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Reversible solid oxide cells (RSOCs) hold enormous potential for efficient direct CO2 reduction or CO oxidation in terms of exceptional faradic efficiency and high reaction kinetics. The identification of an active fuel electrode is highly desirable for enhancing the performance of RSOCs. This study explores the use of a alkaline metal dopant (Na) to modify the perovskite oxide of Na2x(La0.6−xSr0.4−x)FeO3−δ (2x = 0, 0.10, 0.20) materials with powerful CO2 chemical adsorption capacity, high oxygen ion conductivity, and low average valence of Fe sites for CO2/CO redox reactions. The experimental results indicate that the cells with the NaLSF0.10 fuel electrode achieve a current density of 1.707 A cm−2 at 1.5 V/800 °C and excellent stability over 120 hours at 750 °C for pure CO2 electrolysis, approximately 33.4% improvement over the pristine sample. When operated under a mixed CO–CO2 atmosphere under RSOC mode, the cell outputs the performance of 1.589 A cm−2 at 1.5 V and 329 mW cm−2 at 800 °C, and demonstrates relatively durable operation over 25 cycles. The addition of low valence sodium ions with high basicity and low electronegativity reduces the oxygen vacancy formation energy, increases the concentration of oxygen vacancies and modifies the electronic structure of LSF, thus enhancing CO2 adsorption, dissociation processes and charge transfer steps as corroborated by the detailed experimental analysis. Combined with the acceptable anti-carbon deposition capability, we prove here a feasible strategy and provide new insights into designing novel electrodes for SOEC/RSOCs to effectively convert CO2 with potential for renewable energy storage. [ABSTRACT FROM AUTHOR]

Stable and flexible metal nanoparticles (NPs) with regeneration ability are critical for long-term operation of solid oxide electrolysis cells (SOECs). Herein, a novel perovskite electrode with stoichiometric Pr0.4Sr0.6Co0.125Fe0.75Mo0.125O3−δ (PSFCM) is synthesized and studied, which undergoes multiple redox cycles to validate its structural stability and NPs reversibility. The Co-Fe alloy has exsolved from the parent bulk under reducing atmosphere, and is capable of reincorporation into the parent oxide after re-oxidation treatment. During the redox process, we successfully manipulate the size and population density of the exsolved NPs, and find that the average particle size significantly reduces but the population density increases correspondingly. The electrode polarization resistance of the symmetric cell remains stable for 450 h, and even activates after the redox cycling, which may be attributed to the higher quantity and larger specific surface area of the regenerated Co-Fe alloy NPs. Moreover, the electrochemical performance towards carbon dioxide reduction reaction (CO2RR) is evaluated, and the CO2 electrolyzer consisting of CoFe@PSCFM-Ce0.8Sm0.2O1.9 (SDC) dual-phase electrode exhibits an excellent current density of 1.42 A·cm−2 at 1.6 V, which reaches 1.7 times higher than 0.83 A·cm−2 for the pristine PSCFM electrode. Overall, with this flexible and reversible high-performance SOEC cathode material, new options and perspectives are provided for the efficient and durable CO2 electrolysis. [ABSTRACT FROM AUTHOR]

In data-driven materials design where the target materials have limited data, the transfer machine learning from large known source materials, becomes a demanding strategy especially across different crystal structures. In this work, we proposed a deep transfer learning approach to predict thermodynamically stable perovskite oxides based on a large computational dataset of spinel oxides. The deep neural network (DNN) source domain model with "Center-Environment" (CE) features was first developed using the formation energy of 5329 spinel oxide structures and then was fine-tuned by learning a small dataset of 855 perovskite oxide structures, leading to a transfer learning model with good transferability in the target domain of perovskite oxides. Based on the transferred model, we further predicted the formation energy of potential 5329 perovskite structures with combination of 73 elements. Combining the criteria of formation energy and structure factors including tolerance factor (0.7 < t ≤ 1.1) and octahedron factor (0.45 < μ < 0.7), we predicted 1314 thermodynamically stable perovskite oxides, among which 144 oxides were reported to be synthesized experimentally, 10 oxides were predicted computationally by other literatures, 301 oxides were recorded in the Materials Project database, and 859 oxides have been first reported. Combing with the structure-informed features the transfer machine learning approach in this work takes the advantage of existing data to predict new structures at a lower cost, providing an effective acceleration strategy for the expensive high-throughput computational screening in materials design. The predicted stable novel perovskite oxides serve as a rich platform for exploring potential renewable energy and electronic materials applications. [ABSTRACT FROM AUTHOR]

