P. Grutter
McGill University,
Canada
Keywords: electrocatalysis, hydrogen evolution reaction, bubbles, force noise
Summary:
Understanding electron transfer kinetics in electrocatalytic reactions at the molecular level is paramount as these are bottlenecks in creating sustainable energy technologies. Electrochemical processes are complex at the heterogeneous catalytic interface, and understanding molecular-level details remains challenging. Ideally, one would like to measure spatially resolved electrochemical activity and correlate it with atomic scale structure. Here for the first time, we employ Atomic Force Micorscopy to investigate the force fluctuations at the gas-evolving Platinum ultramicroelectrode (UME) during hydrogen evolution reaction. We detect excess force noise when individual bubble detachments are observed from the Pt UME. The excess noise varies linearly with potential and steady-state current on semi-log and log-log plots, respectively. Force noise spectra reveal that H2 bubbles oscillate with 200 Hz frequency at the interface during the bubble growth and detachment. Further, the frequency of the bubble detachment events between Force and current fluctuations is 1-10 Hz within -0.3 to -0.6 V vs RHE. From force fluctuations, we evaluated the H2 gas bubble radius and the thickness of the thin layer of bubble carpet present adjacent to Pt UME. Our report shows an alternative method to probe the gas-evolving interface with high sensitivity. By imaging bubble-forming nucleation sites at the electrochemical surfaces our method could be extended to probe complex nanoscale dynamics at reaction processes at catalytic interfaces.