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PUBLISHED ONLINE: 9 NOVEMBER 2008 DOI: 10.1038/NMAT2317
A metal-free polymeric photocatalyst for hydrogen production from water under visible light
Xinchen Wang1,2*, Kazuhiko Maeda3, Arne Thomas1, Kazuhiro Takanabe3, Gang Xin3, Johan M. Carlsson4, Kazunari Domen3* and Markus Antonietti1
The production of hydrogen from water using a catalyst and solar energy is an ideal future energy source, independent of fossil reserves. For an economical use of water and solar energy, catalysts that are sufciently efcient, stable, inexpensive and capable of harvesting light are required. Here, we show that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacricial donor. Contrary to other conducting polymer semiconductors, carbon nitride is chemically and thermally stable and does not rely on complicated device manufacturing. The results represent an important rst step towards photosynthesis in general where articial conjugated polymer semiconductors can be used as energy transducers.
The search for suitable semiconductors as photocatalysts for the splitting of water into hydrogen gas using solar energy is one of the noble missions of material science. An optimal
material would combine an ability to dissociate the water molecules, having a bandgap that absorbs light in the visible range and to remain stable in contact with water. Besides, it should be non-toxic, abundant and easily processable into a desired shape.During the past 30 years, various inorganic semiconductors and molecular assemblies have been developed as catalysts for hydrogen production from water under visible light112. Semiconductors explored so far are constructed from transition-metal ions with d0 electronic configuration or post-transition-metal ions of d10 configuration, along with group VA or VIA ions as counter-anion components2,412. For photocatalysis to be chemically productive, precious-metal species11 such as Pt and RuO2 must be used in most cases as extra cocatalysts to promote the transfer of photoinduced charge carriers from the bulk to the surface at which water is converted to hydrogen gas. Metal-based complexes (for example, a complex with four manganese ions in photosystem II (ref. 13) and a di-iron centre in hydrogenases14) are in natural enzymes the active sites photocatalysing the decomposition of water. Synthetic polymer semiconductors such as polyparaphenylene15 have also been used for hydrogen production; however, they are active only in the ultraviolet region and have moderate...