Key role of nonprecious oxygen-evolving active site in NiOOH electrocatalysts for oxygen evolution reaction

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 gamma-phase NiOOH. DFT theoretical results suggest that the d-band center of Ni site in the basal plane configuration is -2.37 eV, which is closer to Fermi level than that of the edge configuration (-3.02 eV). The above results lead to the stronger adsorption capacity between the metal active sites and the oxygen intermediates. The consequence of Gibbs free energy indicates that the Ni site in the basal plane configuration (0.75 V) has slightly higher theoretical catalytic activity than the edge configuration (0.81 V). The charge density difference and Bader charge analysis results reveal that the hybridization interactions in the basal plane configuration are stronger and have 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.