Optimizing the synthesis of carbon nanofiber based electrocatalysts for fuel cells

• Published in: Applied catalysis. B, Environmental Vol. 132-133; pp. 22 - 27
• Main Authors: Sebastián, David, Suelves, Isabel, Moliner, Rafael, Lázaro, María Jesús, Stassi, Alessandro, Baglio, Vincenzo, Aricò, Antonino Salvatore
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 27.03.2013; Elsevier
• Subjects: Applied sciences; Carbon nanofibers supports; Catalysis; Catalysts; Chemistry; Colloids; Durability; Electrochemistry; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; General and physical chemistry; Impregnation; Kinetics and mechanism of reactions; Microemulsions; Oxygen–reduction reaction; Platinum; Reduction; Synthesis; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Oxygen–reduction reaction; Durability; Platinum; Fuel cells; Carbon nanofibers supports; Oxygen; Support; Oxygen-reduction reaction; Nanofiber; Transition metal; Chemical reduction; Heterogeneous catalysis; Electrocatalysis; Synthesis; Fuel cell; Carbon fiber; Environmental protection
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2012.11.023

[Display omitted] ► Synthesis of Pt catalyst on low surface area CNF was optimized using four methods. ► Colloidal and microemulsion were appropriate methods to obtain small Pt particles. ► A volcano-shaped curve was obtained for ORR mass activity vs. Pt particle size. ► Degradation tests highlighted the need for initial Pt particles smaller than 3nm. This work deals with an optimization of the platinum dispersion on low surface area carbon nanofibers (CNFs) by using different synthesis procedures and its electrocatalytic activity toward oxygen reduction. The selected CNFs were characterized by a BET surface area of ca. 100 m2g−1 and were in-house synthesized by the decomposition of CH4 at 700°C. Pt nanoparticles were deposited by using four different synthesis routes. A metal concentration of 20wt% was confirmed by EDX and TGA. Two classical impregnation routes were employed, one using NaBH4 as reducing agent at 15°C and the second one using formic acid at 80°C. Two alternative processes consisted in a microemulsion procedure followed by reduction with NaBH4 and a colloidal route by using the sulphite complex method followed by reduction with hydrogen. The main differences regarded the platinum crystal size varying from 2.5nm for the colloidal route to 8.1nm for the impregnation route (formic acid). The classical impregnation procedures did not result appropriate to obtain a small particle size in the presence of this support, whereas microemulsion and colloidal methods fit the requirements for the cathodic oxygen reduction reaction in polymer electrolyte fuel cells, despite the low surface area of CNFs. The catalysts were subjected to an accelerated degradation test by continuous potential cycling. Although the initial activity was the highest for the microemulsion based catalyst, after the accelerated degradation test the colloidal based catalyst experienced a relatively lower loss of performance.