Tensile Strain‐Mediated Cobalt Nitrides by High‐Valence Metal Modulator Enable Oxygen Evolution Performance

Abstract Oxygen evolution reaction (OER) has long been the bottleneck of proton exchange membrane water electrolyzers under harsh oxidative and corrosive environments. It is crucial to remold the reactivity of the OER active site to promote sustainable water splitting. Herein, a lattice strain strategy is developed to advance the electrocatalytic performance of OER by incorporating high‐valence transition‐metal modulator Mo 6+ . Tensile strain by asymmetrical Co─N─Mo coordination weakens the Co─N bonding and builds strong Mo─N bonding, which can enable the transition of CoN to active CoOOH. High‐valence Mo 6+ induces stronger tensile strain than low‐valence Mo 4+ for promoting the catalytic ability of CoN. DFT calculations show the electronic structure modulation of Co by Mo doping and the optimized energy barriers of OER for better performance. Co sites are long‐maintained due to the electron transfer from Mo atoms via bridging N‐bonds that impedes the overoxidation and dissolution of active Co species. Thus, Mo‐CoN achieves a low overpotential of 197 mV at 10 mA cm −2 and works steadily for 100 h with a slight degradation of performance. This work reports that OER performance can be promoted by lattice strain enabled by a high‐valence modulator, offering a new route toward the energetics for OER.