Carbon coated nickel cobalt phosphide with sea urchin-like structure by low temperature plasma processing for hydrogen evolution and urea oxidation

Hydrogen production from organic wastewater splitting is a promising approach to reduce electrical energy consumption and remove organic pollutants simultaneously. The key challenge is to develop an effective electrocatalyst with low-cost, high-performance and high-corrosion resistance in harsh environment. Here, a self-supported carbon coated nickel cobalt phosphide grown on nickel foam ([email protected]/NF) electrode is synthesized by combining hydrothermal synthesis and plasma processing. Surface coating by graphene-like nanostructure and phosphorization are achieved at mild temperature by low temperature CH4 plasma and Ar-H2-P plasma, respectively, enabling retention of the sea urchin-like structure obtained by hydrothermal reaction. Benefiting from the modulated built-in electric field, the self-supporting [email protected]/NF electrode exhibits highly efficient bifunctional catalytic activity for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR), featured for the low voltage of 1.43 V at 20 mA cm−2 of a HER||UOR electrolysis cell. Whether in alkaline solution or organic wastewater, [email protected]/NF electrodes could generate H2 continuously and stably for more than 60 h. DFT calculation indicates that Ni doping modifies the surface charge density, which optimizes the adsorption/desorption of intermediates and facilitates the water dissociation during HER. Moreover, CoNiP possesses strong binding with the C layer, thus promoting the structural stability and charge transfer efficiency of the catalyst.