ONLINE FTIR SPECTROSCOPIC INVESTIGATIONS OF METHANOL OXIDATION IN A DIRECT METHANOL FUEL-CELL

A real-time Fourier transform infrared spectroscopy (FTIRS) analysts o f the products of methanol oxidation in a prototype direct-methanol fu el cell operating at high temperatures (150 to 185 degrees C) is repor ted here. The methanol oxidation products on platinum black and platin um-ruthenium catalyst surfaces were determined as a function of the fu el cell operating temperature, current density, and methanol/water mol e ratio. Neither formaldehyde nor formic acid was detected in anode ex haust gas at all cell operating conditions. The product distributions of methanol oxidation obtained by on-line FTIRS are consistent with ou r previous results obtained by on-line mass spectroscopy under similar conditions. With pure methanol in anode feed, methanaldimethylacetal was found to be the main product, methyl formate and CO2 were also fou nd. However, when water was present in the anode feed, the main produc t was CO2, and the formation of methanaldimethylacetal and methyl form ate decreased significantly with increase of the water/methanol mole r atio. increase of cell operating temperature enhanced the formation of CO2 and decreased the formation of methanaldimethslacetal and methyl formate. Pt/Ru catalyst is more active for methanol oxidation and has a higher selectivity toward CO2 formation than Pt-black. Nearly comple te methanol oxidation, i.e., the product was almost exclusively CO2, w as achieved using a Pt/Ru catalyst and a water/methanol mole ratio of 2 or higher in the anode feed at a temperature of 185 degrees C or abo ve.