Structural characterization of ORR active surface Niobium oxides on partially oxidized Nb carbonitrides

摘要

In order to identify the active sites for the oxygen reduction reaction (ORR) in a partially oxidized Niobium carbo-nitride (Nb-CNO) catalyst, we investigated the structure of Nb-CNO catalysts by using conversion-electron-yield x-ray absorption spectroscopy (CEY-XAS). CEY-XAS measurements made it possible to selectively analyze the surface oxide phases in Nb-CNO catalysts with Nb_2O_5/NbCN core-shell structures. The result showed the decrease of the coordination numbers for Nb-O surface oxide phases in ORR active Nb-CNO particles, indicating that oxygen vacancies were introduced in the surface oxide phase. Thus, oxygen vacancies could work as the active sites for ORR in Nb-CNO, similar to Ta-CNO ORR catalysts.