Visualization of bubble dynamic behaviors during photoelectrochemical water splitting with TiO2 photoelectrode.

Bubble dynamic behaviors from photoelectrochemical water splitting are key issues in the interfacial mass transport on photocatalyst surface. To date, the interaction between gas bubbles and photocatalyst surfaces has received limited attention, especially bubble bouncing behaviors during photoelectrochemical process have rarely been discussed in the literature. In this study, a visualization method by external chopping disturbance was proposed to regulate bubble dynamic behaviors on the TiO 2 photoelectrode surface during photoelectrochemical reaction. Under continuous irradiation, the dominant physics in each bubble growth phase were inertia-controlled, the transition from diffusion-controlled to chemical reaction-controlled and the chemical reaction-controlled. Under rhythmically chopping, the bouncing bubble grew only while in contact with the photoelectrode and its trajectory was approximately to a spiral shape. The proportion of the acceleration stage was very small during the overall rising process, and the bubble rise velocity can be approximately as constant. The main reason for the bubble no longer return is that the rising distance is too far to feel the Marangoni attraction force. • A method to regulate bubble dynamic behaviors by chopping is proposed. • Single bubble evolution is controlled by different dominant physics in each phase. • Bouncing bubbles keep spherical and grow only while in contact with photoelectrode. • The motion trajectory of bouncing bubble is approximately to a spiral shape. • Main reason for no longer return is the bubbles rise too far to feel attraction. [ABSTRACT FROM AUTHOR]