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18. Reverse oxygen spillover triggered by CO adsorption on Sn-doped Pt/TiO2 for low-temperature CO oxidation.

Author

Chen, Jianjun, Xiong, Shangchao, Liu, Haiyan, Shi, Jianqiang, Mi, Jinxing, Liu, Hao, Gong, Zhengjun, Oliviero, Laetitia, Maugé, Françoise, and Li, Junhua

Subjects
X-ray photoelectron spectroscopy, OXYGEN reduction, ADSORPTION (Chemistry), MOLECULAR dynamics, SCISSION (Chemistry), OXIDATION-reduction reaction
Abstract

The spillover of oxygen species is fundamentally important in redox reactions, but the spillover mechanism has been less understood compared to that of hydrogen spillover. Herein Sn is doped into TiO2 to activate low-temperature (<100 °C) reverse oxygen spillover in Pt/TiO2 catalyst, leading to CO oxidation activity much higher than that of most oxide-supported Pt catalysts. A combination of near-ambient-pressure X-ray photoelectron spectroscopy, in situ Raman/Infrared spectroscopies, and ab initio molecular dynamics simulations reveal that the reverse oxygen spillover is triggered by CO adsorption at Pt2+ sites, followed by bond cleavage of Ti-O-Sn moieties nearby and the appearance of Pt4+ species. The O in the catalytically indispensable Pt-O species is energetically more favourable to be originated from Ti-O-Sn. This work clearly depicts the interfacial chemistry of reverse oxygen spillover that is triggered by CO adsorption, and the understanding is helpful for the design of platinum/titania catalysts suitable for reactions of various reactants. Reverse O spillover has opened new opportunities in improving the catalytic activity and selectivity in various reactions. Herein Sn is doped into TiO2 to activate low-temperature (<100 °C) reverse oxygen spillover in Pt/TiO2 catalyst, leading to enhanced CO oxidation activity. [ABSTRACT FROM AUTHOR]

Published
2023
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24. In Situ Modulation of A‐Site Vacancies in LaMnO3.15 Perovskite for Surface Lattice Oxygen Activation and Boosted Redox Reactions

Author

Liu, Xiaoqing, primary, Mi, Jinxing, additional, Shi, Lin, additional, Liu, Haiyan, additional, Liu, Jun, additional, Ding, Yun, additional, Shi, Jianqiang, additional, He, Minghua, additional, Wang, Zisha, additional, Xiong, Shangchao, additional, Zhang, Qinfang, additional, Liu, Yuefeng, additional, Wu, Zhong‐Shuai, additional, Chen, Jianjun, additional, and Li, Junhua, additional

Published
2021
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32. In Situ Modulation of A‐Site Vacancies in LaMnO3.15 Perovskite for Surface Lattice Oxygen Activation and Boosted Redox Reactions.

Author

Liu, Xiaoqing, Mi, Jinxing, Shi, Lin, Liu, Haiyan, Liu, Jun, Ding, Yun, Shi, Jianqiang, He, Minghua, Wang, Zisha, Xiong, Shangchao, Zhang, Qinfang, Liu, Yuefeng, Wu, Zhong‐Shuai, Chen, Jianjun, and Li, Junhua

Subjects
OXIDATION-reduction reaction, STANDARD hydrogen electrode, OXYGEN reduction, PEROVSKITE, OXYGEN, CITRATES
Abstract

Modulation of A‐site defects is crucial to the redox reactions on ABO3 perovskites for both clean air application and electrochemical energy storage. Herein we report a scalable one‐pot strategy for in situ regulation of La vacancies (VLa) in LaMnO3.15 by simply introducing urea in the traditional citrate process, and further reveal the fundamental relationship between VLa creation and surface lattice oxygen (Olatt) activation. The underlying mechanism is shortened Mn−O bonds, decreased orbital ordering, promoted MnO6 bending vibration and weakened Jahn–Teller distortion, ultimately realizing enhanced Mn‐3d and O‐2p orbital hybridization. The LaMnO3.15 with optimized VLa exhibits order of magnitude increase in toluene oxidation and ca. 0.05 V versus RHE (reversible hydrogen electrode) increase of half‐wave potential in oxygen reduction reaction (ORR). The reported strategy can benefit the development of novel defect‐meditated perovskites in both heterocatalysis and electrocatalysis. [ABSTRACT FROM AUTHOR]

Published
2021
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33. Structure-Directing Role of Support on Hg0Oxidation over V2O5/TiO2Catalyst Revealed for NOxand Hg0Simultaneous Control in an SCR Reactor

Author

Shi, Jianqiang, Chen, Jianjun, Xiong, Shangchao, Mi, Jinxing, Liu, Hao, Wang, Zhen, Liu, Haiyan, Wang, Jiancheng, and Li, Junhua

