{"title":"Effect of the Chemical States of Copper on Methanol Decomposition and Oxidation","authors":"Jianyu Wang, Chaoran Li, Yaguang Zhu, Shyam Patel, Jorge Anibal Boscoboinik and Guangwen Zhou*, ","doi":"10.1021/acs.jpcc.4c00049","DOIUrl":null,"url":null,"abstract":"<p >The decomposition and oxidation reactions of CH<sub>3</sub>OH over metallic Cu(100) and Cu<sub>2</sub>O-covered Cu(100) surfaces are studied by using a combination of in situ ambient-pressure X-ray photoelectron spectroscopy, Auger electron spectroscopy, and density functional theory calculations. We identify the sequential chemical transformation pathways from bond cleavage to the formation of intermediates and final products under operational conditions. Accumulative surface adsorption of CH<sub>3</sub>O species on metallic Cu(100) impedes the decomposition of CH<sub>3</sub>OH. Co-dosing on metallic Cu(100) with low pressures of 1 × 10<sup>–4</sup> Torr CH<sub>3</sub>OH + 1 × 10<sup>–4</sup> Torr O<sub>2</sub> results in partial oxidation of CH<sub>3</sub>OH, where the chemisorbed O<sub>ads</sub> reduces surface sites available for CH<sub>3</sub>O adsorption, decreasing the surface activity for CH<sub>3</sub>OH decomposition. In contrast, the Cu<sub>2</sub>O overlayer formed under the elevated pressures of 0.33 Torr CH<sub>3</sub>OH + 0.66 Torr O<sub>2</sub> promotes the total oxidation of CH<sub>3</sub>OH into the final products of CO<sub>2</sub> and H<sub>2</sub>O, arising from the active reaction between lattice O within Cu<sub>2</sub>O and intermediates of CH<sub>3</sub>O, CH<sub>2</sub>O, HCOO, and CO. Despite the more favorable O–H bond scission, C–O bond scission also occurs to result in surface accumulation of CH<sub><i>x</i></sub> on metallic Cu(100), blocking active sites for decomposition reactions of CH<sub>3</sub>OH and CH<sub>3</sub>O. By comparison, the CH<sub><i>x</i></sub> species on the Cu<sub>2</sub>O-covered Cu(100) undergo oxidation into CO<sub>2</sub> and H<sub>2</sub>O with lattice O in the Cu<sub>2</sub>O overlayer, thereby freeing active sites for the total oxidation of CH<sub>3</sub>OH. These results highlight the distinct roles of metallic Cu and Cu<sub>2</sub>O in the pathways of CH<sub>3</sub>OH decomposition and oxidation reactions, offering practical insights for the design of Cu-based catalysts with tailored reactivity and selectivity.</p>","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"128 11","pages":"4559–4572"},"PeriodicalIF":3.2000,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Journal of Physical Chemistry C","FirstCategoryId":"1","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acs.jpcc.4c00049","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
The decomposition and oxidation reactions of CH3OH over metallic Cu(100) and Cu2O-covered Cu(100) surfaces are studied by using a combination of in situ ambient-pressure X-ray photoelectron spectroscopy, Auger electron spectroscopy, and density functional theory calculations. We identify the sequential chemical transformation pathways from bond cleavage to the formation of intermediates and final products under operational conditions. Accumulative surface adsorption of CH3O species on metallic Cu(100) impedes the decomposition of CH3OH. Co-dosing on metallic Cu(100) with low pressures of 1 × 10–4 Torr CH3OH + 1 × 10–4 Torr O2 results in partial oxidation of CH3OH, where the chemisorbed Oads reduces surface sites available for CH3O adsorption, decreasing the surface activity for CH3OH decomposition. In contrast, the Cu2O overlayer formed under the elevated pressures of 0.33 Torr CH3OH + 0.66 Torr O2 promotes the total oxidation of CH3OH into the final products of CO2 and H2O, arising from the active reaction between lattice O within Cu2O and intermediates of CH3O, CH2O, HCOO, and CO. Despite the more favorable O–H bond scission, C–O bond scission also occurs to result in surface accumulation of CHx on metallic Cu(100), blocking active sites for decomposition reactions of CH3OH and CH3O. By comparison, the CHx species on the Cu2O-covered Cu(100) undergo oxidation into CO2 and H2O with lattice O in the Cu2O overlayer, thereby freeing active sites for the total oxidation of CH3OH. These results highlight the distinct roles of metallic Cu and Cu2O in the pathways of CH3OH decomposition and oxidation reactions, offering practical insights for the design of Cu-based catalysts with tailored reactivity and selectivity.
期刊介绍:
The Journal of Physical Chemistry A/B/C is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, and chemical physicists.