| AVS 60th International Symposium and Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS+EN-ThM |
| Session: | Photocatalysis and Photochemistry at Surfaces |
| Presenter: | R.E. Palmer, University of Birmingham, UK |
| Authors: | R.E. Palmer, University of Birmingham, UK M. Cuddy, University of Birmingham, UK K. Arkill, University of Birmingham, UK Z.W. Wang, University of Birmingham, UK N.V. Rees, University of Birmingham, UK |
| Correspondent: | Click to Email |
The green production of hydrogen by photocatalytic splitting of water molecules requires the catalyst both to absorb solar photons and to supply excited carriers of the correct energy to split water. MoS2 is a new and abundantly available candidate catalyst material with a layered structure in the bulk; it is believed that quantum confinement in MoS2 nanoparticles will allow the band gap and energy levels to be tuned to maximize the efficiency of water splitting. Here we report the atomic structure of size-selected nanoparticles (clusters) of MoS2, generated by magnetron sputtering of a bulk target and condensation in helium gas, then size selection with a novel lateral time-of-flight mass filter [1] prior to deposition onto carbon supports. X-Ray Photoelectron Spectroscopy (XPS) of cluster ensembles confirms that approximately stoichiometric compound clusters, with average formula MoS1.95, are produced (although we find they are somewhat sensitive to oxygen).
Atomic-scale imaging of the deposited MoS2 clusters by aberration-corrected Scanning Transmission Electron Microscopy (STEM) [2] of the MoS2 clusters shows layered nanoparticle structures (as opposed to e.g. fullerene structures), presenting ordered hexagonal arrays of Mo atoms. The cluster growth is remarkably anisotropic, such that as cluster size increases from 150-1000 MoS2 units (always mass selected) the lateral diameter of the clusters increases but the mean vertical height (2.3±1.0 layers) remains constant. These clusters demonstrate efficient electrocatalytic activity in the hydrogen evolution reaction, probably at edge sites, confirming these new nanosystems as intriguing candidates for water splitting.
[1] S. Pratontep, S. J. Carroll, C. Xirouchaki, M. Streun, and R. E. Palmer, Review of Scientific Instruments 76, 045103 (2005).
[2] Z. W. Wang and R. E. Palmer, Nano Letters 12, 91 (2012).