NiPS Nanosheet-Graphene Composites as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction.

Developing new electrocatalysts is essentially important for efficient water splitting to produce hydrogen. Two-dimensional (2D) materials provide great potential for high-performance electrocatalysts because of their high specific surface area, abundant active edges, and tunable electronic structure. Here, we report few-layer NiPS nanosheet-graphene composites for high-performance electrocatalysts for oxygen evolution reaction (OER). The pure NiPS nanosheets show an overpotential of 343 mV for a current density of 10 mA cm, which is comparable to that for IrO and RuO catalysts. More importantly, the NiPS nanosheet-graphene composites show significantly improved OER activity due to the synergistic effect. The optimized composite shows a very low overpotential of 294 mV for a current density of 10 mA cm, 351 mV for a current density of 100 mA cm, a small Tafel slope of 42.6 mV dec, and excellent stability. These overall performances are far better than those of the reported 2D materials and even better than those of many traditional materials even at a much lower mass loading of NiPS.