(295d) Surface Sensitive Measurement Techniques for Enhanced Understanding of Electrocatalytic Processes

Electrocatalytic processes will play a vital role in energy storage and electrified chemical manufacturing, which are necessary components of a decarbonized economy. Optimization of these reactions requires fundamental understanding of surface kinetics under applied potentials. To date, it has been challenging to extract this information, due to many intertwined chemical and physical phenomena occurring near the electrode-electrolyte interface in aqueous electrocatalytic environments. Here, I present two examples of surface-sensitive measurement techniques that target these near-surface processes to enhance understanding of intrinsic catalytic chemistry. First, chip-interfaced electrochemical mass spectrometry combined with surface enhanced Raman spectroscopy via SHINERS enabled discovery of a surface-hydride phase formation on Cu(111) under potentials relevant for electrocatalytic CO₂ reduction and other hydrogenation reactions. This active site could impact intermediate binding energies to affect overall mechanistic pathways. Second, pH-sensing rotating ring disk electrodes (RRDEs) enabled measurement of reaction-induced local pH changes on an electrode surface during CO₂ reduction and hydrogen evolution reactions. The RRDE was modeled with reaction-convection-diffusion equations to reveal up to an 8 pH unit shift in the local environment for unbuffered electrolyte, contrasting with almost no measured pH change in bicarbonate buffered electrolyte at the same current densities. These presented surface sensitive techniques are applicable to a variety of electrocatalytic processes, which should help decouple the near-surface phenomena in electrocatalytic processes that are crucial for a decarbonized future.