In situ studies of the solid-liquid interface of model catalysts for alternative oxidation reactions to the oxygen evolution reaction

Over the past few years, we have developed expertise in various micro-electrochemical cells to obtain chemical information from solid-liquid electrified interfaces. However, the oxygen evolution reaction (OER) continues to be a significant challenge in producing hydrogen via water electrolysis with minimal environmental impact. Replacing the OER with alternative oxidation reactions (AORs) of small molecules that are thermodynamically more favorable and have lower oxidation is a hot topic. Using these cells, we propose to investigate the interface chemistry of transition metal electrocatalyst nanoparticles (NPs) during OER and AORs (e.g., Urea and Methanol Oxidation). Although metals like Ni, Co, and Fe are efficient OER/AOR catalysts, detailed molecular-level insights are still lacking. We must understand factors such as the chemical state, hydroxyl coverage, and water molecule orientation near the electrocatalyst surface to address problems such as the slow kinetics and deactivation mechanisms. Our experiments will use carbonate/bicarbonate buffer solutions and will be conducted under constant-potential and slow linear anodic sweep conditions. We will analyze the Co, Fe, and Ni 2p regions with AP-XPS and their L2,3 edges with NEXAFS spectroscopy to determine chemical states. We will use the O1s region and O K-edge to assess hydroxyl, oxide, and water coverage. Photon energies will be set for a kinetic energy of around 500 eV, and photon flux will be reduced to minimize beam damage. The CIRCE beamline is well-suited for these measurements, offering TEY NEXAFS spectroscopy with the same setup used for AP-XPS and allowing better signal-to-noise ratios with emission current measurements compared to drain current measurements.
By using these reactor cells, we aim to provide a more complete picture of the underlying reaction mechanisms than has ever been available before.