Reconstruction of Oxygen Evolution Precatalysts: Effects of Leaching, Electrolyte Concentration and Iron...

Fe-containing Ni oxyhydroxides are among the most active alkaline oxygen evolution catalysts, whose structures and performances strongly depend on precursor reconstruction and Fe location. However, achieving precise control over precursor design, reconstruction, and Fe incorporation remains highly challenging. Here, we report the low-temperature synthesis of intermetallic Ni2In3 nanoparticles as a precursor and uncover their in situ reconstruction behavior modulated by electrolyte concentration. Compared with similarly sized Ni nanoparticle-derived catalysts, the Ni2In3-derived catalysts exhibit significantly enhanced activity and stability. The optimal catalyst, after activation in 6 M KOH with Fe spiking, requires an overpotential of only 284 mV for 10 mA cm-2, along with a low Tafel slope of 31 mV dec-1. Combined electrochemical analyses, in situ/ex situ characterizations, and theoretical calculations reveal that In leaching induces electronic structure modulation and surface undercoordinated site enrichment, thereby facilitating interfacial Fe incorporation to form NiFe active centers. In an anion exchange membrane water electrolyzer, the catalyst demonstrates excellent stability of 260 h at 1 A cm-2 at 80 °C. These findings highlight the importance of electrolyte- and precursor-dependent reconstruction in modulating the electronic structure and promoting interfacial Fe incorporation, thereby enabling the design of oxygen evolution electrocatalysts.