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PUBLISHED ONLINE: 26 AUGUST 2012 | http://www.nature.com/doifinder/10.1038/nchem.1439
Web End =DOI: 10.1038/NCHEM.1439
Ekaterina Mirzakulova1, Renat Khatmullin1, Janitha Walpita1, Thomas Corrigan1,Nella M. Vargas-Barbosa2, Shubham Vyas3, Shameema Oottikkal3, Samuel F. Manzer3, Christopher M. Hadad3 and Ksenija D. Glusac1*
The success of solar fuel technology relies on the development of efcient catalysts that can oxidize or reduce water. All molecular water-oxidation catalysts reported thus far are transition-metal complexes, however, here we report catalytic water oxidation to give oxygen by a fully organic compound, the N(5)-ethylavinium ion, Et-Fl1. Evolution of oxygen was detected during bulk electrolysis of aqueous Et-Fl1 solutions at several potentials above 11.9 V versus normal hydrogen electrode. The catalysis was found to occur on glassy carbon and platinum working electrodes, but no catalysis was observed on uoride-doped tin-oxide electrodes. Based on spectroelectrochemical results and preliminary calculations with density functional theory, one possible mechanistic route is proposed in which the oxygen evolution occurs from a peroxide intermediate formed between the oxidized avin pseudobase and the oxidized carbon electrode. These ndings offer an organic alternative to the traditional water-oxidation catalysts based on transition metals.
Conversion of the suns energy into electricity is a promising approach for the development of renewable-energy sources1.However, as a result of temporal and spatial uctuations in
the availability of sunlight on the Earths surface, it is not feasible to achieve a steady production of electricity; thus, storage of the electrical energy in the form of fuels, such as molecular hydrogen, is needed. Inspired by photochemical water splitting in natural photo-synthesis2, signicant scientic efforts are aimed towards the development of solar fuel cells3. These devices are envisioned to use sunlight to split water into H2 and O2. The recombination of these gases in a fuel cell can produce electricity whenever and wherever power is needed. Photochemical water splitting appears deceptively simple, but its realization requires the development of appropriate photoelectrodes4, membranes5 and gas-evolving catalysts6,7.
Oxygen-evolving catalysts are particularly difcult to design, mostly for the following reasons810: (1) the oxidation potential of
the catalyst needs to be slightly above the thermodynamic potential for the oxidation of water to oxygen; (2) to avoid high-energy intermediates, oxidation of the catalyst must be coupled with proton transfer, followed by efcient OO bond formation; (3) the catalytic
reaction should occur...