Modifying d–p orbital hybridization of Ni/FeO species by high-valence ruthenium doping to enhance oxygen evolution performance

Abstract

The electron distribution of catalysts can be modulated by high-valence metal doping, thus enhancing the intrinsic activity. Herein, we adopt Ru modification to adjust the d–p orbital hybridization of Ni-Fe oxyhydroxides, significantly increasing the oxygen evolution reaction (OER) activity. The amorphous NiFe_0.5Ru_0.1O_xH_y catalyst synthesized by sol–gel method exhibits excellent OER activity, far superior to commercial RuO₂. In situ Raman and XPS results confirm that the NiOOH/FeOOH active species gradually form with increasing applied voltage. Density functional theory (DFT) calculations reveal that high-valence Ru dopants can effectively regulate the hybridization of d–p orbital of Ni/FeO, significantly increase the electron density around Fermi level, promote charge transfer, make them have more anti-bonding orbitals, enhance the binding ability of active sites to intermediates, reduce the reaction energy barrier of the rate-determining step (H₂O → *OH), and thus improve the OER activity. In addition, NiFeRuO_xH_y as a cathode catalyst in a rechargeable zinc-air battery shows an outstanding cycle life of 600 h. This study provides a promising hybrid orbital method for designing high-performance OER catalysts for water splitting and rechargeable zinc-air batteries.