Fe-Co dual-sites p-d orbital hybridization: Electronic restructuring for accelerated oxygen evolution kinetics

The sluggish anodic oxygen evolution reaction (OER) kinetics remains a critical bottleneck for sustainable hydrogen production via water electrolysis. Guided by Density Functional Theory (DFT) calculations, we engineered Fe-CoS₂/Ni₃S₄ dual-site catalysts where Co³⁺ and Fe³⁺ centers synergistically optimize p-d orbital hybridization to enhance OER kinetics. Operando analyses reveal Co³⁺ as primary active sites facilitating rate-limiting OOH* → O₂ desorption with Gibbs free energy (ΔG) reduced by 0.94 eV, while Fe-induced electron delocalization lowers intermediate coupling barriers. Notably, the catalyst facilitates dynamic reconstruction, generating metastable Co³⁺ species with optimized eg orbital occupancy (t₂g⁵eg¹ configuration) and strengthened p-d hybridization via Fe-mediated charge transfer. This electronic synergy enables ultralow overpotentials of 156 mV (hydrogen evolution reaction HER) and 230 mV (OER) at 50 mA cm^-2, with a cell voltage of 1.48 V for overall water splitting at 10 mA cm^-2. The dual-site architecture simultaneously suppresses metal dissolution (<12 % after 20 h) while maintaining 89.2 % initial activity. This work establishes a dual-regulation strategy: atomic-level orbital engineering for OER intermediate optimization and dynamic surface reconstruction for HER-active phase stabilization, offering a paradigm for designing robust bifunctional electrocatalysts.