Water

ABSTRACT: Single-walled carbon nanotubes (SWNTs) catalyzed hydrogen production from water containing various electron donors under visible light ( > 420 nm). As-received SWNTs were effective for hydrogen production, yet the effect vanished when they underwent surface chemical treatments. Upon coupling with CdSe particles, however, the surface treated SWNTs were far superior to non-treated SWNTs by a factor of ~30 for hydrogen production. Solar hydrogen production has been received wide attention over the past four decades particularly in semiconductor systems.1 Unfortunately, the benchmark solar-to-hydrogen (STH) efficiency is still as low as ~2 % even though complicated materials and systems are designed. For high STH efficiency, semiconductors of interest should absorb wide spectrum of sunlight, display efficient charge separation and transfer, and effectively catalyze water splitting.2 In the latter, many auxiliary metals and metal oxides3-5 have been coupled to base semiconductors to hurdle the uphill activation energy barrier. Recently, inexpensive carbon materials including nanotubes, nanofibers, graphites, and graphenes have been found to effectively catalyze hydrogen production from water.6-10 The electric conductivity of carbon materials was found to be a primary factor in determining the STH efficiency of semiconductor/carbon composites.10 Among these carbon materials, single-walled carbon nanotubes (SWNTs) were found to be capable of producing hydrogen under visible light even in the absence of semiconductor particles. The hydrogen production was significantly affected by electron donors, while coupling of Pt particles on SWNTs reduced H2 production