Biochar as catalysts support: synthesis, characterization and applications

MARÍA LUZ, NIEVA LOBOS; VANINA, COMIGNANI; JUAN MANUEL, SIEBEN; MARÍA ALICIA, VOLPE; E. LAURA, MOYANO

Carlos Paz, Córdoba

Congreso; CLAFQO-13, 13a CONFERNCIA LATINOAMERICANA DE FÍSICO-QUÍMICA ORGÁNICA.; 2015

Carbon supported Pt-based electrocatalysts are commonly used for the anodic oxidation of fuelsand the cathodic reduction of oxygen in low temperature fuel cells. However, the high cost of theplatinum limits its use. Thus, a great effort has been devoted to the development of fuel cellelectrocatalysts with the aims of increasing their activity and reducing the noble metal content.The use of carbon materials with high surface area as catalysts support improves catalystperformance and reduces the amount of catalysts and thus their costs. Charcoal (biochar) is a byproductof biomass pyrolysis. Feedstock as well as pyrolysis conditions influence the charcoalproduction varying its physical and chemical properties. The main purpose of this work was tocharacterize and evaluate the utilization of biochars, obtained from fast pyrolysis of microcrystallinecellulose (BMCC) and phosphoric acid-pretreated microcrystalline cellulose (B-TMCC), as carbonsupport 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 thatthe conditions of the material support have a strong influence on the behavior of the nanostructuredcatalysts. 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 observedthat the particles are smaller and have homogeneous size distribution in the catalysts synthesizedusing B-TMCC. The composition of the materials was determined by EDX and ICP-AES while theformation of core-shell structures has been confirmed by XRD. The catalytic activity of theelectrodes for the electrooxidation of MeOH and EtOH was evaluated by cyclic voltammetry andchronoamperometry. Electrochemical measurements showed that a Cu@Pt-Ru/B-TMCC catalystwas more active material that Cu@Pt-Ru/B-MCC for alcohol oxidation. Also, it has been shown thatthe catalytic activity of Cu@Pt-Ru/B-TMCC catalyst is more superior that obtained with acommercial Pt-Ru/C with high Pt content. The specific surface areas of the catalysts were in therange of 210-250 m2 g-1.Thus, trimetallic catalysts type core@shell with low Pt content were prepared using biochar ascatalysts support. This biochar, obtained from fast pyrolysis of cellulose, exhibited an improvedcatalytic activity for alcohols oxidation when compare to commercial Pt-Ru/C catalysts