Nanotubules-supported Ru nanoparticles for preferential CO oxidation in H2-rich stream

CO present in H2 provided as fuel for polymer electrolyte membrane fuel cells (PEMFC) can degrade the electrochemical performance and needs efficient removal, which can be accomplished by CO preferential oxidation (PROX). PROX catalytic activities in a H2-rich stream were tested and compared using ruthenium (Ru) nanoparticles supported on two different nanotubularly structured materials, carbon nanotubes (CNTs) and halloysite nanotubes (HNTs). In both of the support materials the morphology remains unchanged after Ru deposition and reduction, demonstrating that their tubular structure is thermally-stable. The catalytic results show that the Ru/HNTs perform better than Ru/CNTs at temperatures below about 110 °C, owing to the easier reducibility of Ru particles over the former than the latter. However, Ru/HNTs can only reach a maximum CO conversion of 55%, with an O2 selectivity of around 27% applying an O2/CO mole ratio = 1 at 123 °C, which is insufficient for PROX applications. CNTs, on the other hand, provide larger surface area and have functional groups with stronger interaction with Ru nanoparticles, presenting a better Ru dispersion, which accounts for the superior catalytic activity at higher reaction temperature. Ru/CNTs catalyst exhibits a CO conversion over 90% and O2 selectivity of around 50% applying the same O2/CO mole ratio at temperatures above 120 °C.