Concepts and Technologies of Selected Seed Treatments

Abstract

The electrooxidation of 0.1m ethanol in 0.5m HClO4 is studied withdifferential electrochemical mass spectrometry (DEMS) and cyclicvoltammetry (CV) over two different carbon-supportedplatinum-nanoparticle catalysts (20 wt% metal). As documented bytransmission electron microscopy (TEM), the catalysts have similar meanparticle sizes but different particle size distributions. One catalystis composed almost entirely (> 99%) of particles less than or equal to3.5 nm while a significant fraction (21%) of the other catalyst iscomposed of particles larger than 3.5 nm. The presence of the largerparticles increases the peak oxidation current density by 116% (from0.06 to 0.13 mAcm(-2)). However, the presence of the larger particlesreduces the efficiency for complete ethanol electrooxidation to CO2 from13% to 6.4% over the full potential sweep. These differences inactivity and selectivity of the two catalysts are discussed in thecontext of previously established changes in the bonding strength ofreaction intermediates as a function of the catalyst particle size.