Carbon-Coated Nickel Phosphide Nanosheets as Efficient Dual-Electrocatalyst for Overall Water Splitting

Low-cost and efficient electrocatalysts for overall water splitting are in high demand for a wide range of applications across renewable and clean energy. Here, we report a simple one-step synthesis of a three-dimensional (3D) carbon-coated Ni₈P₃ nanosheet array as bifunctional catalyst for both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). The nanosheet array possesses low overpotentials, high current densities, and small Tafel slopes in both HER and OER and shows high electrocatalytic activities and long-term stability. The carbon layer with high electric conductivity serves not only as a protective layer to prevent Ni₈P₃ dissolution but also as an active layer to decrease the electrocatalysis overpotential. The nanosheet array has HER outstanding activity in both acid and alkaline media. Its superior performance in OER can be due to the synergistic interaction at the Ni₈P₃/NiO_x heterojunction. Furthermore, cell voltage as low as 1.65 V can achieve 10 mA cm^-2 current density for full water splitting in an alkaline water electrolyzer, indicating potential application of C@ Ni₈P₃ as bifunctional catalyst for clean and renewable energy utilization.