| AVS 55th International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS2+NC-ThM |
| Session: | Catalysis on Nanoclusters |
| Presenter: | B.L. Abrams, Technical University of Denmark |
| Authors: | B.L. Abrams, Technical University of Denmark P.C.K. Vesborg, Technical University of Denmark S. Dobrin, Technical University of Denmark D. Mowbray, Technical University of Denmark I. Chorkendorff, Technical University of Denmark |
| Correspondent: | Click to Email |
Nanocluster catalysts in the small size regime (<10nm) offer the opportunity for enhanced catalytic reactivity due to increased active site availability. This reactivity is also materials dependent and related to how tightly or weakly the nanocatalyst binds the reactants of interest such as hydrogen for the hydrogen evolution reaction (HER).1,2 Corresponding to the decrease in size is an increase in nanocatalyst surface area. The high surface to volume ratio of nanoclusters in this small size regime thus allows for the ability to impact their catalytic properties by altering their surface chemistry. In this work we alter the cluster surface chemistry by varying the type of surfactants present on metal and metal alloy nanoclusters such as Pt, Au, AuPt, AgPt. These nanoclusters are synthesized using a modified inverse micelle3 technique where the presence of surfactant molecules (non-ionic or cationic) is crucial to maintaining the nanocluster monodispersity. Following synthesis in the solution phase, the nanoclusters are evaluated electrochemically as a function of surfactant type and amount. In the case of Pt nanoclusters stabilized by a non-ionic surfactant, the HER activity is comparable to standard polycrystalline Pt. The negligible suppression of HER indicates that the surfactant may not significantly block the active sites necessary for HER. In relation to the activity measurements, we have studied the attachment mechanism of the surfactants to the cluster surface utilizing density functional theory (DFT) calculations. An evaluation of the charge transfer processes and reactions as revealed by electrochemical measurements will be presented for each material as a function of surface chemistry alterations. Preliminary result for other reactions of interest to fuel cells such as the hydrogen oxidation reaction will also be discussed.
1J.K. Nørskov,et al.,“Trends in the Exchange Current for Hydrogen Evolution” J. Electrochem. Soc. (152), J23 (2005).
2Greeley,J.,et al.,“Computational High-Throughput Screening of Electrocatalytic materials for Hydrogen Evolution”, Nature Materials, 5,909-913(2006).
3Wilcoxon, J.P; Abrams, B.L., “Synthesis, Structure and Properties of Metal Nanoclusters” Chemical Society Reviews, 35,1162-1194(2006).