Photothermal catalysis is a widely researched field in which the reaction mechanism is usually investigated based on the photochemical behavior of the catalytic material.Considering that the adsorption of reactants is...Photothermal catalysis is a widely researched field in which the reaction mechanism is usually investigated based on the photochemical behavior of the catalytic material.Considering that the adsorption of reactants is essential for catalytic reactions to occur,in this study,the synergistic effect of photothermal catalysis is innovatively elucidated in terms of the electron transfer behavior of reactant adsorption.For the H_(2)+O2 or CO+H_(2)reaction systems over a ZnO catalyst,UV irradiation at 25°C or heat without UV irradiation did not cause H_(2)oxidation or CO reduction;only photothermal conditions(100 or 150°C+UV light)initiated the two reactions.This result is related to the electron transfer behavior associated with the adsorption of CO or H_(2)on ZnO,in which H_(2)or CO that lost an electron could be oxidized by O2 or hydroxyls.However,the electron‐accepting CO could be reduced by the electron‐donating H_(2)into CH4 under photothermal conditions.Based on the in‐situ characterization and theoretical calculation results,it was established that the synergistic effect of the photothermal conditions acted on the(002)crystal surface of ZnO to stimulate the growth of zinc vacancies,which resulted in the formation of defect energy levels,adsorption sites,and an adjusted Fermi level.As a result,the electron transfer behavior between adsorbed CO or H_(2)and the crystal surface varied,which further affected the photocatalytic behavior.The results show that the effect of photothermal synergy may not only produce the expected kinetic energy,but more importantly,produce energy that can change the activation mode of the reactant gas.This study provides a new understanding of the CO catalytic oxidation and reduction processes over semiconductor materials.展开更多
Though GaN nanoribbons （GaNNRs） with H atoms terminating both edges are nonmagnetic semiconductors, the extra dangling bond bands around the Fermi level lead to a transition from semiconducting to metallic, except f...Though GaN nanoribbons （GaNNRs） with H atoms terminating both edges are nonmagnetic semiconductors, the extra dangling bond bands around the Fermi level lead to a transition from semiconducting to metallic, except for the armchair edge GaNNRs （AGaNNRs） with bare N and Ga edges, which are still nonmagnetic semiconductors due to the strong coupling of the dangling bonds of dimeric N and Ga atoms at the same edge. The larger difference in the charge density （pUp_pdown） for edge bare N atoms and decaying for N sub-lattices away from the edge, as well as the smaller difference in the charge density for edge bare Ga atoms and without decaying for Ga sub-lattices away from the edge is consistent with the magnetic moment of a GaNNR with bare N edge being larger than that of a GaNNR with bare Ga edge. The magnetic moment of a zigzag edge GaNNR （ZGaNNR） with bare N （Ga） edge has nearly half the value of the magnetic moment of a AGaNNR with bare N （Ga） edge. Such a relationship also exists in the number of extra dangling bond states appearing around the Fermi level in the band structures. For ZGaNNRs, the magnetic moment of bare N and Ga edges is larger than either bare N edge or bare Ga edge, but smaller than their sum, implying that there exists an interaction between the dangling bonds at both edges of bare N and Ga edges.展开更多
文摘Photothermal catalysis is a widely researched field in which the reaction mechanism is usually investigated based on the photochemical behavior of the catalytic material.Considering that the adsorption of reactants is essential for catalytic reactions to occur,in this study,the synergistic effect of photothermal catalysis is innovatively elucidated in terms of the electron transfer behavior of reactant adsorption.For the H_(2)+O2 or CO+H_(2)reaction systems over a ZnO catalyst,UV irradiation at 25°C or heat without UV irradiation did not cause H_(2)oxidation or CO reduction;only photothermal conditions(100 or 150°C+UV light)initiated the two reactions.This result is related to the electron transfer behavior associated with the adsorption of CO or H_(2)on ZnO,in which H_(2)or CO that lost an electron could be oxidized by O2 or hydroxyls.However,the electron‐accepting CO could be reduced by the electron‐donating H_(2)into CH4 under photothermal conditions.Based on the in‐situ characterization and theoretical calculation results,it was established that the synergistic effect of the photothermal conditions acted on the(002)crystal surface of ZnO to stimulate the growth of zinc vacancies,which resulted in the formation of defect energy levels,adsorption sites,and an adjusted Fermi level.As a result,the electron transfer behavior between adsorbed CO or H_(2)and the crystal surface varied,which further affected the photocatalytic behavior.The results show that the effect of photothermal synergy may not only produce the expected kinetic energy,but more importantly,produce energy that can change the activation mode of the reactant gas.This study provides a new understanding of the CO catalytic oxidation and reduction processes over semiconductor materials.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51071098 and 11104175)the State Key Development for Basic Research of China (Grant No. 2010CB631002)
文摘Though GaN nanoribbons （GaNNRs） with H atoms terminating both edges are nonmagnetic semiconductors, the extra dangling bond bands around the Fermi level lead to a transition from semiconducting to metallic, except for the armchair edge GaNNRs （AGaNNRs） with bare N and Ga edges, which are still nonmagnetic semiconductors due to the strong coupling of the dangling bonds of dimeric N and Ga atoms at the same edge. The larger difference in the charge density （pUp_pdown） for edge bare N atoms and decaying for N sub-lattices away from the edge, as well as the smaller difference in the charge density for edge bare Ga atoms and without decaying for Ga sub-lattices away from the edge is consistent with the magnetic moment of a GaNNR with bare N edge being larger than that of a GaNNR with bare Ga edge. The magnetic moment of a zigzag edge GaNNR （ZGaNNR） with bare N （Ga） edge has nearly half the value of the magnetic moment of a AGaNNR with bare N （Ga） edge. Such a relationship also exists in the number of extra dangling bond states appearing around the Fermi level in the band structures. For ZGaNNRs, the magnetic moment of bare N and Ga edges is larger than either bare N edge or bare Ga edge, but smaller than their sum, implying that there exists an interaction between the dangling bonds at both edges of bare N and Ga edges.
