Regensburg 2007 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 44: Poster Session II (Semiconductors; Oxides and Insulators: Adsorption, Clean Surfaces, Epitaxy and Growth; Surface Chemical Reactions and Heterogeneous Catalysis; Surface or Interface Magnetism; Solid-Liquid Interfaces; Organic, Polymeric, Biomolecular Films; Particles and Clusters; Methods: Atomic and Electronic Structure; Time-resolved Spectroscopies)

O 44.75: Poster

Mittwoch, 28. März 2007, 17:00–19:30, Poster C

Experimental identification of the “active site” on a nano catalyst: — Thomas Jaramillo¹, Kristina Jørgensen¹, Jacob Bonde¹, Jane Nielsen¹, •Sebastian Horch², and Ib Chorkendorff¹ — ¹Center for Individual Nanoparticle Functionality (CINF), NanoDTU, Department of Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark — ²Center for Atomic-scale Materials Design (CAMD), NanoDTU, Department of Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark

One of the most important problems in heterogeneous catalysis is the identification of the “active site”. Only when this site and its relative abundance are known, it is possible to determine turnover-rates per active site (cf. our contribution on CO dissociation on Ni(111)).

We have determined the active site of a well-known model system: single-layered MoS₂ nanoparticles as catalyst for hydrogen evolution. MoS₂ nanoparticles were grown on Au(111) under UHV. Particle sizes were tuned by controlled sintering. Morphological details of the model systems were revealed with STM under UHV. The same samples were subsequently characterized in an electrochemical cell under ambient conditions, where it was found that the electrocatalytic hydrogen evolution scales linearly with the number of edge sites of the nanoparticles — and not the area of the exposed basal plane — regardless of particle size. These findings are in excellent agreement with theoretical predictions for hydrogen evolution catalysts.