Pulse electrodeposition of Ni on Ti substrates for hydrogen evolution across acidic, alkaline, and neutral electrolytes

Electrodeposition offers a scalable, low-cost route to nanostructured electrocatalysts, yet the quantitative relationships between deposition parameters, and electrocatalytic function remain poorly established. Here, we report a stepwise optimization of nickel (Ni) electrodeposition onto titanium (Ti) substrates, targeting efficient and durable hydrogen evolution reaction (HER) operable across the full pH range. By independently tuning deposition current density, time, and pulse number, we show that Ni deposition on Ti proceeds via a Volmer-Weber three-dimensional island growth mode and identify a critical transition from nucleation to growth-dominated deposition. Pulsed galvanostatic deposition (8 pulses, − 5 mA cm −2 , 120 s) yields a uniform, nanostructured Ni particles with well-dispersed interparticle voids. The optimized Ni/Ti electrode delivers markedly enhanced HER activity over bare Ti across acidic (0.5 M H 2 SO 4 ), alkaline (1.0 M KOH), and neutral Phosphate Buffered Saline (PBS) media with Tafel slopes of 149 ± 3, 151 ± 4, and 329 ± 18 mV dec −1 . The values in acid and alkali are intermediate and consistent with a Volmer-Heyrovsky mechanism where the Heyrovsky step is partially rate-limiting. The dramatically elevated Tafel slope in PBS reflects multi-step, mass-transport-influenced kinetics where both proton supply and water dissociation contribute to the overall rate limitation. Benchmarked against a commercial Ni mesh, the pulse-deposited electrode (Ni/Ti) performed comparably at − 50 mA cm −2 under acidic HER for 18 h, demonstrating that careful process engineering of earth-abundant metals on corrosion-resistant supports is a viable alternative.