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

Abstract

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