Extensive catalyst: atomic-level Ni doping enhanced the built-in electric field to promote water oxidation

Abstract

Developing efficient oxygen evolution reaction (OER) electrocatalysts for clean hydrogen production is important for transitioning away from conventional energy resources. Herein, this work presents a metal–organic-framework-derived Ni-doped Co₉S₈ catalyst confined in nitrogen-doped carbon (Ni-Co₉S₈@NC), featuring enhanced charge-transfer kinetics due to the large electrochemically active surface area and high conductivity of the conductive carbon. In situ characterization and density functional theory calculations reveal that the Ni-Co₉S₈ component was reconstructed into the built-in electric field structure (i.e., the extensive catalyst structure: Ni-doped Co(OH)₂/CoOOH shell coated on Ni-Co₉S₈ core) during the OER. This Ni-doped built-in electric field regulated the d-band centers of interface Co sites and optimized the adsorption/desorption energies of OER intermediates, thus enhancing the adsorbate evolution mechanism pathway and obtaining excellent OER performance. The anion exchange membrane electrolyzer of the above as-prepared catalyst achieved a cell voltage of 1.85 V at a high current density of 1 A cm⁻², outperforming a noble-metal catalyst-based RuO₂‖Pt/C electrolyzer (2.11 V @ 1 A cm⁻²). This work provides an atomic-level Ni-doping strategy to tailor the built-in electric field for obtaining high-performance noble-metal-free catalysts for scalable green hydrogen production.