence of the interfacial Mn-S bond on the ZnIn_(2)S_(4)/MnS S-scheme heterojunction to achieve efficient photocatalytic hydrogen production and provides relevant guidance for carrying out rational structural/interfacial modulation.展开更多
Oxidative coupling of methane(OCM)is a catalytic partial oxidation process that directly converts methane into C_(2) products.For this high temperature reaction,understanding the radical behavior through experimental ...Oxidative coupling of methane(OCM)is a catalytic partial oxidation process that directly converts methane into C_(2) products.For this high temperature reaction,understanding the radical behavior through experimental investigation is important in correlating the catalytic activity and the products.In this work,a spatial resolution online mass spectrometry(MS)system was developed and applied to a Mn-Na_(2)WO_(4)/SiO_(2) catalyzed OCM system.In addition to the residue gas analysis,the system obtained the distribution information of the reactants and products in the reactor.At various setting temperatures,all species online MS signals were collected at different positions,mapping the reaction activity covering parameters including temperature,time and space.The distribution behavior of the catalytic activity,selectivity,and apparent activation energy were kinetically analyzed.Selectivity and additional carbon balance analysis strongly supported the radical coupling model of OCM and indicated that after the catalytic bed layer,there is a significant length in the reactor(>2 mm)filled with radicals.Based on the result,a designed new method by tuning the temperature field in the reactor was found effectively to improve the catalytic activity,especially the C_(2) yield from 702 to 773℃.展开更多
基金the National Nature Science Foundation of China(No.22108069)Natural Science Foundation of Hunan Province,China(No.2021JJ40260)for the financial support。
文摘Rapid carrier recombination and slow charge transfer dynamics have significantly reduced the performance of photocatalytic hydrogen production.Construction of heterojunctions via utilizing the sulfur-edge and metal-edge sites of metal sulfide semiconductor for improving photocatalytic activity remains a significant challenge.Herein,a novel ZnIn_(2)S_(4)/MnS S-scheme heterojunction was prepared by hydrothermal synthesis to accelerate charge carrier transfer for efficient photocatalysis.Notably,ZnIn_(2)S_(4)/MnS exhibited excellent photocatalytic hydrogen evolution activity(7.95 mmol g^(-1)h^(-1))under visible light irradiation(≥420 nm),up to 4.7 times higher than that of pure ZnIn_(2)S_(4).Additionally,cycling experiments showed that ZM-2 remained high stability after four cycles.Density-functional theory(DFT)calculations and in situ XPS results confirm the formation of S-scheme heterojunction,indicating that the tight interfacial contact between ZnIn_(2)S_(4)and Mn S with the presence of Mn-S bonds(the unsaturated Mn edges of MnS and the uncoordinated S atoms in the edge of ZnIn_(2)S_(4))promoted faster charge transfer.Besides,the unsaturated S atom on the surface of Mn S is an active site with strong H+binding ability,which can effectively reduce the overpotential or activation barrier for hydrogen evolution.This study illustrates the critical influence of the interfacial Mn-S bond on the ZnIn_(2)S_(4)/MnS S-scheme heterojunction to achieve efficient photocatalytic hydrogen production and provides relevant guidance for carrying out rational structural/interfacial modulation.
文摘Oxidative coupling of methane(OCM)is a catalytic partial oxidation process that directly converts methane into C_(2) products.For this high temperature reaction,understanding the radical behavior through experimental investigation is important in correlating the catalytic activity and the products.In this work,a spatial resolution online mass spectrometry(MS)system was developed and applied to a Mn-Na_(2)WO_(4)/SiO_(2) catalyzed OCM system.In addition to the residue gas analysis,the system obtained the distribution information of the reactants and products in the reactor.At various setting temperatures,all species online MS signals were collected at different positions,mapping the reaction activity covering parameters including temperature,time and space.The distribution behavior of the catalytic activity,selectivity,and apparent activation energy were kinetically analyzed.Selectivity and additional carbon balance analysis strongly supported the radical coupling model of OCM and indicated that after the catalytic bed layer,there is a significant length in the reactor(>2 mm)filled with radicals.Based on the result,a designed new method by tuning the temperature field in the reactor was found effectively to improve the catalytic activity,especially the C_(2) yield from 702 to 773℃.
