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

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 S_BET, 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.