In Situ Spectroscopy of Complex Surface Reactions on Supported Pd-Zn, Pd-Ga, and Pd(Pt)-Cu Nanoparticles

被引:65
作者
Foettinger, Karin [1 ]
Rupprechter, Guenther [1 ]
机构
[1] Vienna Univ Technol, Inst Mat Chem, A-1060 Vienna, Austria
基金
奥地利科学基金会;
关键词
STEAM REFORMING CATALYSTS; REFLECTION-ABSORPTION SPECTROSCOPY; INTERMETALLIC COMPOUND ZNPD; SUM-FREQUENCY GENERATION; SELECTIVE HYDRODECHLORINATION; ALLOY NANOPARTICLES; CHEMICAL-PROPERTIES; ULTRAHIGH-VACUUM; METHANOL; TRICHLOROETHYLENE;
D O I
10.1021/ar500220v
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
CONSPECTUS: It is well accepted that catalytically active surfaces frequently adapt to the reaction environment (gas composition, temperature) and that relevant "active phases" may only be created and observed during the ongoing reaction. Clearly, this requires the application of in situ spectroscopy to monitor catalysts at work. While changes in structure and composition may already occur for monometallic single crystal surfaces, such changes are typically more severe for oxide supported nanoparticles, in particular when they are composed of two metals. The metals may form ordered intermetallic compounds (e.g. PdZn on ZnO, Pd2Ga on Ga2O3) or disordered substitutional alloys (e.g. PdCu, PtCu on hydrotalcite). We discuss the formation and stability of bimetallic nanoparticles, focusing on the effect of atomic and electronic structure on catalytic selectivity for methanol steam reforming (MSR) and hydrodechlorination of trichloroethylene. Emphasis is placed on the in situ characterization of functioning catalysts, mainly by (polarization modulated) infrared spectroscopy, ambient pressure X-ray photoelectron spectroscopy, X-ray absorption near edge structure, and X-ray diffraction. In the present contribution, we pursue a two-fold, fundamental and applied, approach investigating technologically applied catalysts as well as model catalysts, which provides comprehensive and complementary information of the relevant surface processes at the atomic or molecular level. Comparison to results of theoretical simulations yields further insight. Several key aspects were identified that control the nanoparticle functionality: (i) alloying (IMC formation) leads to site isolation of specific (e.g. Pd) atoms but also yields very specific electronic structure due to the (e.g. Zn or Ga or Cu) neighboring atoms; (i) for intermetallic PdZn, the thickness of the surface alloy, and its resulting valence band structure and corrugation, turned out to be critical for MSR selectivity; (ii) the limited stability of phases, such as Pd2Ga under MSR conditions, also limits selectivity; (iii) favorably bimetallic catalysts act bifunctional, such as activating methanol AND water or decomposing trichlorothylene AND activating hydrogen; (iv) bifunctionality is achieved either by the two metals or by one metal and the metal-oxide interface; (v) intimate contact between the two interacting sites is required (that cannot be realized by two monometallic nanoparticles being just located close by). The current studies illustrate how rather simple bimetallic nanoparticles may exhibit intriguing diversity and flexibility, exceeding by far the properties of the individual metals. It is also demonstrated how complex reactions can be elucidated with the help of in situ spectroscopy, in particular when complementary methods with varying surface sensitivity are applied.
引用
收藏
页码:3071 / 3079
页数:9
相关论文
共 55 条
[1]   The Intermetallic Compound ZnPd and Its Role in Methanol Steam Reforming [J].
Armbruester, M. ;
Behrens, M. ;
Foettinger, K. ;
Friedrich, M. ;
Gaudry, E. ;
Matam, S. K. ;
Sharma, H. R. .
CATALYSIS REVIEWS-SCIENCE AND ENGINEERING, 2013, 55 (03) :289-367
[2]   How to Control the Selectivity of Palladium-based Catalysts in Hydrogenation Reactions: The Role of Subsurface Chemistry [J].
