Investigation of Sr_0.7Ca_0.3FeO₃ Oxygen Carriers with Variable Cobalt B‐Site Substitution

Abstract

A‐site and B‐site substitutions are effective methods towards improving well‐studied oxygen carrier materials that are vital for emerging gasification technologies. Such materials include SrFeO3, which greatly benefits from the inclusion of calcium and/or cobalt, and Sr0.8Ca0.2Fe0.4Co0.6O3 has been regarded as the best‐performing composition. In this study, systems with higher calcium and lower cobalt contents are investigated with a view to lessening the societal and economic burdens of these dual‐doped carriers. Density functional theory calculations are performed to illustrate the Fe−O bonding and relaxation contributions to the oxygen vacancy formation energy in Sr1‐xCaxFe1‐yCoyO3 systems (x=0.1875, 0.25, 0.3125; y=0.125, 0.25, 0.375, 0.5) and determine that increased calcium A‐site substitution requires the use of less cobalt B‐site doping to reach the same oxygen vacancy formation. These findings are experimentally validated in situ and ex situ characterization of bulk Sr0.7Ca0.3Fe1‐yCoyO3 materials. Sr0.7Ca0.3Fe0.7Co0.3O3 is found to have similar O2 adsorption/desorption rates and storage capacity to Sr0.8Ca0.2Fe0.4Co0.6O3 in air/N2 cycling experiments. Additionally, both materials are outperformed by Sr0.7Ca0.3Fe1‐yCoyO3 systems with y=0–0.10 at 400–500 °C, which cycle 1.5 wt% O2 in under ten minutes.

Investigation of AFeO3 (A=Ba, Sr) Perovskites for the Oxidative Dehydrogenation of Light Alkanes under Chemical Looping Conditions

“…The synthesis of BFO and SFO was completed using a solid-state method previously discussed in our prior work. [18][19][20] To begin, a stoichiometric amount of strontium (II) carbonate [SrCO 3 , 99.9 %, Sigma-Aldrich] or barium (II) carbonate [BaCO 3 , 99.8 %, Alfa Aesar] was added to an agate mortar along with an appropriate amount of iron (III) oxide [Fe 2 O 3 , 99.9 %, Alfa Aesar]. An agate pestle was used to manually grind the powders for approximately 15 min to produce homogeneity.…”

“…BaFeO 3 and SrFeO 3 , along with their derivatives are wellestablished oxygen carriers that have been extensively researched for their oxygen mobility, surface structure, and oxygen release thermodynamics in chemical looping air separation, including the contributions from our prior work. [18][19][20][21] Although these factors are critical for improved olefin production, both systems have been underexplored as ODH catalysts. Additionally, SrFeO 3 has low toxicity and does not contain expensive rare earth elements and precious metals, making it attractive for applications in environmental remediation and sustainable energy supply.…”

“…BaFeO 3 and SrFeO 3 , along with their derivatives are well‐established oxygen carriers that have been extensively researched for their oxygen mobility, surface structure, and oxygen release thermodynamics in chemical looping air separation, including the contributions from our prior work [18–21] . Although these factors are critical for improved olefin production, both systems have been underexplored as ODH catalysts.…”

Oxygen Storage Property and Catalytic Performance of Ti-Doped FeNbO4

“…Fe-based oxides, which are inexpensive and readily valence-changeable, have gained much attention as novel OSMs. − In a simple Fe-based oxide such as Fe 3 O 4 , oxide ions form a close-packed structure, and Fe cations occupy the gaps. Consequently, oxygen release leads to the collapse of the close-packed structure, resulting in significant rearrangement of the cations and oxide ions. , To avoid such irreversible structural changes, we focused on orthorhombic FeNbO 4 ( Pbcn space group).…”