Dynamically Restructuring NixCryO Electrocatalyst for Stable Oxygen Evolution Reaction in Real Seawater

In the pursuit of long-term stability for oxygen evolution reaction (OER) in seawater, retaining the intrinsic catalytic activity is essential but has remained challenging. Herein, we developed a Ni_xCr_yO electrocatalyst that manifested exceptional OER stability in alkaline condition while improving the activity over time by dynamic self-restructuring. In 1 M KOH, Ni_xCr_yO required overpotentials of only 270 and 320 mV to achieve current densities of 100 and 500 mA cm⁻², respectively, with excellent long-term stability exceeding 475 h at 100 mA cm⁻² and 280 h at 500 mA cm⁻². The combination of electrochemical measurements and in situ studies revealed that leaching and redistribution of Cr during the prolonged electrolysis resulted in increased electrochemically active surface area. This eventually enhanced the catalyst porosity and improved OER activity. Ni_xCr_yO was further applied in real seawater from the Red Sea (without purification, 1 M KOH added), envisaging that the dynamically evolving porosity can offset the adverse active site-blocking effect posed by the seawater impurities. Remarkably, Ni_xCr_yO exhibited stable operation for 2000, 275 and 100 h in seawater at 10, 100 and 500 mA cm⁻², respectively. The proposed catalyst and the mechanistic insights represented a step towards realization of non-noble metal-based direct seawater splitting.