Comparative study of the electrochemical promotion of CO2 hydrogenation on Ru using Na+, K+, H+ and O2 − conducting solid electrolytes

Abstract

The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2− conducting solid electrolyte supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing pH2 and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing pH2 and decreases with increasing pCO2. These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD)>0 and (∂r/∂Φ)(∂r/∂pA)<0, where r denotes a catalytic rate, Φ is the catalyst work function and pDandpA denote the electron donor and electron acceptor reactant partial pressures respectively.