Surface alkali promotion of carbon dioxide hydrogenation for conservation of carbon sources: Cyclic voltammetry study

Conversion of CO₂ captured from biogas upgrading process into useful chemicals or fuels e.g. methane is an attractive route towards conservation of carbon sources. Sustainable hydrogenation route could be achieved by combining the process with hydrogen generated from water electrolysis. In this work, cyclic voltammetry was used as preliminary technique to probe the electrochemical behaviour of Na-modified Pt/YSZ as model catalyst under CO2 hydrogenation. The reaction is irreversible and the voltammogram features are not easily distinguishable under reaction conditions. The increase in cathodic peak height and the decrease in peak potential with addition of sodium at low coverage (0.32%) indicated that the charge transfer reaction was enhanced and thus the methanation reaction could be electrochemically promoted given sufficient amount of H2 flow. However, increasing Na coverage was found to decrease the current hysteresis possibly due to formation of sodium compounds such as carbonates or oxides that populate the three-phase-boundary (tpb) active sites, thus deactivating the catalyst.