Product Distributions and Efficiencies for Ethanol Oxidation in a Proton Exchange Membrane Electrolysis Cell

The stoichiometry, efficiency, and product distribution for ethanol oxidation in fuel cell hardware has been determined at 80°C for commercial Pt/C, PtRu/C and PtSn/C anode catalysts. The amounts of ethanol consumed and acetic acid and acetaldehyde produced were determined by proton NMR spectroscopy while CO 2 was measured with a non-dispersive infrared CO 2 monitor. The Pt/C catalyst was most selective for the complete oxidation of ethanol to CO 2 at all potentials and therefore produced the highest number of electrons per ethanol molecule (stoichiometry). Consequently, it would provide the highest efficiency for a fuel cell, and for an electrolysis cell at high current densities. However, PtRu/C provided much higher currents at low overpotentials and therefore better electrolysis efficiency than Pt/C at low current densities. The main product at the PtRu/C catalyst was acetic acid, with ≥ 86% conversion at potentials ≥ 0.35 V vs. a dynamic hydrogen electrode. The PtSn/C catalyst also provided high yields of acetic acid (65–75%), with substantial production of CO 2 (26–27%) at high potentials.