Lujiaxi Lecture: Water Splitting on Some Heterogeneous Photocatalysts

Topic: Water Splitting on Some Heterogeneous Photocatalysts

Lecturer: Prof. Kazunari Domen

Professor, Department of Chemical System Engineering, School of Engineering, the University of Tokyo

Time: 10:00-11:00, October 26, 2014 (Sunday)

Location: Room 202, Lujiaxia Building

Prof. Kazunari Domen joined Chemical Resources Laboratory, Tokyo Institute of Technology in 1982 as Assistant Professor and was subsequently promoted to Associate Professor in 1990 and Professor in 1996. Moving to the University of Tokyo as Professor in 2004 Domen has been working on overall water splitting reaction on heterogeneous photocatalysts to generate clean and recyclable hydrogen. In 1980, he reported NiO-SrTiO3 photocatalyst for overall water splitting reaction, which was one of the earliest examples achieving stoichiometric H2 and O2 evolution on a particulate system. In 2005, he has succeeded in overall water splitting under visible light (400 nmHis research interests now include heterogeneous catalysis and materials chemistry, with particular focus on surface chemical reaction dynamics, photocatalysis, solid acid catalysis, and mesoporous materials.

Abstract:

Water Splitting on Some Heterogeneous Photocatalysts

Kazunari Domen

Department of Cheical System Engineering, School of Engineering,
The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

domen@chemsys.t.u-tokyo.ac.jp

Photocatalytic water splitting under sunlight has been studied as a means of large-scale production of renewable hydrogen. It is necessary to harvest long-wavelength visible light to achieve sufficient solar-to-hydrogen conversion efficiencies with reasonable quantum efficiencies. The author has studied the water splitting reaction on various forms of semiconductor photocatalysts under visible light illumination. In this talk, recent progress in the photocatalytic water splitting reaction is presented.

Some (oxy)nitride semiconductors have band gap the potential of which is suitable for overall water splitting under visible light. (Ga1-xZnx)(N1-xOx) and ZrO2-modified TaON are representative examples. However, their potential for solar energy conversion is limited because their absorption edge wavelengths are shorter than 500 nm. Recently, it was found that LaMg1/3Ta2/3O2N could be activated in the overall water splitting reaction under visible light irradiation up to approximately 600 nm by appropriate surface modifications to suppress the self-oxidation.

Z-scheme systems can utilize visible light efficiently because the energy required to drive each photocatalyst can be lowered compared with the overall water splitting reaction. A major challenge in developing high-performing Z-scheme systems lies in ensuring efficient transfer of electrons between two different photocatalysts without deteriorating their intrinsic photocatalytic properties. Recently, it was found that a Z-scheme system consisting of a hydrogen evolution photocatalyst and an oxygen evolution photocatalyst immobilized onto a metal thin layer for electron transport showed significantly higher photocatalytic activity for overall water splitting than a conventional powder suspension system. The newly-developed solid-state Z-scheme device offers an advanced concept to overcome limitations of the earlier Z-scheme systems.