A novel biofuel cell based on galactose oxidase and bilirubin oxidase for efficient glycerol conversion and electricity generation

A new biofuel cell (BFC) was designed by assemblying a galactose oxidase (GalOx)-based bioanode and a bilirubin oxidase (BOD)-based biocathode. For the bioanode, GalOx was integrated within a poly(1-vinylimidazole-co-allylamine)-[Os(bispyridine) 2 Cl] redox polymer hydrogel nanostructured with multi-walled carbon nanotubes (MWCNTs), generating an electrocatalytic current density exceeding 1 mA cm −2 in the presence of 1 M glycerol. The biocathode was formed by immobilizing BOD on carbon cloth grafted with 4-aminobenzoic acid, showing efficient oxygen reduction reaction (ORR). When used as a gas diffusion electrode (GDE), the biocathode demonstrated improved ORR due to enhanced oxygen diffusion. The biocathode functioning as a GDE allows the bioanode working under oxygen-free conditions, enabling the construction of a membraneless BFC, generating a high power output. Crucially, the BFC operates with glycerol as the fuel, generating electricity while simultaneously converting glycerol into glyceraldehyde as a product with added value. In contrast with previous strategies requiring an energy input for the electrochemical oxidation of glycerol, converting an energy-consuming process into an energy-generating one. The membraneless BFC achieved a power density of (64 ± 3) μW cm −2 and an open circuit voltage (OCV) of (0.45 ± 0.02) V. When the system was operated in a two-compartment configuration, the power density increased to (143 ± 23) μW cm −2 , as both the anode and cathode could be operated under their respective optimal conditions. This work presents a novel BFC device, offering a sustainable and environmentally friendly method for producing both electricity and value-added chemicals by combining chemical, electrochemical, and enzymatic catalysis.