Stable and efficient seawater splitting on a porous phosphate-intercalated NiFe (oxy)hydroxide@NiMoO4 core-shell micropillar electrode

Seawater splitting powered by solar or wind sources is a significant renewable energy storage technology for the production of green hydrogen energy. However, both the chlorine evolution reaction and chloride corrosion are intractable issues in seawater splitting. Here, a porous electrode based on a phosphate-intercalated NiFe (oxy)hydroxide shell coated on a nickel molybdate (NiMoO4) micropillar core (denoted as P-NiFe@NiMoO4) is synthesized through an electrochemical oxidation strategy. During the electrochemical oxidation process, the etching of MoO2 promotes the reconstruction of NiFe (oxy)hydroxide and the formation of porous structures in an alkaline solution. The optimized P-NiFe@NiMoO4 electrocatalysts afford a low overpotential of 258 mV at a current density of 100 mA/cm2 in alkaline seawater. By pairing the anode with a cathode of as-synthesized P-NiMoO, the electrolyzer presents a low voltage of 1.63 V at 100 mA/cm2 in alkaline seawater with excellent stability. Moreover, the remarkable stability of the anode seems to be attributed to the in-situ phosphate formed during the electrochemical oxidation process to passivate chloride corrosion.