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PUBLISHED ONLINE: 25 MARCH 2012 | http://www.nature.com/doifinder/10.1038/nchem.1301
Web End =DOI: 10.1038/NCHEM.1301
A molecular ruthenium catalyst with water-oxidation activity comparable to that of photosystem II
Lele Duan1, Fernando Bozoglian2, Sukanta Mandal2, Beverly Stewart3, Timofei Privalov3*, Antoni Llobet2,4* and Licheng Sun1,5*
Across chemical disciplines, an interest in developing articial water splitting to O2 and H2, driven by sunlight, has been motivated by the need for practical and environmentally friendly power generation without the consumption of fossil fuels.
The central issue in light-driven water splitting is the efciency of the water oxidation, which in the best-known catalysts falls short of the desired level by approximately two orders of magnitude. Here, we show that it is possible to close that two orders of magnitude gap with a rationally designed molecular catalyst [Ru(bda)(isoq)2] (H2bda 5 2,2-bipyridine-6,6-dicarboxylic acid; isoq 5 isoquinoline). This speeds up the water oxidation to an unprecedentedly high reaction rate with a turnover frequency of >300 s21. This value is, for the rst time, moderately comparable with the reaction rate of 100400 s21 of the oxygen-evolving complex of photosystem II in vivo.
Splitting water into O2 and H2 using sunlight is a clean and sustainable proposition for addressing many of the energy and environmental problems encountered in our society,
because solar energy and water are generally plentiful, and hydrogen is a clean fuel. Water oxidation (2H2O 4H 4e2 O2), as one
half of the reaction for water splitting, provides electrons and protons for the second half reaction (hydrogen production), which is catalysed by a proton reduction catalyst. It is the water oxidation step that has long been considered the bottleneck of the water-splitting process, so the invention of highly active and rugged water oxidation catalysts (WOCs) is a key step in the development of light-driven water splitting14.
In the naturally occurring photosystem II (PSII), water oxidation occurs at a [Mn4CaO5] cluster embedded in a complex protein environment5 known as the oxygen-evolving complex (OEC), which produces oxygen at rates estimated at 100400 s21 (ref. 6).Because replication of the OEC is extremely difcult, a relatively simple metal-containing complex is currently sought that will combine adequate catalytic activity with chemical stability.Indeed, there have been notable developments in relation to mono- and di-nuclear ruthenium- (refs 79), iridium- (refs 1012), manganese- (refs...