Copper‐Cobalt‐Sulfide and Cu‐MOF Nanoflower Composite on Copper Foam: Highly Efficient Bifunctional Catalysis for Low‐Barrier Overall Water Splitting

Abstract The increasing demand for clean energy has catalyzed significant research into electrochemical water splitting for hydrogen production. However, the intrinsically slow kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) necessitate the development of efficient and cost‐effective electrocatalysts. In this study, Cu‐MOF arrays are first grown on copper foam and then partially transformed them into copper‐cobalt sulfide through vulcanization, yielding a heterogeneous composite catalyst (Cu‐Co‐S@Cu‐MOF/CF). The resulting hierarchical nanoflower architecture effectively maximizes the exposure of active sites while concurrently promoting electrolyte diffusion and facilitating gas release. More importantly, the synergistic effects of copper incorporation and strong interfacial coupling between Cu‐Co‐S and Cu‐MOF precisely modulate the electronic configuration of cobalt active sites. This dual optimization simultaneously reduces the energy barrier for water dissociation in the HER while accelerating the reaction kinetics of the OER under alkaline conditions. The optimized catalyst exhibits outstanding performance, achieving overpotentials of just 72 mV for HER and 136 mV for OER at 10 mA cm ⁻² . Remarkably, for overall water splitting, it requires only 1.48 V to drive the same current density while maintaining stability for over 100 h—surpassing the performance of most non‐noble metal catalysts reported to date.