BIOCHAR AS CATALYST SUPPORT: PRODUCTION, CHARACTERIZATION AND APLICATION

MARIA LUZ NIEVA; MARIA ALICIA VOLPE; VANINA COMIGNANI; JUAN MANUEL SIEBEN; ELIZABETH L. MOYANO

VILLA CARLOS PAZ - CORDOBA

Conferencia; 13rd Latin American Conference on Physical Organic Chemistry (CLAFQO-13); 2015

Facultad de Cs. Quimicas - UNC

Carbon supported Pt-based electrocatalysts are commonly used for the anodic oxidation of fuels and the cathodic reduction of oxygen in low temperature fuel cells [1]. However, the high cost of the platinum limits its use. Thus, a great effort has been devoted to the development of fuel cell electrocatalysts with the aims of increasing their activity and reducing the noble metal content [2]. The use of carbon materials with high surface area as catalysts support improves catalyst performance and reduces the amount of catalysts and thus their costs. Charcoal (biochar) is a by-product of biomass pyrolysis. Feedstock as well as pyrolysis conditions influence the charcoal production varying its physical and chemical properties. The main purpose of this work was to characterize and evaluate the utilization of biochars, obtained from fast pyrolysis of microcrystalline cellulose (BMCC) and phosphoric acid-pretreated microcrystalline cellulose (B-TMCC), as carbon support of Cu core Pt-Ru shell nanoparticles for the electro-oxidation of alcohols in acid media. Biochars were characterized in order to establish several physicochemical properties: TEM, XRD, BET, SEM, TGA, EDX and conventional electrochemical techniques. All analyzes have shown that the conditions of the material support have a strong influence on the behavior of the nanostructured catalysts. TEM observations show that the catalysts could be consider as nano-size metal grains, between 4 and 5 nm, interconnected via grain boundaries (nanostructured). It has been observed that the particles are smaller and have homogeneous size distribution in the catalysts synthesized using B-TMCC. The composition of the materials was determined by EDX and ICP-AES while the formation of core-shell structures has been confirmed by XRD. The catalytic activity of the electrodes for the electrooxidation of MeOH and EtOH was evaluated by cyclic voltammetry and chronoamperometry. Electrochemical measurements showed that a Cu@Pt-Ru/B-TMCC catalyst was more active material that Cu@Pt-Ru/B-MCC for alcohol oxidation. Also, it has been shown that the catalytic activity of Cu@Pt-Ru/B-TMCC catalyst is more superior that obtained with a commercial Pt-Ru/C with high Pt content. The specific surface areas of the catalysts were in the range of 210-250 m2 g_1. Thus, trimetallic catalysts type core@shell with low Pt content were prepared using biochar as catalysts support. This biochar, obtained from fast pyrolysis of cellulose, exhibited an improved catalytic activity for alcohols oxidation when compare to commercial Pt-Ru/C catalysts.