Performance evaluation of Pd/TiO_{2 and Pt/TiO_{2 photocatalysts for hydrogen production from ethanol-water mixtures

This study compares the photocatalytic activity of Pd/TiO 2 and Pt/TiO 2 photocatalysts (metal loadings 0.5 wt.% and 2 wt.%) for H 2 production from ethanol-water mixtures under UV excitation. Cationic Pd(II) and Pt(IV)/Pt(II) species were deposited on Degussa P25 TiO 2 (85% anatase, 15% rutile) via the deposition-precipitation with urea method. Subsequent H 2 treatment at 350ºC reduced the adsorbed cationic species to predominantly Pd 0 and Pt 0 , respectively. TEM analyses of the Pd/TiO 2 and Pt/TiO 2 photocatalysts revealed supported Pd and Pt nanoparticles of size <3 nm. XPS studies confirmed that the platinum was present primarily in metallic form, whereas palladium was present as both Pd 0 and PdO or Pd(OH) 2 . Photoluminescence measurements demonstrated that Pd and Pt nanoparticles suppress electron-hole pair recombination in TiO 2 by acting as electron acceptors. The Pt/TiO 2 and Pd/TiO 2 photocatalysts exhibited high activity and stability for H 2 production, with the optimum metal loadings being 0.5 wt.% for Pt (H 2 production rate = 41 mmol h –1 g –1 ) and 2 wt.% for Pd (H 2 production rate = 34 mmol h –1 g –1 ). Results confirm that the presence of zero valent Pd or Pt is critical for efficient H 2 production, and that both Pt/TiO 2 and Pd/TiO 2 photocatalysts are promising materials for solar H 2 production from biofuels.