Nanostructured materials for direct methanol PEM fuel cells: the role of the catalyst pore size and support on the electrochemical efficiency

HORACIO R CORTI; ESTEBAN A. FRANCESCHINI; MARIANO M. BRUNO; FEDERICO A. VIVA; AGUSTINA PETRUCCELLI

Napa Valley

Conferencia; Hydrogen and Fuel Cells Conference; 2013

Zing Conferences

Monolithic and grinded mesoporous carbon (MC) with controlled pore size and optimal properties for DMFC1 were used as support of nanoparticulated (NP) and electrodeposited mesoporous (EM) catalysts, with the goals of increasing dispersion and electrochemical active surface area, improving methanol accessibility, and optimizing the transport of reaction products out of the MEA. Thus, PtRu and PdNi2 NP were supported on a high specific area MC as anodic and cathodic electrodes, respectively, and tested under DMFC conditions. PdNi2/MC cathodes have high catalytic activity for the ORR with the advantage of a very low noble metal loading, and an excellent methanol tolerance in acid media.2 PtRu/MC anodes exhibit ECSA up to 45% higher than PtRu supported on Vulcan, higher methanol oxidation current, lower poisoning rate, and 8% higher conversion efficiency to CO2 as determined by DEMS.3,4 In DMFC tests using 1 M methanol and O2, PtRu/MC anodes show peak power 67 mW.cm-2 at 60 oC (30% higher than the Vulcan supported catalyst).5 On the other hand mesoporous Pt and Pt/Ru catalysts with 2D-hexagonal mesostructure were synthesized using a triblock copolymer (Pluronic F127®) template.6 Pt/Ru alloy exhibit lower onset potential and more than three times the limit mass activity for methanol oxidation, while the mesoporous Pt electrocatalyst, characterized for the ORR shows a high efficiency of conversion to H2O, and in DMFC cathode test exhibit a high methanol to CO2 conversion efficiency and high tolerance to CO poisoning.7 Global results indicates that mesoporous PtRu catalyst with pore size close to 10 nm are more efficient in DMFC than those with smaller pore size and MC with a distribution of pore size and very high specific area is an optimal support for NP or EM catalyst. The interplay between pore size, methanol accessibility, and transport of products out of the interface will be discussed in order to rationalize the observed behavior.