Abstract
Multielectron storage and hydrogen generation by light is achieved in aqueous dispersions of ultrafine TiO2 particles (120-Å diameter) when the amphiphilic viologen derivative N-tetradecyl-N′-methyl-4,4′-dipyridinium dichloride (C14MV2+) is used as an electron relay. Consecutive reduction of C14MV2+ to the radical ion (C14MV+) and neutral (C14MV0) was observed after band-gap excitation of the semiconductor particle. Through surface adsorption of the relay, these electron-transfer reactions can occur very rapidly and are completed within less than 100 μsec (pH 11). Two-electron reduction of C14MV2+ can be coupled with H2 generation in alkaline medium in the presence of Pt catalyst codeposited onto the TiO2 particle. Electron-relay-free systems are 1/15th as efficient in producing H2 at the same pH.
Keywords: energy conversion, charge transfer, semiconducting particles, amphiphilic viologens, photoreactions
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