In situ study of the diffusion of hydrogen on TiO2 under the influence of Au during electrolytic reduction of water

Abstract

The behavior of H species on electrocatalysts is important to hydrogen evolution reaction and other H-related catalytic reactions. In this work, the electrolytic reduction of water in alkaline media and the diffusion of hydrogen on TiO₂ and Au supported TiO₂ (Au/TiO₂) were in situ characterized. In contrast to TiO₂ electrode, the Au/TiO₂ electrode showed a notably enhanced reduction current due to the spillover of hydrogen from TiO₂ to Au and subsequent recombination of hydrogen. In situ electrochemistry Raman spectroscopy showed that the produced H species upon water reduction readily diffuses throughout the TiO₂ lattice causing the lattice distortion of TiO₂ on the TiO₂ electrode but not on the Au/TiO₂ electrode. The electrochemical impedance spectroscopy (EIS) investigation revealed the bulk diffusion mechanism for hydrogen diffusion on TiO₂ and surface diffusion mechanism on Au/TiO₂ electrode. This study highlights the critical role of interface and boundary structures in governing hydrogen diffusion behavior at TiO₂ and Au/TiO₂ electrodes and deepens our understanding of the hydrogen behavior in the hydrogen evolution reactions and other hydrogen-related reactions on metal oxide surfaces.