Cerium-bismuth solid solution material prepared and application in automobile exhaust purification

Effect of modified CeO2 on the performance of PdCu/Ce1-xTixO2 catalyst for methanol purification

In this paper, we prepared a series of Ce_1-xTi_xO₂ (x = 0-0.20) nanorods by hydrothermal method, which were used to construct the PdCu/Ce_1-xTi_xO₂ catalysts. The Ce_1-xTi_xO₂ and PdCu/Ce_1-xTi_xO₂ samples were characterized by transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), etc. Catalytic activity, stability, and repeatability of the catalysts for methanol oxidation were investigated. The results show that doping a proper amount of titanium could strengthen the interaction between Ce_1-xTi_xO₂ support and PdCu nanoalloy, thus increasing the oxygen vacancy concentration and promoting Pd species with a higher oxidation state. These modified properties are beneficial for the deep oxidation of methanol. The light-off temperature (T₅₀) and full-conversion temperature (T₉₀) of methanol over the PdCu/CeO₂ catalyst are 108 °C and 159 °C, respectively. The greatest activity improvement is found for PdCu/Ce_0.9Ti_0.1O₂, which shows the lowest T₅₀ of 88 °C and T₉₀ of 138 °C. Furthermore, neither PdCu/CeO₂ nor the modified PdCu/CeO₂ catalyst produces by-products and exhibit excellent stability and repeatability throughout the whole test period. This study provides a reference for in-depth understanding and designing of efficient and stable CeO₂-based oxidation catalysts.

Photocatalytic purification of vehicle exhaust using CeO2-Bi2O3 loaded on white carbon and tourmaline

Photocatalysts are environmentally friendly materials that can be used to degrade vehicle exhaust. CeO₂-Bi₂O₃ loaded on white carbon and tourmaline, as the favorable absorption materials, was prepared respectively for vehicle exhaust photocatalytic purification. Brunauer-Emmett-Teller (BET) adsorption isotherm, scanning electron microscope (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) were applied to characterize the composite materials. The optimum contents of the loading materials were obtained from the comparison of purification efficiency of vehicle exhaust components after a 60-min photocatalytic reaction under visible and ultraviolet (UV) irradiation, including hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO₂), and nitrogen oxides (NO_x). The results show that the proposed preparation method could improve particle dispersion and distribution uniformity, reduce particle agglomeration, and increase specific surface area. The optical response range of the CeO₂-Bi₂O₃ with loading materials can be extended from UV light to visible light. CeO₂-Bi₂O₃ loaded on tourmaline show excellent photocatalytic purification effect under visible light. The purification efficiency of CeO₂-Bi₂O₃ loaded on tourmaline for HC, CO, CO₂, and NO_x were 30.8%, 30.6%, 35.3%, and 47.6%, respectively. Moreover, the concentrations of vehicle exhaust components decrease with time, which is well fitted by the Langmuir-Hinshelwood pseudo-first-order kinetics model, and the purification rate constant of CeO₂-Bi₂O₃ composites under visible light is greater than that under UV light. The prepared photocatalytic materials also exhibit the excellent reusability.

g-C3N4/CeO2 Binary Composite Prepared and Its Application in Automobile Exhaust Degradation

Vehicle exhaust seriously pollutes urban air and harms human health. Photocatalytic technology can effectively degrade automobile exhaust. This work prepared g-C₃N₄/CeO₂ photocatalytic material by constructing heterojunctions. Four kinds of g-C₃N₄/CeO₂ composite photocatalytic materials with different mass ratios were prepared. An indoor exhaust gas purification test was carried out under natural light and ultraviolet light irradiations. The optimum mass ratio of g-C₃N₄ material and CeO₂ material was determined by evaluating the exhaust gas degradation effective. Moreover, the structure and morphology of the g-C₃N₄/CeO₂ composite were investigated with microscopic characterization experiments (including XRD, TG-DSC, FT-IR, UV-Vis, SEM and XPS). The results obtained were that the optimum mass ratio of g-C₃N₄ material to CeO₂ material was 0.75. The degradation efficiencies under ultraviolet irradiation in 60 min for HC, CO, CO₂, NO_X were 7.59%, 12.10%, 8.25% and 36.82%, respectively. Under visible light conditions, the degradation efficiency in 60 min for HC, CO, CO₂ and NO_X were 15.88%, 16.22%, 10.45% and 40.58%, respectively. This work is useful for purifying automobile exhaust in the future.