Phase-dependent electronic structure modulation of nickel selenides by Fe doping for enhanced bifunctional oxygen electrocatalysis†

Bifunctional oxygen electrocatalysis is a pivotal process that underpins a diverse array of sustainable energy technologies, including electrolyzers and fuel cells. Metal selenides have been identified as highly promising candidates for oxygen electrocatalysts with electronic structure engineering that lies at the heart of catalyst design. Two-phase Fe-doped nitrogen carbon (NC)-supported nickel selenides were synthesized using a coordination polymer template. Fe doping offers significant advantages as it enhances electronic interactions, resulting in higher availability of active sites than nickel selenides and optimizing the adsorption energy for reaction intermediates. Owing to the intriguing compositional and structural features, the obtained Ni_xFe_1−xSe₂–NC@400 electrocatalyst displays better catalytic activity with an overpotential (η₁₀) of 253 mV and a lower Tafel slope of 57.1 mV dec⁻¹ for the Oxygen Evolution Reaction (OER) in 1 M KOH. Likewise, the catalyst demonstrated remarkable efficiency in Oxygen Reduction Reaction (ORR) catalysis, achieving a limiting current density comparable to that of the standard Pt/C catalyst and exhibiting an improved Tafel slope of 35.4 mV dec⁻¹ in 0.1 M KOH. This work reveals the influence of Fe dopants in oxygen electrocatalysis and presents an effective approach to tuning the electronic structure for the development of highly active electrocatalysts in alkaline media.