Methanol/Oxygen Enzymatic Biofuel Cell Using Laccase and NAD⁺-Dependent Dehydrogenase Cascades as Biocatalysts on Carbon Nanodots Electrodes

The efficient immobilization of enzymes on favorable supporting materials to design enzyme electrodes endowed with specific catalysis performances such as deep oxidation of biofuels, and direct electron transfer (DET)-type bioelectrocatalysis is highly desired for fabricating enzymatic biofuel cells (BFCs). In this study, carbon nanodots (CNDs) have been used as the immobilizing matrixes and electron relays of enzymes to construct (NAD + )-dependent dehydrogenase cascades-based bioanode for the deep oxidation of methanol and DET-type laccase-based biocathode for oxygen reduction to water. At the bioanode, multiplex enzymes including alcohol dehydrogenase, aldehyde dehydrogenase, and formate dehydrogenase are coimmobilized on CNDs electrode which is previously coated with in situ polymerized methylene blue as the electrocatalyst for oxidizing NADH to NAD + . At the biocathode, fungal laccase is directly cast on CNDs and facilitated DET reaction is allowed. As a result, a novel membrane-less methanol/O 2 BFC has been assembled and displays a high open-circuit voltage of 0.71(±0.02) V and a maximum power density of 68.7 (±0.4) μW cm –2 . These investigated features imply that CNDs may act as new conductive architectures to elaborate enzyme electrodes for further bioelectrochemical applications.