Electrode-assisted catalytic water oxidation by a flavin derivative

Abstract

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.

Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

“…Much effort has been devoted to the development of earth-abundant water oxidation catalysts (11)(12)(13)(14), including a recently reported completely organic catalyst (15). Less attention has been paid to the development of earth-abundant sensitizers-an important problem for WS-DSPECs where absorber-to-catalyst ratios can exceed 1,000:1.…”

Nitrogen-doped carbon nanomaterials as non-metal electrocatalysts for water oxidation

“…Amperometric responses of Pt ring electrodes at a constant potential of 1.51 V in the RRDE system were also monitored for detecting peroxide species formed at the N/C catalyst surface of the disk electrode by following the literature method. 22 As shown in Supplementary Fig. S4, almost no hydrogen peroxide was detected on the ring electrode at a scan potential ranging from 1.0 to 1.8 V (versus RHE), suggesting that the N/C catalyst favoured the four-electron oxidation of water.…”

“…Very recently, N(5)-ethyl-flavinium ions were found to function as organic non-metal electrocatalysts for water oxidation by mediating a four-electron transfer reaction 22 . Although a much higher overpotential is required for this electrocatalyst (0.73 V versus reversible hydrogen electrode (RHE), pH 2) compared with existing transition metal-based catalysts, this work has opened up a new category of OER electrocatalysts.…”

Paper‐Based N‐Doped Carbon Films for Enhanced Oxygen Evolution Electrocatalysis

“…Thus far, there are only a few illustrations of nonmetallic OER electrocatalysts, for example, N(5)‐ethylflavinium,28 N‐doped graphite,18 and graphene‐CNTs hybrid 22. However, most of their activities are still inferior to IrO 2 .…”