| dc.description | Direct ethanol fuel cells require adequate electrocatalysts to promote the carboncarbon
cleavage of ethanol molecule. Typical electrocatalysts are based on
platinum, which have shown improved activity in acidic media. However, Pt-based
catalysts have high cost and are easily deactivated by CO poisoning. Therefore,
novel catalysts have been developed, and among then, palladium-based materials
have shown promising results for the oxidation of ethanol in alkaline media. The
present study reports on the performance of alkaline direct ethanol fuel cel
(ADEFC) by using carbon-supported Pd, PdSn, PdNi, and PdNiSn produced by
impregnation-reduction of the metallic precursors. The effect of chemical
functionalization by acid treatment of the carbon support (Vulcan) was
investigated. The electrocatalysts were studied by thermogravimetric analysis
(TGA), X-rays diffraction (XRD), transmission electron microscopy (TEM), cyclic
voltammetry (CV), and ADEFC tests. TGA measurements of functionalized Vulcan
evidenced the characteristic weight losses attributed to the presence of surface
functional groups due to the acid treatment. A high degree of alloying between Pd
and Sn was inferred from XRD data, whereas in both PdNi and PdNiSn, Ni occurs
mostly segregated in the oxide form. TEM analyses indicated agglomeration of Pd
and PdSn particles, whereas a more uniform particle distribution was observed
for PdNi and PdNiSn samples. CV curves showed that the peak potential for the
oxidation of ethanol shifts towards negative values for all samples supported on
functionalized Vulcan indicating that ethanol oxidation is facilitated.
Microstructural and electrochemical features were confirmed by ADEFC tests,
which revealed that the highest open circuit voltage and maximum power density
were achieved for PdNiSn electrocatalysts supported on functionalized Vulcan
with uniform particle distribution and improved triple phase boundaries. | |
