Enhanced Bioelectrocatalytic Reduction of O2 By Laccase Using an Ethanol-Induced Immobilization on Nitrogen-Rich Carbon Nanofibers

Abstract

The use of carbon nanomaterials as potential alternative materials suitable for energy storage and for applications in metal-free catalytical fuel cells have been studied significantly. This has led to the development of various enzymatic catalysts for bioelectrocatalytic oxygen reduction reaction (ORR) on carbon nanomaterials to enhance their electrochemical properties. The selection of catalytic enzymes and electrodes, and immobilization of enzymes to allow direct electron transfer (DET) are highly desirable for achieving effective enzymatic biofuel cells (BFCs). Laccases, multicopper oxidoreductases, are suitable for such needs in biofuel cells due to its thermostability, substrates-versatility, and high redox potential that can employ direct electron transfer, thus, improving bioelectrocatalytic reactions. Recent studies have revealed that electrocatalysis with laccase can be enhanced by selectively orienting laccase active sites near the electrode, promoting fast and direct electron transfer to allow high current density reached at high redox potential. Here, we present a simple technique of immobilizing laccase on our nitrogen-rich graphitic carbon nanofibers by regulating the enzyme orientation with ethanol treatment. The effect of ethanol on laccase for electrocatalysis has been investigated electrochemically on nitrogen-rich graphitic carbon nanofibers synthesized via a stress-induced pyrolysis. Its performance is also compared to that of glass-like carbon nanofibers, glassy carbon and Toray carbon papers. Our findings show a cost-effective and time-efficient fabrication approach for enhancing bioelectrocatalytic oxygen reduction of laccase using ethanol treatment and the incorporated electrocatalytic effect of graphitic and pyridinic nitrogen groups in pyrolytic carbon nanofibers.