Optimizing Hydrogen Adsorption and Promoting Hydroxyl Transfer Using Ru-Loaded, Ni-Encapsulated Carbon Nanotubes to Boost Alkaline Hydrogen Evolution.

Abstract

The hydrogen evolution reaction (HER) under alkaline conditions exhibits significant potential for industrial hydrogen production. However, effectively coordinating the multistep processes in alkaline solutions, including water dissociation, hydroxyl desorption, and hydrogen generation, remains a critical challenge. This work develops a three-dimensional nanocomposite electrocatalyst composed of in situ-grown carbon nanotubes (CNTs), nickel nanoparticles encapsulated within them, and ruthenium nanoclusters on the surface. The catalyst synergistically facilitates water dissociation, hydroxyl transfer, and hydrogen adsorption, thereby achieving an ultralow overpotential (9.2 mV at 10 mA cm^-2) for alkaline HER. Density functional theory reveals that CNTs facilitate electron transfer with minimal charge transfer resistance, while Ni nanoparticles within CNTs not only optimize the hydrogen adsorption of Ru but also facilitate the transformation of adsorbed hydroxyl (OH_ad) to OH^-. These factors collectively facilitated the OH_ad + e^- ⇌ OH^- process, improving the kinetics of the HER. A solar-panel-powered electrolyzer equipped with this composite electrode achieves a low cell voltage of 1.41 V. This research provides valuable insights on designing Ru-based catalysts in practical alkaline HER applications.