Taking Advantage of Activation Potential Coincidence to Unlock Stable Direct Seawater Splitting

Abstract Electrochemical seawater splitting faces competing chlorine evolution reactions and chlorine corrosion, proposing significant obstacles to commercial applications. In this work, a feasible strategy is developed for the simultaneous oxidation of SO₄²⁻ and CoFe LDH to form an intercalation SO₄²⁻/CoFe LDH, which achieves excellent OER performance (265.2 mV@100 mA cm⁻²) and satisfactory stability (1000 h@500 mA cm⁻²). The presence of SO₄²⁻ is found to enhance the intrinsic activity of CoFe LDH and reduce the corrosion tendency of CoFe LDH. In situ Raman and selected area electron diffraction results demonstrated that CoFe LDH and SO₄²⁻ are simultaneously generated and inserted into the LDH interlayer. DFT calculations further confirmed that the insertion of SO₄²⁻ reduced the tendency of Cl⁻ adsorption, which improved the OER selectivity. Finally, in the flow AEM electrolyzer, the SO₄²⁻/CoFe LDH and Pt/C system exhibited a voltage of only 2.264 V at 500 mA cm⁻² and achieved stable operation in natural seawater for 150 h. The working efficiency in natural seawater is as high as 55.0% with the price per GGE H₂ as low as $1.211, which is promising for a wide range of applications.