Fabrication of three-dimensional nanoporous nickel films with tunable nanoporosity and their excellent electrocatalytic activities for hydrogen evolution reaction

Three-dimensional (3D) nanoporous nickel films were fabricated by a novel and facile method. The fabrication process involved the heat treatment of the electrodeposited zinc layer on nickel substrate and the subsequent electrochemical dealloying. The mutual diffusion of Ni and Zn during the heat treatment resulted in the formation of the Ni₂Zn₁₁ alloy surface film. The 3D nanoporous nickel films with open pores and interconnected ligaments were obtained by the electrochemical dealloying of relatively active zinc from the alloy surface film. As the electrodeposited zinc amount increased, the thickness, pore diameter and pore density of the nanoporous nickel films became larger. In our experimental range, the thickest nanoporous nickel film presented a thickness of 8 μm and an average pore diameter of 700 nm. The as-prepared 3D nanoporous nickel films exhibited much higher electrocatalytic activity for hydrogen evolution reaction (HER) than smooth nickel foil, and their electrocatalytic activities for HER enhanced with increase in the porosity and thickness. It was concluded that the enhanced electrocatalytic activity and excellent electrochemical stability for HER of the as-prepared 3D nanoporous nickel films can be ascribed to their unique nanostructured characteristics.