In Situ AFM Imaging of Platinum Electrode Surface during Oxidation–Reduction Cycles in Alkaline Electrolyte

The development of energy conversion systems depends strongly on our fundamental understanding of the electrochemical interface of the electrocatalyst. Here, we study the changes in the surface morphology of a platinum polycrystalline electrode during oxidation–reduction cycles in a wide potential window (0.05–2.0 V) in sodium hydroxide by in situ atomic force microscopy. Platinum nanoparticles are observed on the surface after cycling due to the redeposition of dissolved platinum ions. The influence of scan rate on platinum redeposition is studied by applying asymmetric potential sweep programs. The negative-going scan rate is the key factor here, as it controls the reduction of platinum oxide, as well as the redeposition of platinum. Moreover, it is found that chloride ions in the electrolyte impede the redeposition by complexing with platinum. This investigation enables us to reveal the surface roughening processes on platinum electrode in alkaline electrolyte and assists in understanding the fundamentals of the stability of platinum-containing energy conversion systems.