(617ek) Understanding Gas Evolution Dynamics on Planar Photoelectrodes

Gas bubbles evolved at the surface of an electrode can result in significant loss in efficiency due to increasing surface coverage of the active material by gas bubbles. Therefore, it becomes crucial to comprehensively understand gas evolution dynamics in these systems so that operating conditions may be chosen and electrodes engineered to minimize the corresponding losses in efficiencies. Scanning photocurrent microscopy (SPCM) can be used to determine the change in photocurrent response of an area of interest and provides a powerful tool for quantifying photocurrent losses associated with individual bubbles. In this study, we employ SPCM as a tool for deconvoluting the optical influence of bubbles from their influence on ohmic- and kinetic losses of a photoelectrode surface. As a basis for this work, Si-based photocathodes are studied, and SPCM is used to systematically investigate the influence of varying bubble size on the performance of these photoelectrodes under varied conditions. This study provides much needed insight into the dynamics of gas bubbles on photoelectrode surfaces and sets the stage for quantitatively modeling bubble-related losses for various photoelectrode geometries and operating conditions.