Abstract
A series of ceria-zirconia solid solutions were synthesized using tobacco leaves, stems and stem-silks as biotemplates. A combination of physicochemical techniques such as powder X-ray diffraction (XRD), N2 adsorption/desorption measurement, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the as-synthesized samples. The results show that the morphologies of the templates were well replicated in the obtained ceria-zirconia solid solutions. Catalytic oxidation activities of CO over the ceria-zirconia solid solutions were then investigated. The catalyst templated by tobacco stem-silk exhibited higher conversion of CO at lower temperature than that of ceria-zirconia solid solutions templated by tobacco leaves and stems or without templates due to its special morphology. The catalyst even showed similar CO conversion when compared to ceria-zirconia solid solutions doped with 1.0 wt % noble metals such as Pt, Ag and Au. The results highlighted the advantages of using tobacco as biotemplate.
Highlights
Catalytic oxidation of CO at low temperature is becoming increasingly important recently due to its significance in pollution control for automobile exhausts and many industrial processes [1,2].Cerium oxide, which is an important and less expensive rare earth oxide, has been widely investigated for applications to reduce the emissions of CO, NOx, and hydrocarbons from automobile exhausts [3,4,5].pure ceria is not very usable because of its relatively low oxygen storage capacity (OSC)and poor thermal stability [6]
The X-ray diffraction (XRD) patterns of the samples prepared with different Ce/(Ce + Zr) molar ratio are shown in Nitrogen adsorption/desorption isotherms for the prepared ceria-zirconia solid solutions with different Ce/(Ce + Zr) molar ratios are shown in Figures S1–S4, respectively
The morphologies of the templates were well replicated in the ceria-zirconia solid solutions exactly
Summary
Catalytic oxidation of CO at low temperature is becoming increasingly important recently due to its significance in pollution control for automobile exhausts and many industrial processes [1,2].Cerium oxide, which is an important and less expensive rare earth oxide, has been widely investigated for applications to reduce the emissions of CO, NOx , and hydrocarbons from automobile exhausts [3,4,5].pure ceria is not very usable because of its relatively low oxygen storage capacity (OSC)and poor thermal stability [6]. Cerium oxide, which is an important and less expensive rare earth oxide, has been widely investigated for applications to reduce the emissions of CO, NOx , and hydrocarbons from automobile exhausts [3,4,5]. Pure ceria is not very usable because of its relatively low oxygen storage capacity (OSC). To enhance the redox properties and thermal stability of pure ceria, zirconia (ZrO2 ) is often mixed as an additive to form solid solutions of the Ce1−x Zrx O2 type (x ≤ 0.5). CeO2 -ZrO2 mixed compound, which act as an oxygen storage component to maintain the air to fuel ratio close to stoichiometric is present in the washcoat deposited on either a ceramic or metallic monolith [7,8]. A number of methods have been developed for the syntheses of Ce1−x Zrx O2 solid solution including solid-state synthesis [9], high-energy milling [10], hydro/solvothermal synthesis [11,12], co-precipitation [13,14], the citrate method [15], inverse
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