Development of active, and stable water-gas-shift reaction catalysts for fuel cell applications

Water-gas-shift (WGS) reaction CO + H2O = CO2 + H2, is a key step in the generation of H2 for fuel cells. Noble metal-based catalysts are promising single stage WGS catalysts because they less sensitive than LTS catalysts (Cu based) and more active than the HTS (Ni) catalysts. High activity in CO conversion at moderate temperatures and stability during start-up - shutdown cycles is essential, especially in transport applications. A series of supported Pt catalysts was studied. Zirconia based catalysts were stable but catalyst activity was low. Pt/TiO2 and Pt/Ti0.5Ce0.5O2 gave the required commercial activity (8.10-5 mole H2 g-1cat/sec, based on a 2 kg catalyst for a 100 kw fuel cell) at 300°C. However, 35 % of initial activity was lost after 24 hr. A new promising catalyst developed has high activity as Pt/TiO2 and was very stable. The reasons for the different activities, deactivation mechanism, and the stability of the newly developed catalysts were discussed. This is an abstract of a paper presented at the 231st ACS National Meeting (Atlanta, GA 3/26-30/2006)

Steam reforming of biomass derived oxygenates to hydrogen: Importance of metal-support boundary

Steam reforming of acetic acid over Pt/ZrO2 catalysts was studied as a model reaction of steam reforming of biomass derived oxygenates. Pt/ZrO2 catalysts were very active; however, the catalyst deactivated in time by formation of oligomers which block the active sites for steam reforming. Temperature programmed oxidation of the used catalysts revealed that there are three types of deposits, on Pt, on ZrO2 close to Pt particles, and on ZrO2. The removal of the second type of deposit was essential to regenerate the catalysts. Thus, it was suggested that the Pt-ZrO2 boundary sites were active sites for steam reforming, where both Pt and ZrO2 participates in the reforming, to activate acetic acid and water, respectively. This is an abstract of a paper presented at the 231st ACS National Meeting (Atlanta, GA 3/26-30/2006)