Self-supported nickel phosphosulphide nanosheets for highly efficient and stable overall water splitting

Abstract

Self-supported nickel phosphosulfide (NiP_0.62S_0.38) nanosheets are fabricated by convenient one-step programming annealing in phosphorus and sulfur gas in series. The as-prepared NiP_0.62S_0.38 only needs overpotentials of 52 and 240 mV to achieve a current density of 10 mA cm⁻² (j₁₀) in alkaline media for HER and OER, respectively. The DFT calculation results reveal that the electronegative phosphosulfide species shift ΔG_H* to the thermo-neutral position and achieve a balance of hydrogen adsorption and detachment on nickel sites. The excellent OER activity of NiP_0.62S_0.38 is attributed to the formation of NiP_0.62S_0.38/NiOOH heterojunctions during water oxidation. Two identical NiP_0.62S_0.38 electrodes as anode and cathode are utilized to construct an alkaline electrolyzer, which delivers a j₁₀ at a small potential of 1.52 V, and can stably sustain the j₁₀ for 200 h, rivalling the integrated state-of-the-art Pt/C and IrO₂.