Interfaces coupling of Co8FeS8-Fe5C2 with elevated d-band center for efficient water oxidation catalysis

Maximizing the oxygen evolution reaction (OER) catalytic activity of carbon coated core-shell electrocatalysts is significant for the application of water electrolyzers and rechargeable metal-air batteries, yet the modulation of the catalytic properties through interfaces coupling remains challenging. Here, we construct Fe5C2 phase interlayered between carbon shell and Co8FeS8 core (Co8FeS8-Fe5C2@C) for enhancing the alkaline OER catalytic performance. By altering the interlayer phase with Co1−xS as the control sample (Co8FeS8-Co1−xS@C), synchrotron X-ray absorption spectroscopy analysis integrated with density functional theory calculations indicate that the induced interfacial electron coupling of Co8FeS8-Co1−xS and Co8FeS8-Fe5C2 can upshift the d-band center toward Fermi level, optimalize Gibbs free energy for oxygen-containing intermediates, facilitate electron transfer between Co8FeS8 and carbon shell. Consequently, the target Co8FeS8-Fe5C2@C catalyst with stronger interface coupling and optimal electron modulation shows an significant overpotential (η10) decrease by 93 mV compared with Co8FeS8@C, along with a Tafel slop of 48.9 mV dec−1 and a long catalytic lifetime, outperforming commercial RuO2 and other reported analogous catalysts. This work opens up further opportunities of interlayer modification in carbon caoted core-shell catalyst to effictivly tailor the d-Band centers for effectively strengthen its catalytic performance.