Uranium oxide-supported gold catalyst for water–gas shift reaction

• Au/UO3 has both micro- and meso-porous structures and Au/U3O8 has only a microporous structure.
• Gold can enhance the reducibility of UO3 and U3O8.
• Au/UO3 has higher surface gold atomic concentration than Au/U3O8.
• Au/UO3 shows better water–gas shift reaction activity than Au/U3O8.

The orange yellow UO3 and bottle green U3O8 phases were prepared by thermal decomposition of uranyl nitrate hexahydrate at 400 °C and 500 °C, respectively. Gold catalysts supported on two oxides were prepared by incipient wetness impregnation for water–gas shift reaction. The gold catalysts were characterized by the techniques such as nitrogen physical adsorption, X-ray diffraction, temperature-programmed reduction, and X-ray photoelectron spectroscopy. The Au/UO3 catalyst has both microporous and mesoporous structures while the Au/U3O8 catalyst has only microporous structure. The presence of gold on the oxide surface greatly facilitates the reduction of uranium oxide support. The active sites for water–gas shift reaction are likely dominant metallic gold with a small portion of oxidized gold species due to UO2 +/U4 + redox property. The Au/UO3 catalyst shows higher activity with 55% conversion of CO in comparison with Au/U3O8. High activity on Au/UO3 catalyst is attributed to facile the reducibility of UO3 and its high surface gold atomic concentration.