Nickel nanoparticles and superstructures: a chemical approach for optimized catalyst’s surfaces

Nickel-based nanostructures are widely investigated as cost-effective alternatives to precious metal catalysts for hydrogen evolution reaction (HER) in alkaline electrolysis. However, controlling the growth of nickel nanoparticles (NiNPs) on conductive substrates remains a challenge for optimizing their catalytic performance. In this study, we explored the controlled growth of NiNPs on two distinct substrates: 316L stainless steel plated with nickel and 316L stainless steel coated with graphene oxide (GO). The NiNPs synthesis involved a simple chemical approach that entailed immersing the substrate plates in a solution containing nickel nitrate, sodium citrate, and sodium borohydride as a reducing agent. Various experimental parameters were examined, including variations in the concentration of Ni2⁺ ions, sequential NiNPs deposition on the surface, and temperature adjustments. Scanning electron microscopy (SEM) images revealed significant differences in the distribution and size of NiNPs. The NiWatts-coated substrate (Ni-SS) exhibited a higher nanoparticle coverage (72 ± 5% surface coverage) and more uniform distribution, while the GO-coated substrate (GO-Ni-SS) presented larger (average diameter: 85 ± 10 nm vs. 45 ± 8 nm for Ni-SS) and more widely dispersed nanoparticles. Preliminary alkaline electrolysis experiments demonstrated that both substrates exhibit excellent electrocatalytic activity for the hydrogen evolution reaction, with Ni-SS achieving a lower overpotential of − 270 ± 5 mV at 10 mA cm⁻2 compared to − 310 ± 7 mV for GO-Ni-SS.