Chloride‐Induced Descriptor Shift in the Oxygen Evolution Reaction on Metal‐Doped Cobalt Phosphides: A First‐Principles Study

Seawater electrolysis is a promising route for sustainable hydrogen production but is challenged by chloride‐induced performance loss at the anode. Density functional theory calculations were employed to investigate the oxygen evolution reaction (OER) on metal‐doped cobalt phosphide surfaces under chloride‐containing environments. Competitive adsorption between *OH and *Cl was examined on CoP (011) and (211) facets to evaluate surface selectivity. The results indicate a thermodynamic preference for oxygen intermediates, particularly on the (211) surface, which suppresses chloride adsorption. On clean surfaces, OER activity follows conventional scaling relations where ΔG(*OOH)−ΔG(*O) governs the activity trend. In contrast, the presence of adsorbed chloride perturbs surface energetics and shifts the governing descriptor toward ΔG(*OH), suggesting a chloride‐induced modification of the OER reaction landscape. Dopant elements modulate the d‐band center and surface charge, influencing both catalytic activity and chloride tolerance. These findings highlight the limitations of clean‐surface descriptors and provide theoretical insight into catalyst behavior under chloride‐containing environments relevant to seawater electrolysis.