Abstract
The use of high surface monolithic carbon as support for catalysts offers important advantage, such as elimination of the ohmic drop originated in the interparticle contact and improved mass transport by ad-hoc pore design. Moreover, the approach discussed here has the advantage that it allows the synthesis of materials having a multimodal porous size distribution, with each pore size contributing to the desired properties. On the other hand, the monolithic nature of the porous support also imposes new challenges for metal loading. In this work, the use of Hierarchical Porous Carbon (HPC) as support for PtPd nanoparticles was explored. Three hierarchical porous carbon samples (denoted as HPC-300, HPC-400 and HPC-500) with main pore size around 300, 400 and 500 nm respectively, are used as porous support. PtPd nanoparticles were loaded by impregnation and subsequent chemical reduction with NaBH4. The resulting material was characterized by EDX, XRD and conventional electrochemical techniques. The catalytic activity toward formic acid and methanol electrooxidation was evaluated by electrochemical methods, and the results compared with commercial carbon supported PtPd. The Hierarchical Porous Carbon support discussed here seems to be promising for use in DFAFC anodes.
Highlights
The use of liquid fuel in low temperature polymeric electrolyte membrane fuel cells (PEMFC)combines high power density and simplicity for fuel handling
The results show that the electrochemically active surface area (ESA, expressed in terms of m2 g−1) for all tree catalysts synthesized in this work is smaller than the commercial catalyst, being of 38.8 m2 g−1 for the
PtPd nanoparticles were loaded by impregnation and subsequent chemical reduction with NaBH4, resulting in well dispersed metal catalysts with surface area of about 50 m2 g−1
Summary
The use of liquid fuel in low temperature polymeric electrolyte membrane fuel cells (PEMFC). The use of carbon material as support meets these requirements: low cost, acceptable electronic resistance and chemical stability. 20% and 60% of the whole mass, requires widespread anchorage sites for catalysts nanoparticles, which results in the need for high surface materials [4]. The use of new synthetic routes allows the surface area to stay high enough, and improves the mass transport by the ad-hoc pore design in hierarchical levels. It has been proposed that severe mass transport limitations are associated to the hydrophilic character of the formic acid [8]. For these reasons, a careful material design for an efficient mass transport is necessary.
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