Synergy between Mo dopants and Ni vacancies in NiOOH for enhanced oxygen evolution reaction

Abstract

Optimizing the electronic structure lies at the core of promoting the intrinsic activity of electrocatalyst for oxygen evolution reaction (OER). Herein, we incorporated Mo dopants and Ni vacancies into two-dimensional ultrathin NiOOH to boost the OER activity. Experimental results exhibited that the integration of two defects modulate the electronic structure and generate more high-valance Ni species under OER conditions, which greatly enhance the catalytic performance by delivering a high current density of 30 mA cm−2 at a low overpotential of 280 mV. Density functional theory calculations identified the most active center of a surface Ni site that is close to a sublayer Ni vacancy separated by a sublayer Mo dopant, where the optimized electronic structure moves the Gibbs free energy of (ΔGO*) close to the midpoint between ΔGOOH* and ΔGOH*, greatly decreasing the catalytic overpotential and enhancing the catalytic activity. This study emphasizes the importance of exploring the synergy between different defect structures to break the scaling relation for promoted catalytic performance.