Investigation of reactive cerium-based oxides for H2 production by thermochemical two-step water-splitting

Abanades, Stéphane; Cordier, Anne; Péraudeau, G.; Flamant, Gilles; Julbe, A.

doi:10.1007/s10853-010-4506-4

Cited by 217 publications

(160 citation statements)

References 21 publications

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“…Among the dopants, we rst discuss Zr and Hf tetravalent dopants which aid the redox performance, 24,30,[32][33][34] before discussing those dopants which do not, i.e. di-, tri-, Ti-, and pentavalent dopants, 16,20,[23][24][25][26][27][28][29][30][31] in that order. In each case, we investigated the elements from periodic table rows 4, 5, and 6, and detail the row 5 elements and then compare the row 4 and 6 elements to the exemplar.…”

Section: Resultsmentioning

confidence: 99%

“…Di-, tri-and pentavalent dopants, including Li, Mg, Cu, Zn, Sr, Al, Sc, Cr, Mn, Fe, Co, Ni, Y, La, Pr, Sm, Gd, and Ta provide little, if any, improvement in the H 2 production capacity of ceria, although some prevent sintering and grain growth. 16,20,[23][24][25][26][27][28][29][30][31] Tetravalent Zr and Hf, however, have been shown to signicantly improve the redox capacity of ceria. 24,30,[32][33][34] To date the selection of dopants for STWS is mostly based on trial and error; therefore, we attempt to bring an understanding of ceria dopants to the STWS community.…”

Section: Oxidationmentioning

confidence: 99%

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Principles of doping ceria for the solar thermochemical redox splitting of H₂O and CO₂

Muhich

Steinfeld

2017

J. Mater. Chem. A

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Ceria-based metal oxides are promising redox materials for solar H 2 O/CO 2 -splitting thermochemical cycles. Density functional theory (DFT) computations are applied to elucidate the underlying mechanism of the role of dopants in facilitating ceria based redox cycles; specifically, we explain why some dopants increase performance, while others do not. Firstly, we find that Zr and Hf dopants increase the oxygen exchange capacity of ceria because they store energy in tensilely strained Zr-or Hf-O bonds which is released upon O-vacancy formation. This finding corrects a long held assumption that Zr and Hf decrease the O-vacancy formation energy by compensating for ceria expansion upon reduction.Although the released strain energy decreases the O-vacancy formation energy, O-vacancy formation remains sufficiently endothermic to split H 2 O and CO 2 . Secondly, we show that two electrons must be promoted into the high energy Ce f-band during reduction if the O-vacancies are to store sufficient energy to drive the oxidative gas splitting step. This means that di-and trivalent dopants are not suitable for this process. Lastly, we show that dopants which break O bonds due to their small size or strongly covalent character, such as Ti and the pentavalent dopants, substantially decrease the O-vacancy formation energy because only three O bonds must break during reduction. These vacancies, therefore, are too low in energy to drive gas splitting. Based on these findings, we develop guidelines for new ceria doping strategies to facilitate solar thermochemical gas splitting cycles.

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Section: Resultsmentioning

confidence: 99%

Section: Oxidationmentioning

confidence: 99%

Principles of doping ceria for the solar thermochemical redox splitting of H₂O and CO₂

Muhich

Steinfeld

2017

J. Mater. Chem. A

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“…A test campaign at the High-Flux Solar Simulator of ETH Zurich confirmed the feasibility of a ceria-based cavity reactor [37,38] and innovative reactor designs are promising in regard to the overall process efficiency [39]. eria with zirconia or lanthanides enhances the impact of zirconia doping in ce via the citrate nitrate auto by X-ray diffraction (X hesized materials was inve cycle performance [40][41][42].…”

Section: Introductionmentioning

confidence: 84%

Thermogravimetric Analysis of Zirconia-Doped Ceria for Thermochemical Production of Solar Fuel

