Hydrothermal Synthesized Co-Ni 3 S 2 Ultrathin Nanosheets for Efficient and Enhanced Overall Water Splitting

We used the one-step hydrothermal controlled synthesis method for Co-Ni3S2 ultrathin nanosheets grown directly on nickel foam(NF). The as-synthesized Co-Ni3S2/NF showed enhanced activities in the hydrogen evolution reaction(HER), oxygen evolution reaction(OER) and better overall water splitting(OWS) efficiency than the un-doped Ni3S2/NF. The voltage of Co-Ni3S2/NF for OWS was only 1.58 V at the current density of 10 mA/cm2 and with long time(>30 h) current output during the current-density(i-t) test. The good i-t performance was also observed in both HER and OER processes. Additionally, the Co-Ni3S2/NF showed a large current density(>1 A/cm2) for both HER and OER. When the current densities reached 100 and 1000 mA/cm2, the required overpotentials for Co-Ni3S2/NF were 0.35 and 0.75 V for OER and 0.30 and 0.85 V for HER. Therefore, after introducing Co, th e activity of Ni3S2-based material was strongly enhanced.