Tailoring the d-band center of porous CoS2 nanospheres via low-electronegative Fe for weakened OH* adsorption and boosted oxygen evolution

Abstract

The development of high-performance metallic cobalt pyrite OER catalysts with suitable electronic structures remains a challenge. In this paper, a low-electronegative Fe-substituted cobalt pyrite (Fe_xCo_1−x)S₂ OER catalyst with controllable morphology and electronic structure was designed and prepared, and it exhibited excellent catalytic activity owing to the conversion of (Fe_xCo_1−x)S₂ to Fe–CoOOH during the OER process. Benefiting from the morphology of porous nanospheres and the modulated electronic structure, Fe_0.25Co_0.75OOH exhibits an OER overpotential of 274 mV and a Tafel slope of 33.6 mV dec⁻¹ at a current density of 10 mA cm⁻². Experimental and theoretical calculation methods show that the introduction of Fe into CoOOH can modulate the d-band center of the Co site because the low electronegativity of Fe induces charge aggregation at the Co site to optimize the binding energy between Co and oxygen-containing intermediates. This study provides prospective insights into understanding the synergistic effects of bimetals in the (Fe_xCo_1−x)S₂ system and offers a new strategy for exploring other efficient catalysts with controllable electronic structures and controllable morphologies.