<p>Seawater electrolysis is a highly promising method to produce high energy density hydrogen, especially in dry areas that have scarce freshwater sources. However, application of seawater electrolysis is confronted by two major problems associated with catalysts employed for the anodic oxygen evolution reaction (OER) including the competitive hypochlorite evolution reaction (HCER) and strong chloridion (Cl⁻) triggered corrosion. In studies aimed at overcoming these problems, a facile method has been developed to synthesize a homologous CoS₂ heterojunction as an OER catalyst. Owing to a difference in work functions at the interface and increased electron density, this material has directed electron transfer and strong chloridion repulsion properties, respectively. Studies have shown that CoS₂ achieves low overpotentials of 289 and 322 mV at 10 mA cm⁻² current density in respective alkaline (1 M KOH) and alkaline simulated seawater electrolytes. Moreover, the outstanding stability of CoS₂ is reflected in a negligible decline in activity during promotion of the OER for 100 h. Results of density functional theory calculations reveal that the homologous CoS₂ heterojunction promotes directed electron transport for optimizing adsorption/ desorption of reactive species and heightens the Cl⁻ adsorption energy for strongly repulsing Cl⁻, phenomena that enhance OER performance in alkaline simulated seawater.</p>