Propane Activation on Pt Electrodes at Room Temperature: Quantification of Adsorbate Identity and Coverage.

C-H bond activation is the first step in manufacturing chemical products from readily available light alkane feedstock and typically proceeds via carbon-intensive thermal processes. The ongoing emphasis on decarbonization via electrification motivates low-temperature electrochemical alternatives that could lead to sustainable chemicals production. Platinum (Pt) electrocatalysts have shown activity towards reacting alkanes; however, little is known about propane electrocatalytic activation and conditions suitable for enabling selective oxidation to valuable products. Herein, we utilize a combination of electrochemical mass spectrometry (ECMS) and density functional theory (DFT) calculations to elucidate the potential dependence of propane activation on Pt electrocatalysts. Results show a strong dependence of adsorption on the applied potential in room-temperature aqueous acidic electrolyte, with a maximum coverage of propane-derived adsorbates at 0.30 V vs RHE. Using charge deconvolution and deuterated experiments, the mechanism of adsorption was elucidated, and C3H2* was determined as the average dehydrogenated propane-derived adsorbate species. DFT calculations further corroborate these results, showing that the formation of deeply dehydrogenated species is energetically accessible at room temperature. The combined theoretical and experimental findings yield insights for selective activation of paraffinic C-H bonds at room temperature, aqueous conditions - a critical step towards decarbonized chemical manufacturing.