(Invited)The Role of the Catalyst Microenvironment in the Electrochemical Reduction of Carbon Monoxide

Abstract

Carbon monoxide is already an important raw material for the synthesis of different bulk chemicals (e.g., phosgene and different products thereof). Considering that it can be a building block for the synthesis of virtually any organic compound, carbon monoxide might play an important role in the production of synthetic fuels and other typical petrochemical products. This can be performed under high temperature and pressure conditions in the Fischer-Tropsch process, but electrochemical methods also offer a possible way of forming different chemicals from carbon monoxide.Because of the low solubility of carbon monoxide in water, instead of the routinely used H-cells, its reduction must be performed in gas-fed electrolyzer cells, ensuring a short diffusion length for the reactant. However, even in such devices the surface of the catalyst (nano)particles is typically surrounded by a thin water shell under operating conditions, caused by various effects such as electrowetting, or wetting by the formed products. The practical insolubility of carbon monoxide (that is ca. 30 times lower compared to the solubility of CO2) makes it vital to ensure that the thickness of this hydration layer is minimized, hence the reactant can reach the catalysts' surface in gas phase, meanwhile just enough amount of a proton source – water – is in the immediate vicinity.The phase boundary between the catalyst particles, the liquid phase and the gas reactant can be engineered by using functional catalyst layer additives. Here we will demonstrate a commercial pore sealer for this purpose, ensuring the formation of C2+ products in CORR with high selectivity and rate.1 As no specific interaction between the polymer and the CO reactant was found, we assumed that the most important role of this polymer is to increase the hydrophobicity of the catalyst layer. To challenge this theory, various, systematically chosen polymeric materials were tested as catalyst binders to reveal any possible further contribution of certain motifs (e.g., functional groups, fluorinated backbone etc.), present in these polymers. The electrochemical results are contrasted with the detailed characterization of the structure, wetting and gas adsorption properties of the catalyst layer. Reference Kormányos, B. Endrődi, Z. Zhang, A. Samu, L. Mérai, G. F. Samu, L. Janovák, & C. Janáky (2023). EES Catalysis. https://doi.org/10.1039/D3EY00006K