{"title":"铁置换增强 CeO2 还原性的核级和价级光谱研究--对热分水反应的启示","authors":"H. Idriss","doi":"10.3390/inorganics12020042","DOIUrl":null,"url":null,"abstract":"The reduction of Ce cations in CeO2 can be enhanced by their partial substitution with Fe cations. The enhanced reduction of Ce cations results in a considerable increase in the reaction rates for the thermal water-splitting reaction when compared to CeO2 alone. This mixed oxide has a smaller crystallite size when compared to CeO2, in addition to a smaller lattice size. In this work, two Fe-substituted Ce oxides are studied (Ce0.95Fe0.05O2-δ and Ce0.75Fe0.25O2-δ; δ < 0.5) by core and valence level spectroscopy in their as-prepared and Ar-ion-sputtered states. Ar ion sputtering substantially increases Ce4f lines at about 1.5 eV below the Fermi level. In addition, it is found that the XPS Ce5p/O2s ratio is sensitive to the degree of reduction, most likely due to a higher charge transfer from the oxygen to Ce ions upon reduction. Quantitatively, it is also found that XPS Ce3d of the fraction of Ce3+ (uo, u′ and vo, v′) formed upon Ar ion sputtering and the ratio of Ce5p/O2s lines are higher for reduced Ce0.95Fe0.05O2-δ than for reduced Ce0.75Fe0.25O2-δ. XPS Fe2p showed, however, no preferential increase for Fe3+ reduction to Fe0 with increasing time for both oxides. Since water splitting was higher on Ce0.95Fe0.05O2-δ when compared to Ce0.75Fe0.25O2-δ, it is inferred that the reaction centers for the thermal water splitting to hydrogen are the reduced Ce cations and not the reduced Fe cations. These reduced Ce cations can be tracked by their XPS Ce5p/O2s ratio in addition to the common XPS Ce3d lines.","PeriodicalId":507601,"journal":{"name":"Inorganics","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":"{\"title\":\"A Core and Valence-Level Spectroscopy Study of the Enhanced Reduction of CeO2 by Iron Substitution—Implications for the Thermal Water-Splitting Reaction\",\"authors\":\"H. Idriss\",\"doi\":\"10.3390/inorganics12020042\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The reduction of Ce cations in CeO2 can be enhanced by their partial substitution with Fe cations. The enhanced reduction of Ce cations results in a considerable increase in the reaction rates for the thermal water-splitting reaction when compared to CeO2 alone. This mixed oxide has a smaller crystallite size when compared to CeO2, in addition to a smaller lattice size. In this work, two Fe-substituted Ce oxides are studied (Ce0.95Fe0.05O2-δ and Ce0.75Fe0.25O2-δ; δ < 0.5) by core and valence level spectroscopy in their as-prepared and Ar-ion-sputtered states. Ar ion sputtering substantially increases Ce4f lines at about 1.5 eV below the Fermi level. In addition, it is found that the XPS Ce5p/O2s ratio is sensitive to the degree of reduction, most likely due to a higher charge transfer from the oxygen to Ce ions upon reduction. Quantitatively, it is also found that XPS Ce3d of the fraction of Ce3+ (uo, u′ and vo, v′) formed upon Ar ion sputtering and the ratio of Ce5p/O2s lines are higher for reduced Ce0.95Fe0.05O2-δ than for reduced Ce0.75Fe0.25O2-δ. XPS Fe2p showed, however, no preferential increase for Fe3+ reduction to Fe0 with increasing time for both oxides. Since water splitting was higher on Ce0.95Fe0.05O2-δ when compared to Ce0.75Fe0.25O2-δ, it is inferred that the reaction centers for the thermal water splitting to hydrogen are the reduced Ce cations and not the reduced Fe cations. These reduced Ce cations can be tracked by their XPS Ce5p/O2s ratio in addition to the common XPS Ce3d lines.\",\"PeriodicalId\":507601,\"journal\":{\"name\":\"Inorganics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2024-01-27\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Inorganics\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.3390/inorganics12020042\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Inorganics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3390/inorganics12020042","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 1
摘要
CeO2 中 Ce 阳离子的还原性可通过用 Fe 阳离子部分取代而得到增强。与单独的 CeO2 相比,Ce 阳离子的还原性增强使得热分水反应的反应速率大大提高。与 CeO2 相比,这种混合氧化物除了晶格尺寸较小之外,结晶尺寸也较小。在这项工作中,通过核光谱和价级光谱研究了两种 Fe 取代的 Ce 氧化物(Ce0.95Fe0.05O2-δ 和 Ce0.75Fe0.25O2-δ;δ < 0.5)的制备状态和氩离子溅射状态。氩离子溅射大大增加了费米级以下约 1.5 eV 处的 Ce4f 线。此外,研究还发现 XPS Ce5p/O2s 比率对还原程度很敏感,这很可能是由于还原时氧向铈离子的电荷转移较多。定量研究还发现,氩离子溅射时形成的 Ce3+ 部分(uo,u′ 和 vo,v′)的 XPS Ce3d 以及 Ce5p/O2s 线的比率,还原 Ce0.95Fe0.05O2-δ 要高于还原 Ce0.75Fe0.25O2-δ。然而,XPS Fe2p 显示,随着时间的延长,两种氧化物中的 Fe3+ 还原成 Fe0 的比例并没有增加。与 Ce0.75Fe0.25O2-δ 相比,Ce0.95Fe0.05O2-δ 上的水分裂率更高,因此可以推断,热水分裂成氢的反应中心是还原的 Ce 阳离子,而不是还原的 Fe 阳离子。除了常见的 XPS Ce3d 线之外,还可以通过其 XPS Ce5p/O2s 比值跟踪这些还原的 Ce 阳离子。
A Core and Valence-Level Spectroscopy Study of the Enhanced Reduction of CeO2 by Iron Substitution—Implications for the Thermal Water-Splitting Reaction
The reduction of Ce cations in CeO2 can be enhanced by their partial substitution with Fe cations. The enhanced reduction of Ce cations results in a considerable increase in the reaction rates for the thermal water-splitting reaction when compared to CeO2 alone. This mixed oxide has a smaller crystallite size when compared to CeO2, in addition to a smaller lattice size. In this work, two Fe-substituted Ce oxides are studied (Ce0.95Fe0.05O2-δ and Ce0.75Fe0.25O2-δ; δ < 0.5) by core and valence level spectroscopy in their as-prepared and Ar-ion-sputtered states. Ar ion sputtering substantially increases Ce4f lines at about 1.5 eV below the Fermi level. In addition, it is found that the XPS Ce5p/O2s ratio is sensitive to the degree of reduction, most likely due to a higher charge transfer from the oxygen to Ce ions upon reduction. Quantitatively, it is also found that XPS Ce3d of the fraction of Ce3+ (uo, u′ and vo, v′) formed upon Ar ion sputtering and the ratio of Ce5p/O2s lines are higher for reduced Ce0.95Fe0.05O2-δ than for reduced Ce0.75Fe0.25O2-δ. XPS Fe2p showed, however, no preferential increase for Fe3+ reduction to Fe0 with increasing time for both oxides. Since water splitting was higher on Ce0.95Fe0.05O2-δ when compared to Ce0.75Fe0.25O2-δ, it is inferred that the reaction centers for the thermal water splitting to hydrogen are the reduced Ce cations and not the reduced Fe cations. These reduced Ce cations can be tracked by their XPS Ce5p/O2s ratio in addition to the common XPS Ce3d lines.