Facile fabrication of an enhanced electrodeposited nickel electrode for alkaline hydrogen evolution reaction

Electrodeposited nickel (Ni) electrode for alkaline hydrogen evolution reaction (HER) has low cost and high stability advantages, but its catalytic performance is unsatisfactory. In this study, a Ni electrode with a pentagonal pyramid microstructure was first fabricated by electrodeposition, and then the surface microstructure and chemical composition of the electrode were elaborately modified by a simple acid etching treatment which significantly enhanced the HER catalytic performance. The HER over-potential at 10 mA cm−2 on the electrode which was etched for 60 min was reduced from 238 mV to 60 mV compared to the un-etched one. The fabricated electrode could maintain stable catalytic stability at a current density of 100 mA cm−2 beyond 360 h. The surface microstructures and chemical compositions of the electrodes were characterized and the catalytic kinetics were investigated by electrochemical methods. The steps on the pentagonal pyramids on the Ni electrode were preferentially dissolved in the etching treatment and the surface became undulating, which efficiently increased the electrochemically active surface area (ECSA). The etching treatment improved the surface wettability and accelerated the hydrogen bubble detachment speed on the electrode. Meanwhile, the electrode surface was further oxidized in the etching treatment. Metallic Ni and crystal NiO were alternately presented on the electrode surface. The generated NiO could facilitate the Volmer step in the HER, which led to the change of the rate-controlling step from the Volmer step to the Heyrovsky step. Further, the synergistic effect between Ni and NiO with a suitable ratio improved the HER catalytic performance of the electrode.