Probing Dynamic Proton Flux in Nanoscale Electrochemical Cells

This talk presents most recent progress on challenge-to-characterize proton flux in dynamic light-driven materials and chemical environments. Our lab studies a class of catalytic nanomaterials called photocatalysts. The surfaces of these materials are distributed with nanoscale electrochemical cells featuring coupled photophysical, photochemical and transport processes during light-driven catalysis. We discovered an emerging phenomenon that arises from coupling photocatalytic reaction pairs with proton transport near photocatalyst reaction environment. Despite the <0.1 mM concentration of local CO2(aq), we discovered this molecular flux catalysis based on the CO2(aq) flux, replacing the saturated CO2(aq) that would conventionally be needed to facilitate CO2 reduction. We systematically quantify the contribution of H+ flux and H+ concentrations to CO2-reduction catalysis by developing in situ analytical spectroscopic techniques including fluorescent pH and Raman spectroscopy in fluid flow, and then employ multi-physics digital-twin modeling. One impact is directly utilizing dissolved carbon to make sustainable fuels, chemicals, and materials from seawater or captured carbon from the air. Importantly, we achieved light-driven selective CO2 reduction by valorizing a 2-millimolar dissolved carbon, without continuous CO2-gas purging. To summarize, we combine protective coatings and photocatalyst design to advance such flux-based cascade electrochemistry.