Abstract

The crystal structure of TiO2strongly influences the physiochemical properties of supported active sites and thus the catalytic performance of the as-synthesized catalyst. Herein, we synthesized TiO2with different crystal forms (R = rutile, A = anatase, and B = brookite), which were used as supports to prepare vanadium-based catalysts for Hg0oxidation. The Hg0oxidation efficiency over V2O5/TiO2-B was the best, followed by V2O5/TiO2-A and V2O5/TiO2-R. Further experimental and theoretical results indicate that gaseous Hg0reacts with surface-active chlorine species produced by the adsorbed HCl and the reaction orders of Hg0oxidation over V2O5/TiO2catalyst with respect to HCl and Hg0concentration were approximately 0 and 1, respectively. The excellent Hg0oxidation efficiency over V2O5/TiO2-B can be attributed to lower redox temperature, larger HCl adsorption capacity, and more oxygen vacancies. This work suggests that to achieve the best simultaneous removal of NOxand Hg0on state-of-the-art V2O5/TiO2catalyst, a combination of anatase and brookite TiO2-supported vanadyl tandem catalysts is supposed to be employed in the SCR reactor, and the brookite-type catalyst should be on the downstream of the anatase-based catalyst due to the inhibition of NH3on Hg0oxidation.

Published
2022
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37. Penetration of Arsenic and Deactivation of a Honeycomb V2O5–WO3/TiO2Catalyst in a Glass Furnace

Author

Chen, Gongda, Xiong, Shangchao, Chen, Xiaoping, Chu, Xuefeng, Yin, Rongqiang, Liu, Changdong, Chen, Jianjun, and Li, Junhua

Abstract

Deactivation of honeycomb V2O5–WO3/TiO2catalysts by arsenic has been studied widely in coal-fired power plants but rarely in glass furnaces. In this paper, deactivated catalysts that had been used for more than 4000 h were analyzed. We maintained the catalysts in their original monolith shape to retain their adhered substance and used appropriate methods to strip the substance layer by layer. With various characterization techniques, it was determined that the adhered substance was composed almost entirely of Na2SO4and CaSO4. We also quantified the penetration depth of arsenic visually, which was more than 370 μm. A three-stage penetration and deactivation process induced by arsenic was proposed. It was pointed out that molten and volatile As2O3played a key role in the deactivation process, while substances in the solid state had little impact on the deep bulk of the catalyst. In this study, we proposed an integrated deactivation process consisting of adhesion, penetration, and deactivation in a honeycomb V2O5–WO3/TiO2catalyst by arsenic in a glass furnace. Finally, we also provided guidance on alleviating the deactivation caused by arsenic. The key is to convert molten and volatile As2O3to solid-state substances before it contacts the catalyst.

Published
2021
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46. Roles of Oxygen Vacancies in the Bulk and Surface of CeO2for Toluene Catalytic Combustion

Author

Su, Ziang, Yang, Wenhao, Wang, Chizhong, Xiong, Shangchao, Cao, Xingzhong, Peng, Yue, Si, Wenzhe, Weng, Yibin, Xue, Ming, and Li, Junhua

Abstract

Catalytic combustion technology is one of the effective methods to remove VOCs such as toluene from industrial emissions. The decomposition of an aromatic ring via catalyst oxygen vacancies is usually the rate-determining step of toluene oxidation into CO2. Series of CeO2probe models were synthesized with different ratios of surface-to-bulk oxygen vacancies. Besides the devotion of the surface vacancies, a part of the bulk vacancies promotes the redox property of CeO2in toluene catalytic combustion: surface vacancies tend to adsorb and activate gaseous O2to form adsorbed oxygen species, whereas bulk vacancies improve the mobility and activity of lattice oxygen species via their transmission effect. Adsorbed oxygen mainly participates in the chemical adsorption and partial oxidation of toluene (mostly to phenolate). With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improves the oxidation of toluene to CO2.

Published
2020
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49. H3PW12O40Grafted on CeO2: A High-Performance Catalyst for the Selective Catalytic Reduction of NOxwith NH3

Author

Geng, Yang, Xiong, Shangchao, Li, Bo, Liao, Yong, Xiao, Xin, and Yang, Shijian

Abstract

CeO2showed a poor selective catalytic reduction (SCR) activity due to its poor ability to adsorb NH3. To improve the SCR performance of CeO2, tungstophosphoric acid (i.e., HPW, H3PW12O40) with a high acidic strength was grafted on CeO2by the adsorption of HPW on CeO2in a HPW solution. The grafting of HPW on the surface of CeO2was demonstrated with characterizations by XPS, XRF, TG-DSC, and in situ DRIFT spectra. As HPW on HPW/CeO2-500 still retained the Keggin structure, HPW/CeO2-500 exhibited an excellent ability for NH3adsorption. Both HPW and CeO2on/in HPW/CeO2-500 played their functions to the greatest limit for the SCR reaction. CeO2in HPW/CeO2-500 played the role in the activation of adsorbed NH3and NO, and the grafted HPW on HPW/CeO2-500 acted as the active sites for NH3adsorption. Therefore, HPW/CeO2-500 showed a superior SCR performance at 200–450 °C and an excellent H2O/SO2resistance above 300 °C.

Published
2024
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