Alcohol Dehydrogenase Immobilized on TiO₂Nanotubes for Ethanol Microfluidic Fuel Cells

Abstract

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 TiO 2 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.

Mini-Review: Recent Technologies of Electrode and System in the Enzymatic Biofuel Cell (EBFC)

“…Enzymes are placed or immobilized on the surface of support materials, and the efficient immobilization of the enzyme is challenging. There are various ways to immobilize the enzyme on the electrode surface, such as encapsulation [3], physical adsorption, entrapment in conduction polymer [29], crosslinking [30], layer-by-layer assembly [31], and covalent attachment [32], in which the enzyme can be reusable, cost-effective, and recyclable [33]. For more understanding, the reader can view the technologies of immobilization from this reference [34].…”

“…The activity and stability of immobilized enzymes depend on the conditions and microenvironment in which enzyme molecules are confined [36]. Not only that, the materials to be used to immobilize the enzyme need to consider the hardness and electrical conductivity of the materials [33]. A novel approach by Sakthivel et al [37] used the defect and dislocation of nickel-doped MoSe 2 nanoplates for enzyme entrapment for both the bioanode and biocathode.…”

“…A convenient immobilization method recommended for interaction between enzyme and support [30] needs to increase the enzyme's storage, solvent, pH, and thermal stability [3,33,38]. However, some factors have been detected behind enzyme-support interactions that lead to low power and energy density.…”

“…The high porosity and low cost of this material increase the active site for the enzyme and give 1.37 times higher power density than without CNTs. A convenient immobilization method recommended for interaction between e and support [30] needs to increase the enzyme's storage, solvent, pH, and thermal s [3,33,38]. However, some factors have been detected behind enzyme-support inter that lead to low power and energy density.…”

“…Fe-based nanoparticles with a magnetic field gradient feature help the DET process from enzyme to electrode surface while increasing the lifetime of the EBFC. However, some studies use an additive or adhesive agent to help electron transfer, such as Nafion [33,59], n-type semiconductor polymer [25], and ferritin (Frt) [15]. created a double layer of carbon electrode in which the mesoporous carbon nanoparticle and carbon-coated magnetic nanoparticle, referring to the first and second layers of carbon electrode, activated both MET and DET, respectively.…”