(623b) Using Operando Mass Spectrometry to Study Room Temperature C-H Bond Activation of Propane on Pt Electrocatalyst in Aqueous Acidic Electrolyte.

C-H bond activation is an important step in order to enable processes, such as alkane to alcohol conversion and alkane dehydrogenation, that produce industrially relevant products from readily available light alkane feedstock. However, high-temperature processes, typically utilized for such endothermic activations, are energy-intensive and ultimately lead to a large carbon footprint. Therefore, there is a need to enable C-H activation at lower temperatures, and an electrochemical pathway, powered by renewable energy, is a promising alternative. An electrocatalyst can utilize potential as a driving force to initialize the reactivity of light alkanes via activating a C-H bond. Electrochemically, Pt has shown activity towards functionalizing alkanes, although producing an undesired byproduct, CO₂, with high faradaic efficiency. Furthermore, little is known about the adsorption mechanism, identity of adsorbate species, and potential conditions suitable for enabling selective oxidation to valuable intermediates.

Our work uses Electrochemical Mass Spectrometry to elucidate the potential dependence of propane activation on Pt electrocatalyst. Potentiodynamic profiles enable quantification of charge involved in the proposed faradaic pathway while mass spectrum analysis reveals the identity and quantity of gas-phase species produced. We found that propane adsorption on Pt is potential dependent where it reaches a maximum coverage at an adsorption potential of 0.3 VvsRHE. An oxidative charge transience is observed when propane is introduced to the cell, which is consistent with a dissociative chemisorption mechanism – via a C-H bond activation. Additionally, the identity of propane-derived adsorbate species was determined via a combination of coulometry and mass spectrometry to quantify the extent of dehydrogenation of C₃^* adsorbates. These results show that propane-derived adsorbate species can be further oxidized or reduced by varying the potential at the electrocatalyst surface. Our findings can be directly applied to tune electrocatalysts to selectively activate paraffinic C-H bond at room temperature, aqueous conditions, for decarbonized chemical manufacturing.