A self-adaptive ternary NiCoMo-carbon composite as a bifunctional electrocatalyst for high-current-density water splitting

Abstract

Developing non-noble bifunctional electrocatalysts that adapt their surface structure under high-current operation is crucial for advancing industrial water electrolysis. Herein, we present a high-performance self-supported ternary NiCoMo@C bifunctional electrocatalyst via a straightforward one-step electrodeposition method in a deep eutectic solvent. The integration of a carbon matrix with the ternary alloy yields a three-dimensional hierarchical architecture composed of nanoflower-like units, while Mo incorporation effectively modulates the electronic structure of Ni/Co sites, collectively boosting catalytic activity through synergistic effects. In situ spectroscopic analyses reveal that the surface of the Mo-doped alloy undergoes potential-driven transformation: reducing to metallic states for the hydrogen evolution reaction (HER) while forming γ-Ni(Co, Mo)OOH during the oxygen evolution reaction (OER). This reconfiguration enables exceptional bifunctional activity, with low overpotentials of 289 mV (HER) and 354 mV (OER) at 1000 mA cm⁻². When assembled into a two-electrode electrolyzer, the system achieves a low cell voltage of 1.64 V at 100 mA cm⁻² and demonstrates outstanding durability over 200 hours of continuous operation at 1000 mA cm⁻². This work provides valuable insights into the design of high-performance non-noble metal bifunctional electrocatalysts and offers important guidance for the industrial application of water electrolysis for hydrogen production.