Boosting the water gas shift reaction on Pt/CeO2-based nanocatalysts by compositional modification: Support doping versus bimetallic alloying

Abstract

The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells. The influence of support doping and bimetallic alloying on the catalytic performance of Pt/CeO2-based nanocatalysts in water gas shift reaction was reported in this work. Various lanthanide ions and 3d transition metals were respectively introduced into the CeO2 support or Pt to form Pt/CeO2:Ln (Ln = La, Nd, Gd, Tb, Yb) and PtM/CeO2 (M = Fe, Co, Ni) nanocatalysts. The sample of Pt/CeO2:Tb showed the highest activity (TOF at 200 °C = 0.051 s−1) among the Pt/CeO2:Ln and the undoped Pt/CeO2 catalysts. Besides, the sample of PtFe/CeO2 exhibited the highest activity (TOF at 200 °C = 0.12 s−1) among PtM/CeO2 catalysts. The results of the multiple characterizations indicated that the catalytic activity of Pt/CeO2:Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria support. However, the different activity of PtM/CeO2 bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on ceria. The study of the reaction pathway indicated that both the samples of Pt/CeO2 and Pt/CeO2:Tb catalyzed the reaction through the formate pathway, and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water dissociation. As for the sample of PtFe/CeO2, its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.