Ni2P–Co2P Nanowire Arrays on Nickel Foam as a Robust pH-Universal Electrocatalyst for High-Efficiency Hydrogen Evolution Reaction

Splitting water to produce hydrogen through an efficient and low-cost way requires the development of catalysts based on earth-abundant elements. Among transition metal phosphides, bimetal phosphides demonstrate superior hydrogen evolution reactivity to monometal phosphides. Therefore, we synthesized Ni2P–Co2P nanowire arrays on nickel foam with excellent catalytic performance by hydrothermal and low-temperature phosphorization. In 1 M KOH, the catalyst demonstrates low overpotentials of 99 and 161 mV to reach current densities of 10 and 100 mA cm–2, respectively. In 0.5 M H2SO4, the overpotentials of Ni2P–Co2P are only 94 and 159 mV at current densities of 10 and 100 mA cm–2, respectively. In a neutral solution, the overpotentials of the catalyst are also only 146 and 309 mV at current densities of 10 and 100 mA cm–2, respectively. The Tafel slopes of Ni2P–Co2P are only 53.1, 48.26, and 138.3 mV dec–1 in acid, alkaline, and neutral solutions, respectively. Moreover, the outperformance of its durability was tested for 20 h in acid and alkaline solutions, which maintained a stable current density of 10 mA cm–2. This work demonstrates a feasible route to design transition metal phosphides used in pH-universal HER electrocatalysts.