A Critical View on the Quantification of Model Catalyst Activity

IF 2.8 3区 化学 Q2 CHEMISTRY, APPLIED
Johanna Reich, Sebastian Kaiser, Ueli Heiz, Jan-Dierk Grunwaldt, Manfred M. Kappes, Friedrich Esch, Barbara A. J. Lechner
{"title":"A Critical View on the Quantification of Model Catalyst Activity","authors":"Johanna Reich, Sebastian Kaiser, Ueli Heiz, Jan-Dierk Grunwaldt, Manfred M. Kappes, Friedrich Esch, Barbara A. J. Lechner","doi":"10.1007/s11244-024-01920-0","DOIUrl":null,"url":null,"abstract":"<p>The conversion of reactants, reaction rate referred to catalyst mass, and turnover frequency (TOF) are values typically employed to compare the activity of different catalysts. However, experimental parameters have to be chosen carefully when systems of different complexity are compared. In order to characterize UHV-based model systems, we use a highly sensitive sniffer setup which allows us to investigate the catalytic activity by combining three different measurement modes: temperature-programmed desorption, continuous flow, and pulsed-reactivity experiments. In this article, we explore the caveats of quantifying catalytic activity in UHV on the well-studied and highly defined reference system of CO oxidation on Pt(111), which we later compare to the same reaction on Pt<sub>19</sub> clusters deposited on Fe<sub>3</sub>O<sub>4</sub>(001). We demonstrate that we can apply fast heating ramps for TOF quantification, thus inducing as little sintering as possible in the metastable clusters. By changing the reactant ratio, we find transient reactivity effects that influence the TOF, which should be kept in mind when comparing catalysts. In addition, the TOF also depends on the surface coverage that itself is a function of temperature and pressure. At a constant reactant ratio, in the absence of transient effects, however, the TOF scales linearly with total pressure over the entire measured temperature range from 200 to 700 K since the reaction rate is dependent on both reactant partial pressures with temperature-dependent reaction order. When comparing the maximum TOF at this particular reactant ratio, we find a 1.6 times higher maximum TOF for Pt<sub>19</sub>/Fe<sub>3</sub>O<sub>4</sub>(001) than for Pt(111). In addition, pulsed-reactivity measurements help identify purely reaction-limited regimes and allow for a more detailed investigation of limiting reactants over the whole temperature range.</p>","PeriodicalId":801,"journal":{"name":"Topics in Catalysis","volume":"121 1","pages":""},"PeriodicalIF":2.8000,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Topics in Catalysis","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1007/s11244-024-01920-0","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, APPLIED","Score":null,"Total":0}
引用次数: 0

Abstract

The conversion of reactants, reaction rate referred to catalyst mass, and turnover frequency (TOF) are values typically employed to compare the activity of different catalysts. However, experimental parameters have to be chosen carefully when systems of different complexity are compared. In order to characterize UHV-based model systems, we use a highly sensitive sniffer setup which allows us to investigate the catalytic activity by combining three different measurement modes: temperature-programmed desorption, continuous flow, and pulsed-reactivity experiments. In this article, we explore the caveats of quantifying catalytic activity in UHV on the well-studied and highly defined reference system of CO oxidation on Pt(111), which we later compare to the same reaction on Pt19 clusters deposited on Fe3O4(001). We demonstrate that we can apply fast heating ramps for TOF quantification, thus inducing as little sintering as possible in the metastable clusters. By changing the reactant ratio, we find transient reactivity effects that influence the TOF, which should be kept in mind when comparing catalysts. In addition, the TOF also depends on the surface coverage that itself is a function of temperature and pressure. At a constant reactant ratio, in the absence of transient effects, however, the TOF scales linearly with total pressure over the entire measured temperature range from 200 to 700 K since the reaction rate is dependent on both reactant partial pressures with temperature-dependent reaction order. When comparing the maximum TOF at this particular reactant ratio, we find a 1.6 times higher maximum TOF for Pt19/Fe3O4(001) than for Pt(111). In addition, pulsed-reactivity measurements help identify purely reaction-limited regimes and allow for a more detailed investigation of limiting reactants over the whole temperature range.

对模型催化剂活性量化的批判性观点
反应物的转化率、与催化剂质量相关的反应速率和翻转频率 (TOF) 是比较不同催化剂活性的常用值。然而,在比较不同复杂程度的系统时,必须谨慎选择实验参数。为了表征基于超高压的模型系统,我们使用了一种高灵敏度的嗅探器装置,通过结合三种不同的测量模式来研究催化活性:温度编程解吸、连续流和脉冲反应实验。在本文中,我们探讨了在超高真空条件下量化催化活性的注意事项,该催化活性是在铂(111)上一氧化碳氧化这一经过充分研究和高度定义的参考系统上进行的,随后我们将其与沉积在铁3O4(001)上的铂19团簇上的相同反应进行了比较。我们证明,我们可以采用快速加热斜坡来进行 TOF 定量,从而尽可能减少逸散簇的烧结。通过改变反应物比例,我们发现瞬时反应性效应会影响 TOF,在比较催化剂时应注意这一点。此外,TOF 还取决于表面覆盖率,而表面覆盖率本身又是温度和压力的函数。然而,在反应物比例恒定、没有瞬态效应的情况下,由于反应速率取决于反应物分压和随温度变化的反应顺序,因此在 200 至 700 K 的整个测量温度范围内,TOF 与总压呈线性关系。在比较特定反应物比率下的最大 TOF 时,我们发现 Pt19/Fe3O4(001) 的最大 TOF 比 Pt(111) 高 1.6 倍。此外,脉冲反应测量有助于确定纯粹的反应受限体系,并可对整个温度范围内的受限反应物进行更详细的研究。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
Topics in Catalysis
Topics in Catalysis 化学-物理化学
CiteScore
5.70
自引率
5.60%
发文量
197
审稿时长
2 months
期刊介绍: Topics in Catalysis publishes topical collections in all fields of catalysis which are composed only of invited articles from leading authors. The journal documents today’s emerging and critical trends in all branches of catalysis. Each themed issue is organized by renowned Guest Editors in collaboration with the Editors-in-Chief. Proposals for new topics are welcome and should be submitted directly to the Editors-in-Chief. The publication of individual uninvited original research articles can be sent to our sister journal Catalysis Letters. This journal aims for rapid publication of high-impact original research articles in all fields of both applied and theoretical catalysis, including heterogeneous, homogeneous and biocatalysis.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信