Dual-anion regulation engineering enhances chloridion corrosion resistance for long-lasting industrial-scale seawater splitting

Developing non-precious metal electrocatalysts with high activity and high chlorine (Cl^-) corrosion resistance at industrial current densities remains challenging for large-scale seawater splitting. To address this problem, we rationally design an amorphous cobalt-iron layered double hydroxide with intercalated borate anions (B₄O₅(OH)₄ ^2--CoFe-LDH) grown over crystalline sulfurized cobalt molybdate with a sulfate-rich surface (SO₄ ^2--CoMoO₄) nanohybrid (B₄O₅(OH)₄ ^2--CoFe-LDH/SO₄ ^2--CoMoO₄). Through sulfidation and amorphous/crystalline interface construction, multiple synergistic effects are induced, effectively modulating the electronic structure, increasing the number of accessible active sites, and promoting electron transfer. The density functional theory calculations and <i>in situ</i> spectroscopy measurements demonstrate that the integration of B₄O₅(OH)₄ ^2--CoFe-LDH and SO₄ ^2--CoMoO₄ synergistically optimizes the adsorption energy of intermediates, lowers the reaction energy barrier, and facilitates the formation of CoOOH active species, enhancing the catalytic activity for the oxygen evolution reaction. The unique B₄O₅(OH)₄ ^2-/SO₄ ^2- dual-anion layers block the unfavorable adsorption of Cl^- and contribute to increased resistance to Cl^-, enabling long-term corrosion protection for stable seawater splitting. Inspiringly, the B₄O₅(OH)₄ ^2--CoFe-LDH/SO₄ ^2--CoMoO₄ nanohybrid stably sustains the industrial current density (1 A cm^-2) in alkaline simulated seawater for 720 hours, with only a minimal concentration of hypochlorite (ClO^-, 0.0003%) in the electrolyte.