Enhanced methanol electro-oxidation activity of PtNi alloy nanoparticles on the large surface area porous carbon

A kind of porous carbon (AC-K) with high surface area 2972 m(2)/g was obtained by treating activated carbon (AC) with KOH, which was investigated as the support for direct methanol fuel cell. PtNi nanoparticles were synthesized by chemical reduction with hydrazine using PVP as a stabilizer and deposited onto AC-K to produce PtNi/AC-K catalyst. Pt/AC-K and Pt/AC catalysts were also prepared under similar condition with the same nominal metal loading 20 wt.%. Their structures, morphologies, and electrocatalytic properties were investigated and compared. X-ray diffraction shows the alloy formation for Pt and Ni for PtNi/AC-K catalyst. Transmission electron microscopy reveals Pt/AC-K has a lower degree of agglomeration than Pt/AC. Moreover, PtNi/AC-K consists of nanoparticles with the lowest average particle size and best dispersion among the three catalysts. Nitrogen sorption at 77 K indicates that the potassium hydroxide activation can remarkably increase specific surface area and micropore volumes, which may be favorable for anchoring metal nanoparticle. Pt alloying with Ni may also contribute to the smaller particle size and better dispersion. Consequently, the activities of methanol oxidation investigated by cyclic voltammograms follow the order of PtNi/AC-K > Pt/AC-K > Pt/AC. Hence, the porous carbon AC-K and the corresponding catalyst PtNi/AC-K show great potential as support and less expensive electrocatalyst respectively for methanol electrooxidation in alkaline media in direct methanol fuel cells.