Natural gas (~96% methane) is flared at remote oil and gas extraction facilities lacking the infrastructure to store gaseous fuel. Selective partial oxidation to liquid methanol would yield a storable fuel source and chemical feedstock. In contrast to conventional industrial processes for this conversion, electrochemical processes can be carried out at ambient conditions and are modular enabling their implementation at remote oil and gas extraction facilities. Studies in the literature have incorporated oxide supports to enhance the activity of the electrochemical oxidation of methane in sulphate- and carbonate-containing electrolytes, however missing is an understanding of the role such supports play in methane activation and conversion. Studies have shown that the Lewis and Brönsted acid sites on the surface of zirconia enable adsorption of carbonate, which we predict is essential for carbonate activation and subsequent methane oxidation. Here, we investigate CuO on a number of oxide supports for methane electrooxidation in carbonate media, detecting methanol online via rotating ring disk electrode measurements. We observe that the acidity of the support influences both total oxidation current and selectivity toward methanol, which we hypothesize is related to the ability to stabilize adsorbed carbonate species from the electrolyte. These findings will facilitate the incorporation of oxide supports to stabilize adsorbates, increasing the activity and tailoring the selectivity of a given electrocatalyst.

Electrochemical oxidation of methane to methanol: Effect of acidity of the support on methane activation

ACS Spring 2022

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