β-Ga_(2)O_(3)以其较高的导带底(Conduction Band Minimum,CBM)和较低的价带顶(Valence Band Maximum,VBM),赋予其光生电子和空穴较强的还原与氧化能力,但其宽禁带和高载流子复合率限制了在光催化中的应用.金属离子掺杂被认为是提升光...β-Ga_(2)O_(3)以其较高的导带底(Conduction Band Minimum,CBM)和较低的价带顶(Valence Band Maximum,VBM),赋予其光生电子和空穴较强的还原与氧化能力,但其宽禁带和高载流子复合率限制了在光催化中的应用.金属离子掺杂被认为是提升光催化性能的有效途径.本文基于第一性原理系统研究了Sr、Ba、V、Nb、Ta等二十种元素掺杂对β-Ga_(2)O_(3)光催化性能的影响,研究发现:Sr、Nb、Ta、Mn、Fe、Zn、Hg七种元素掺杂β-Ga_(2)O_(3)后,材料除能保持合适的带边位置外,还具有更高的电子空穴分离效率以及更低的形成能,表明这些元素的引入可有效提升β-Ga_(2)O_(3)光催化效率;Nb、Ta掺杂可显著增强材料在红外光区的吸收,Mn、Fe掺杂则显著提升材料在紫外和可见光区的吸收能力,其中,Nb在0.5 eV处光吸收系数高达1.38×10^(5)cm^(−1),Mn、Fe掺杂在3 eV处光吸收系数可达1×10^(5)cm^(−1),在不同波段均呈现出良好的光吸收能力.此外,Hg掺杂表现出跨红外至深紫外的宽波段增强效果,Hg掺杂后,电子空穴相对有效质量高达109,说明Hg掺杂显著提升载流子分离能力,同时由于其在宽波段显著增强的光吸收效果,因此,Hg可作为β-Ga_(2)O_(3)在光催化制氢中理想的金属掺杂元素,以上研究结果为β-Ga_(2)O_(3)光催化分解水制氢研究提供了价值参考.展开更多
Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Co...Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Consequently,it is desired to investigate the mechanisms of the FLP-catalyzed hydrogenation of C=C and C=O and provide insight into the modification of CeO_(2)catalysts for the selective hydrogenation.In this work,the reaction mechanism of the hydrogenation of CH_(2)=CH_(2)and CH_(3)CH=O at the FLP sites constructed on CeO_(2)(110)surface was investigated by density functional theory(DFT),with the classical Lewis acid-base pairs(CLP)site as the reference.The results illustrate that at the CLP site,the dissociated hydride(H^(δ−))forms a stable H−O bond with the surface O atom,while at the FLP site,H^(δ−)is stabilized by Ce,displaying higher activity on the one hand.On the other hand,the electron cloud density of the Ce atom at the FLP site is higher,which can transfer more electrons to the adsorbed C_(C=C)and O_(C=O)atoms,leading to a higher degree of activation for C=C and C=O bonds,as indicated by the Bader charge analysis.Therefore,compared to the CLP site,the FLP site exhibits higher hydrogenation activity for CH_(2)=CH_(2)and CH_(3)CH=O.Furthermore,at the FLP sites,it demonstrates high efficiency in catalyzing the hydrogenation of CH_(2)=CH_(2)with the rate-determining barrier of 1.04 eV,but it shows limited activity for the hydrogenation of CH_(3)CH=O with the rate-determining barrier of 1.94 eV.It means that the selective hydrogenation of C=C can be effectively achieved at the FLP sites concerning selective hydrogenation catalysis.The insights shown in this work help to clarify the reaction mechanism of the hydrogenation of C=C and C=O at FLP site on CeO_(2)(110)and reveal the relationship between the catalytic performance and the nature of the active site,which is of great benefit to development of rational design of heterogeneous FLP catalysts.展开更多
文摘β-Ga_(2)O_(3)以其较高的导带底(Conduction Band Minimum,CBM)和较低的价带顶(Valence Band Maximum,VBM),赋予其光生电子和空穴较强的还原与氧化能力,但其宽禁带和高载流子复合率限制了在光催化中的应用.金属离子掺杂被认为是提升光催化性能的有效途径.本文基于第一性原理系统研究了Sr、Ba、V、Nb、Ta等二十种元素掺杂对β-Ga_(2)O_(3)光催化性能的影响,研究发现:Sr、Nb、Ta、Mn、Fe、Zn、Hg七种元素掺杂β-Ga_(2)O_(3)后,材料除能保持合适的带边位置外,还具有更高的电子空穴分离效率以及更低的形成能,表明这些元素的引入可有效提升β-Ga_(2)O_(3)光催化效率;Nb、Ta掺杂可显著增强材料在红外光区的吸收,Mn、Fe掺杂则显著提升材料在紫外和可见光区的吸收能力,其中,Nb在0.5 eV处光吸收系数高达1.38×10^(5)cm^(−1),Mn、Fe掺杂在3 eV处光吸收系数可达1×10^(5)cm^(−1),在不同波段均呈现出良好的光吸收能力.此外,Hg掺杂表现出跨红外至深紫外的宽波段增强效果,Hg掺杂后,电子空穴相对有效质量高达109,说明Hg掺杂显著提升载流子分离能力,同时由于其在宽波段显著增强的光吸收效果,因此,Hg可作为β-Ga_(2)O_(3)在光催化制氢中理想的金属掺杂元素,以上研究结果为β-Ga_(2)O_(3)光催化分解水制氢研究提供了价值参考.
基金supported by the National Natural Science Foundation of China(22302115,22072079)the Fundamental Research Program of Shanxi Province(202303021221056).
文摘Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Consequently,it is desired to investigate the mechanisms of the FLP-catalyzed hydrogenation of C=C and C=O and provide insight into the modification of CeO_(2)catalysts for the selective hydrogenation.In this work,the reaction mechanism of the hydrogenation of CH_(2)=CH_(2)and CH_(3)CH=O at the FLP sites constructed on CeO_(2)(110)surface was investigated by density functional theory(DFT),with the classical Lewis acid-base pairs(CLP)site as the reference.The results illustrate that at the CLP site,the dissociated hydride(H^(δ−))forms a stable H−O bond with the surface O atom,while at the FLP site,H^(δ−)is stabilized by Ce,displaying higher activity on the one hand.On the other hand,the electron cloud density of the Ce atom at the FLP site is higher,which can transfer more electrons to the adsorbed C_(C=C)and O_(C=O)atoms,leading to a higher degree of activation for C=C and C=O bonds,as indicated by the Bader charge analysis.Therefore,compared to the CLP site,the FLP site exhibits higher hydrogenation activity for CH_(2)=CH_(2)and CH_(3)CH=O.Furthermore,at the FLP sites,it demonstrates high efficiency in catalyzing the hydrogenation of CH_(2)=CH_(2)with the rate-determining barrier of 1.04 eV,but it shows limited activity for the hydrogenation of CH_(3)CH=O with the rate-determining barrier of 1.94 eV.It means that the selective hydrogenation of C=C can be effectively achieved at the FLP sites concerning selective hydrogenation catalysis.The insights shown in this work help to clarify the reaction mechanism of the hydrogenation of C=C and C=O at FLP site on CeO_(2)(110)and reveal the relationship between the catalytic performance and the nature of the active site,which is of great benefit to development of rational design of heterogeneous FLP catalysts.
