Photo-induced H2 production from a CH3OH-H2O solution at insulator surface

In a conventional photocatalytic or photochemical process, either a photocatalyst or a molecule is excited by irradiation light that has energy greater than the forbidden band (i.e., the band gap) of the semiconductor or the transition energy of an excited state of the molecule, respectively, for a reaction to occur. However, in this work, we found that a considerable amount of H2 can be generated from a CH3OH-H2O solution at a quartz surface using light with energy far outside the electronic absorbance range of the CH3OH-H2O solution; this process should not occur in principle via either conventional photocatalysis or a photochemical process. The H2 production was further confirmed using 266 nm and 355 nm lasers as light sources. Our work demonstrates that photo-induced H2 production can occur on insulator surfaces (e.g., quartz), which were commonly believed to be inert, and will shed light on the surface nature of insulators.