The first report of catalytic water oxidation by a fully organic compound, N(5)-ethylflavinium ion, Et-Fl+ is presented. Cyclic voltammograms of Et-Fl+ in acetonitrile solutions containing varying amounts of pH=2 water exhibit a catalytic peak at +1.9 V vs. NHE. Evolution of oxygen was detected during bulk electrolysis of aqueous Et-Fl+ solutions at several potentials above +1.9 V. However, the formation of H2O2 was not observed during rotating ring-disk electrode (RRDE) experiments. The catalysis was found to occur on glassy carbon and platinum working electrodes, while no catalysis was observed on fluoride-doped tin oxide (FTO) electrode. Using UV/Vis spectroelectrochemical experiments, 4a-hydroxyflavin pseudobase radical cation Et-FlOH+ was identified as the first intermediate in the catalytic cycle. Density functional theory calculations were conducted to investigate the possible mechanism of carbon electrode mediated water oxidation catalysis by Et-Fl+.Based on the calculated thermodynamic values, a mechanism is proposed in which the oxygen evolution occurs from a peroxide intermediate formed between the oxidized flavin pseudobase and the oxidized carbon electrode.

Electrode-assisted catalytic water oxidation by N(5)-ethylflavinium cation

244th National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.