Phosphorus-doped cobalt oxide/cobalt sulfide heterostructure for enhanced oxygen evolution

Regulating the distribution of valence charges near the Fermi level and d-band center of metal atom active sites is crucial for developing highly efficient and stable catalysts for oxygen evolution reaction (OER), yet it remains a significant challenge. In this study, we prepared phosphorus-doped Co ₃O ₄/Co ₉S ₈ catalysts with a mesoporous nanorod morphology and Mott-Schottky heterojunction. Compared to Co ₃O ₄, Co ₉S ₈ and Co ₃O ₄/Co ₉S ₈, this catalyst exhibits enhanced OER properties with an overpotential of 156 mV at 10 mA cm ⁻², 380 mV at 50 mA cm ⁻², and 450 mV at 100 mA cm ⁻² . Moreover, when a voltage of 2.0 V vs. RHE is applied, the current density reaches 350 mA cm ⁻². Density functional theory (DFT) calculations reveal that the coupling of Co ₃O ₄ and Co ₉S ₈ interfaces and phosphorus doping lead to the rearrangement of d-orbital electrons of Co atoms on the crystal plane, optimizing the d-band center. Crystal orbital Hamilton population (COHP) analysis shows that the partial anti-bonding state transitions into the unoccupied region, reducing the anti-bonding state and enhancing the bonding state, thus significantly improving the adsorption for the target intermediate (*OOH), resulting in higher intrinsic activity. This study demonstrates that the pathway of doping this heterojunction with P synergistically enhances the catalytic activity of this composite for OER in water splitting electrocatalysis.