<i>In situ</i> constructed chromate cover stabilizes seawater oxidation via competitively repelling chloride ions

The electrolysis of natural seawater powered by abundant offshore renewable energy is widely considered as a sustainable hydrogen production technique. However, the competitive chlorine evolution reaction severely damages the catalyst durability in the anodic seawater oxidation. Here, we demonstrate that the in situ chromate cover restructured from a preformed Cr-based metal organic framework (MIL-101(Cr)) stabilizes anodic seawater oxidation while maintaining high activity on an optimized NiFe-layered double hydroxide (NiFe-LDH) array catalyst. Impressively, such a cover enables an over 20-fold reduction in overpotential attenuation rate (0.11 mV h^-1) in comparison to the unmodified NiFe-LDH counterpart (2.38 mV h^-1) against a stable 185 hours operation. A combination of experiment studies and theoretical calculations has unveiled that the in situ generated chromate cover weaken unfavorable Cl^- adsorption more notably over reactive OH^-, therefore mitigating the Cl-related corrosion on the NiFe-LDH. The present study advances a stability breakthrough in the feasible implementation of direct seawater electrolysis for sustainable green hydrogen production.