Congratulations to Hongfei Dai for his successful PhD defense

On 21 October 2026, M.Sc. Hongfei Dai successfully defended his dissertation entitled "Mass Transfer Mechanisms of Oxygen Bubbles Interacting with Solid Boundaries: An Experimental Investigation Using Advanced Optical Methods".

His research addresses oxygen bubble dynamics in the anode circulation of PEM water electrolysers, where bubble retention and accumulation increase mass transfer resistance and limit operational efficiency. To elucidate the underlying phenomena, Hongfei developed combined optical diagnostic systems integrating planar laser-induced fluorescence (PLIF), shadowgraphy, and micro-particle image velocimetry (µPIV). This approach enabled the simultaneous, high-resolution measurement of dissolved oxygen concentration fields, fluid velocity fields, and bubble morphology for both wall-attached and bouncing bubble regimes.

The results demonstrate that hydrophilic surfaces alleviate oxygen accumulation near the three-phase contact line and facilitate bubble detachment. Furthermore, bubble bouncing accompanied by shape oscillations enhances interfacial mass transfer by approximately 20% compared to classical convection-dominated predictions. Based on these findings, an extended Sherwood number correlation was proposed to account for boundary and oscillation effects. This work provides fundamental insights for optimizing multiphase flow and bubble management in PEM electrolysers.