High Redox Potential Cathode Based on Laccase Covalently Attached to Gold Electrode

A new strategy for oriented covalent immobilization of Trametes hirsuta laccase on gold electrodes is presented. The strategy is based on the gold surface modification with a mixed monolayer of an aromatic diazonium salt derivative and 6-mercapto-1-hexanol for further use as scaffold for the enzyme’s covalent linkage. This strategy offers a variety of advantages such as high stability and laccase-friendly support morphology, which turns it into a suitable metal–enzyme interface. Conditions aiming at optimum orientation for direct electron transfer (DET) via the T1 copper site were studied. Current density values up to 40 μA·cm–2 were measured for the electrocatalytic reduction of O2 in the absence of redox mediators. This strategy is a big step forward in the development of laccase-modified gold electrodes for bioelectrocatalytic reduction of O2.