Turing Charge Distribution via S-Doping of Porous CoMoP₂ for Efficient Overall Water Splitting Electrocatalysis

Advancing green hydrogen evolution critically depends on the design of bifunctional electrocatalysts that are both highly economical and efficient for overall water decomposition. Herein, we report the sulfur-doped porous CoMoP₂ catalyst synthesized on nickel foam (S-CoMoP/NF) via a simple step-by-step hydrothermal approach. Through extensive physicochemical characterization, it is verified that S atoms are effectively immobilized into the CoMoP₂ lattice, thereby tuning the electronic structure while retaining a porous framework. As evidenced by electrochemical testing conducted in 1.0 M KOH, S-CoMoP/NF possesses exceptional bifunctional capability, attaining overpotentials as low as 191 mV for the hydrogen evolution reaction and 331 mV for the oxygen evolution reaction at a current density of 100 mA cm^-2. According to density functional theory (DFT) calculations, the introduction of S dopants triggers charge redistribution, elevates the d-band center, and fine-tunes the adsorption, consequently accelerating the catalytic kinetics. The S-CoMoP/NF||S-CoMoP/NF electrolyzer achieves 100 mA cm^-2 at 1.82 V and demonstrates a stabilized performance throughout 80 h. Beyond presenting a high-performance non-noble bifunctional electrocatalyst, this work further elucidates how anionic doping modulates charge distribution to enable efficient water splitting.