MWCNT-COOH supported PtSnNi electrocatalysts for direct ethanol fuel cells: Low Pt content, selectivity and chemical stability.

PtSnNi electrocatalysts (60: 40: 40 mass ratio) supported on Vulcan® XC-72 (Cabot) carbon and COOH-functionalized multiwalled carbon nanotubes (Cheaptubes®) with 15% of metal loading were prepared. The nanoparticles size of 2–3 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 12 mW cm−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. Image 1 • The MWCNT-COOH support originated species for ethanol oxidation reaction. • PtSnNi/MWCNT-COOH presented greatest activity with good chemical stability. • PtSnNi/MWCNT-COOH selectively produces acetic acid and acetaldehyde. [ABSTRACT FROM AUTHOR]