Cobalt sulfide circular nanosheets with trace platinum on nickel foam toward efficient electrocatalytic overall water splitting

The development of efficient bifunctional electrocatalysts capable of driving both hydrogen and oxygen evolution reactions (HER/OER) remains a critical task for renewable as well as sustainable water decomposition systems. Herein, we presented an electrocatalyst comprising cobalt sulfide (Co₃S₄) circular nanosheets decorated with trace platinum (Pt) nanoparticles, directly grown on nickel foam (Co-S-Pt@NF). Through synergistic integration of uniformly dispersed Pt and sulfur-rich coordination environments, the catalyst achieved exceptional dual-functional activity in alkaline medium (1 M KOH). The overpotentials of Co-S-Pt@NF at 100 mA cm - ² current density were 68 mV (HER) as well as 353 mV (OER), respectively, exceeding those of Pt-C@NF as well as Ru-O@NF. The density functional theory (DFT) calculations were conducted to investigate mechanism. When Co-S-Pt@NF was adopted as two electrodes in an electrolyze for overall water decomposition, the system could provide 100 mA cm - ² at a low cell voltage of 1.59 V and maintained stable efficiency operation in the 1 M KOH solution for 100 h. This work provided a potential example for the design of cost-effective and high activity “trace precious metal + transition metal supports” bifunctional catalysts.