Bromide anion exchange, a method that consists of the introduction of KBr before the reduction of precursor salts by sodium borohydride, has enabled the synthesis of AuPt nanoparticles. Physicochemical techniques have been used to analyze these carbon Vulcan-modified catalytic powders that exhibit face-centered cubic structures. The powders of the bimetallic materials were mainly composed of solid solutions. These materials were utilized in the preparation of electrocatalysts toward the oxidation of carbon monoxide and glucose. In situ reflectance infrared spectroscopy measurements demonstrated that AuPt anodes were more active than Pt in the removal of adsorbed CO at ca. 0.2 V vs. RHE and for the dehydrogenation of glucose to gluconate.In the design of a suitable material for the anode of a biofuel cell (glucose/O 2 ), it has been demonstrated that it must contain platinum, which is the most favorable catalyst for the oxidation of glucose as a fuel at low potentials, in obtaining a high open circuit voltage. Previous studies have shown that glucose electrooxidation proceeds via the dehydrogenation of the carbon in the C1-position at the Pt surface 1-7 :This oxidation mechanism has been successfully demonstrated by Largeaud et al. 8,9 in the performance of chronoamperometric measurements at 0.3 V vs. RHE, i.e. in the adsorption/desorption region of the Pt electrode. As the activation energy for the dehydrogenation of glucose is reversely proportional to the increase in temperature, 5 the oxidation process was carried out at 2 • C in order to enhance the β-anomer, which is its electro-reactive form in aqueous solution. 6,8,9 The analysis of the electrolytic solution by chromatography and mass spectrometry has shown that the primary reaction product was glucono-δ-lactone, which evolved via hydrolysis to gluconic acid. The selective oxidation of glucose with two involved electrons/molecule on the Pt surface is similar to its specific transformation of glucose oxidase (GOx). 10 This leads to imagine the realization of a biofuel cell in which O 2 reduction would take place on an enzyme (e.g., bilirubin oxidase -BOD or laccase), and the anode would be an abiotic catalyst, such as platinum. It is also known that the crossover of O 2 in the anodic compartment causes the production of hydrogen peroxide on GOx. 11 Recent investigations on the cathode have shown that BOD was an efficient catalyst in the reduction of O 2 to H 2 O without the generation of intermediate species such as hydrogen peroxide. 12 This leads to select the best catalyst of a fuel cell (an abiotic anode material) for the construction of a hybrid biofuel cell. Moreover, the utilization of a Pt based anode catalyst enables the avoidance of a redox mediator, which may lead to diffusion limited glucose oxidation. With the use of platinum, other challenges appear: platinum is expensive and its catalytic sites are very sensitive to adsorbed species. This leads to reduce its content in bimetallic material compositions through the addition of gold. The latter ...

This paper reports on the electroreduction of oxygen catalyzed by bilirubin oxidase (BOD) without H 2 O 2 production. The enzyme was immobilized in a Nafion® matrix in the presence of either a commercial mediator, the 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), or a synthesized osmium redox complex to increase the kinetically slow bio-electroreaction. The use of a rotating ring-disk electrode system demonstrated for the first time the absence of hydrogen peroxide production during the oxygen reduction reaction at the active BOD centers mediated by ABTS. These results were compared with those obtained on Pt-based catalyst. We showed that BOD has the advantage to reduce O 2 at a smaller overpotential value (100 mV) than Pt (260 mV).

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