Core-shell structured Co_xH_yPO₄/NiCo₂S₄ composites towards electrocatalytic oxygen evolution

Exploring non-precious metal oxygen evolution reaction (OER) electrocatalysts with high activity and stability is pivotal for electrolytic hydrogen production. Herein, we employ a photo-reduction deposition technique to load amorphous cobalt hydrogen phosphate (Co_xH_yPO₄, denoted as Co-Pi) onto the surface of porous NiCo₂S₄ (NCS) yolk-shell microspheres, successfully fabricating Co-Pi/NCS composite material. Through the integration of density functional theory (DFT) calculations with experimental investigations, the influence of Co-Pi introduction on the electronic structure and electrocatalytic performance of NCS is probed. The formation of heterogeneous interfaces and reconstruction of chemical bonds enhance the conductivity of Co-Pi/NCS, and modulate charge transfer between the catalyst and reaction intermediates, thereby altering adsorption strength and Gibbs free energy of the reaction, ultimately optimizing OER catalytic activity. Consequently, Co-Pi/NCS demonstrates commendable activity and durability, exhibiting low overpotential of 335 mV at current density of 10 mA·cm⁻² and maintaining prolonged stability for 14 h in 1 mol/L KOH solution. This work holds promise for advancing the utilization of transition metal sulfides in electrochemical oxygen production processes.