Call¹,

Roeb²,

Schmücker³

et al. 2013

AJAC

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Developing an efficient redox material is crucial for thermochemical cycles that produce solar fuels (e.g. H 2 and CO), enabling a sustainable energy supply. In this study, zirconia-doped cerium oxide (Ce 1−x Zr x O 2 ) was tested in CO 2 -splitting cycles for the production of CO. The impact of the Zr-content on the splitting performance was investigated within the range 0 ≤ x < 0.4. The materials were synthesized via a citrate nitrate auto combustion route and subjected to thermogravimetric experiments. The results indicate that there is an optimal zirconium content, x = 0.15, improving the specific CO 2 -splitting performance by 50% compared to pure ceria. Significantly enhanced performance is observed for 0.15 ≤ x ≤ 0.225. Outside this range, the performance decreases to values of pure ceria. These results agree with theoretical studies attributing the improvements to lattice modification. Introducing Zr 4+ into the fluorite structure of ceria compensates for the expansion of the crystal lattice caused by the reduction of Ce 4+ to Ce 3+ . Regarding the reaction conditions, the most efficient composition Ce 0.85 Zr 0.15 O 2 enhances the required conditions by a temperature of 60 K or one order of magnitude of the partial pressure of oxygen p(O 2 ) compared to pure ceria. The optimal composition was tested in long-term experiments of one hundred cycles, which revealed declining splitting kinetics.

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“…It has been widely used in fuel cells 1,2 , treatment of industrial wastewater [3][4][5] . In addition, they have been used as polishing media in optics 6 , as components for H 2 production 7 and as efficient catalysts 8 . More recently, ceria doped with metal ions has exhibited novel properties in many aspects.…”

Section: Introductionmentioning

confidence: 99%

Facile preparation of Mn-doped CeO2 Submicrorods by composite-hydroxide-salt-mediated approach and their magnetic property

Tan

Zhang

et al. 2013

Mat. Res.

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Mn-CeO 2 submicrorods have been obtained from anomalous CeO 2 particles though a novel composite-hydroxide-salt-mediated (CHSM) approach. This method is based on a reaction between a metallic salt and a metallic oxide in a solution of composite-hydroxide-salt eutectic at ~225 °C and normal atmosphere without using an organic dispersant or capping agent. The magnetic measurement of the Mn-CeO 2 submicrorods exhibits an enhanced ferromagnetic property at room temperature with a remanence magnetization (M r ) of 1.4 × 10 -3 emu.g -1 and coercivity (H c ) of 75 Oe. The UV-visible spectra reveal that the absorption peak of the CeO 2 shifts from ultraviolet region to visible light region after being doped with Mn ions. The room temperature ferromagnetic properties and light absorption of the Mn-CeO 2 submicrorods would have wide applications in spintroics and photocatalysis field.

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Investigation of reactive cerium-based oxides for H2 production by thermochemical two-step water-splitting

Cited by 217 publications

References 21 publications

Principles of doping ceria for the solar thermochemical redox splitting of H₂O and CO₂

Principles of doping ceria for the solar thermochemical redox splitting of H₂O and CO₂

Thermogravimetric Analysis of Zirconia-Doped Ceria for Thermochemical Production of Solar Fuel

Facile preparation of Mn-doped CeO2 Submicrorods by composite-hydroxide-salt-mediated approach and their magnetic property

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Investigation of reactive cerium-based oxides for H2 production by thermochemical two-step water-splitting

Cited by 217 publications

References 21 publications

Principles of doping ceria for the solar thermochemical redox splitting of H2O and CO2

Principles of doping ceria for the solar thermochemical redox splitting of H2O and CO2

Thermogravimetric Analysis of Zirconia-Doped Ceria for Thermochemical Production of Solar Fuel

Facile preparation of Mn-doped CeO2 Submicrorods by composite-hydroxide-salt-mediated approach and their magnetic property

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Principles of doping ceria for the solar thermochemical redox splitting of H₂O and CO₂

Principles of doping ceria for the solar thermochemical redox splitting of H₂O and CO₂