Solvent effects on formation of Cr-doped Ce0.2Zr0.8O2 synthesized with cinnamic acid and their catalysis in oxidation of NO

• We prepared Cr-doped Ce0.2Zr0.8O2 with cinnamic acid as the precipitant in four solvents.
• The catalysts are in small particle sizes with nonuniform dopant concentration.
• Most of Ce and Cr are enriched on the surface while ethylene glycol was adopted as solvent.
• These catalysts show good catalytic performance.

Cr-doped Ce0.2Zr0.8O2 was synthesized with cinnamic acid as ligand, and four different solvents (H2O, ethanol, ethylene glycol and isopropanol) were added into the precursor solution to contrast with each other. These catalysts were investigated in detail by means of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, High resolution transmission electron microscope (HR-TEM), Ultra violet–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS) and NO(O2) Temperature-programmed desorption (NO(O2)-TPD). The results indicated that the preparation process adopted with one-step method simplified the experimental procedure, decreased the size of particle and increased the specific surface area of the catalysts. Moreover, the solvent with appropriate polarity could decrease the band gap of the catalysts and benefit for more generation of Ce3+ and Cr6+ on the surface of the catalyst, which was beneficial for the adsorption of NO and O2. All catalysts showed broad activity temperature window and the catalyst adopted with ethylene glycol as solvent exhibited the highest NO conversion, which achieved 66.32% at 350 °C.

The research studied the solvent effects on the formation of Cr-doped ceria–zirconia solid solution (Cr/Ce0.2Zr0.8O2), and solvent with the appropriate polarity benefited for Cr6+ and Ce3+ enriched on the surface of the catalyst. Then NO was adsorbed on the site of Cr6+, and O2 was adsorbed on the site Ce3+. Finally, the adsorbed NO interacted with the adsorbed O2 to generate NO.Figure optionsDownload as PowerPoint slide