A Study of Cerium–Manganese Mixed Oxides for Oxidation Catalysis

Gong, Zhengliang; Shah, Parag R.; Gorte, Raymond J.

doi:10.1007/s10562-007-9299-y

Cited by 49 publications

(31 citation statements)

References 35 publications

(51 reference statements)

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“…(2) and (3). The unsatisfactory attempts to cycle the pure manganese oxides are attributed to kinetics constraints in line with the poor oxygen mobility in manganese oxides [50,51].…”

Section: Resultsmentioning

confidence: 99%

Earth-abundant transition metal oxides with extraordinary reversible oxygen exchange capacity for efficient thermochemical synthesis of solar fuels

et al. 2018

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Efficient storage of solar and wind power is one of the most challenging tasks still limiting the utilization of the prime but intermittent renewable energy sources. The direct storage of concentrated solar power in renewable fuels via thermochemical splitting of water and carbon dioxide on a redox material is a scalable approach with up to 54% solar-to-fuel conversion efficiency. Despite progress, the search for earth-abundant materials that can provide and maintain high H 2 and CO production rates over long period of high-temperature cycles continues. Here, we report a strategy to unlock the use of manganese, the 12th most abundant element in the Earth's crust, for thermochemical synthesis of solar fuels, achieving superior thermochemical stability, oxygen exchange capacity, and up to seven times higher mass-specific H 2 and CO yield than cerium dioxide. We observe that incorporation of a small fraction of cerium ions in the manganese (II,III) oxide crystal lattice drastically increases its oxygen ion mobility, allowing its reduction from oxide to carbide during methane partial oxidation with simultaneous Ce exsolution. High CO 2 and H 2 O splitting rates are achieved by re-oxidation of the carbide to manganese (II) oxide with simultaneous reincorporation of the cerium ions. We demonstrate that the oxide to carbide reaction is highly reversible achieving remarkable CO 2 splitting rates over 100 thermochemical cycles of methane partial oxidation and CO 2 splitting, and preserving the initial oxygen exchange capacity of 0.65 mol O − mol Mn 1 and 89% of the fuel production rates. Due to this extraordinarily high reversible oxygen exchange capacity, the 3% Ce-doped manganese oxide achieves an average mass-specific CO yield for CO 2 splitting of 17.72 mmol CO g −1 , which is significantly higher than that previously achieved in thermochemical redox cycles. More generally, these findings suggest that incorporation of small soluble amounts of cerium in earth-abundant transition metal oxides like manganese oxide is a powerful approach to enable solar thermochemical fuel synthesis.

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“…(2) and (3). The unsatisfactory attempts to cycle the pure manganese oxides are attributed to kinetics constraints in line with the poor oxygen mobility in manganese oxides [50,51].…”

Section: Resultsmentioning

confidence: 99%

Earth-abundant transition metal oxides with extraordinary reversible oxygen exchange capacity for efficient thermochemical synthesis of solar fuels

et al. 2018

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“…It was found that the reducibility of the catalyst should be optimum for high activity. There have been investigations on the effect of redox properties of the support on the activity toward WGS and other redox reactions 33, 34. Similarly, Baldychev et al35 observed high rates of WGS with Fe supported over alumina and zirconia.…”

Section: Resultsmentioning

confidence: 99%

A mechanistic model for the water‐gas shift reaction over noble metal substituted ceria

2009

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The water-gas shift (WGS) reaction was carried out in the presence of Pd and Pt substituted nanocrystalline ceria catalysts synthesized by solution combustion technique. The catalysts were characterized by powder XRD and XPS. The noble metals were found to be present in ionic form substituted for the cerium atoms. The catalysts showed high activity for the WGS reaction with high conversions below 250 C. The products of reaction were only carbon dioxide and hydrogen, and no hydrocarbons were observed even in trace quantities. The reactions were carried out with different amounts of noble metal ion substitution and 2% Pt substituted ceria was found to be the best catalyst. The various possible mechanisms for the reaction were proposed and tested for their consistency with experimental data. The dual site mechanism best described the kinetics of the reaction and the corresponding rate parameters were obtained.

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“…A detailed description of the coulometric titration cell and apparatus has been reported previously [21][22][23][24][25] and only a brief description will be given here. Approximately 0.4 g of sample was loaded into a yttria stabilized zirconia (YSZ) tube, which was sealed at one end by an O 2 sensor consisting of a dense YSZ wafer with porous Ag electrodes on both its inner and outer surfaces.…”

Section: Measurement Of Redox Isothermsmentioning

confidence: 99%

Redox Isotherms for Vanadia Supported on Zirconia

2008

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Redox isotherms were measured for zirconiasupported vanadia between 10 -2 and 10 -28 atm at 748 K for two vanadia loadings, 2.9 and 5.8 V/nm 2 , corresponding to isolated VO 4 species and monolayer, polymeric vanadates. The catalyst with isolated VO 4 species, which is expected to have predominantly V-O-Zr linkages, had a redox isotherm that showed a well-defined step corresponding to one oxygen per V. By contrast, the redox isotherm for the catalyst with polymeric vanadates changed more gradually with P O 2 and the change in the oxygen stoichiometry corresponded to 0.85 O/V. Comparison of these results to the redox isotherms for bulk vanadates suggests that oxidation of the isolated vanadates proceeds by a direct transition from V +3 $ V +5 , while transitions from V +3 $ V +4 and V +4 $ V +5 are possible with the polyvanadates. Rate measurements for methanol and propane oxidation over the two supported vanadia catalysts and several bulk vanadates showed that specific rates for each reaction were similar on all of the samples, suggesting that that the V-O bond strength does not affect the rate determining step of these reactions.

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A Study of Cerium–Manganese Mixed Oxides for Oxidation Catalysis

Cited by 49 publications

References 35 publications

Earth-abundant transition metal oxides with extraordinary reversible oxygen exchange capacity for efficient thermochemical synthesis of solar fuels

Earth-abundant transition metal oxides with extraordinary reversible oxygen exchange capacity for efficient thermochemical synthesis of solar fuels

A mechanistic model for the water‐gas shift reaction over noble metal substituted ceria

Redox Isotherms for Vanadia Supported on Zirconia

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