MWCNT-COOH supported PtSnNi electrocatalysts for direct ethanol fuel cells

Abstract

PtSnNi electrocatalysts (60: 40: 40 mass ratio) supported on Vulcan® XC-72 (Cabot) carbon and COOHfunctionalized multiwalled carbon nanotubes (Cheaptubes®) with 15% of metal loading were prepared. The nanoparticles size of 2e3 nm for both supports was estimated by HRTEM. In the direct ethanol fuel cell experiments, PtSnNi/C presents 50 mA cm 2 reaching the maximum power density (MPD) of 12mWcm 2 and decreasing at higher currents, while PtSnNi/MWCNT-COOH obtains similar values of MPD (60 mA cm 2), but keeping the best performance. By GC (gas chromatography) technique, it was possible to observe that the electrocatalyst supported on MWCNT-COOH favored the ethanol oxidation to acetaldehyde and acetic acid, although the material supported on Vulcan® XC-72 carbon presented almost 100% of selectivity for acetaldehyde. This behavior was maintained also when the current of 0.1 A was applied for 80 min. For the PtSnNi/C electrocatalyst, the selectivity to only acetaldehyde can be related to Sn and Ni dissolution process that can become the electrocatalytic activity similar to Pt/C, decreasing the power density as observed in our experiments. Established by EDS analysis, after 80 min of polarization, the Ni and Sn relative atomic ratio was lower on the catalytic anodic layer of PtSnNi/C than on PtSnNi/MWCNT-COOH.