High-Valent Nickel Promoted by Atomically Embedded Copper for Efficient Water Oxidation
Mei Han, Ning Wang, Biao Zhang, Yujian Xia, Jun Li, Jingrui Han, Kaili Yao, Congcong Gao, Chunnian He, Yongchang Liu, Zumin Wang, Ali Seifitokaldani, Xuhui Sun, Hongyan Liang
Abstract
Efficient and low-cost electrocatalysts for oxygen evolution reaction (OER), particularly in neutral conditions, are of significant importance for renewable energy technologies such as CO2 reduction and seawater splitting electrolysis. High-valent transition-metal sites have been considered as OER active sites; however, the rational design and construction of these sites remain a big challenge. Here, we report a trimetallic NiFeCu oxyhydroxide electrocatalyst, in which high-valent Ni sites are promoted and stabilized by the atomically embedded Cu, as evidenced by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Through compositional optimization, Ni6Fe1Cu1 catalysts achieved an overpotential of 385 mV at 10 mA cm–2, a Tafel slope of 164 mV dec–1, and a stability of 100 h at pH = 7.2. Density function theory calculations demonstrated that the Cu-doping facilitates the formation of high-valent Ni and thus promotes OER electrocatalysis through modulating the d-band center of Ni and reducing the adsorption energy of oxygenated intermediates on the surface of the catalyst. This work paves a promising avenue for the construction of desired high-valent metal OER catalysts by embedding redox inactive metals.