title: Methane activation on nickel oxide clusters with a concerted mechanism: a density functional theory study of the effect of silica support.
abstract: The support effect is an important issue in heterogeneous catalysis. A systematic density functional theory (DFT) study was performed to investigate the support effect of a silica model on the initial step of methane activation on NixOx (x =2,3) clusters with a concerted mechanism. Four reactions were examined by exploring their potential energy surfaces (PES): CH4 reacting with unsupported Ni2O2, with silica-supported Ni2O2, with unsupported Ni3O3, and with silica-supported Ni3O3. For each reaction, PES with different spin states were explored. For CH4 activation taking place via a concerted mechanism, the reaction barriers in terms of free energy and reaction free energy increased with the involvement of the model silica support. Only one PES made a major contribution to the overall reaction rate of all four reactions examined. No spin transition process was required for the reactions to undergo their most-favorable pathway from their starting reactants. These results provide a deeper insight into the support effect on C-H bond activation of small alkanes in general, and of methane in particular, on supported transition metal catalysts.
authors.affiliation: State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China.|College of Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Xi
authors.affiliation: College of Science, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China.
authors.forename: Bili
authors.initials: B
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China. hatrick2009@upc.edu.cn.|College of Science, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China. hatrick2009@upc.edu.cn.|Key Laboratory of Catalysis of China National Petroleum Corporation, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China. hatrick2009@upc.edu.cn.
authors.forename: Xufeng
authors.initials: X
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China.|College of Science, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China.
authors.forename: Chuangye
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China.|College of Science, China University of Petroleum (East China), Qingdao, 266580, People's Republic of China.
authors.forename: Hui
authors.initials: H
authors.lastname: Fu
keywords: Concerted mechanism; Density functional theory; Methane; Nickel oxide cluster; Support effect