Probing the tunneling of electrons from SnO2 to ZnO in dye sensitization of composite SnO2/ZnO by use of generated H2O2 via reduction of O-2

A composite system of SnO2/ZnO semiconductors was found to generate a highe r H2O2 yield than individual oxide semiconductors when they were sensitized with various dyes. The optimum quantum yields for H2O2 generation were fou nd to be 6.00 x 10(-2), 4.05 x 10(-2) and 3.33 x 10(-2), respectively, for Eosin Y, Rose Bengal and Rhodamine 6G. Under similar conditions, Eosin Y sh owed quantum yields of 2.03 x 10(-2) and 2.34 x 10-(3), respectively, for Z nO and SnO2 particles. With the higher yield of H2O2 for the composite syst em, the possibility of electron transfer from the low band position semicon ductor to the high band position semiconductor is demonstrated and is attri buted to the transfer of injected high-energy electrons from the excited dy e molecules on SnO2 to ZnO particles.