Electrochemical Promotion of the low temperature water-gas shift reaction on Pt/YSZ

S. SOUENTIE; L. LIZARRAGA; A. KAMBOLIS; J.L. VALVERDE; P. VERNOUX

Glasgow

Congreso; EuropaCat X; 2011

The electrochemical promotion [1] of the water-gas shift (WGS) reaction for H2 production [2] was investigated in a Pt/YSZ/Pt fuel-cell type electrocatalytic reactor [1] at temperatures from 300ºC to 400ºC. Figure 1 shows the steady-state effect of CO P on the CO2 formation catalytic rate and CO conversion for constant H O P 2, under open-circuit state and polarization conditions at 350ºC. As shown, a slightly negative order dependence of the rate on the CO P was found under open circuit conditions, where the conversion of CO decreases from 43% at 0.1 kPa CO to 10% at 0.37 kPa CO. Positive polarization (+2.5V), i.e. Oδ- species were supplied to the catalyst surface, caused a small decrease of the catalytic rate. On the contrary, negative polarization (-1.5V) resulted in a pronounced increase of the rate; higher at high H O CO P / P 2 ratios, where the CO conversion approached the thermodynamic equilibrium value (~98%). The rate enhancement upon negative polarization was up to 200%, while the apparent Faradaic efficiency was up to 60, establishing the high energy efficiency of the process. The increase of the rate upon negative polarization was partially attributed to the reduction of the YSZ surface and formation of active sites for water activation and dissociation [3,4], which is a Faradaic process, but also to the weakening of the Pt-CO bond strength due to Oδ- ions pumping from the catalyst surface and the concomitant decrease on Pt work function [1]. The results are promising and show the strong potential of electropromoted reactors for practical application of electrochemical promotion of catalysis effect on H2 production via the WGS reaction.