Enhanced Hydrogen Production from Methanol/Water Photo-Splitting in TiO2 Including Pd Component

The future use of hydrogen as an energy source is expected to increase on account of its environmentally friendliness. In order to enhance the production of hydrogen, Pd ions (0.01, 0.05, 0.1, and 0.5 mol%) were incorporated TiO2 (Pd-TiO2) and used as a photocatalyst. The UV-visible absorbance decreased with increasing level of palladium incorporation without a wavelength shift. Although all the absorption plots showed excitation characteristics, there was an asymmetric tail observed towards a higher wavelength caused by scattering. However, the intensity of the photoluminescence (PL) curves of Pd-TiO2 was smaller, with the smallest case being observed at 0.1 and 0.5 mol% Pd-TiO2, which was attributed to recombination between the excited electrons and holes. Based on these optical characteristics, the evolution of H-2 from methanol/water (1: 1) photo-splitting over Pd-TiO2 in the liquid system was enhanced, compared with that over pure TiO2. In particular, 2.4 mL of H-2 gas was produced after 8 h when 0.5 g of a 1.0 mol% Pd-TiO2 catalyst was used. H-2 was stably evolved even after 28 h without catalytic deactivation, and the amount of H-2 produced reached 14.5 mL after 28 h. This is in contrast to the case of the Pd 0.1 mol% impregnated TiO2 of H-2 evolution of 17.5 mL due to the more decreasedelectron-hole recombination.