Design of Carbon Nanotube‐Based Gas‐Diffusion Cathode for O₂ Reduction by Multicopper Oxidases

Abstract

Multicopper oxidases, such as laccase or bilirubin oxidase, are known to reduce molecular oxygen at very high redox potentials, which makes them attractive biocatalysts for enzymatic cathodes in biological fuel cells. By designing an enzymatic gas‐diffusion electrode, molecular oxygen can be supplied through the gaseous phase, avoiding solubility and diffusion limitations typically associated with liquid electrolytes. In doing so, the current density of enzymatic cathodes can theoretically be enhanced. This publication presents a material study of carbon/Teflon composites that aim to optimize the functionality of the gas‐diffusion and catalytic layers for application in enzymatic systems. The modification of the catalytic layer with multiwalled carbon nanotubes, for example, creates the basis for stronger π–π stacking interactions through tethered enzymatic linkers, such as pyrenes or perylene derivates. Cyclic voltammograms show the effective direct electron contact of laccase with carbon nanotube‐modified electrodes via tethered crosslinking molecules as a model system. The polarization behavior of laccase‐modified gas‐diffusion electrodes reveals open‐circuit potentials of +550 mV (versus Ag/AgCl) and current densities approaching 0.5 mA cm2 (at zero potential) in air‐breathing mode.

Direct Electrochemistry of Bilirubin Oxidase from Magnaporthe orizae on Covalently‐Functionalized MWCNT for the Design of High‐Performance Oxygen‐Reducing Biocathodes

“…[27] Microporous GDEs were first modified with at hin layer of MWCNTs. [12,16,19,[28][29][30] CV of the GDE is displayed on Figure 5.…”

Biohydrogen for a New Generation of H2/O2 Biofuel Cells: A Sustainable Energy Perspective

“…[175,323,324] Sugar/airbreathing EBFCs were recently developed and helped to overcome this issue, because oxygen is brought as a gas and not as a dissolved species. [218,[325][326][327] In view of the removal of the membrane separator in H 2 /O 2 EBFCs, mixtures of H 2 and O 2 must be controlled outside their explosive limits. This requires a search for enzymes that display high affinity toward their substrates.…”

Three Dimensional Carbon Nanosheets as a Novel Catalyst Support for Enzymatic Bioelectrodes

“…[9][10][11][12][13] Among these methods, laccase tethered with multiwalled carbon nanotubes (MWNT) exhibited very high DET for the oxygen reduction reaction (ORR), as demonstrated previously. [14][15][16] The enhancement of DET in tethered laccase-MWNT conjugates has been attributed to the high electrical conductivity and large surface area of MWNT for enzyme immobilization, and the intimate connection made possible by the molecular tethering. The benign properties of MWNTs for electrocatalysis through DET have been demonstrated using other enzymes.…”