Amorphous/amorphous Ni–P/Ni(OH)2 heterostructure nanotubes for an efficient alkaline hydrogen evolution reaction

Abstract

Amorphous/amorphous heterostructures with a large surface area are theoretically anticipated to promote the alkaline hydrogen evolution reaction (HER) activity and stability. However, the growth, characterization and theoretical simulation of amorphous/amorphous nanostructured heterostructures are still challenging due to their atomic isotropy. Herein, a novel and simple strategy is developed to synthesize amorphous/amorphous Ni–P/Ni(OH)₂ heterostructure nanotubes by immersing Zn@Ni–P nanowires grown by axial screw dislocation in alkaline solution. When used as an HER catalyst, the Ni–P/Ni(OH)₂ nanotubes achieve considerably high electrocatalytic activity and decent stability. The significantly low overpotential of 54.7 mV at a current density of 10 mA cm⁻² is among the best values reported for transition metal phosphides in alkaline solution. Density functional theory calculations indicate that the abundant defect structures of amorphous Ni–P would shift the Ni 3d band center toward the Fermi level, demonstrating an energy barrier decrease for H₂ generation. Furthermore, the synergistic effect of amorphous Ni–P and Ni(OH)₂ could significantly enhance H₂O dissociation to supply sufficient protons for the HER.