Armbruester, Marc ;
Behrens, Malte ;
Cinquini, Fabrizio ;
Foettinger, Karin ;
Grin, Yuri ;
Haghofer, Andreas ;
Kloetzer, Bernhard ;
Knop-Gericke, Axel ;
Lorenz, Harald ;
Ota, Antje ;
Penner, Simon ;
Prinz, Jan ;
Rameshan, Christoph ;
Revay, Zsolt ;
Rosenthal, Dirk ;
Rupprechter, Nther ;
Sautet, Philippe ;
Schloegl, Robert ;
Shao, Lidong ;
Szentmiklosi, Laszlo ;
Teschner, Detre ;
Torres, Daniel ;
Wagner, Ronald ;
Widmer, Roland ;
Wowsnick, Gregor .
CHEMCATCHEM, 2012, 4 (08) :1048-1063
[3]   Hydrodechlorination of trichloroethylene on noble metal promoted Cu-hydrotalcite-derived catalysts [J].
Barrabes, N. ;
Cornado, D. ;
Foettinger, K. ;
Dafinov, A. ;
Llorca, J. ;
Medina, F. ;
Rupprechter, G. .
JOURNAL OF CATALYSIS, 2009, 263 (02) :239-246
[4]   Study of Pt-CeO2 interaction and the effect in the selective hydrodechlorination of trichloroethylene [J].
Barrabes, N. ;
Foettinger, K. ;
Dafinov, A. ;
Medina, F. ;
Rupprechter, G. ;
Llorca, J. ;
Sueiras, J. E. .
APPLIED CATALYSIS B-ENVIRONMENTAL, 2009, 87 (1-2) :84-91
[5]   Pretreatment Effect on Pt/CeO2 Catalyst in the Selective Hydrodechlorination of Trichloroethylene [J].
Barrabes, Noelia ;
Foettinger, Karin ;
Llorca, Jordi ;
Dalinov, Anton ;
Medina, Francesc ;
Sa, Jacinto ;
Hardacre, Christopher ;
Rupprechter, Guenther .
JOURNAL OF PHYSICAL CHEMISTRY C, 2010, 114 (41) :17675-17682
[6]   Electronic properties of thin Zn layers on Pd(111) during growth and alloying [J].
Bayer, A ;
Flechtner, K ;
Denecke, R ;
Steinrück, HP ;
Neyman, KM ;
Rösch, N .
SURFACE SCIENCE, 2006, 600 (01) :78-94
[7]   Hydrogen-assisted 1,2-dichloroethane dechlorination catalyzed by Pt-Cu/SiO2:: Evidence for different functions of Pt and Cu sites [J].
Borovkov, VY ;
Luebke, DR ;
Kovalchuk, VI ;
d'Itri, JL .
JOURNAL OF PHYSICAL CHEMISTRY B, 2003, 107 (23) :5568-5574
[8]   The role of Pd-Ga bimetallic particles in the bifunctional mechanism of selective methanol synthesis via CO2 hydrogenation on a Pd/Ga2O3 catalyst [J].
Collins, Sebastian E. ;
Delgado, Juan J. ;
Mira, Cesar ;
Calvino, Jose J. ;
Bernal, Serafin ;
Chiavassa, Dante L. ;
Baltanas, Miguel A. ;
Bonivardi, Adrian L. .
JOURNAL OF CATALYSIS, 2012, 292 :90-98
[9]   The effect of CO on intermetallic PdZn/ZnO and Pd2Ga/Ga2O3 methanol steam reforming catalysts: A comparative study [J].
Foettinger, Karin .
CATALYSIS TODAY, 2013, 208 :106-112
[10]   Dynamic Structure of a Working Methanol Steam Reforming Catalyst: In Situ Quick-EXAFS on Pd/ZnO Nanoparticles [J].
Foettinger, Karin ;
van Bokhoven, Jeroen A. ;
Nachtegaal, Maarten ;
Rupprechter, Guenther .
JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 2011, 2 (05) :428-433