Structure-activity relationship in water-gas shift reaction over gold catalysts supported on Y-doped ceria

Abstract

The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas shift reaction at low temperature. The aim of the present study was to investigate the effect of: (i) different preparation methods (impregnation and coprecipitation) to obtain a modified ceria support, and (ii) the amount of Y2O3 (1.0 wt%, 2.5 wt%, 5.0 wt% and 7.5 wt%) as dopant on the water-gas shift activity of Au/CeO2 catalysts. An extended characterization by means of SBET, XRD, HRTEM/HAADF, FTIR, H2-TPR and CO-TPR measurements in combination with careful evaluation of the catalyst behavior allowed to shed light on the parameters governing the water-gas shift activity. The catalysts show very high activity (>90% CO conversion) in the temperature range 180–220 °C, with a slightly better performance of the gold catalysts on supports prepared by impregnation. The decreased activity with increasing Y2O3 concentration is related to the hindering of oxygen mobility due to ordering of surface oxygen vacancies in vicinity of segregated Y3+. The effect of catalyst pre-treatments and the stability of the best performing samples were examined as well.