Single bubble dynamics on a TiO2 photoelectrode surface during photoelectrochemical water splitting

The bubble evolution on the photoelectrode surface in photoelectrochemical water splitting can change the mass transfer of gaseous products and induce additional resistance. In this paper, the growth and nucleation of a single oxygen bubble over a titanium dioxide (TiO2) nanorod-array electrode was investigated. The results indicate that the resistance decreases significantly due to the decrease of dissolved gas concentration at the beginning of bubble growth period. Because the effect of electrolyte constriction offsets the concentration-lowering effect, the resistance is almost constant in the later stage of bubble growth. The increase of light intensity leads to longer bubble waiting time and growth time, larger bubble diameter and smaller contact angle. Moreover, the bubble nucleation frequency increases due to the improved reaction rates at higher potential. A force balance model is constructed to predict the bubble departure diameter. It is found that the forces preventing the bubble departure from the photoelectrode surface are mainly surface tension and Marangoni force, which account for 82% and 18%, respectively.

Automated summary

This paper investigates the evolution of bubbles on the photoelectrode surface and their impact on mass transfer and resistance in photoelectrochemical water splitting. It is found that the resistance decreases significantly at the beginning of bubble growth, but remains almost constant in the later stages. Bubble diameter and contact angle are influenced by light intensity, while bubble nucleation frequency is affected by reaction rates. A force balance model predicts that surface tension and Marangoni force are the main forces preventing bubble departure from the electrode surface.