Insight into pH-controlled bubble dynamics on a Pt electrode during electrochemical water splitting

Abstract

Bubbles adhering to the electrode surface are the major factors causing the decreased efficiency of water electrolysis. In this work, the dynamic behaviors of oxygen bubbles on vertical platinum sheet electrodes were investigated by a high-speed camera and their corresponding current densities were measured simultaneously using an electrochemical workstation. The impact of wide range of electrolyte pH values (i.e., 1–13) on both the bubble nucleation number and the dynamics behaviors of bubbles was investigated under different applied voltages. When the applied voltage was increased from 1.6 to 1.7 V vs the saturated calomel electrode, the radius of bubbles upon detachment increased in acidic environments (pH = 1–7) and decreased in alkaline environments (pH = 7–13). In an alkaline environment, the Marangoni force plays an essential role here. Furthermore, the bubble detachment radius predicted by the force balance model is well matched with our experimental results. Our results demonstrate that bubble detachment is not favorable in a strongly acidic environment, whereas oxygen bubbles exhibit rapid detachment from the electrode surface in a strongly alkaline environment.