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We report the preparation of hybrid nanostructured bioanodes containing the enzyme alcohol dehydrogenase (ADH) with either Au, Pt, or Pt0.75Sn0.25 nanoparticles for use in ethanol/O2 hybrid biofuel cells. We describe two different methodologies for the preparation of the bioanodes: in a first case, multi walled carbon nanotubes (MWCNTs) were employed as a support for the metallic nanoparticles and TBAB-modified Nafion® aided enzyme immobilization. In the second case, we immobilized the enzymes using dendrimers-encapsulated nanoparticles as the agent for enzyme anchoring. The biofuel cell tests showed that the addition of metallic nanoparticles to the bioanode structure enhanced the overall biofuel cell performance. The bioelectrode containing Au nanoparticles displaying the best performance, with an open circuit potential of 0.61 ± 0.05 V and a maximum power density of 155 ± 11 μW cm−2. NADH cyclic voltammetric experiments indicated that Au nanoparticles behaved as a catalyst toward NADH oxidation. Comparing the two protocols we used to synthetized nanoparticles, the sample containing the Au nanoparticles supported on MWCNTs furnished fourfold higher values. Therefore, from the satisfactory results obtained, it can be inferred that the combination of small amounts of metallic nanoparticles with enzymes improve bioanode performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] The architecture of bioanodes layers makes a great difference in the wiring between de CNTs and the ADH enzyme. [•] MWCNTs enhance the activity of the enzymatic reaction between EtOH and the NAD+. [•] The anode configuration carbon cloth/poly-MG/PAMAM/MWCNTs/ADH is potentially applicable in miniaturized energy devices. [•] Power density and open circuit potential (OCP) of 0.278±0.038mWcm−2 and 0.459±0.025V were obtained for the best anode configuration investigated. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the use of the electrostatic layer-by-layer (LbL) technique for the preparation of bioanodes with potential application in ethanol/O2 biofuel cells. More specifically, the LbL technique was employed for immobilization of dehydrogenase enzymes and polyamidoamine (PAMAM) dendrimers onto carbon paper support. Both mono (anchoring only the enzyme alcohol dehydrogenase, ADH) and bi-enzymatic (anchoring both ADH and aldehyde dehydrogenase, AldDH) systems were tested. The amount of ADH deposited onto the Toray® paper was 95ngcm−2 per bilayer. Kinetic studies revealed that the LbL technique enables better control of enzyme disposition on the bioanode, as compared with the results obtained with the bioanodes prepared by the passive adsorption technique. The power density values achieved for the mono-enzymatic system as a function of the enzyme load ranged from 0.02 to 0.063mWcm−2 for the bioanode containing 36 ADH bilayers. The bioanodes containing a gas diffusion layer (GDL) displayed enhanced performance, but their mechanical stability must be improved. The bi-enzymatic system generated a power density of 0.12mWcm−2. In conclusion, the LbL technique is a very attractive approach for enzyme immobilization onto carbon platform, since it enables strict control of enzyme disposition on the bioanode surface with very low enzyme consumption. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the preparation and application of a novel bioanode for use in ethanol/O2 biofuel cells based upon immobilization of alcohol dehydrogenase (ADH) and polyamidoamine (PAMAM) dendrimers onto carbon cloth platforms. The power density measurements indicated a direct relationship between the amount of anchored ADH and the anode power values, which increased upon enzyme loading. The power density values ranged from 0.04 to 0.28mWcm−2, and the highest power density was achieved with the bioanode prepared with 28U of ADH, which provided a power density of 0.28mWcm−2 at 0.3V. The latter power output values were the maximum observed, even for higher enzyme concentrations. Stability of the bioanodes was quite satisfactory, since there was no appreciable reduction of enzymatic activity during the measurements. The method of bioanode preparation described here has proven to be very effective. The PAMAM dendrimer represents a friendly environment for the immobilization of enzymes, and it is stable and capable of generating high power density compared to other immobilization methods. [ABSTRACT FROM AUTHOR]