(123d) Probing the Electrocatalytic Surface for Ambient Electrochemical Oxidation of Methane over Cuti Bimetallic Catalyst

CH₄ is a major source of energy being the main component of natural gas. It is also a valuable feedstock for various petrochemicals, plastics, and pharmaceuticals. The discovery of shale gas reservoirs in recent times has led to the development of efficient CH₄ utilization processes, however, since CH₄ is a symmetric and stable molecule, all the industrially relevant processes using CH₄ as a feedstock predominantly use energy-intensive thermocatalytic routes to produce oxygenated chemicals. Therefore, investigating electrocatalytic routes to utilize CH₄ is particularly attractive because of its high control over product selectivity, high reaction rates, and relatively milder operating conditions to help circumvent thermocatalytic problems like high-temperature requirements and periodic sintering/poisoning of catalysts. To synthesize low overpotential, highly efficient electrocatalysts, it is important to study the interaction between the catalytic sites and methane and a preferred reaction pathway on the catalyst for methane oxidation electrocatalyst. Moreover, due to the low solubility of CH₄ in aqueous electrochemical systems, methane oxidation reaction (MOR) is mass transfer limited and is dominated by the competing oxygen evolution reaction (OER). In the present work, we show a systematic study to tackle these challenges. To enhance the mass transfer of CH₄, a gas diffusion electrode (GDE) of a CuTi bimetallic catalyst is fabricated. In-situ ATR-SEIRAS is done to understand the propagation of MOR by observing the adsorption of intermediate species on the catalyst surface to gain mechanistic insight into the reaction pathway. The electrochemical study is done in a compact CH4-sparged GDE and a well-mixed-electrolyte H-cell using a 3-electrode setup with Pt as the counter, Ag/AgCl as the reference, and CuTi as the working electrode. The MOR products are determined by GC and HPLC and the product distribution, partial current densities, and Faradaic efficiencies over catalysts are also shown as a part of this work.