{"title":"Reversed Charge Transfer Enables Dual Active Sites on Ir/hBN for Synergistic N2O Valorization and Propane Selective Oxidation","authors":"Yunshuo Wu, Yuxin Sun, Xuanhao Wu, Haiqiang Wang, Zhongbiao Wu","doi":"10.1021/acscatal.4c03697","DOIUrl":null,"url":null,"abstract":"Valorization of nitrous oxide (N<sub>2</sub>O) as a mild oxygen source for light alkanes presents a promising and economical method for mitigating global warming. However, activating N<sub>2</sub>O and alkane together often leads to overoxidation and poor selectivity of the products. To disentangle the trade-off between activity and selectivity, herein, an Ir-based hexagonal boron nitride (hBN) catalyst was synthesized to obtain a reversed charge transfer (RCT) from the support to metal centers, forming dual active sites on Ir clusters and the separation of redox centers, as determined via operando near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and density functional theory (DFT) calculations. Ir/hBN demonstrated a high N<sub>2</sub>O conversion (99.5%) and syngas yield (95.9 mol of CO kg<sub>cat</sub><sup>–1</sup> h<sup>–1</sup> and 41.9 mol of H<sub>2</sub> kg<sub>cat</sub><sup>–1</sup> h<sup>–1</sup>) during the selective oxidation of propane (C<sub>3</sub>H<sub>8</sub>) at 450 °C. The electron-rich Ir interfacial perimeter sites (Ir<sup>δ−</sup>) enhance N<sub>2</sub>O adsorption and N–O bond dissociation to produce active O*; however, facial metallic Ir<sup>0</sup> sites effectively facilitate C<sub>3</sub>H<sub>8</sub> activation, including dehydrogenation and cracking. The separation of H* and O* intermediates, along with the frustrated H*/O* spillover, effectively facilitates the formation of H<sub>2</sub>. The *CH<sub>2</sub> intermediate from C<sub>3</sub>H<sub>8</sub> breakage migrates and reacts with O* bound to Ir interfacial sites, where it is oxidized to CO<sub>3</sub><sup>2–</sup> and subsequently liberates CO. This study provides mechanistic insights into the O element valorization from N<sub>2</sub>O with synergetic enhancement in selective oxidation of light alkanes.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":11.3000,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"ACS Catalysis ","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/acscatal.4c03697","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
Valorization of nitrous oxide (N2O) as a mild oxygen source for light alkanes presents a promising and economical method for mitigating global warming. However, activating N2O and alkane together often leads to overoxidation and poor selectivity of the products. To disentangle the trade-off between activity and selectivity, herein, an Ir-based hexagonal boron nitride (hBN) catalyst was synthesized to obtain a reversed charge transfer (RCT) from the support to metal centers, forming dual active sites on Ir clusters and the separation of redox centers, as determined via operando near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and density functional theory (DFT) calculations. Ir/hBN demonstrated a high N2O conversion (99.5%) and syngas yield (95.9 mol of CO kgcat–1 h–1 and 41.9 mol of H2 kgcat–1 h–1) during the selective oxidation of propane (C3H8) at 450 °C. The electron-rich Ir interfacial perimeter sites (Irδ−) enhance N2O adsorption and N–O bond dissociation to produce active O*; however, facial metallic Ir0 sites effectively facilitate C3H8 activation, including dehydrogenation and cracking. The separation of H* and O* intermediates, along with the frustrated H*/O* spillover, effectively facilitates the formation of H2. The *CH2 intermediate from C3H8 breakage migrates and reacts with O* bound to Ir interfacial sites, where it is oxidized to CO32– and subsequently liberates CO. This study provides mechanistic insights into the O element valorization from N2O with synergetic enhancement in selective oxidation of light alkanes.
期刊介绍:
ACS Catalysis is an esteemed journal that publishes original research in the fields of heterogeneous catalysis, molecular catalysis, and biocatalysis. It offers broad coverage across diverse areas such as life sciences, organometallics and synthesis, photochemistry and electrochemistry, drug discovery and synthesis, materials science, environmental protection, polymer discovery and synthesis, and energy and fuels.
The scope of the journal is to showcase innovative work in various aspects of catalysis. This includes new reactions and novel synthetic approaches utilizing known catalysts, the discovery or modification of new catalysts, elucidation of catalytic mechanisms through cutting-edge investigations, practical enhancements of existing processes, as well as conceptual advances in the field. Contributions to ACS Catalysis can encompass both experimental and theoretical research focused on catalytic molecules, macromolecules, and materials that exhibit catalytic turnover.