Session: Advances in Electrochemistry:

Phase transition is long-lasting topic in the research of physical chemistry. Gas bubble nucleation can be is an excellent prototype for studying the mechanism of nucleation behavior. Traditional experimental investigations of nucleation behavior involves the detection of changes in temperature, optical properties or hydrodynamic behavior, which are typically associated with numeral assemble rather than individual nucleation event. In this study, we reported the study of gas nanobubble nucleation at single event using the stat of the art scanning probe microscopy-scanning electrochemical cell microscopy (SECCM). Local gas supersaturation is facilitated by electrochemical current from gas precursors and single nucleation behavior is detected by the ultrasensitive electrochemical current based mass transport. Distribution of gas supersaturation on the electrode is obtained from the electrochemical mapping of bubble nucleation on electrode surface. More importantly, extra electrochemically inert seed (SiO₂ nanospheres) with variable dimensions are introduced to manipulate the heterogeneous nucleation process. We observed a dependence of gas supersaturation (free energy barrier) for nucleation on the nuclei size and remarkably, a minimum of supersaturation is found at a diameter of 10 nm. We speculated that such critical size of SiO₂ seed is in the same dimension with nanobubble nucleation critical nuclei and this argument is supported by theoretical calculations based on the free energy change from classic nucleation theory. Our work demonstrate excellent agreement between the experimental and theoretical prediction from single nucleation event and this measurement strategy will find many application in other crystalline nucleation study.

Xiaoxi Lu

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