Molecular Hydrogen Formation from Photocatalysis of Methanol on TiO_2(110)

摘要

It is well established that adding methanol to water could significantly enhance H_2 production by TiO_2. Recently, we have found that methanol can be photocatalytically dissociated on TiO_2(110) at 400 nm via a stepwise mechanism. However, how molecular hydrogen can be formed from the photocatalyzed methanol/ TiO_2(110) surface is still not clear. In this work, we have investigated deuterium formation from photocatalysis of the fully deuterated methanol (CD_3OD) on TiO_2(110) at 400 nm using a temperature programmed desorption (TPD) technique. Photocatalytic dissociation products formaldehyde (CD_2O) and D-atoms on BBO sites (via D_2O TPD product) have been detected. In addition to D_2O formation by heating the photocatalyzed methanol/ TiO_2(110) surface, we have also observed D_2 product formation. D_2 is clearly formed via thermal recombination of the D-atoms on the BBO sites from photocatalysis of methanol. Experimental results indicate that D_2O formation is more important than D_2 formation and that D_2 formation is clearly affected by the D_2O formation process.