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Electrocatalytic IrO 2 -RuO 2 supported on Sb-doped SnO 2 (ATO) nanoparticles is very active towards the oxygen evolution reaction. The IrO 2 -RuO 2 material is XRD amorphous and exists as clusters on the surface of the ATO.Systematic changes to the surface chemical composition of the ATO as a function of the IrO 2 :RuO 2 ratio suggests an interaction between the IrO 2 -RuO 2 and ATO. Cyclic voltammetry indicates that the electrochemically active surface area of IrO 2 -RuO 2 clusters is maximised when the composition is 75 mol% IrO 2 -25 mol% RuO 2 . Decreasing the loading of IrO 2 -RuO 2 on ATO reduces the electrochemically active surface area, although there is evidence to support a decrease in the clusters size with decreased loading. Tafel slope analysis shows that if the clusters are too small, the kinetics of the oxygen evolution reaction are reduced. Overall, clusters of IrO 2 -RuO 2 on ATO have similar or better performance for the oxygen evolution reaction than many previously reported materials, despite the low quantity of noble metals used in the electrocatalysts. This suggests that these oxides may be of economic

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Enzymatic digestion is proposed as a method for concentrating gold nanoparticles produced in plants. The mild conditions of digestion are used in order to avoid an increase in the gold particle size, which would occur with a high-temperature process, so that material suitable for catalysis may be produced. Gold nanoparticles of a 5-50-nm diameter, as revealed by transmission electron microscopy (TEM), at concentrations 760 and 1120 ppm Au, were produced within Brassica juncea grown on soil with 22-48 mg Au kg(-1). X-ray absorption near edge spectroscopy (XANES) reveals that the plant contained approximately equal quantities of Au in the metallic (Au0) and oxidized (Au+1) states. Enzymatic digestion dissolved 55-60 wt% of the plant matter. Due to the loss of the soluble gold fraction, no significant increase in the total concentration of gold in the samples was observed. However, it is likely that the concentration of the gold nanoparticles increased by a factor of two. To obtain a gold concentration suitable for catalytic reactions, around 95 wt% of the starting dry biomass would need to be solubilized or removed, which has not yet been achieved.