Hydrogen bubble evolution and gas transport mechanism on a microelectrode determined by cathodic potential and temperature

Abstract

Enhancing the efficiency of hydrogen production by optimizing gas product transfer within water electrolysis systems is essential. Employing high-speed photography and electrochemical techniques, the entire process of single hydrogen bubble evolution on a Pt microelectrode surface was measured. Results reveal a notable reduction in both bubble detachment radius and growth time with decreasing absolute potential (from −7 to −3 V) and increasing reaction temperature (from 30 °C to 50 °C). Additionally, a comprehensive model estimating bubble coverage on the microelectrode is presented, incorporating bubble radius and current as key influencing factors. This enables an accurate evaluation of mass transfer coefficients during bubble evolution in the absence of forced flow. Furthermore, findings reveal the dominance of bubble-induced micro-convection as the primary mass-transfer mechanism for gas products at high current densities [O (105–106 A/m2)]. The results also indicate that the mass transfer coefficient increases during the inertia-controlled growth stage of bubbles and decreases during the stage controlled by chemical reactions.