Kinetics study of H₂ bubble evolution in photocatalytic H₂ generation on Ni₂P/CdS nanorods

Photocatalytic splitting of water for hydrogen (H₂) evolution under visible light renders an ideal route for the conversion and storage of solar energy. Understanding the dynamics of H₂ bubbles' formation, growth, and detachment during the H₂ evolution reaction (HER) is crucial for the development of the technology. To this end, the evolution process of three typical-sized H₂ bubbles in photocatalytic HER on Ni₂P-decorated CdS nanorods was studied. The results demonstrated that cage-like cells in the catalyst were conducive to the formation of long strip bubbles, which had smaller detachment diameters and faster evolution frequencies. The wake of bubbles’ detachment and the coalescence significantly enhanced the growth and detachment rate of long strip bubbles. The rapid detachment of bubbles releases more active sites, promoting the nucleation of new H₂ bubbles. The growth of long strip bubbles was controlled by diffusion, surface renewal, and surface chemical reaction. The result suggests that the construction of cage-like cells through the deposition or assembly of primary particles with specific morphologies, like nanorods, will contribute to the generation of H₂ bubbles. We believe that this work will provide useful insights for the understanding of H₂ production and the development of highly efficient photocatalysts for HER.