RESUMEN
This work consisted in the preparation of platinum-based catalysts supported on carbon (Vulcan XC-72) and investigation of their physicochemical and electrochemical properties. Catalysts of the C/Pt-Ni-Sn-Me (Me = Ru or Ir) type were prepared by the Pechini method at temperature of 350°C. Four different compositions were homemade: C/Pt(60)Sn(10)Ni(30), C/Pt(60)Sn(10)Ni(20)Ru(10), C/Pt(60)Sn(10)Ni(10)Ru(20), and C/Pt(60)Sn(10)Ni(10)Ir(20). These catalysts were electrochemically and physically characterized by cyclic voltammetry (CV), chronoamperometry (CA) in the presence of glycerol 1.0 mol dm(-3), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). XRD results showed the main peaks of face-centered cubic Pt. The particle sizes obtained from XRD and HRTEM experiments were close to values ranging from 3 to 8.5 nm. The CV results indicate behavior typical of Pt-based catalysts in acid medium. The CV and CA data reveal that quaternary catalysts present the highest current density for the electrooxidation of glycerol.
Asunto(s)
Electroquímica/métodos , Glicerol/química , Carbono/química , Catálisis , Microscopía Electrónica de Transmisión , Nanotecnología/métodos , Oxidación-Reducción , Tamaño de la Partícula , Platino (Metal)/química , Difracción de Rayos XRESUMEN
This paper describes the use of the electrostatic layer-by-layer (LbL) technique for the preparation of bioanodes with potential application in ethanol/O(2) 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 95 ng cm(-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 0.063 mW cm(-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 0.12 mW cm(-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.
Asunto(s)
Fuentes de Energía Bioeléctrica , Etanol/metabolismo , Nanoestructuras , Alcohol Deshidrogenasa , Aldehído Deshidrogenasa , Carbono , Dendrímeros , Enzimas Inmovilizadas , Cinética , Microelectrodos , Nanotecnología , Oxidación-Reducción , Papel , Electricidad EstáticaRESUMEN
This paper describes the preparation and application of a novel bioanode for use in ethanol/O(2) 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 0.28 mW cm(-2), and the highest power density was achieved with the bioanode prepared with 28 U of ADH, which provided a power density of 0.28 mW cm(-2) at 0.3 V. 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.