PHOTOINDUCED HYDROGEN-PRODUCTION FROM AN AQUEOUS-SOLUTION OF ETHYLENE-GLYCOL OVER ULTRAFINE GOLD SUPPORTED ON TIO2

Photocatalytic H-2 production from aqueous solutions of ethylene glycol was studied using a catalyst consisting of gold supported on TiO2. The catalysts were prepared by the deposition-precipitation method, using TiO2 powder and an aqueous solution of chloroauric acid. Transmission electron microscopy showed that Au was deposited as highly dispersed particles with mean diameters of 2 to 5 nm, depending on the method of pretreatment of the precursor. The effects of precursor calcination temperature, duration of irradiation, gold loading, concentration of ethylene glycol, initial pH and temperature on H-2 production were investigated. The gas phase products of the reaction were mainly H-2 and CO2. The precursor calcined in air at 673 K proved to be the most active photocatalyst. The yield of H-2 exhibited a weak maximum at a gold loading of about 2 wt.%. The rate of H-2 production was strongly dependent on the initial pH of the suspension; it increased with pH up to neutral pH and decreased thereafter. Increasing the concentration of ethylene glycol and the temperature had a positive effect on the H-2 yield. The activation energy of H-2 production, as given by an Arrhenius plot over the temperature range 284-340 K, was 15 kJ mol-1.