Production of Hydrogen: Photocatalytic Decomposition of Dimethyl Ether over Metal-Promoted TiO₂ Catalysts

Abstract

The photo-induced vapor-phase decomposition of dimethyl ether was investigated on Pt metals deposited on pure and N-doped TiO 2 . Infrared spectroscopic measurements revealed that adsorption of dimethyl ether on TiO 2 samples underwent partial dissociation to methoxy species. Illumination of the (CH 3 ) 2 O-TiO 2 and (CH 3 ) 2 O-M/TiO 2 systems led to the conversion of methoxy into adsorbed formate. In the case of metal-promoted TiO 2 catalysts, CO bonded to the metals was also detected. Pure titania exhibited a very little photoactivity. Deposition of Pt metals on TiO 2 markedly enhanced the extent of photocatalytic decomposition of dimethyl ether to give H 2 and CO 2 as the major products. A small amount of CO and methyl formate was also identified in the products. The most active metal was the Rh followed by Pd, Ir, Pt and Ru. When the bandgap of TiO 2 was lowered by N-doping, the photocatalytic activity of metal/TiO 2 catalysts appreciably increased. The effect of metals was explained by a better separation of charge carriers induced by illumination and by enhanced electronic interaction between metal nanoparticles and TiO 2 .