Novel Perovskite Materials for Thermal Water Splitting at Moderate Temperature

Materials with the formula Sr2CoNb1−xTixO6−δ (x=1.00, 0.70; δ=number of oxygen vacancies) present a cubic perovskite‐like structure. They are easily and reversibly reduced in N2 or Ar and re‐oxidized in air upon heating. Oxidation by water (wet N2), involving splitting of water at a temperature as l...

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Published in:ChemSusChem 2019-09, Vol.12 (17), p.4029-4037
Main Authors: Azcondo, M. Teresa, Orfila, María, Marugán, Javier, Sanz, Raúl, Muñoz‐Noval, Alvaro, Salas‐Colera, Eduardo, Ritter, Clemens, García‐Alvarado, Flaviano, Amador, Ulises
Format: Article
Language:English
Subjects:
Cycles
hydrogen generation
Hydrogen production
Organic chemistry
Oxidation
Oxygen
perovskite phases
Perovskites
solar fuel
thermochemical cycle
Valence
Water splitting
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Summary:Materials with the formula Sr2CoNb1−xTixO6−δ (x=1.00, 0.70; δ=number of oxygen vacancies) present a cubic perovskite‐like structure. They are easily and reversibly reduced in N2 or Ar and re‐oxidized in air upon heating. Oxidation by water (wet N2), involving splitting of water at a temperature as low as 700 °C, produces hydrogen. Both compounds displayed outstanding H2 production in the first thermochemical cycle, the Sr2CoNb0.30Ti0.70O6−δ material retaining its outstanding performance upon cycling, whereas the hydrogen yield of the x=1 oxide showed a continuous decay. The retention of the materials’ ability to promote water splitting correlated with their structural, chemical, and redox reversibility upon cycling. On reduction/oxidation, Co ions reversibly changed their oxidation state to compensate the release/recovery of oxygen in both compounds. However, in Sr2CoTiO6−δ, two phases with different oxygen contents segregated, whereas in Sr2CoNb0.30Ti0.70O6−δ this effect was not evident. Therefore, this latter material displayed a hydrogen production as high as 410 μmolH2  g−1perovskite after eight thermochemical cycles at 700 °C, which is among the highest ever reported, making this perovskite a promising candidate for thermosolar water splitting in real devices. Clean hydrogen can be produced through water splitting at moderate temperature (700 °C) by two‐step reversible thermochemical cycles based on the perovskite oxides Sr2CoNb1−xTixO6−δ (x=1, 0.7; δ=number of oxygen vacancies). These compounds show outstanding hydrogen yield, making them potentially useful for real applications.
ISSN:1864-5631
1864-564X
DOI:10.1002/cssc.201901484