Theoretical investigation of loading Ni clusters on the α-Ga_2O_3 surfaces for photocatalytic hydrogen evolution  

作　　者：Jiaxin Zhang Yidan Wang Hao Dong Xin Zhou 

机构地区：[1]School of Chemistry and Chemical Engineering, Liaoning Normal University [2]College of Environment and Chemical Engineering, Dalian University

出　　处：《Journal of Energy Chemistry》2019年第3期8-18,共11页能源化学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China under Grants 21473183 and 21303079

摘　　要：In the semiconductor-based photocatalysts for overall water splitting, loading proper cocatalysts play a crucial role in enhancing the photocatalytic activity. In this work, we have chosen Ni_n/α-Ga_2O_3 as a model and provided detailed density functional theory calculations to investigate the function of cocatalysts in hydrogen evolution reaction(HER). We have studied the formation and stability of Ni_n(n = 1–4) cluster on two stable surfaces of α-Ga_2O_3(001) and(012). In a Ni_n/α-Ga_2O_3 system, as the Ni 3d states well overlap with O and Ga states, the excited electrons transferred from Ga to Ni may participate in HER. We theoretically predict that introduction of Nincluster on(012) surface can elevate the Fermi level toward the conduction band, which is favorable for the occurrence of HER. Electrochemical computations are used to explore the mechanism of HER. It is found that, in most of Ni_n/α-Ga_2O_3 systems, the active sites of HER are on Ni_n clusters. Loading Ni_n clusters not only importantly reduces the Gibbs free energy of HER but also improves the reaction activity of surface O and Ga sites in HER. Our calculations reasonably explain the experimental observation on significant enhancement of activity for generating hydrogen after loading nickel oxide cocatalysts.In the semiconductor-based photocatalysts for overall water splitting, loading proper cocatalysts play a crucial role in enhancing the photocatalytic activity. In this work, we have chosen Ni_n/α-Ga_2O_3 as a model and provided detailed density functional theory calculations to investigate the function of cocatalysts in hydrogen evolution reaction(HER). We have studied the formation and stability of Ni_n(n = 1–4) cluster on two stable surfaces of α-Ga_2O_3(001) and(012). In a Ni_n/α-Ga_2O_3 system, as the Ni 3d states well overlap with O and Ga states, the excited electrons transferred from Ga to Ni may participate in HER. We theoretically predict that introduction of Nincluster on(012) surface can elevate the Fermi level toward the conduction band, which is favorable for the occurrence of HER. Electrochemical computations are used to explore the mechanism of HER. It is found that, in most of Ni_n/α-Ga_2O_3 systems, the active sites of HER are on Ni_n clusters. Loading Ni_n clusters not only importantly reduces the Gibbs free energy of HER but also improves the reaction activity of surface O and Ga sites in HER. Our calculations reasonably explain the experimental observation on significant enhancement of activity for generating hydrogen after loading nickel oxide cocatalysts.

关 键 词：PHOTOCATALYTIC hydrogen evolution reaction COCATALYSTS Electronic structure calculation Density FUNCTIONAL theory GA2O3 

分 类 号：O643.36[理学—物理化学] TQ116.2[理学—化学]