An unexpected enhancement in methanol electro-oxidation on an ensemble of Pt(111) nanofacets: a case of nanoscale single crystal ensemble electrocatalysis

Pt nanoparticles having the same size (10 nm) but different shapes (cubic or octahedral/tetrahedral), as determined by transmission electron microscopy, were synthesized via a polyol-based synthetic procedure. Their respective electrocatalytic activities for methanol oxidation were characterized by cyclic voltammetry and chronoamperometry in both sulfuric and perchloric acid electrolytes, which showed clear shape (surface orientation) dependences. Furthermore, the octahedral/tetrahedral Pt nanoparticles displayed an unexpectedly large enhancement in methanol electro-oxidation activity; about 3-fold increase in transient intrinsic activity and 10-fold increase in CO tolerance steady-state activity when compared to commercial Pt black. Gaseous and methanolic CO adsorption on the synthesized nanoparticles were also investigated by surface-enhanced IR absorption spectroscopy in perchloric acid electrolyte, which suggested that the different trends observed might be related to the electronic effects specific to a given ensemble of the nanofacets.