Issue 1, 2015

Laser-induced pinpoint hydrogen evolution from benzene and water using metal free single-walled carbon nanotubes with high quantum yields

Abstract

Metal-free photocatalytic hydrogen evolution occurred efficiently in benzene containing single-walled carbon nanotubes under laser irradiation at 532 nm with an extremely high turnover number of 2 000 000 and a high quantum yield of 130%. The rate of hydrogen evolution increased with increasing laser intensity to exhibit a fourth power dependence, suggesting that hydrogen was evolved via four-photon processes in which the coupling of two radical anions derived from benzene is the rate-determining step and the benzene radical anion is produced by electron transfer from benzene to the doubly excited state of single-walled carbon nanotubes, which requires two photons. Polymerisation of benzene was induced by the photogenerated C6H6˙, accompanied by hydrogen evolution, resulting in a leverage effect to increase the quantum yield of hydrogen evolution to well over the 25% expected for the four-photon process. Laser-induced hydrogen evolution also occurred in water containing single-walled carbon nanotubes. In contrast to the case of benzene, water was not oxidized but hydrogen evolution from water was accompanied by the multi-oxidation of single-walled carbon nanotubes. The yield of hydrogen based on one mole of single-walled carbon nanotubes with 1.4 nm diameter and 1–5 mm length was determined to be 2 700 000%, when oxidations of single-walled carbon nanotubes occurred to produce the polyhydroxylated product.

Graphical abstract: Laser-induced pinpoint hydrogen evolution from benzene and water using metal free single-walled carbon nanotubes with high quantum yields

Supplementary files

Article information

Article type
Edge Article
Submitted
30 Jul 2014
Accepted
09 Sep 2014
First published
09 Sep 2014
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2015,6, 666-674

Author version available

Laser-induced pinpoint hydrogen evolution from benzene and water using metal free single-walled carbon nanotubes with high quantum yields

K. Ohkubo, N. Kohno, Y. Yamada and S. Fukuzumi, Chem. Sci., 2015, 6, 666 DOI: 10.1039/C4SC02269F

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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