Cyclic production of syngas and hydrogen through methane-reforming and water-splitting by using ceria–zirconia solid solutions in a solar volumetric receiver–reactor

Jang, Jong Tak; Yoon, Ki June; Bae, Jong Wook; Han, Gui Young

doi:10.1016/j.solener.2014.08.024

Cited by 16 publications

(12 citation statements)

References 24 publications

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“…A4). Similar amount of methane cracking and carbon deposit have also been reported for the benchmark cerium dioxide in thermochemical CO 2 and H 2 O splitting cycles with MPO reduction [6,52,53]. While carbon formation by methane cracking decreases the amount of CO produced in the reduction step, the CO deficit can be recovered in the oxidation step during CO 2 splitting by the reverse Boudouard reaction.…”

Section: Resultssupporting

confidence: 72%

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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Section: Resultssupporting

confidence: 72%

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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“…3,6 The addition of high valence dopant cations, such as Zr 4+ , proved effective in increasing the thermodynamic driving force of CeO2 reduction at lower temperatures, [7][8][9] and the effect of zirconium content in the two step water splitting reaction has been widely studied. [10][11][12][13][14] Its presence favours CeO2 reduction under inert atmosphere at temperatures lower than 1500°C preventing sublimation and the consequent yield loss; moreover, the increased oxygen storage of ceria-zirconia positively affects O2…”

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confidence: 99%

“…18 For this reason the majority of studies on the water splitting reaction over ceriazirconia solid solutions focused on compositions with a zirconia content in the range up to 70 mol% CeO2, [10][11][12][13][14][15][16][17] although it has been recently reported that the occurrence of compositional heterogeneities may have a benefical effect on the H2 production step. 11 With the aim of gaining insights into this latter aspect and of exploring the potential application of ZrO2-rich compositions in the WS reaction, despite their thermodynamic instability, we investigate here the reactivity and structural transformations of Ce0.85Zr0.15O2 in the reduction and oxidation step of the cycle.…”

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confidence: 99%

Water splitting reaction on Ce_0.15Zr_0.85O₂ driven by surface heterogeneity

Pappacena

Boaro

Armelao

et al. 2016

Catal. Sci. Technol.

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The compositional and structural heterogeneity of a sample of Ce0.15Zr0.85O2 subjected to a two-step thermochemical water splitting reaction was investigated by means of X-ray powder diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and High-Resolution Transmission Electron Microscopy (HRTEM) analysis. High temperature treatment under N2 resulted in segregation of a Zr-rich monoclinic phase on one side and a Ce-rich cubic phase on the other. The treatment also led to a higher reducibility of the material compared to similar studies on Ce-rich compositions. HRTEM revealed the presence of a zirconia based superstructure that it is identifiable with an oxynitride phase Zr2ON2, while ceria surface enrichment was detected via XPS. H2 yield, investigated at 800°C by pulsing water over several redox cycles, showed a six-fold increase after the first cycle remaining constant after at least three subsequent cycles. The presence of zirconia oxynitride was found to be beneficial for both the oxidation and reduction steps. Solar thermochemical water splitting cycles (WSC) are an attractive carbon-free approach to H2 production from water and sunlight.1 Two-step metal oxide based cycles generate H2 through high temperature (~1500-2000°C) reduction in inert atmosphere and the subsequent water oxidation at a lower (~400-1300°C) temperature making water splitting (WS) possible at temperatures lower than the thermodynamic value (2300°C). 2 Among many metal oxides investigated in literature, ceria is one of the most viable candidates, 3 and it can deliver pure oxygen and hydrogen according to the following two-step redox cycleThe main drawback of this cycle is that a significant reduction of ceria occurs only at temperatures higher than 1800°C, where sublimation can occur with a decrease of the yield over cycles. 5 It follows that studies on ceria-based systems have been focused on lowering the reduction temperature of the Ce 4+ /Ce 3+ redox couple, while maintaining the high reactivity of reduced Ce 3+ species towards water. 3,6 The addition of high valence dopant cations, such as Zr 4+ , proved effective in increasing the thermodynamic driving force of CeO2 reduction at lower temperatures, 7-9 and the effect of zirconium content in the two step water splitting reaction has been widely studied. [10][11][12][13][14] Its presence favours CeO2 reduction under inert atmosphere at temperatures lower than 1500°C preventing sublimation and the consequent yield loss; moreover, the increased oxygen storage of ceria-zirconia positively affects O2yield. On the other hand, the H2 productivity depends on the number of exposed surface redox sites, and thus on the textural, morphological and structural properties of these materials. It was reported that in these materials the kinetics of water splitting is often hampered by gassolid diffusion limitations due to the simultaneous occurence of sintering processes. Several efforts have been made to overcome this issue, and the change of the morphological and structural properties o...

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“…Regarding the amount of H 2 and CO obtained as a function of pressure changes as shown in Figure , the oxidation of the oxygen carrier could be achieved at any reaction temperature . However, as shown in Figure a,b, the formation of the product gases becomes more important as oxidation of oxygen carrier goes completion for high reaction temperatures.…”

Section: Resultsmentioning

confidence: 92%

Analysis of Two‐Step Solar Thermochemical Looping Reforming of Fe₃O₄ Redox Cycles for Synthesis Gas Production

et al. 2019

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A two‐step solar thermochemical looping reforming (STCLR) of CH4—Fe3O4 redox cycles via H2O and CO2 splitting is investigated for H2 and CO production. The P1 approximation is adopted for the radiation heat transfer and high‐temperature thermal characteristics of active materials in the reaction medium. A benchmark experimental setup for the conversion of solar energy to syngas based on the solar thermochemical technology is presented. The effects of operating conditions on the yield of H2 and CO as well as syngas production are investigated at both thermal reduction and oxidation steps. It is found that the key performance of two‐step CH4—Fe3O4 redox cycles for a higher H2 and CO production depends on the efficiency of methane and oxidizer (H2O and CO2) conversion. Furthermore, a substantial amount of H2 and CO production with carbon deposition is obtained when the thermal reduction is extended to the mixed oxide solid solution (FeO—Fe). Among the oxygen carriers, FeO exhibits a higher oxygen exchange for H2 production. However, the synergetic effect of FeO—Fe reactivity strongly contributes to syngas yield. The present solar reactor model can significantly contribute to the reduction of greenhouse gas emission by utilizing 40% of CO2 emissions into solar fuels such as H2 and syngas. The results indicate that highly selective syngas with an H2/CO ratio close to 2 can be obtained with a strong control of γ = H2O/CO2.

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Cyclic production of syngas and hydrogen through methane-reforming and water-splitting by using ceria–zirconia solid solutions in a solar volumetric receiver–reactor

Cited by 16 publications

References 24 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

Water splitting reaction on Ce_0.15Zr_0.85O₂ driven by surface heterogeneity

Analysis of Two‐Step Solar Thermochemical Looping Reforming of Fe₃O₄ Redox Cycles for Synthesis Gas Production

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Cyclic production of syngas and hydrogen through methane-reforming and water-splitting by using ceria–zirconia solid solutions in a solar volumetric receiver–reactor

Cited by 16 publications

References 24 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

Water splitting reaction on Ce0.15Zr0.85O2 driven by surface heterogeneity

Analysis of Two‐Step Solar Thermochemical Looping Reforming of Fe3O4 Redox Cycles for Synthesis Gas Production

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Water splitting reaction on Ce_0.15Zr_0.85O₂ driven by surface heterogeneity

Analysis of Two‐Step Solar Thermochemical Looping Reforming of Fe₃O₄ Redox Cycles for Synthesis Gas Production