Integrating energy-saving hydrogen production with methanol electrooxidation over Mo modified Co4N nanoarrays

Abstract

The intrinsically sluggish kinetics of the anodic oxygen evolution reaction (OER) is deemed to be the bottleneck for highly efficient electrocatalytic hydrogen production, and the by-product is less value-added oxygen. Herein, we report rational construction of Mo doped Co₄N nanoarrays (Mo-Co₄N) with an open skeleton structure as a robust bifunctional electrocatalyst for concurrent electrolytic high-purity hydrogen and value-added formate productions in the cathodic and anodic process. Benefitting from Mo doping, the unique structure characteristics of more exposed active sites, and optimized electronic synergy, Mo-Co₄N exhibits intriguing hydrogen evolution reaction (HER) activity with an exceptionally small overpotential of 45 mV at 10 mA cm⁻² and a low Tafel slope of 42 mV dec⁻¹. Meanwhile, when the anodic partial methanol oxidation reaction (MOR) is used to replace the OER, the oxidation potential is significantly reduced to 1.356 V at 10 mA cm⁻². In particular, a two-electrode electrolyzer employing Mo-Co₄N as a bifunctional catalyst only requires an ultralow cell voltage of 1.427 V to achieve a current density of 10 mA cm⁻², featuring low energy consumption in comparison to traditional overall water splitting. Furthermore, high Faraday efficiencies approaching 100% for hydrogen evolution and value-added formate production are achieved, as well as excellent 60 h long-term durability.