Tailoring Nickel Porous Structure via Dynamic Hydrogen Bubble Template for Efficient Alkaline Hydrogen Evolution.

Abstract

Nanoporous nickel (Ni_np) films were synthesized via a dynamic hydrogen bubble template (DHBT) to be applied as a catalyst for the hydrogen evolution reaction (HER) in alkaline media. This research highlights the critical role of deposition parameters in controlling the structure, morphology, and catalytic activity of Ni_np. Ti and Ni were employed as substrates to promote hydrogen bubble evolution and the nucleation and growth of homogeneous Ni_np. The influence of deposition current density (0.5-2.0 A cm^-2) and duration (50-300 s) on the morphology, electrochemical performance, and mechanical stability of the Ni_np were systematically investigated. Scanning electron microscopy (SEM) revealed that higher current densities and longer deposition times promoted pore nucleation and growth, resulting in a homogeneous Ni_np network with a cauliflower-like morphology. Electrochemical characterizations showed that electrodes prepared at 2.0 A cm^-2 for 300 s exhibited the lowest overpotentials (158 ± 13.3 mV on Ti and 180 ± 37.1 mV on Ni substrates) and maintained stable current densities over 24 h of chronoamperometric testing. Electrochemical impedance spectroscopy highlighted the influence of the substrate and deposition parameters on charge transfer resistance and electrode roughness. Density functional theory calculations indicated that interstitial oxygen in the Ti substrate induces charge depletion on the surface Ti atoms, enhancing hydrogen adsorption. This work demonstrates that DHBT method offers an efficient approach for developing high-performance nanoporous Ni as electrocatalysts toward sustainable hydrogen production.