Solid oxide electrolysis cells (SOECs) can efficiently convert the greenhouse‐gas CO2 to valuable fuel CO at the cathodes. Herein, fluorine is doped into mixed ionic–electronic conducting Sr2Fe1.5Mo0.5O6‐δ (SFM), to evaluate its potential use as a cathode for CO2 reduction reaction (CO2‐RR). SFM retains its cubic structure after doped with fluorine, forming perovskite oxyfluoride Sr2Fe1.5Mo0.5O6‐δF0.1 (F‐SFM). The substitution of oxygen by fluorine increases CO2 adsorption by a factor of ≈2, bulk oxygen vacancy concentration by 35–37% at 800 °C, and consequently enhances the surface reaction rate constant for CO2‐RR and chemical bulk diffusion coefficient by factors of 2–3. The faster kinetics are also reflected by a lower polarization resistance of 0.656 Ω cm2 for F‐SFM than 1.130 Ω cm2 for SFM at 800 °C in symmetrical cells. Furthermore, the single cell with F‐SFM cathode exhibits the best CO2 electrolysis performance among the reported perovskite electrodes, achieving current density of 1.36 A cm−2 at 1.5 V and excellent stability over 120 h at 800 °C under harsh conditions. The theoretical computations confirm that fluorine doping is energetically favorable to CO2 adsorption and dissociation. The present work provides a promising strategy for the design of robust cathodes for direct CO2 electrolysis in SOECs. Solid oxide electrolysis cells are promising energy conversion devices that can efficiently convert CO2 to CO and O2. However, their use is impeded mainly due to the absence of a highly active and durable cathode. This work successfully demonstrates that a SOEC with fluorine‐doped perovskite Sr2Fe1.5Mo0.5O6‐δ cathode enables direct electrolyzing of CO2 with excellent performance and durability. [ABSTRACT FROM AUTHOR]

Abstract Double perovskite PrBaCo 2 O 5+δ (PBC) has received much attention as cathode material for solid oxide fuel cells (SOFCs) due to its excellent catalytic activity for oxygen reduction reaction (ORR), especially at intermediate temperature up to 800 °C. However, its high thermal expansion coefficient (C TE), about twice as the electrolytes, usually results in poor durability. This work presents the effect of C TE reduction by doping fluorine ion to the oxygen-site of PrBaCo 2 O 5+δ. The fluorine doping, which is confirmed with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy investigations, can substantially reduce C TE , from 24.03 × 10−6 K−1 down to 16.78 × 10−6 K−1 as determined with dilatometry while from 26.52 × 10−6 K−1 to 17.46 × 10−6 K−1 with high-temperature XRD. Consequently, the durability is improved by a factor of ∼3.0 when the electrodes are subjected to 200–800 °C thermal cycles. In addition, the fluorine doping does not deteriorate but maintains or even improves the oxygen transport properties and electrochemical performance for ORR of PBC, demonstrating that fluorine doping is very attractive for the development of promising cathode materials for intermediate-temperature SOFCs. Highlights • F is successfully doped to PrBaCo 2 O 5+δ (PBC) by combustion method. • F doping significantly reduces the thermal expansion coefficient of PBC. • The thermal cycling durability is remarkably improved by doping F to PBC. • F doping enhances PBC's oxygen transport property & catalytic activity of ORR. [ABSTRACT FROM AUTHOR]