To 200 mL of distilled water under vigorous stirring were added dropwise 115 mg of a 30 % (w/w) solution of the metal precursor (HAuCl4) followed by 1.2 mL of a 2 % polyvinylalcohol water solution. Then, 5 mL of a 0.2 M NaBH4 water solution was added dropwise, and the reaction mixture was stirred for 30 min, then 1 g of CaO was added. The amount of support was calculated to give a total final metal loading of 2 wt.% (nominal).