Keywords: photocatalysis, hydrogen production, ethanol–water mixtures, ethanol, biofuels, titania, palladium, platinum, water, nanoparticles, nanotechnology
Performance evaluation of Pd/TiO2 and Pt/TiO2 photocatalysts for hydrogen production from ethanol–water mixtures
This study compares the photocatalytic activity of Pd/TiO2 and Pt/TiO2 photocatalysts (metal loadings 0.5 wt.% and 2 wt. %) for H2 production from ethanol–water mixtures under UV excitation. Cationic Pd(II) and Pt(IV)/Pt(II) species were deposited on Degussa P25 TiO2 (85% anatase, 15% rutile) via the deposition–precipitation with urea method. Subsequent H2 treatment at 350°C reduced the adsorbed cationic species to predominantly Pd0 and Pt0, respectively. TEM analyses of the Pd/TiO2 and Pt/TiO2 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 Pd0 and PdO or Pd(OH)2. Photoluminescence measurements demonstrated that Pd and Pt nanoparticles suppress electron–hole pair recombination in TiO2 by acting as electron acceptors. The Pt/TiO2 and Pd/TiO2 photocatalysts exhibited high activity and stability for H2 production, with the optimum metal loadings being 0.5 wt. % for Pt (H2 production rate = 41 mmol h−1 g−1) and 2 wt. % for Pd (H2 production rate = 34 mmol h−1 g−1). Results confirm that the presence of zero valent Pd or Pt is critical for efficient H2 production, and that both Pt/TiO2 and Pd/TiO2 photocatalysts are promising materials for solar H2 production from biofuels.