In Situ Investigation of Oxygen Bubble Evolution at Photoanode Surface Affected by Reaction Temperature

A significant challenge associated with photoelectrochemicalwatersplitting is the reduction of the anode photocurrent due to bubbleadhesion. To achieve in situ observation of bubble evolution on theelectrode surface, an electrochemistry system coupled with a high-speedcamera was developed. The relations between photocurrent curves andbubble morphology were clarified on a fixed TiO2 thin-filmelectrode at various reaction temperatures (303.15-343.15 K).The photocurrent during the nucleation waiting, growth, and detachmentof bubble evolution increased approximately linearly with the reactiontemperature, indicating a higher reaction rate and a reduction inthe impedance that must be overcome during bubble growth. The shortenednucleation waiting period was illustrated via a homogeneous nucleationmodel. The study found that the required concentration of dissolvedgas for bubble nucleation decreased with an increasing reaction temperature.The bubble oscillations (& SIM;25 Hz) under high reaction temperaturespromoted the bubble mass transfer from the perspective of gas evolutionefficiency. Besides, a force balance model was established based onthe experimental data of bubbles. Because of the decrease of solutalMarangoni force with the increase of reaction temperature, the bubblegrowth periods were shortened, along with the relatively large bubbledetachment diameter, thereby efficiently accelerating bubble removalfrom the electrode surface.