Key Role of Nonprecious Oxygen-Evolving Active Site in Niooh Electrocatalysts for Water Splitting

Abstract

Nickel-based materials are the most promising electrocatalysts to date for the alkaline oxygen evolution reaction (OER). Identifying the phase transformation in the catalytic process and comparing the theoretical catalytic activity of different crystal facets are important for understanding OER mechanism and rational design. Herein, we calculate the theoretical catalytic activity of the basal plane and edge sites, respectively-two representative configurations in the OER-activate γ-phase NiOOH. DFT theoretical results suggest that the d-band center of Ni site in the basal plane configuration is closer to Fermi level and the surface Ni site possesses the lower eg-filling, compared to the edge configuration. It leads to the stronger adsorption capacity between the metal active sites and the oxygen intermediates. The consequence of Gibbs free energy indicates that the Ni sites in the basal plane configuration has slightly higher theoretical catalytic activity. The charge density difference and Bader charge analysis results reveal that the hybridization interactions in the basal plane configuration are stronger and has more electron transfer between the surface Ni sites and absorbed OER intermediates. This present study highlights that regulating the optimal electronic structure of metal active site is conductive to high catalytic activity.

Keywords: oxygen evolution reaction, electrocatalysts, d-band center, electronic structure