In situ electrochemical AFM imaging of Pt electrode in sulfuric acid under potential cycling conditions

Abstract

Understanding the electrochemical behavior of Pt at the solid/liquid interface is of significant importance for the development of efficient electrochemical devices, such as fuel cells and water electrolyzers. In this work, the evolution of the surface morphology of a polycrystalline platinum under potential cycling condition was investigated by in situ electrochemical atomic force microscopy (EC-AFM). After 50 cycles between 0.05-1.8 V in 0.1 M H2SO4, the Pt surface is coarsened and nanoparticles of several nanometers appear on the surface. The critical upper and lower potential for the formation of nanoparticles are found to be 1.8 and 0.8 V, respectively. The in situ AFM observation coupled with CV reveals the periodic disappearance and reappearance of the nanoparticles, based on which the formation of nanoparticles is attributed to the deposition of dissolved Pt from solution, and a model for the nanoparticle formation is proposed. While the formation of a thick oxide layer is a prerequisite, the reduction process is found to have a strong influence on Pt nanoparticles formation as well. This investigation provides a visualization of the Pt electrode surface under electrochemical control in a large potential window, enabling a broader understanding of the Pt electrode roughening mechanisms.