ZIF-67-Derived Cation Regulation of Metal Sulfides for Boosting Oxygen Evolution Activity

Transition metal sulfides exhibit superior oxygen evolution reaction electrocatalytic performance due to their unique electronic structures and significant surface reconstructions. The electronic structure of transition metal sulfides can be effectively regulated via heteroatom doping, vacancy engineering, interface engineering, and structure engineering, and surface reconstructions can also be coordinated via coupling with electron-donating carbon materials. Herein, a facile cation regulation strategy is reported to boost the oxygen evolution reaction (OER) activity of transition metal sulfides by pyrolyzing and sulfurizing the Fe²⁺- and Ni²⁺-modified ZIF-67 precursor (FeNi/ZIF-67). Crucially, Fe doping and Ni substitution in the final products are achieved by a simple room-temperature ion-exchange strategy, significantly boosting the OER activity. Meanwhile, conductive porous carbon from the organic ligand improves the mass transfer and active-site accessibility. As anticipated, Fe-doped CoS₂ and NiCo₂S₄ embedded in N-doped porous carbon (NC) on carbon cloth (CoFe₁Ni₂S@NC/CC) demonstrate excellent hydrophilicity and OER activity, representing a very low overpotential of 175 mV at 20 mA cm^–2, fast reaction kinetics (R_ct = 0.51 Ω cm^–2), and considerable electrocatalytic durability in 1.0 M KOH. This work offers a simple and low-cost cation regulation method for designing efficient cobalt-based sulfide hybrid electrocatalysts for OER, advancing their application in electrochemical water splitting.