Functionalization of Contacted Carbon Nanotube Forests by Dip Coating for High-Performance Biocathodes

This work focuses on the use of electrically contacted carbon nanotube forests as an electrode material for the bioelectrocatalytic reduction of oxygen to water. The forests are directly grown by chemical vapor deposition on a conductive tantalum layer, which provides enough mechanic stability during several functionalization and enzyme immobilization steps. A pyrene bis-anthraquinone derivative (pyr-(AQ)(2)) was attached via pi-stacking throughout the forest and was used as an anchor molecule for oriented immobilization of laccase. This led to high-performance biocathodes for oxygen reduction via direct electron transfer with absolute maximum current densities up to 0.84 mA cm(-2) at 0.2 V vs Ag/AgCl. The morphological changes during the wet chemical processes were studied by scanning electron microscopy (SEM) revealing cellular patterning of the forest structure. Despite these changes, the forest remained attached and electrically connected to the tantalum layer. The resulting bioelectrodes performed with satisfying stabilities under constant discharge conditions and kept 75 % of its initial performances after one week.