Multiple Bubble Removal Strategies to Promote Oxygen Evolution Reaction: Mechanistic Understandings from Orientation, Rotation, and Sonication Perspectives

Abstract

Bubble coverage of catalytically active sites is one of the well-known bottlenecks to the kinetics of the oxygen evolution reaction (OER). Herein, various bubble removal approaches (electrode orientation, rotating, and sonication) were considered for the OER performance evaluation of a state-of-the-art Ir-based electrocatalyst. Key parameters, such as catalyst mass loss, activity, overpotential, and charge- and mass-transfer mechanisms, were analyzed. First, it was suggested that a suitable orientation of the working electrode facilitates coalescence and sliding bubble effects on the catalyst surface, leading to better electrochemical performance than those of the traditional rotating disk electrode (RDE) configuration. Then, the convection and secondary Bjerknes force were explained as the responsible phenomena in improving the OER activity in the RDE and sonication methods. Finally, simultaneous implementation of the methods enhanced the catalyst mass activity up to 164% and provided fast charge-transfer kinetics and low double-layer capacitance, which eventually led to a 22% reduction in overpotential, while the catalyst loss slightly increased from 1.93 to 3.88%.

Enhanced electrochemical dissolution of iridium oxide in acidic electrolytes through presence of metal ions: shortened lifetime and hope for recovery

“…Further, 2 cycles were recorded at a scan rate of 10 mV s −1 between the specified potential window and the second cycle was shown here. Although no rotation was applied to the WE for removal of the generated gas bubbles, 40 no visible accumulation of bubbles on WE was observed during the CV recording.…”

Bubbles Management for Enhanced Catalytic Water Splitting Performance

“…As the WE direction increases, the mass loss of Ir increases. Changing the WE orientation has a significant impact on OER activity [93]. In addition, the OER activity and Ir loss mechanism of the catalyst can be corrected through rotational speed.…”