The efficient immobilization and orientation of bilirubin oxidase from Myrothecium verrucaria on multi-walled carbon nanotube electrodes by using π-stacked porphyrins as a direct electron-transfer promoter is reported. By comparing the use of different types of porphyrin, the rational effect of the porphyrin structure on both the immobilization and orientation of the enzyme is demonstrated. The best performances were obtained for protoporphyrin IX, which is the natural precursor of bilirubin. These electrodes exhibit full orientation of the enzyme, as confirmed by the observable non-catalytic redox system corresponding to the T1 copper center associated with pure Nernstian electrocatalytic behavior with high catalytic currents of almost 5 mA cm(-2) at neutral pH.

We report the controlled orientation of bilirubin oxidases (BOD) from Myrothecium verrucaria on multiwalled carbon nanotubes (MWCNTs) functionalised by electrografting of 6-carboxynaphthalenediazonium and 4-(2-aminoethyl)benzenediazonium salts. On negatively charged naphthoate-modified MWCNTs, a high-potential (0.44 V vs. SCE) oxygen reduction electrocatalysis is observed, occurring via the T1 copper centre. On positively charged ammonium-modified MWCNTs, a low-potential (0.15 V) oxygen reduction electrocatalysis is observed, occurring through a partially oxidised state of the T2/T3 trinuclear copper cluster. Finally, chemically modified naphthoate MWCNTs exhibit high bioelectrocatalytic current densities of 3.9 mA cm(-2) under air at gas-diffusion electrode.

A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H /2 H interconversion from pH 0 to 9, with catalytic preference for H oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm , only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm , a new efficiency record for a hydrogen biofuel cell with base metal catalysts.