Operando Chlorination Engineering in PEMWE for Direct Brine Electrolysis to Produce Green Hydrogen

Direct seawater electrolysis in proton exchange membrane water electrolyzers is severely bottlenecked by competitive chlorine evolution and catalyst corrosion. Here, we report an operando chlorination strategy that harnesses corrosive ions (Cl^-, SO₄ ^{2 -}) to self-assemble a renewable catalytic layer on a defective RuIrAg pre-catalyst for highly selective water oxidation. In acidic brine (0.5 M H₂SO₄ + 3.0 M KCl), it achieves a remarkably low oxygen evolution reaction (OER) overpotential of 108 mV at 10 mA cm^{- 2}, with a full-cell energy consumption of 41.01 kWh kg^{- 1} H₂ at 1 A cm^{- 2}. In seawater containing 0.25 M Na₂SO₄, the system ensures exclusive OER, completely suppressing chlorine evolution up to 3.0 A cm^{- 2}, and demonstrates 200 h of continuous stability at 1 A cm^{- 2} (2.59 V). Mechanistically, this robust performance stems from Ag-induced frustrated Lewis pairs (FLPs). These continuously regenerating FLPs accelerate OER kinetics via enhanced water activation. Simultaneously, the spatially offset FLPs, synergizing with embedded lattice chlorines and AgCl domains, strictly block Cl^- chemisorption and dimerization to prohibit Cl₂ evolution. This work establishes a new paradigm for high-performance electrolysis via operando chlorination and provides a viable route to green hydrogen from direct seawater.