Kinetics of hydrogen evolution reaction on skeleton nickel and nickel–titanium electrodes obtained by thermal arc spraying technique

Thermal arc spraying technique was used to prepare electroactive coatings on steel substrate. A combination of two different wires has been used: Ni and Al, respectively, NiTi and Al. After deposition the coatings were treated with alkaline solution at 80∘C to leach out the aluminum. High surface area skeleton Ni and NiTi electrodes were obtained. The hydrogen evolution reaction (HER) was studied in 1 M NaOH solution by steady-state polarization and electrochemical impedance spectroscopy (EIS). The kinetic parameters were determined for the prepared electrodes. It was found that the increased activity for the HER is due to an increased real surface area in case of the skeleton Ni electrodes and to the catalytic effect of Ti in case of the skeleton NiTi electrodes. The temperature influence on the HER was investigated and the electrochemical activation energy was determined for the skeleton NiTi electrodes. EIS measurements performed in 1 M NaOH solution at different overpotentials indicated that at high overpotential a fraction of the inner surface of the skeleton electrodes is blocked by hydrogen bubbles. The rate constants of the forward and backward reactions were evaluated by a nonlinear fitting procedure. It has been found that the main pathway for the HER is Volmer–Heyrovsky.