Oxygen Mobility in Pre-Reduced Nano- and Macro-Ceria with Co Loading: An AP-XPS, In-Situ DRIFTS and TPR Study

Sohn, Hyuntae
Çelik, Gökhan
Gunduz, Seval
Dogu, Doruk
Zhang, Shiran
Shan, Junjun
Tao, Franklin Feng
Ozkan, Umit S.
The size effect of ceria nanoparticles on surface oxygen mobility and formation of surface oxygen vacancies in ethanol steam reforming was investigated. Higher concentration of Ce3+ surface sites of the ceria nano-particles (~4 nm, NP) was observed compared to the micro-particles (~120 nm, MP). Similarly, studies using ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) exhibited higher intensity of O1s assigned to the hydroxyl group bonding to Ce3+ and significantly lower intensity for lattice oxygen, stemming from an increase in the number of oxygen vacancies and enhanced oxygen mobility in the nano-ceria under ethanol steam reforming conditions. The presence of fully reduced cobalt particles (Coo) facilitated ceria reduction through hydrogen spillover. The comparison of cerium oxidation states between pre-reduced CeO2 and pre-reduced Co/CeO2 indicated higher extent of reduction of cerium in the case of Co/CeO2 for ethanol steam reforming. These results, together with our previous investigations where higher Ce3+ was observed over CeO2 compared to Co/CeO2 after pre-oxidation treatments, indicate that the initial state of cobalt in Co/CeO2 affects the oxidation state of cerium. Lastly, both nano-ceria and micro-ceria bare supports showed moderate C–C cleavage activities in ethanol steam reforming where better activity was observed over nano-ceria. Formate species were observed predominantly in the DRIFTS spectra of the nano-ceria whereas major species were acetates for micro-ceria. The dissimilarity in the reaction network was attributed to the difference in the number of surface oxygen vacancies. The Co/CeO2-NP catalyst was found more active compared to Co/CeO2-MP with higher hydrogen yield and ethanol conversion.
Catalysis Letters


Zeolite framework stabilized nickel(0) nanoparticles: Active and long-lived catalyst for hydrogen generation from the hydrolysis of ammonia-borane and sodium borohydride
Zahmakiran, Mehmet; Ayvali, Tugce; Akbayrak, Serdar; Caliskan, Salim; Celik, Derya; Özkar, Saim (Elsevier BV, 2011-07-19)
Among the hydrogen storage materials, ammonia-borane and sodium borohydride appear to be promising candidates as they can release hydrogen on hydrolysis in aqueous solution under mild conditions. Here, we report the development of a cost-effective and highly active nickel(0) nanoparticles catalyst for the hydrolysis of ammonia-borane and sodium borohydride. Nickel(0) nanoparticles confined in zeolite framework were prepared by using our previously established procedure and characterized by ICP-OES, XRD, TEM...
Oxygen adsorption on Pt/TiO2 catalysts
Üner, Deniz; Ozen, I; Uner, M (Elsevier BV, 2003-09-30)
Oxygen adsorption overPt/TiO2 surfaces were investigated as a function of metal loading. Oxygen adsorption over pure TiO2 was molecular at all pressure ranges investigated. On the other hand, differential heats of adsorption measured by adsorption calorimetry indicated that oxygen adsorption was dissociative over Pt/TiO2 surfaces until the Pt surface was saturated with oxygen. The saturation coverage of atomic oxygen on Pt was determined as approximately one from adsorption calorimetry. The initial heat of ...
Methane to higher hydrocarbons via halogenation
Degirmenci, V; Üner, Deniz; Yılmaz, Ayşen (Elsevier BV, 2005-10-15)
Activation of methane with a halogen followed by the metathesis of methyl halide is a novel route from methane to higher hydrocarbons or oxygenates. Thermodynamic analysis revealed that bromine is the most suitable halogen for this goal. Analysis of the published data on the reaction kinetics in a CSTR enabled us to judge on the effects of temperature, reactor residence time and the feed concentrations of bromine and methane to the conversion of methane and the selectivity towards mono or dibromomethane. Th...
Oxidative coupling of methane over NbO (p-type) and Nb2O5 (n-type) semiconductor materials
Erarslanoglu, Y; Onal, I; Doğu, Timur; Senkan, S (Springer Science and Business Media LLC, 1996-01-01)
Oxidative coupling of methane to higher hydrocarbons was investigated using two types of semiconductor catalysts, NbO (p-type) and Nb2O5 (n-type) at 1 atm pressure. The ratio of methane partial pressure to oxygen partial pressure was changed from 2 to 112 and the temperature was kept at 1023 K in the experiments conducted in a cofeed mode. The results indicated a strong correlation between C-2+ selectivity performance and the electronic properties of the catalyst in terms of p- vs. n-type conductivity. The ...
Coke Minimization in Dry Reforming of Methane by Ni Based Mesoporous Alumina Catalysts Synthesized Following Different Routes: Effects of W and Mg
ARBAĞ, HÜSEYİN; YAŞYERLİ, SENA; YAŞYERLİ, NAİL; Doğu, Timur; DOĞU, GÜLŞEN (Springer Science and Business Media LLC, 2013-12-01)
Ni based mesoporous alumina (MA) catalysts were synthesized by sol-gel (SGA) and hydrothermal (MA) methods, following impregnation and one-pot synthesis routes and catalytic performances of these materials were tested in dry reforming of methane. Results proved the importance of synthesis procedure of the MA supports on the activity and coke resistance of the synthesized materials, containing 16 % Ni. Among these catalysts, MA prepared by the sol-gel technique (Ni@SGA) showed the highest activity in dry ref...
Citation Formats
H. Sohn et al., “Oxygen Mobility in Pre-Reduced Nano- and Macro-Ceria with Co Loading: An AP-XPS, In-Situ DRIFTS and TPR Study,” Catalysis Letters, pp. 2863–2876, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/38591.