TY - JOUR
T1 - Low-temperature water-gas shift on Pt/Ce0.8La0.2O2-δ-CNT
T2 - The effect of Ce0.8La0.2O2-δ/CNT ratio
AU - Petallidou, K. C.
AU - Polychronopoulou, K.
AU - Fierro, J. L.G.
AU - Efstathiou, A. M.
N1 - Funding Information:
The European Regional Development Fund, the Republic of Cyprus and the Research Promotion Foundation of Cyprus are gratefully acknowledged for their financial support through the project TECHNOLOGY/0308(BE)/05. The Rossetter Holdings Ltd is also acknowledged for providing the CNTs (Ros1-E13). The authors also thank Profs. Soghomon Boghosian (University of Patras, Greece) and Mika Huuhtanen (Oulu University, Finland) for Raman and FE-SEM studies, respectively.
Publisher Copyright:
© 2015 Elsevier B.V. All rights reserved.
PY - 2015/9/5
Y1 - 2015/9/5
N2 - Hybrid materials of (100 - x) wt% Ce0.8La0.2O2-δ-x wt% CNT composition (x = 0, 7.5, 20.5, 32.5, 44.1 and 100) were synthesized using the urea-assisted co-precipitation method and used as supports of 0.5 wt% Pt toward the low-temperature WGS (LT-WGS) reaction. The main focus of this work was to provide fundamental understanding of the effect of Ce0.8La0.2O2-δ/CNT ratio on the LT-WGS catalytic activity of such materials. It was found that the material containing 44.1 wt% CNT presented the best catalytic activity (kinetic rate and CO conversion), result that is correlated with the following parameters: (i) Pt-CO bond strength (TPD-CO), (ii) extent of dispersion of the Ce0.8La0.2O2-δ phase in the hybrid support system and, thus of the Pt phase; the larger dispersion of the Ce0.8La0.2O2-δ phase had a direct impact on its reducibility ability (labile oxygen species), (iii) concentration of surface Ce3+ species (XPS), indication for an increased concentration of oxygen vacant sites, (iv) Pt-H bond strength (H2-TPD studies), and (v) concentration of active carbon-containing intermediates, "C-pool" formed around each Pt nanoparticle (SSITKA studies). WGS kinetic studies at 300°C revealed that the reaction order with respect to CO was 0.17 and 0.13 for the catalysts containing 20.5 and 44.1 wt% CNT, respectively, while the reaction order with respect to H2O was 1.40 for the latter CNT loading. Oxidation of CNTs over the catalyst containing 44.1 wt% of CNTs occurred at temperatures larger than 400°C, result of practical importance for the LT-WGS reaction. The proposed WGS reaction mechanism over the present catalytic materials is that of "redox" in parallel with the "associative with -OH group regeneration" mechanism.
AB - Hybrid materials of (100 - x) wt% Ce0.8La0.2O2-δ-x wt% CNT composition (x = 0, 7.5, 20.5, 32.5, 44.1 and 100) were synthesized using the urea-assisted co-precipitation method and used as supports of 0.5 wt% Pt toward the low-temperature WGS (LT-WGS) reaction. The main focus of this work was to provide fundamental understanding of the effect of Ce0.8La0.2O2-δ/CNT ratio on the LT-WGS catalytic activity of such materials. It was found that the material containing 44.1 wt% CNT presented the best catalytic activity (kinetic rate and CO conversion), result that is correlated with the following parameters: (i) Pt-CO bond strength (TPD-CO), (ii) extent of dispersion of the Ce0.8La0.2O2-δ phase in the hybrid support system and, thus of the Pt phase; the larger dispersion of the Ce0.8La0.2O2-δ phase had a direct impact on its reducibility ability (labile oxygen species), (iii) concentration of surface Ce3+ species (XPS), indication for an increased concentration of oxygen vacant sites, (iv) Pt-H bond strength (H2-TPD studies), and (v) concentration of active carbon-containing intermediates, "C-pool" formed around each Pt nanoparticle (SSITKA studies). WGS kinetic studies at 300°C revealed that the reaction order with respect to CO was 0.17 and 0.13 for the catalysts containing 20.5 and 44.1 wt% CNT, respectively, while the reaction order with respect to H2O was 1.40 for the latter CNT loading. Oxidation of CNTs over the catalyst containing 44.1 wt% of CNTs occurred at temperatures larger than 400°C, result of practical importance for the LT-WGS reaction. The proposed WGS reaction mechanism over the present catalytic materials is that of "redox" in parallel with the "associative with -OH group regeneration" mechanism.
KW - Carbon nanotubes
KW - CeLaO
KW - SSITKA
KW - Supported Pt
KW - Urea co-precipitation synthesis
KW - WGS reaction
UR - http://www.scopus.com/inward/record.url?scp=84942368804&partnerID=8YFLogxK
U2 - 10.1016/j.apcata.2015.03.001
DO - 10.1016/j.apcata.2015.03.001
M3 - Article
AN - SCOPUS:84942368804
SN - 0926-860X
VL - 504
SP - 585
EP - 598
JO - Applied Catalysis A: General
JF - Applied Catalysis A: General
ER -