Wenqing Xu , Yixi Wang , Hong He , Jun Yang , Yang Yang , Jinzhu Ma , Chaoqun Li , Tingyu Zhu
{"title":"Insight into hydroxyl groups in anchoring Ir single–atoms on vacancy–deficient rutile TiO2 supports for selective catalytic oxidation of ammonia","authors":"Wenqing Xu , Yixi Wang , Hong He , Jun Yang , Yang Yang , Jinzhu Ma , Chaoqun Li , Tingyu Zhu","doi":"10.1016/j.apcatb.2023.123684","DOIUrl":null,"url":null,"abstract":"<div><p>High–performance catalysts are extremely required for controlling NH<sub>3</sub><span> emission via selective catalytic oxidation (SCO), and the anchoring structural feature of active sites is a key prerequisite for developing them. This study confirms the importance of hydroxyl groups on vacancy–deficient reducible oxides as active groups. On the one hand, spontaneous atomic dispersion of active metal Ir is promoted by the abundant terminal hydroxyl groups. On the other hand, Ir cations anchor on the TiO</span><sub>2</sub> surface through exchange with H<sup>+</sup> in Ti–OH groups, and thus occupy the Brönsted acid sites. The adsorption strength of NH<sub>3</sub> is another key factor affecting the reaction rate–determining step, namely NH<sub>3</sub><span> dehydrogenation, which occurs at a faster rate in the coordinated L–NH</span><sub>3</sub> rather than the ionic B–NH<sub>4</sub><sup>+</sup>. Meanwhile, the coordinated L–NH<sub>3</sub> significantly avoids the competitive adsorption of water vapor in the NH<sub>3</sub>–SCO reaction by reducing the number of hydrogen bonding. The TOF of preferred 0.8Ir/TiO<sub>2</sub> sample is significantly higher than 0.2Ir/TiO<sub>2</sub> sample, although Ir is almost always atomic dispersed. Finally, NH<sub>3</sub> conversion is 85% in a wet circumstance (5% H<sub>2</sub>O) at 240 °C (GHSV = 85 000 h<sup>–1</sup>), with a N<sub>2</sub> selectivity of up to 65% on 0.8Ir/TiO<sub>2</sub> sample.</p></div>","PeriodicalId":244,"journal":{"name":"Applied Catalysis B: Environmental","volume":"345 ","pages":"Article 123684"},"PeriodicalIF":20.2000,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied Catalysis B: Environmental","FirstCategoryId":"1","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0926337323013279","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
High–performance catalysts are extremely required for controlling NH3 emission via selective catalytic oxidation (SCO), and the anchoring structural feature of active sites is a key prerequisite for developing them. This study confirms the importance of hydroxyl groups on vacancy–deficient reducible oxides as active groups. On the one hand, spontaneous atomic dispersion of active metal Ir is promoted by the abundant terminal hydroxyl groups. On the other hand, Ir cations anchor on the TiO2 surface through exchange with H+ in Ti–OH groups, and thus occupy the Brönsted acid sites. The adsorption strength of NH3 is another key factor affecting the reaction rate–determining step, namely NH3 dehydrogenation, which occurs at a faster rate in the coordinated L–NH3 rather than the ionic B–NH4+. Meanwhile, the coordinated L–NH3 significantly avoids the competitive adsorption of water vapor in the NH3–SCO reaction by reducing the number of hydrogen bonding. The TOF of preferred 0.8Ir/TiO2 sample is significantly higher than 0.2Ir/TiO2 sample, although Ir is almost always atomic dispersed. Finally, NH3 conversion is 85% in a wet circumstance (5% H2O) at 240 °C (GHSV = 85 000 h–1), with a N2 selectivity of up to 65% on 0.8Ir/TiO2 sample.
期刊介绍:
Applied Catalysis B: Environment and Energy (formerly Applied Catalysis B: Environmental) is a journal that focuses on the transition towards cleaner and more sustainable energy sources. The journal's publications cover a wide range of topics, including:
1.Catalytic elimination of environmental pollutants such as nitrogen oxides, carbon monoxide, sulfur compounds, chlorinated and other organic compounds, and soot emitted from stationary or mobile sources.
2.Basic understanding of catalysts used in environmental pollution abatement, particularly in industrial processes.
3.All aspects of preparation, characterization, activation, deactivation, and regeneration of novel and commercially applicable environmental catalysts.
4.New catalytic routes and processes for the production of clean energy, such as hydrogen generation via catalytic fuel processing, and new catalysts and electrocatalysts for fuel cells.
5.Catalytic reactions that convert wastes into useful products.
6.Clean manufacturing techniques that replace toxic chemicals with environmentally friendly catalysts.
7.Scientific aspects of photocatalytic processes and a basic understanding of photocatalysts as applied to environmental problems.
8.New catalytic combustion technologies and catalysts.
9.New catalytic non-enzymatic transformations of biomass components.
The journal is abstracted and indexed in API Abstracts, Research Alert, Chemical Abstracts, Web of Science, Theoretical Chemical Engineering Abstracts, Engineering, Technology & Applied Sciences, and others.