Metal-oxoacid-mediated oxyhydroxide with proton acceptor to break adsorption energy scaling relation for efficient oxygen evolution

Abstract

Metal oxyhydroxides (MOOH) generated from irreversible reconstructions of transition metal compounds are intrinsic active species for oxygen evolution reaction, whose activities are still constrained by sluggish deprotonation kinetics and inherent adsorption energy scaling relations. Herein, we construct a tunable proton acceptor (TPA) on oxyhydroxides by in-situ reconstruction of metal oxoacids such as NiC2O4 to accelerate deprotonation and break adsorption energy scaling relations during OER. The modified C2O42− as a TPA can easily extract H of *OH (forming *HC2O4 intermediate) and then promote deprotonation by the transmitted hydrogen bond with *OOH along conjugated (H···)OC–O(–H) chain. As a result, NiOOH-C2O4 shows non-concerted proton-electron transfer and improved deprotonation rate, and delivers a good OER activity (270 mV@10 mA cm−2). The conjugate acidity coefficient (pKa) of the modified oxoacid group can be a descriptor for TPA selection. This TPA strategy can be universally applied to Co-, Fe-, and Ni-based oxyhydroxides to facilitate OER efficiency.