<p>Copper sulfide (CuS) exhibits significant advantages as an electrocatalyst in energy conversion and storage, particularly in electrocatalytic reactions. Heterogeneous electrocatalysis typically involves charge transfer between the electrocatalyst surface and the reactants. In this study, a Co₃O₄/CuS p–p heterojunction was synthesized using a facile hydrothermal method, followed by high-temperature calcination. Its electrocatalytic performance toward the oxygen evolution reaction (OER) was evaluated. The as‑prepared Co₃O₄/CuS nanoparticle electrocatalysts exhibited relatively high activity toward the OER, requiring only a low overpotential of 347 mV to achieve a current density of 10&#xa0;mA cm⁻², outperforming most copper‑based catalysts. The intricate flower‑like morphology enhanced the contact between reactant molecules and the catalyst surface. The results indicated that the electric field at the Co₃O₄/CuS p–p heterojunction interface, originating from the energy level mismatch, facilitated charge transfer and improved the conductivity of the heterojunction electrocatalyst. Furthermore, spontaneous electron transfer at the Co₃O₄/CuS heterogeneous interface induced local charge redistribution, facilitating the electrostatic adsorption of OH⁻ at the interface. The as‑prepared Co₃O₄/CuS p–p heterojunction exhibited a well‑tuned electronic structure and demonstrated outstanding electrocatalytic activity toward the OER. This study proposes a novel strategy for regulating the surface and interface charge states of electrocatalysts, thereby enhancing their OER catalytic activity, and provides a new avenue for the discovery of superior electrocatalysts.</p> Graphical Abstract <p></p>