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Bubbles evolving from electrode surface are the results of the multi-processes, interfacial mass transfer, chemical reaction, micro fluid flow, etc. In this paper, the investigations on the bubble growth mechanism during photoelectrochemical and electrochemical conversions are carried out. The experimental results show two different growth laws during photoelectrochemical and electrochemical conversions, which are chemical reaction and diffusion controlled respectively, caused by the difference in the effective surface area of the electrode. And mathematical models for bubble growth describing the two effects are established. [ABSTRACT FROM AUTHOR]

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]

This paper presents a study on single bubble photogenerated by 376 nm laser light at TiO 2 nanorod-array electrode during photoelectrochemical (PEC) conversion. The surface properties of TiO 2 nanorod-array electrode were investigated at first for a better understanding of the three-phase contact line behavior. The results indicate the light-induced hydrophilic effect of TiO 2 nanorod-array electrode under illumination, which makes bubble tend to be pseudo-sphere shape during attaching on electrode. The experimental investigation on photogenerated bubble at TiO 2 nanorod-array electrode shows that there is a linear relationship between cubic root of time and bubble radius, demonstrating the gas products from the surface reaction transferring into bubble through bubble bottom according to the analysis of the relative size between bubble and effective solid surface. Furthermore, the coupling effects between bubble and irradiance were discussed. The bubble scatter effect on light causes a local light intensity increase at electrode surface area on both sides of bubble, and leads to photocurrent increase especially at small bubble size. While the increase of irradiance causes the parameters of bubble evolution period, dissolved gas concentration for nucleation and departure diameter increase, but leads to bubble evolution rate and incident photon conversion efficiency (IPCE) decrease. These results suggest a lower irradiance is preferred for a higher PEC conversion efficiency from the aspects of IPCE and bubble evolution rate. [ABSTRACT FROM AUTHOR]