Counterintuitive Chloride Utilization for Efficient and Stable Hydrogen Production from Cl–-Rich Water

Abstract

The direct electrolysis of Cl–-rich water offers a sustainable pathway for green hydrogen production but is severely hindered by chloride-induced corrosion of anodes, particularly under industrially relevant, ampere-level current densities. Here, we report a robust and highly active organic–inorganic hybrid electrocatalyst, (MoNi)3S2 modified with sodium benzoate (BA), designed to overcome the above challenge. The (MoNi)3S2-BA catalyst exhibits exceptional oxygen evolution reaction performance, achieving an ultralow overpotential of 183 mV at 10 mA cm–2 and, remarkably, maintaining stable operation for over 2500 h at 500 mA cm–2 in a Cl–-containing alkaline electrolyte. Comprehensive experimental analyses combined with density functional theory calculations reveal a unique “electron buffer” mechanism responsible for its outstanding durability. It demonstrates that the BA modifier selectively traps Cl– within its conjugated structure, functioning as a sacrificial adsorbent that redirects corrosive chloride away from the active Ni/Mo sites. Crucially, BA also sequesters the excess electrons released from adsorbed Cl–, preserving the pristine electronic structure of the catalytic metal centers. This dual functionality effectively suppresses the competing chlorine evolution reaction and prevents metal dissolution, ensuring long-term catalytic stability without compromising activity. This work introduces a paradigm of using molecular modifiers as electronic buffers to achieve selective anion management, offering a new strategy for designing durable catalysts for direct seawater electrolysis and advancing the path toward sustainable hydrogen production.