Alcohol Dehydrogenase Immobilized on TiO2 Nanotubes for Ethanol Microfluidic Fuel Cells

In this work, an alcohol dehydrogenase (ADH) enzyme was used for ethanol oxidation in an air-breathing type microfluidic fuel cell. A bioanode was prepared using a catalytic ink prepared by using a mixture of ADH enzyme, tetrabutylammonium bromide, and Nafion and subsequently immobilized on TiO2 nanotubes, previously synthesized by electrochemical anodization. Several techniques were used to determine the successful immobilization of the enzyme and the operational parameters of the bioanode (temperature and pH). Using scanning electrochemical microscopy, the photocatalytic activity was confirmed in the bioanode from the enhanced oxidizing current densities while preserving the enzymatic activity. Finally, the as-prepared bioanode was evaluated in a microfluidic device using a Pt/C commercial as the cathode, obtaining a good performance over an open circuit potential greater than 0.9 V.