Riboflavin as a Bioorganic Solar Fuel: Photoredox Chemistry Rationalized and Accelerated in a Miniaturized Flow Photoreactor

Abstract

With the depletion of fossil‐fuel‐based energies and the corresponding growing environmental concerns, the design of new strategies to store renewable solar energy is highly attractive. Herein, we studied a biomimetic organic solar fuel (Riboflavin – Vitamin B2) to photochemically store solar light into its amphoteric form (leucodeuteroflavin), working as a charge carrier towards a flow fuel cell. We demonstrate that miniaturization of the photoreactor permits significant reduction of the full time solar charge. Nevertheless, due to inherent leucodeuteroflavin (LDH2) degradation into lumichrome (LC), the maximum system charge (at pH=5) is limited to 13 % corresponding to a maximum power density of 0.11 mW cm−2 after 90 min. In comparison with other described photoredox electroactive systems (e. g. polyoxometalates, quinones), organic solar fuels based on flavins appear particularly promising and their chemical structure should be optimized to fit both photostability and economical requirements. In any case, this study enables a clear rationalization and quantification of the mechanism of riboflavin degradation under anaerobic conditions, which has been the topic of many discussions during the last century, and opens the way towards the development of a new generation of low‐cost renewable organic solar fuels.

Tuning the Quantum Chemical Properties of Flavins via Modification at C8

“…Furthermore, the detailed analysis presented on the electronic structure can guide development of novel flavin-based light-utilizing materials with desired spectral properties. 89,93,94 ■ ASSOCIATED CONTENT * sı Supporting Information…”

“…This information is transferable to the protein environment for understanding the differential reactivity of chemically modified flavins. Furthermore, the detailed analysis presented on the electronic structure can guide development of novel flavin-based light-utilizing materials with desired spectral properties. ,, …”

Photoswitchable Fluorescent Liquid Crystal Nanoparticles and Their Inkjet‐Printed Patterns for Information Encrypting and Anti‐Counterfeiting

“…Meanwhile, the LC components stabilize the FM4 molecules in a well‐dispersed condition within the nanocolloids. As is well known that, dicyanodistyrylbenzene‐based compounds are very ideal choice for multifunctional materials due to their remarkable optical and electrical properties that derive from their designable chemical structures . The unique AIEE effect makes them have an extensive application in condense states.…”

Mediated formic acid flow fuel cell (MFAFFC) based on biomimetic electrolytes

“…We limit the list of possible candidates to Riboflavin and Folic Acid for their low cost in the preview of eventual larger scale evaluation. In a previous study, we have demonstrated that Riboflavin can be degraded when acting as a photochemical fuel [15] leading us to focus our effort on its natural degradation side product the Lumichrome to produce biomimetic models. In this context, since Lumichrome is not water soluble, we envisaged, according to a procedure already described in literature by Janáky and Rajeshwar [16] , to add ammonium chains on the two acidic nitrogens of alloxazine skeleton in order to increase their water solubility and as a consequence their overall fuel cell capacity.…”