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Coupling orientation and mediation strategies for efficient electron transfer in hybrid biofuel cells


Enzymes are promising electrocatalysts for electron transfer (ET) in many biological processes. Strategies to enhance ET between enzymes and electroactive surfaces include orientation and immobilization of the enzymes and electron mediation. Here, we develop a strategy to couple orientation and electron mediation on electrodes based on carbon nanotubes. This is achieved by the synthesis of a redox mediator that contains an enzyme-orientation site (pyrene), an electron-carrier redox mediator (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS)) and an electropolymerizable monomer (pyrrole). The coupling of an enzymatic orientation and a mediated ET in the same chemical structure (pyrrole–ABTS–pyrene (pyrr–ABTS–pyr)) provides a much-improved performance in the bioelectrocatalysis. We demonstrate two fuel cells for the synthesized redox mediator. In a proton-exchange membrane hydrogen/air fuel cell and in a membraneless fuel cell, the pyrr–ABTS–pyr biocathode provides a power density of 1.07 mW cm−2 and 7.9 mW cm−2, respectively. The principle of coupling an enzyme orientation and a redox mediator allows a great variety of mediators to be engineered and provides vast possibilities for the development of fuel cells.

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Fig. 1: The as-designed poly(pyrr)–ABTS–pyr film.
Fig. 2: Electropolymerization of the pyrr–ABTS–pyr monomer.
Fig. 3: Structural features of pyrr–ABTS–pyr redox film.
Fig. 4: The pyrr–ABTS–pyr monomer as a redox mediator for the bioelectrocatalytic reduction of oxygen by Lac.
Fig. 5: QCM measurement during the immobilization of Lac.
Fig. 6: Chronoamperometry on pyrr–ABTS–pyr for the bioelectrocatalytic reduction of oxygen by Lac.
Fig. 7: MlFC performance.
Fig. 8: PEMFC performance.


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This project is funded by the National Research Foundation, Prime Minister’s Office, Singapore, under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.

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K.E., A.C.F. and J.-M.L. designed the chemical structures. K.E. developed the protocol for the organic synthesis. D.C. made the fuel cell reactor. K.E. and A.F. carried out the electrochemical characterization. J.-M.L. designed the electrode functionalized with polymers and Lac, and K.E. conducted all the experiments. J.-M.L. was responsible for the project management. K.E and J.-M.L. prepared the manuscript.

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Correspondence to Jong-Min Lee.

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Elouarzaki, K., Cheng, D., Fisher, A.C. et al. Coupling orientation and mediation strategies for efficient electron transfer in hybrid biofuel cells. Nat Energy 3, 574–581 (2018).

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