Speakers
Description
The structure of interfacial hydration layers plays a crucial role in energy and chemical conversion processes, impacting the kinetics of electrocatalytic reactions such as CO2 electroreduction (CO2RR) and hydrogen evolution (HER). We reveal the intricate interplay between carbon and proton sources within the microenvironment of bicarbonate electrolytes and highlight the inherent impact of the local interfacial water structure on the competing mechanisms of CO2RR and HER on gold electrocatalysts, by combining in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) with online differential electrochemical mass spectrometry (DEMS). We discover carbonate anion radicals (CO3•–) during CO2RR, acting as a carbon source for the formation of aldehyde species in addition to CO. At high cathodic potentials, HER is accelerated by rapid proton delivery from ordered interfacial hydration networks induced by carbonate molecules. Our molecular-level findings indicate water as the primary proton donor for CO2RR and the Volmer step of HER. These findings hold significance for rationally optimizing electrified solid-liquid interfaces and electrocatalysts. To interrogate interfacial hydration layer ordering effects, the interfacial viscosity of a KClO4 aqueous electrolyte can be probed by in situ friction force measurements, employing atomic force microscopy (AFM). We observe a decrease in the friction coefficient with increasing electrolyte concentration over the concentration range up to 25 mM, while adhesion force variations are found to be negligible. Qualitatively, this lubrication effect can be rationalized by accounting for the mildly chaotropic effect of K+ ions. For imaging of spatial variations in electrocatalytic activity across solid-electrolyte interfaces, an advanced scanning electrochemical microscope is being developed, involving electrically conductive AFM microcantilevers with an insulating and passivating top coating made by plasma vapour deposition of inorganic materials.
