A sulfur defective Mn-doped Ni₃S_2-nanosheet for enhanced overall water splitting

Non-precious and stable electrocatalysts towards both oxygen and hydrogen evolution reaction (OER/HER) are essential for effective overall water splitting in alkaline solution. In this study, a sulfur defective and manganese-doped nickel sulfide nanosheet that uniformly grown on nickel foam substrate (Mn-Ni₃S_2-@NF) is synthesized. In alkaline solution, the Mn-Ni₃S_2-@NF showed a low overpotential of 76 and 110 mV for OER and HER at 10 mA cm^-2, respectively, together exhibiting excellent stability for both OER and HER reaction. It was confirmed by the experimental results that sulfur defects and Mn-doping synergistically optimized the electronic structure of Mn-Ni₃S_2-with increased electrical conductivity and enhanced OER/HER activity. Moreover, amorphous nickel oxyhydroxide (NiOOH) was observed byin situRaman during the OER condition, suggesting NiOOH is the active phase for OER reaction. Furthermore, the electrolyzer assembled by Mn-Ni₃S_2-@NF merely needs 1.46 V to reach 10 mA cm^-2and shows good stability as well. This study provides a feasible way to prepare high-efficiency bifunctional catalysts for overall water splitting.