Low Zn-doped Co3O4 nanorods for enhanced hydrogen evolution reaction

Abstract

Transition metal oxides have been identified as the best potential candidates to replace Pt-based HER catalysts. But they are still limited by the high HER overpotential, due to the undesirable adsorption/desorption of surface hydrogen. In this work, Zn with low concentrations were incorporated into the tetrahedral Co²⁺ sites of Co₃O₄ by hydrothermal and subsequent annealing treatment. They exhibit excellent HER performance. Particularly, when the Zn content in Co₃O₄ is 6.3 at%, an overpotential of 79.2 mV at the current density of 10 mA cm⁻² was obtained in alkaline medium, which significantly better than pure Co₃O₄ catalyst (196.3 mV). Moreover, the current density of the Zn-doped Co₃O₄ catalyst can maintained 93 % after 10 h and 80 % after 20 h. DFT calculations reveal that the ΔG_H* of Zn-doped Co₃O₄ (0.827 eV) is smaller and closer to zero than pure Co₃O₄ (1.023 eV). This work provides a deep insight into the rational design of low-level metal-doped cobalt oxide-based electrocatalysts.