Electrochemical promotion and characterization of PdZn alloy catalysts with K and Na ionic conductors for pure gaseous CO2 hydrogenation

Abstract

A PdZn alloy has been used for the first time as a catalytic electrochemical film for CO2 hydrogenation. Three different electrochemical systems were prepared to study the influence of the Pd/Zn ratio and the presence of potassium and sodium ions. These catalysts were characterized by XRD, SEM and cyclic voltammetry and then tested in the hydrogenation of CO2 at three different H2/CO2 feed ratios (3, 9 and 39) and three temperatures (300, 320 and 340°C) with electrochemical promotion by Na+ and K+ ions. CH3OH and CO were the only two products detected. During the electrochemical promotion, a low quantity of ions increases the formation rate of CH3OH and a high quantity leads to the poisoning of the PdZn active sites. The catalysts which have palladium and the palladium-zinc alloy in their structure show an electrophilic behavior in the CO formation and when only the alloy is formed in the catalyst, the CO has the same behavior found for the methanol. Apparent Faradaic efficiency values above 1000 were obtained under the different conditions tested.