Electrochemical promotion of the water–gas shift reaction on Pt/YSZ

The effect of electrochemical promotion of catalysis was investigated for the water–gas shift reaction over porous Pt catalyst electrodes interfaced with 8%mol Yttria-stabilized Zirconia. A fuel cell type electrochemical reactor was used at temperatures from 300 °C to 400 °C, under image ratio values from 2.85 to 31. A negative order dependence of the catalytic reaction rate on PCO and a positive one on image was found under open-circuit and polarization conditions. Positive potential application (+2.5 V), i.e., O2− supply to the catalyst surface, causes a small decrease in the catalytic reaction rate, while negative potential application (−1.5 V) results in a pronounced rate increase, up to 200%, with apparent faradaic efficiency values up to 110. The rate increase obtained with negative polarization can be attributed to the weakening of the Pt–CO bond strength but also, to the increase in surface concentration of oxygen ion vacancies near the Pt-gas-support three-phase boundaries necessary for water dissociation.