Praseodymia-titania mixed oxide supported gold as efficient water gas shift catalyst: modulated by the mixing ratio of oxides

Weixuan Zhao; Junjie Shi; Mingyue Lin; Libo Sun; Huijuan Su; Xun Sun; Toru Murayama; Caixia Qi

doi:10.1039/d1ra08572g

Praseodymia-titania mixed oxide supported gold as efficient water gas shift catalyst: modulated by the mixing ratio of oxides

RSC Adv. 2022 Feb 14;12(9):5374-5385. doi: 10.1039/d1ra08572g. eCollection 2022 Feb 10.

Authors

Weixuan Zhao¹, Junjie Shi^{1

2}, Mingyue Lin^{3

4}, Libo Sun¹, Huijuan Su¹, Xun Sun¹, Toru Murayama^{1

5

6}, Caixia Qi¹

Affiliations

¹ Shandong Applied Research Centre of Gold Nanotechnology, School of Chemistry & Chemical Engineering, Yantai University Yantai 264005 China qicx@ytu.edu.cn junjieshiding@gmail.com.
² Department of Chemical Engineering, University of Florida Gainesville Florida 32611 USA.
³ Shanghai Environmental Protection Key Laboratory on Environmental Standard and Risk Management of Chemical Pollutants, East China University of Science and Technology Shanghai 200237 China.
⁴ State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, School of Resources and Environmental Engineering, East China University of Science and Technology Shanghai China.
⁵ Research Center for Gold Chemistry, Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University 192-0397 Tokyo Japan.
⁶ Research Center for Hydrogen Energy-based Society, Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University Tokyo 192-0397 Japan.

Abstract

Modulating the active sites for controllable tuning of the catalytic activity has been the goal of much research, however, this remains challenging. The O vacancy is well known as an active site in reducible oxides. To modify the activity of O vacancies in praseodymia, we synthesized a series of praseodymia-titania mixed oxides. Varying the Pr : Ti mole ratio (2 : 1, 1 : 2, 1 : 1, 1 : 4) allows us to control the electronic interactions between Au, Pr and Ti cations and the local chemical environment of the O vacancies. These effects have been studied study by X-ray photoelectron spectroscopy (XPS), CO diffuse reflectance Fourier transform infrared spectroscopy (CO-DRIFTS) and temperature-programmed reduction (CO-TPR, H₂-TPR). The water gas shift reaction (WGSR) was used as a benchmark reaction to test the catalytic performance of different praseodymia-titania supported Au. Among them, Au/Pr₁Ti₂O _x was identified to exhibit the highest activity, with a CO conversion of 75% at 300 °C, which is about 3.7 times that of Au/TiO₂ and Au/PrO _x . The Au/Pr₁Ti₂O _x also exhibited excellent stability, with the conversion after 40 h time-on-stream at 300 °C still being 67%. An optimal ratio of Pr content (Pr : Ti 1 : 2) is necessary for improving the surface oxygen mobility and oxygen exchange capability, a higher Pr content leads to more O vacancies, however with lower activity. This study presents a new route for modulating the active defect sites in mixed oxides which could also be extended to other heterogeneous catalysis systems.