Single-phase Ni5P4–copper foam superhydrophilic and aerophobic core–shell nanostructures for efficient hydrogen evolution reaction

Abstract

The facile synthesis of a highly durable, low-cost and robust electrocatalyst for hydrogen generation from water is vital to address the existing environmental issues, as well as to provide an environmentally-friendly clean and green energy supply. Electrochemical deposition of single-phase nickel phosphide on galvanostatically deposited copper foam (Cuf@Ni₅P₄) core–shell nanostructure offers an innovation in the structural design of a new platform for novel electrocatalysts. The Cuf@Ni₅P₄ provides a superior three-dimensional conductive channel for ion transport during the catalytic process. The catalyst exhibits an excellent electrocatalytic activity towards the hydrogen evolution reaction (HER) in acidic media. The superhydrophilic and aerophobic properties of the porous electrode help the H₂ gas bubbles to quickly leave the surface. Interestingly, it requires a very low overpotential of 90 mV for HER at a current density of 10 mA cm⁻². The very small Tafel slope of 49 mV dec⁻¹ and the very high exchange current density (∼0.76 mA cm⁻²) originate from the large electrochemically active surface area and the fast mass and electron transfer efficiency of the Cuf@Ni₅P₄ catalyst. A theoretical study was performed to investigate the mechanism underlying the HER activity in Cu-supported Ni₅P₄ at an atomic scale. Density functional theory (DFT) calculations suggest a very high negative Gibbs free energy change (ΔG_H*) in Ni₅P₄ (0001)/Cu (111) upon hydrogen adsorption, which is actually responsible for the excellent HER activity of the catalyst. Furthermore, it shows remarkable durability for hydrogen generation under low (10 mA cm⁻²) and high current densities (160 mA cm⁻²) for >84 h with ∼96% retention of the overpotential, establishing a low-cost and efficient catalyst for sustainable, future energy generation strategies.