Magnetron sputtering of gold nanoparticles onto WO₃ and activated carbon

In this paper we describe the production and investigation of two supported gold catalyst systems prepared by magnetron sputtering: Au on WO₃ and Au on activated carbon. The magnetron sputtering technique entails using an argon plasma to sputter a high purity gold target producing a flux of gold atoms which are deposited onto a constantly tumbling support material. This technique offers a number of advantages over conventional chemical preparation methods. One advantage is the ability to create gold nanoparticles (diameters <3 nm) on unusual support materials, such as WO₃ and carbon, which are generally not accessible using the ubiquitous deposition-precipitation technique. We present data demonstrating the formation of catalytic gold nanoparticles with average diameters of 1.7 nm (Au/C) and 2.1 nm (Au/WO₃), as well as a substantial number of single atom species on the Au/C sample. Prototypical carbon monoxide oxidation (Au/WO₃) and glycerol oxidation (Au/C) reactions were performed in order to gauge the activity of these catalysts. The WO₃ supported catalyst exhibits substantial catalytic activity from room temperature to 135 °C (0.0018-0.082 mol CO/mol Au s) with an activation energy near 23 kJ/mol. The activity of the Au/C catalyst was compared to a Au/C catalyst prepared from a poly(vinyl alcohol) (PVA) sol. The smaller catalysts prepared by sputtering are more active than the large gold particles prepared using the PVA sol, however the larger gold nanoparticles are substantially more selective towards the production of intermediate products from the oxidation of glycerol.