Molecular Hydrogen Formation from Photocatalysis of Methanol on TiO2(110)

It is well established that adding methanol to water could significantly enhance H-2 production by TiO2. Recently, we have found that methanol can be photocatalytically dissociated on TiO2(110) at 400 nm via a stepwise mechanism. However, how molecular hydrogen can be formed from the photocatalyzed methanol/TiO2(110) surface is still not clear. In this work, we have investigated deuterium formation from photocatalysis of the fully deuterated methanol (CD3OD) on TiO2(110) at 400 nm using a temperature programmed desorption (TPD) technique. Photocatalytic dissociation products formaldehyde (CD2O) and O-atoms on BBO sites (via D2O TPD product) have been detected. In addition to D2O formation by heating the photocatalyzed methanol/TiO2(110) surface, we have also observed D-2 product formation. O-2 is dearly formed via thermal recombination of the O-atoms on the BBO sites from photocatalysis of methanol. Experimental results indicate that D2O formation is more important than D-2 formation and that D-2 formation is clearly affected by the D2O formation process.