Efficiency of Site‐Specific Clicked Laccase–Carbon Nanotubes Biocathodes towards O 2 Reduction

A maximization of a direct electron transfer (DET) between redox enzymes and electrodes can be obtained through the oriented immobilization of enzymes onto an electroactive surface. Here, a strategy for obtaining carbon nanotube (CNTs) based electrodes covalently modified with perfectly control‐oriented fungal laccases is presented. Modelizations of the laccase‐CNT interaction and of electron conduction pathways serve as a guide in choosing grafting positions. Homogeneous populations of alkyne‐modified laccases are obtained through the reductive amination of a unique surface‐accessible lysine residue selectively engineered near either one or the other of the two copper centers in enzyme variants. Immobilization of the site‐specific alkynated enzymes is achieved by copper‐catalyzed click reaction on azido‐modified CNTs. A highly efficient reduction of O 2 at low overpotential and catalytic current densities over −3 mA cm −2 are obtained by minimizing the distance from the electrode surface to the trinuclear cluster.