Nonprecious and shape-controlled Co3O4-CoO@Co electrocatalysts with defect-rich and spin-state altering properties to accelerate hydrogen evolution reaction at large current densities over a wide pH range

Abstract

In this study, efficient HER activity is achieved through the successful preparation of Co3O4-CoO@Co catalysts that are morphology-dependent. It is proposed that the distinctive skeletal polyhedron (SPH) morphology of the Co3O4-CoO@Co catalyst shows outstanding HER performances over the universal pH range. The heterostructure catalyst exhibits a current density of 50 mAcm−2 at an ultra-low overpotential of 28, 62, and 138 mV under 0.5 M H2SO4, 1 M KOH, and 1 M PBS electrolytes, respectively. Experimental and theoretical studies indicate that electron-enriched Co2+ in the CoO site is favorable for H+ cation adsorption and high valence Co3+ in the Co3O4 site is favorable for H2O molecule activation and dissociation in acidic, neutral, and alkaline electrolytes. Benefitting from an empty eg 3d orbital with a strong Jahn–Teller effect, a high density of spin states, and a large number of oxygen vacancies, the SPH-Co3O4-CoO@Co catalyst is demonstrated to provide faster hydrogen evolution reaction.