Deciphering the role of nano-CeO2 morphology on the dry reforming of methane over Ni/CeO2 using transient and isotopic techniques
Michalis A. Vasiliades, Constantinos M. Damaskinos, Maria Lykaki, Sofia Stefa, Vassiliοs Binas, Theocharis Kentri, Soghomon Boghosian, Michalis Konsolakis, Angelos M. Efstathiou
Abstract
The effect of ceria morphology, nanorods-NR and nanopolyhedra-NP on important kinetic parameters of the dry reforming of methane (DRM) over Ni/nano-ceria (d Ni ∼20 nm) was investigated by transient and isotopic experiments. Transient isothermal reduction by hydrogen evidenced lower activation energy and higher reduction rates of lattice oxygen in the case of CeO 2 -NR compared to those of CeO 2 -NP. Transient 16 O/ 18 O isotopic exchange provided a lower E app of bulk oxygen diffusion (by ∼90 kJ mol −1 ) for CeO 2 -NR compared to CeO 2 -NP. 18 O/ 16 O isotopic exchange followed by DRM revealed higher carbon oxidation rates by lattice oxygen to C 18 O(g) in the case of CeO 2 -NR compared to those of CeO 2 -NP, in harmony with the lower amount of carbon accumulated in the former catalyst. The lower E app of DRM and carbon oxidation by lattice oxygen confirm the higher DRM activity on Ni/CeO 2 -NR compared to Ni/CeO 2 -NP. HAADF-STEM and Raman studies were linked to the observed transient kinetic results.