Adsorption of Methane at Platinum Electrodes Under Potentiodynamic Control at Ambient Conditions, and Characterization of Adsorbed Intermediates Via ATR-FTIR Spectroscopy

Abstract

Electrochemical oxidation of methane is a promising route towards the direct production of high value oxygenates such as methanol, formaldehyde, and formic acid. Compared to traditional catalytic processes such as methane steam reforming and Fischer-Tropsch reactions that operate at high temperatures and pressures, electrochemical oxidation of methane has the benefit of operating at ambient temperatures and pressures. However, there are still many challenges associated with electrochemical methane oxidation including catalyst activity and selectivity. Previous work has established platinum as one of the few catalysts able to oxidize methane to CO2 at room temperature and pressure. By applying a constant potential within the capacitance region of platinum in methane saturated aqueous electrolytes an ad layer can be built up on the platinum surface. The adsorbed intermediates can then be stripped from the platinum surface by sweeping to more anodic potentials. In this work, the aforementioned electrochemical methods are coupled with in-situ infrared spectroscopy to identify reaction intermediates and determine their dependence on applied potential, pH, and time. Improving our understanding of the mechanism of methane oxidation on platinum is necessary for the design of more active and selective catalysts. With better catalysts, fuel cell technologies could allow for the utilization of stranded natural gas for the production of electricity and oxygenates.