Photocatalytic hydrogen evolution using 9-phenyl-10-methyl-acridinium ion derivatives as efficient electron mediators and Ru-based catalysts

Yusuke Yamada, Kentaro Yano, Shunichi Fukuzumi

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Photocatalytic hydrogen evolution has been performed by photoirradiation (λ>420nm) of a mixed solution of a phthalate buffer and acetonitrile (MeCN) (1:1 (v/v)) containing EDTA disodium salt (EDTA), [RuII(bpy) 3]2+ (bpy=2,2′-bipyiridine), 9-phenyl-10- methylacridinium ion (Ph-Acr+-Me), and Pt nanoparticles (PtNPs) as a sacrificial electron donor, a photosensitiser, an electron mediator, and a hydrogen-evolution catalyst, respectively. The hydrogen-evolution rate of the reaction system employing Ph-Acr+-Me as an electron mediator was more than 10 times higher than that employing a conventional electron mediator of methyl viologen. In this reaction system, ruthenium nanoparticles (RuNPs) also act as a hydrogen-evolution catalyst as well as the PtNPs. The immobilization of the efficient electron mediator on the surface of a hydrogen-evolution catalyst is expected to enhance the hydrogen-evolution rate. The methyl group of Ph-Acr+-Me was chemically modified with a carboxy group (Ph-Acr +-CH2COOH) to interact with metal oxide surfaces. In the photocatalytic hydrogen-evolution system using Ph-Acr+-CH2COOH and Pt-loaded ruthenium oxide nanoparticles (Pt/RuO2NPs) as electron donor and hydrogen-evolution catalyst, respectively, the hydrogen-evolution rate was 1.5-2 times faster than the reaction system using Ph-Acr+-Me as an electron mediator. On the other hand, no enhancement in the hydrogen-evolution rate was observed in the reaction system using Ph-Acr +-CH2COOH with PtNPs. Thus, the enhancement of hydrogen-evolution rate originated from the favourable interaction between Ph-Acr +-CH2COOH and RuO2NPs. These results suggest that the use of Ph-Acr+-Me as an electron mediator enables the photocatalytic hydrogen evolution using PtNPs and RuNPs as hydrogen-evolution catalysts, and the chemical modification of Ph-Acr+-Me with a carboxy group paves the way to utilise a supporting catalyst, Pt loaded on a metal oxide, as a hydrogen-evolution catalyst.

Original languageEnglish
Pages (from-to)1573-1581
Number of pages9
JournalAustralian Journal of Chemistry
Issue number12
StatePublished - 2012

Bibliographical note

Funding Information:
This work was supported by a Grant-in-Aid (Nos. 20108010 to SF and 24350069 to YY) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, NRF/MEST of Korea through WCU (R312008-000-10010-0) and GRL (2010-00353) Programs (to SF). The authors acknowledge the Research Center for Ultra-Precision Science & Technology, Osaka University for TEM measurements and Prof. Norimitsu Tohnai for powder X-ray diffraction measurements.


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