Synthesis, characterization, and durability study of Pt-Co hollow nanoparticles deposited on carbon xerogel electrocatalysts for Proton Exchange Membrane Fuel Cells (PEMFC)

摘要

Proton exchange membrane fuel cell (PEMFC) catalysts are generally made of carbon black (CB)supported platinum-based nanoparticles. However, the properties of CBs, as described by RodríguezReinoso [1], are not optimal for electrocatalysis. A possible solution to the drawbacks of CBs is the use of synthetic nanostructured materials with a controllable and reproducible texture and with a pure, known and constant chemical composition; carbon xerogels (CX) exhibit such properties [2].Recently, various highly dispersed CX-supported Pt nanoparticles catalysts (Pt/CX) have been synthesized via several methods, such as the strong electrostatic adsorption (SEA) [3] or the charge-enhanced dry impregnation (CEDI) [4].However, the decrease of the Pt mass contained in the PEMFC electrodes, in particular at the cathode where the oxygen reduction reaction (ORR) is processed, remains a major challenge. Improving the ORR mass activity is currently best achieved by alloying Pt with 3d-transition metal atoms such as cobalt (Co). These alloys perform better than the ORR because the substitution of some Pt atoms by 3d-metal atoms with smaller radius leads to a modified Pt electronic structure [5]. The synthesis and durability of Pt-Co hollow particles/CX (Fig. 1) is currently being studied in our groups. The results indicate that the specific and mass activity of the bimetallic hollow particles dispersed on CX is ca. 10 times higher than that of pure Pt/CB. The first durability results show good stability of the hollow particles structure. Performances and accelerated stress tests (ASTs) in PEMFCs were finally performed.