Preparation of PdAu/C-Sbsub(2)-SnOsub(2) electrocatalysts by borohydride reduction process for direct formic acid fuel cell

Abstract

Pd/C-Sb2O5·SnO2 and PdAu/C-Sb2O5·SnO2 electrocatalysts with different PdAu atomic ratio (90:10, 70:30, and 50:50) were prepared by borohydride reduction method, and characterized by X-ray diffraction, transmission electron microscopy, cyclic voltammetry, chronoamperommetry, and performance test on direct formic acid fuel cell at 100 °C. Xray diffraction showed for Pd/C-Sb2O5·SnO2 the presence of Pd face-centered cubic (fcc) system, while for PdAu/C-Sb2O5·SnO2 it showed the presence of Pd fcc phase, PdAu fcc alloys and a segregated phases fcc Pd-rich and Au-rich phases. TEM micrographs and histograms for all electrocatalysts showed that the nanoparticles where not well dispersed on the support and some agglomerates were present. The electrochemical studies showed that PdAu/C-Sb2O5·SnO2 (70:30) had superior performance for formic acid electro-oxidation at 25 °C compared to others electrocatalysts prepared while PdAu/C-Sb2O5·SnO2 (90:10) showed superior performance in direct formic acidic fuel cell at 100 °C. These results indicated that the addition of 10–30 % Au to Pd favor the electro-oxidation of formic acid. This effect could be attributed to the synergy between the constituents of the electrocatalyst (metallic Pd and Au, SnO2, and Sb2O5·SnO2).