Theoretical study of the alkaline hydrogen oxidation reaction on Ni-Based nanocluster Catalysts: Effects of graphene supports and dopants

Abstract

The Ni-based catalysts are considered to be the most promising non-noble metal catalysts for the hydrogen oxidation reaction (HOR) in alkaline fuel cells (AFCs). However, their further optimization is restricted by the unclear HOR mechanism. In this work, the density functional theory calculations were carried out to study the alkaline HOR on pure Ni13 and Ni13 supported on graphene (Ni13/G) and B- and N-doped graphene (Ni13/BG and Ni13/NG). The calculations indicate that the HOR proceeds preferentially through the Tafel-Volmer mechanism, in which the adsorption of H* plays a dominant role in the HOR activity. The graphene support and B/N dopants can apparently lower the d-band center of Ni13, thereby weakening the adsorption of H*, which leads to the HOR activity sequence of Ni13 < Ni13/G < Ni13/BG < Ni13/NG. Furthermore, compared to pure Ni13, the oxidation resistance of Ni13/G, Ni13/BG and Ni13/NG is also improved via elevating onset potential of the OH* phase and reducing energy barriers of the OH* reduction with H* and H2*. An efficient way to improve the HOR performance is tuning the adsorption of H* to accelerate the HOR rate and regulating the adsorption of OH* to enhance the antioxidant capacity.