Electrochemical promotion of the CO2 hydrogenation reaction using thin Rh, Pt and Cu films in a monolithic reactor at atmospheric pressure

A monolithic electropromoted reactor(MEPR) with up to 22 thin Rh/YSZ/Pt or Cu/TiO2/YSZ/Au plate cells was used to investigate the hydrogenation of CO2 at atmospheric pressure and temperatures 220-380 degrees C. The Rh/YSZ/Pt cells lead to CO and CH4 formation and the open-circuit selectivity to CH4 is less than 5%. Both positive and negative applied potentials enhance significantly the total hydrogenation rate but the selectivity to CH4 remains below 12%. The Cu/TiO2/YSZ/Au cells produce CO, CH4 and C2H4 with selectivities to CH4 and C2H4 up to 80% and 2%. Both positive and negative applied potential significantly enhance the hydrogenation rate and the selectivity to C2H4. It was found that the addition of small (similar to 0.5 kPa) amounts of CH3OH in the feed has a pronounced promotional effect on the reaction rate and selectivity of the Cu/TiO2/YSZ/Au cells. The selective reduction of CO2 to CH4 starts at 220 degrees C (vs 320 degrees C in absence of CH3OH) with near 100% CH4 selectivity at open-circuit and under polarization conditions at temperatures 220-380 degrees C. The results show the possibility of direct CO2 conversion to useful products in a MEPR via electrochemical promotion at atmospheric pressure. (C) 2009 Elsevier B.V. All rights reserved.