We combine first-principles calculations with EXAFS studies to investigate the origin of high oxygen storage capacity in ceriazirconia solid solution, prepared by solution combustion method. We find that nanocrystalline Ce 0.5 Zr 0.5 O 2 can be reduced to Ce 0.5 Zr 0.5 O 1.57 by H 2 upto 850°C with an OSC of 65 cc/gm which is extremely high. Calculated local atomic-scale structure reveals the presence of long and short bonds resulting in four-fold coordination of the cations, confirmed by the EXAFS studies. Bond valence analysis of the microscopic structure and energetics is used to evaluate the strength of binding of different oxide ions and vacancies. We find the presence of strongly and weakly bound oxygens, of which the latter are responsible for the higher oxygen storage capacity in the mixed oxides than in the pure CeO 2 .

We determine chemical origins of increase in the reducibility of CeO 2 upon Ti substitution using a combination of experiments and first-principles density functional theory calculations. Ce 1-x Ti x O 2 (x ) 0.0-0.4) prepared by a single step solution combustion method crystallizes in a cubic fluorite structure, confirmed by Rietveld profile analysis. Ce 1-x Ti x O 2 can be reduced by hydrogen to a larger extent compared to CeO 2 or TiO 2 . Temperature programmed reduction of CeO 2 , TiO 2 , Ce 0.75 Ti 0.25 O 2 and Ce 0.6 Ti 0.4 O 2 up to 700 °C in H 2 gave CeO 1.96 , TiO 1.92 , Ce 0.75 Ti 0.25 O 1.81 , and Ce 0.6 Ti 0.4 O 1.73 , respectively. An extended X-ray absorption fine structure (EXAFS) study of mixed oxides at the Ti K-egde showed that the local coordination of Ti is 4:4, with Ti-O distances of 1.9 and 2.5 Å, respectively, which are also confirmed by our first-principles calculations. Bond valence analysis of the microscopic structure and energetics determined from first principles is used to evaluate the strength of binding of different oxygen atoms and vacancies. We find the presence of strongly and weakly bound oxygens in Ce 1-x Ti x O 2 , of which the latter are responsible for the higher oxygen storage capacity in the mixed oxides than in pure CeO 2 .

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We have investigated the concept of hydrogen spillover by a density functional theory (DFT) approach in combination with experimental observations. A H/Pt molar ratio of 5 to 9 is observed over Ce 1-x Pt x O 2-δ catalyst, where Pt is present in the +2 ionic state. The total hydrogen adsorbed over the catalyst is ∼30 times higher than that over nano-Pt metal particles. NMR study show protonic hydrogen over the catalyst. DFT calculations indeed support the enhanced adsorption of hydrogen on the Pt-ion-doped ceria surface via spillover to the oxide support. Further, the calculations confirm the formation of protonic hydrogen on the catalyst surface in contrast to the formation of hydridic hydrogen on Pt metal.

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Pd ion substituted Ce1-xMxO2-delta (M = Ti, Zr, Hf) have been prepared by a single step solution combustion method. Two atom% Pd ion substitution in the title compounds is confirmed by X-ray diffraction (XRD) and Pd ion charge state and redox properties have been determined by X-ray photoelectron spectroscopy (XPS) and H2/TPR studies. While Pd ion in CeO2 (Ce0.98Pd0.02O2-delta) showed higher catalytic activity for CO oxidation than Pd metal impregnated over CeO2, further increase in the catalytic activity is observed with Pd ion in Ce1-xTi(Hf)xO2 and a decrease in the activity with Pd ion in Ce1-xZrxO2. Effective charge on Pd ion could be varied by its substitution in these solid solutions Ce1-xMxO2 (M = Ti, Zr & Hf) and also in TiO2 compared to Pd ion in PdO. Effective positive charge on Pd ion is determined from the core level binding energy shift of Pd(3d5/2) peak with respect to Pd metal. Rate of CO oxidation increased and activation energy decreased with increase in effective charge on the Pd ion in the Pd ion substituted fluorites.

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Alkyl and non-alkyl cobaloximes with bis(thiophenyl)glyoxime, X/RCo(dSPhgH) 2 Py (X ) Cl, R ) Me, Et, Pr, Bu, Bn) have been synthesized and characterized for the first time. The X-ray structures of the complexes ClCo(dSPhgH) 2 Py, EtCo(dSPhgH) 2 Py, and BuCo(dSPhgH) 2 Py are reported. The orientation of SPh groups with respect to the dioxime plane varies with the steric bulk of the axial ligand and affects the NMR chemical shifts. The cis and trans influence has been studied by 1 H NMR, 13 C NMR, and X-ray diffraction. The steric cis influence of the equatorial thiodioxime affects the Co-C bond reactivity in their cobaloxime complexes. The molecular oxygen insertion into the Co-C bond and steric cis influence are related to each, and both follow the same order, dmestgH . dpgH > chgH > dSPhgH g dmgH > gH. A cyclic voltammetry study shows that the reductions, Co(III)/Co(II) and Co(II)/Co(I), are easier in ClCo(dSPhgH) 2 Py as compared to other chlorocobaloximes (gH, dmgH, dpgH, mestgH).