INVESTIGATION OF PdIr/C ELECTROCATALYSTS
AS ANODE ON THE PERFORMANCE OF DIRECT
AMMONIA FUEL CELL
Ricardo M. Piasentin, Mônica H. M. T. Assumpção, Sirlane G. da Silva, Rodrigo F. B.
de Souza, Guilherme S. Buzzo, Estevam V. Spinacé, Almir O. Neto, Júlio César M.
Silva
Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP. Av. Prof. Lineu
Prestes, 2242 Cidade Universitária, CEP 05508-900, São Paulo, SP, Brazil
[email protected]
Direct ammonia fuel cell (DAFC) performance at 40 ºC and 50 ºC was
investigated using as anode Pd/C, PdIr/C (Pd:Ir atomic ratios of 90:10, 70:30, 50:50,
30:70 and 10:90), Ir/C electrocatalysts prepared by the borohydride reduction process
and NH4OH 1.0, 3.0 and 5.0 mol L-1 in KOH 1.0 mol L-1 as fuel. X-ray analysis of
PdIr/C electrocatalysts suggested the formation of PdIr alloy, while the transmission
electron micrographs showed the average particle diameters between 4.6 and 6.2 nm.
Using PdIr/C 30:70 electrocatalyst and NH4OH 5.0 mol L-1 in KOH 1.0 mol L-1 at 40˚C
a maximum power density was 60% and 30% higher than that obtained using Pd/C and
Ir/C electrocatalysts, respectively. The enhanced synergic effect in these specific ratio
may be assigned to an optimal ratio of Pd sites that dehydrogenate ammonia at low
overpotential with the lower surface coverage of Nads on Ir due to OH- co-adsorption,
and the lower Nads-Ir binding energy than Nads-Pd. Furthermore, electronic effect
between Pd and Ir might also contribute to a decreasing of poisoning on catalyst
surface by Nads. It was also observed for all electrocatalysts evaluated that there was an
increasing in fuel cell performance, increasing the temperature to 50 ºC.
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