Highly efficient Cu/CeO2-hollow nanospheres catalyst for the reverse water-gas shift reaction: Investigation on the role of oxygen vacancies through in situ UV-Raman and DRIFTS
“…After the formation of formate species as intermediate, the reaction with the dissociated hydrogen leads to carbon monoxide and water as products. Therefore, in contrast to the redox mechanism, CO is derived from the association of CO 2 with H 2 [110][111][112][113] . Even though CO 2 hydrogenation over nickel-supported catalysts have been extensively studied, there is not yet a broad consensus regarding the reaction mechanism.…”
Section: Oxidation States In the Near-surface Regionmentioning
Adding Cu to Ni/Al2O3 is an excellent strategy to suppress methane formation and enhance carbon monoxide yield through formation of alloyed nanoparticles.
“…After the formation of formate species as intermediate, the reaction with the dissociated hydrogen leads to carbon monoxide and water as products. Therefore, in contrast to the redox mechanism, CO is derived from the association of CO 2 with H 2 [110][111][112][113] . Even though CO 2 hydrogenation over nickel-supported catalysts have been extensively studied, there is not yet a broad consensus regarding the reaction mechanism.…”
Section: Oxidation States In the Near-surface Regionmentioning
Adding Cu to Ni/Al2O3 is an excellent strategy to suppress methane formation and enhance carbon monoxide yield through formation of alloyed nanoparticles.
“…[5] At present, there are many researches on catalysts for RWGS reaction, which can be roughly divided into supported catalysts and mixed oxide catalysts. Supported catalysts are mainly Cubased, [6] Pt-based [7] and Rh-based, [8] and usually have good CO 2 conversion rate. However, these catalysts bear with one of more shortcomings such as high prices, small amount of by-product methane, high CO 2 conversion only under high ratio of H 2 / CO 2 , [9] Methanation and Sabatier reaction may occur during the reaction.…”
The conversion of CO 2 into other C1 raw materials is considered to be the best way to solve the greenhouse effect and energy crisis. Reverse water gas shift (RWGS) reaction is the best way to obtain high value-added product raw material syngas and its reactor can be realized in any heavy carbon industry. Here, a series of Ga 2 O 3 Ă CeO 2 composite oxide catalysts with different ratios of Ga 2 O 3 and CeO 2 were developed by gel sol-gel method. Compared with pure Ga 2 O 3 , CeO 2 , the composite oxides catalysts have smaller grains and exhibit excellent selectivity of CO in RWGS reaction. It was found that Ga 2 O 3 has different reaction intermediates compared with CeO 2 and Ga 2 O 3 Ă CeO 2 , so it is easy to produce methane under high H 2 conditions, while CeO 2 is beneficial to improve the selectivity of CO. Therefore, Ga 2 O 3 Ă CeO 2 has the potential to serve as a new and highly selective catalyst for reverse water gas shift reaction.
“…The symmetric breathing mode near 450 cm â1 is nearly independent of the cation mass because only the O atoms move 82 â . According to previous publications, Cu/CeO 2 -hollow nanospheres obtained by a hydrothermal method also depicted the F 2g mode close to 458 cm â1 , while another mode about 590 cm â1 was assigned to defect-induced (DI) mode 83 â , bounded with oxygen vacancies owing to the existence of Ce 3+ . Figure 6 Raman spectra of the hybrid structures and the MCC.…”
This study reports the synthesis of hybrid nanostructures composed of cerium dioxide and microcrystalline cellulose prepared by the microwave-assisted hydrothermal route under distinct temperature and pH values. Their structural, morphological and spectroscopic behaviors were investigated by X-Rays Diffraction, Field Emission Gun Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, and Fourier-Transform Infrared, UltravioletâVisible, Raman and Positron Annihilation Lifetime spectroscopies to evaluate the presence of structural defects and their correlation with the underlying mechanism regarding the biocide activity of the studied material. The samples showed mean crystallite sizes around 10Â nm, characterizing the formation of quantum dots unevenly distributed along the cellulose surface with a certain agglomeration degree. The samples presented the characteristic CeâO vibration close to 450Â cmâ1 and a second-order mode around 1050Â cmâ1, which is indicative of distribution of localized energetic levels originated from defective species, essential in the scavenging of reactive oxygen species. Positron spectroscopic studies showed first and second lifetime components ranging between 202â223Â ps and 360â373Â ps, respectively, revealing the presence of two distinct defective oxygen species, in addition to an increment in the concentration of Ce3+-oxygen vacancy associates as a function of temperature. Therefore, we have successfully synthesized hybrid nanoceria structures with potential multifunctional therapeutic properties to be further evaluated against the COVID-19.
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