Mo doping and Se vacancy engineering for boosting electrocatalytic water oxidation by regulating the electronic structure of self-supported Co9Se8@NiSe

Oxygen evolution reactions (OERs) are regarded as the rate-determining step of electrocatalytic overall water splitting, which endow OER electrocatalysts with the advantages of high activity, low cost, good conductivity, and excellent stability. Herein, a facile H₂O₂-assisted etching method is proposed for the fabrication of Mo-doped ultrathin Co₉Se₈@NiSe/NF-X heterojunctions with rich Se vacancies to boost electrocatalytic water oxidation. After step-by-step electronic structure modulation by Mo doping and Se vacancy engineering, the self-standing Mo-Co₉Se₈@NiSe/NF-60 heterojunctions deliver a current density of 50 mA cm^-2 with an overpotential of 343 mV and a cell voltage of only 1.87 V at 50 mA cm^-2 for overall water splitting in 1.0 M KOH. Our study opens up the possibility of realizing step-by-step electronic structure modulation of nonprecious OER electrocatalysts via heteroatom doping and vacancy engineering.