In Situ Electrochemical Oxyanion Steering of Water Oxidation Electrocatalysts for Optimized Activity and Stability

Compared to traditional modulation by metal cations doping, oxyanions offer a higher possibility of mediating the performance of electrocatalysts toward oxygen evolution reaction (OER) due to their special polyanion configurations and large electronegativity. However, the mechanism and rules of oxyanions mediation remain poorly understood. Herein, an in situ electrochemical oxyanion (NO3−, PO43−, SO42−, or SeO42−) steering strategy to study the variation and rules of OER performance for transition-metal (TM = Ni, Fe, Co) hydroxide electrocatalysts is reported. Electrocatalytic experiments indicate both activity and stability of oxyanion-modified TM hydroxides follow the order of PO43− > NO3− > SO42− > SeO42−. Electrochemical incorporation of PO43− or NO3− improves activity and stability of TM hydroxides. Conversely, SO42− or SeO42− doping significantly accelerates TM leaching and thus impairs OER performance. Theoretical calculations reveal that electrochemical oxyanion doping simultaneously modulates TM-O covalency and TM-3d band centers, correlating with TM stability and OER activity of TM hydroxides. This research constructs an oxyanion-mediated rule for designing high-performance electrocatalysts toward energy transformation.