Effect of ionically conductive supports on the catalytic activity of platinum and ruthenium nanoparticles for ethylene complete oxidation

The effect of the support nature on the catalytic activity of platinum and ruthenium nanoparticles is investigated for ethylene complete oxidation in the temperature range of 25-220 degrees C. The nanoparticles (NPs) were deposited on ionically conductive supports: yttria-stabilized zirconia (YSZ) and samarium-doped ceria (SDC), and on non-ionically conductive supports: carbon black (C) and gamma-alumina (gamma-Al2O3) to give <= 0.7 wt% loading and an average particle sizes of 1.9-2.9 nm depending on the support. The presence of O-2-ionic conductivity greatly enhanced Pt and Ru catalytic activity compared with the same metals deposited on non-ionically conductive supports for C2H4 complete oxidation. The light off temperatures of Pt/SDC and Ru/SDC were 60 degrees C and 70 degrees C, respectively, whereas for the same NPs deposited on the high surface area carbon, the higher temperatures of 90 degrees C for Pt/C and 130 degrees C for Ru/C were obtained. The same trend was observed with activation energies, which were 22 and 35.1 kJ/mol for Pt/SDC and Ru/SDC compared with 31 and 52.4 kymol for Pt/C and Ru/C, respectively. It is proposed that metal-support interaction (MSI), in particular, the electronic effect between NPs and ionic conductors is responsible for the high catalytic activity. The electronic effect is manifested by the oxygen ion exchange in the vicinity of the three-phase boundary similar to the electrochemical promotion mechanism, which is thermally self-induced in the case of Pt and Ru NPs deposited on SDC and YSZ. (C) 2014 Elsevier B.V. All rights reserved.