Revealing Enhanced\nActive Oxygen Formation by Incorporating\nChromium into Nickel Hydroxide Nanosheets for Improved Oxygen Evolution\nReaction

Nickel-based oxyhydroxides have emerged as promising\ncatalysts\nfor the oxygen evolution reaction (OER) among Earth-abundant metals.\nWhile the incorporation of foreign elements is recognized to enhance\ncatalytic activity, the origin of this enhancement is still debated.\nWe synthesize and examine Ni hydroxide nanosheets, both with and without\nCr doping, to elucidate the underlying enhancements. Operando UV–vis\nand Raman spectroscopy are employed to unravel the behavior of the\ncatalysts. The Cr doping facilitates the oxidation of Ni, resulting\nin the generation of active oxygen species. The enriched active oxygen\nspecies improves OER performance through a lattice oxygen-mediated\npathway in Fe-free KOH, and further contribute to the creation and\nincreased activity of FeO<sub><i>x</i></sub>H<sub><i>y</i></sub> sites in the presence of Fe impurities. This work\nprovides a mechanistic understanding of the performance enhancement\nin Ni-based catalysts through Cr doping and suggests a strategy for\nthe design of more efficient catalysts in the future.