Chloride-induced easier phase transformation and catalytic synergy for enhanced seawater splitting

Hydrogen production from sustainable seawater splitting technology is restricted by the side reactions of chlorine evolution and chlorine oxidation on the anode. Different from the common catalyst design strategy, i.e., selecting materials repelling chloride ions, herein, we find that the strong adsorption of chloride ions on noble metals can be an advantage. We design a heterostructure catalyst consisting of atomically dispersed Ru doped IrO _x nanoclusters/α-Co(OH)₂ nanosheets. This as-synthesized catalyst only requires an overpotential of 206 mV to drive 100 mA cm^-2, and it can withstand continuous catalysis for as long as 310 h under 500 mA cm^-2. In situ spectroscopy and theoretical calculations show that Cl^- ion adsorption on IrO _x clusters at low overpotentials promotes the phase transition of α-Co(OH)₂ to CoOOH, lowering the OER barrier at the Ru site and resulting in a significantly reduced theoretical overpotential of 200 mV for Ru-IrO _x -Cl/CoOOH. Our work demonstrates a catalyst with Cl^- adsorption-promoted OER activity, in contrast to the traditional Cl^- repelling catalyst design strategy for seawater splitting.