The success of solar fuel technology relies on the development of efficient 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)-ethylflavinium ion, Et-Fl+. Evolution of oxygen was detected during bulk electrolysis of aqueous Et-Fl+ solutions at several potentials above +1.9 V versus normal hydrogen electrode. The catalysis was found to occur on glassy carbon and platinum working electrodes, but no catalysis was observed on fluoride-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 flavin pseudobase and the oxidized carbon electrode. These findings offer an organic alternative to the traditional water-oxidation catalysts based on transition metals.
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We thank T. J. Meyer and C. L. Hill for their useful insights, and F. N. Castellano and T. E. Mallouk for their help with spectroelectrochemical and RRDE experiments. This work was supported by Bowling Green State University, National Science Foundation (CHE-1055397 CAREER award to K.D.G. and CHE-0743258 for C.M.H.) and the Ohio Supercomputer Center. S.V. acknowledges an Ohio State University Presidential Fellowship.
The authors declare no competing financial interests.
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Mirzakulova, E., Khatmullin, R., Walpita, J. et al. Electrode-assisted catalytic water oxidation by a flavin derivative. Nature Chem 4, 794–801 (2012). https://doi.org/10.1038/nchem.1439
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