Regulating coordination environment of Co single-atom through Ni/Co sulphides synergistic heterointerfaces towards efficient bifunctional oxygen electrocatalysts

Abstract

Achieving synergistic catalysis between different components and maintaining a high catalytic activity is an effective way to enhance the efficiencies of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, we employed structural engineering to regulate the coordination environment of Co single-atoms through Ni/Co sulfide heterointerfaces in Ni₃S₂/Co₉S₈@Co-NC, thereby achieving an efficient bifunctional oxygen electrocatalyst. The as-prepared Ni₃S₂/Co₉S₈@Co-NC exhibited a low overpotential of 0.632 V and stably maintained excellent ORR/OER activities for approximately 100 h. In situ Raman spectroscopy, electron paramagnetic resonance spectroscopy, Bode phase plots, and alcohol-phenol probe analysis indicated that the interfacial electronic interactions between the Ni₃S₂ and Co₉S₈ played a key role in accelerating the phase transition of the intermediates during the OER. Furthermore, the synergistic interaction between the metal sulfide and Co single-atoms in the Ni₃S₂/Co₉S₈@Co-NC catalyst boosted the transition of intermediates, thereby leading to superior ORR activity. Remarkably, the Ni₃S₂/Co₉S₈@Co-NC-based zinc–air battery (ZAB) exhibited a voltage of 1.53 V, power density of 187 mW cm⁻², and longer charge–discharge cyclic stability of 1000 cycles, all of which were higher than those of the Pt/Ir/C-based ZAB (1.51 V, 165 mW cm⁻², 450 cycles, respectively). This exceptional performance demonstrates a valuable prospect for designing high-efficiency and non-precious metal-based bifunctional catalysts via interface and atom-level engineering.