Development of an enzymatic cascade immobilized on modified nafion to produce an efficient ethanol/O2 biofuel cell

Biofuel cells are devices that use chemical reactions to produce energy employing biological catalysts (enzymes or micro-organisms), providing clean and renewable energy, moreover present great potential as alternative power sources for low-power electronic devices. Enzymatic biofuel cells have shown a great development, nevertheless, still necessary to increase the service life of the bio cell, the power densitie. This presentation focus is the preparation cascade of enzymatic bioanodes aiming the complete oxidation of ethanol through the immobilization of dehydrogenase enzymes at carbon support surface. Enzymatic immobilization at the bioanode was performed using tetrabutylammonium modified nafion membrane. The electrochemical experiments were carried out using an AUTOLAB potentiostat / galvanostat with a threeelectrode standard cell. The cascade oxidation of ethanol was followed by electrolysis appling a cpnstant potential (0.600 V vc. Ag/AgCl) during 12 hours. The products obtained after 12 hours of electrolysis were analyzed by HPLC-UV / RID in Full-Scan mode. Ethanol / O2 biofuel cells produced power densities of 29.5 μW cm-2 with a single enzyme system, alcohol dehydrogenase (ADH), and 186.0 μW cm-2 with a two enzyme system, alcohol dehydrogenase and aldehyde dehydrogenase (ADH and AldH) on the surface of the carbon paper electrode. This result indicates that bi-enzymatic system is able to further oxidize acetaldehyde (n=2) to acetate (n=4). The maximum current density for the bi-enzymatic system during chronoamperometry was also higher (1.22 mA/cm2) compared to the system with only alcohol dehydrogenase (0.43 mA/cm2). CLAEUV / RID analytical technique was able to demonstrated that the two dehydrogenase enzymes system is able to electrochemically oxidize ethanol (40 mmol) on a carbon electrode by collecting (2< n < 4) electrons, acetaldehyde (n=2) (6.57 mmol) and acetic acid (n=4) (0.72 mmol). We concluded that the modified Nafion membranes with tetrabutylammonium bromide provide an ideal environment for enzymatic immobilization, Thus, the etanol / O2 biofuel cell acts on the first two catabolic steps of ethanol oxidation.