Vacancy Formation Energy Research Articles

Doping strategy on properties and chemical mechanical polishing performance of CeO2 Abrasives: A DFT assisted experimental study

A series of Ce1-xMxO2 abrasives with different types and amounts of doping were prepared by molten salt method. The properties of abrasives were characterized in detail by XRD, SEM, EDS and XPS. For all doping types, the morphology of abrasives changes from spherical to octahedral and their size decreases continuously with the doping increases. The Ce3+ concentration on the CeO2 abrasive surface is also increased by doping. The density functional theory indicates the vacancy formation energy of CeO2 systems are reduced by doping. The mechanism of transition from Ce4+ to Ce3+ induced in CeO2 system by doping is also discussed. CMP experiments show that the efficiency of the abrasives is significantly enhanced by doping. The MRR of Y3+, La3+ and Pr3+ doped CeO2 abrasives increased by 56 %, 40 % and 44 % compared with the pure. It is also shown that the appropriate amount (x = 0.08) should be considered in order to obtain excellent performance. It is confirmed that the substrate surface with almost no damage and low roughness is obtained after polishing. The removal mechanism of CeO2 abrasives on SiO2 substrate is comprehensively analyzed by considering the size, morphology and defects of the abrasives.

Origin of oxygen-redox and transition metals dissolution in Ni-rich LixNi0.8Co0.1Mn0.1O2 cathode.

Recently, Ni-rich LiNixCoyMn1-x-yO2 (x ≥ 0.8) draw significant research attention as cathode materials in lithium-ion batteries due to their superiority in energy density. However, the oxygen release and the transition metals (TMs) dissolution during the (dis)charging process lead to serious safety issues and capacity loss, which highly prevent its application. In this work, we systematically explored the stability of lattice oxygen and TM sites in LiNi0.8Co0.1Mn0.1O2(NCM811) cathode via investigating various vacancy formations during lithiation/delithiation, and properties such as the number of unpaired spins (NUS), net charges, and d band center were comprehensively studied. In the process of delithiation (x = 1 → 0.75 → 0), the vacancy formation energy of lattice oxygen [Evac(O)] has been identified to follow the order of Evac(O-Mn) > Evac(O-Co) > Evac(O-Ni), and Evac(TMs) shows a consistent trend with the sequence of Evac(Mn) > Evac(Co) > Evac(Ni), demonstrating the importance of Mn to stabilize the structural skeleton. Furthermore, the |NUS| and net charge are proved to be good descriptors for measuring Evac(O/TMs), which show linear correlations with Evac(O) and Evac(TMs), respectively. Li vacancy plays a pivotal role on Evac(O/TMs). Evac(O/TMs) at x = 0.75 vary extremely between the NiCoMnO layer (NCM layer) and the NiO layer (Ni layer), which correlates well with |NUS| and net charge in the NCM layer but aggregates in a small region in the Ni layer due to the effect of Li vacancies. In general, this work provides an in-depth understanding of the instability of lattice oxygen and transition metal sites on the (104) surface of Ni-rich NCM811, which might give new insights into oxygen release and transition metal dissolution in this system.

Development of a Novel Pt3V Alloy Electrocatalyst for Highly Efficient and Durable Industrial Hydrogen Evolution Reaction in Acid Environment

AbstractAlloying platinum with early transition metals is a promising approach to optimize the adsorption behaviors of catalysts. Nevertheless, the large negative redox potential between early transition metals and Pt hinders the fabrication of such alloys. Herein, a strategy combining the thermal shock technique with electrochemical activation to prepare Pt3V alloy as a hydrogen evolution reaction catalyst is reported for the first time. Electrochemical tests show that the as‐prepared catalyst exhibits exceptional catalytic activity and durability in 0.5 m H2SO4, surpassing the state‐of‐the‐art 20 wt.% Pt/C. The catalyst can maintain its activity after 100 h tests without evident decay under the current density of 500 mA cm−2. Theoretical calculations demonstrate that the optimized hydrogen absorption and high vacancy formation energy of Pt3V contributes to the enhanced electrocatalytic activity and stability. This work may spur future research for other Pt‐based early transition metal alloy catalysts for electrocatalysis.

PO6 geometric configuration unit enhanced electrocatalytic performance of Co3O4 in acidic oxygen evolution

It is challenging to develop high-efficient and stable nonprecious metal-based electrocatalyst for oxygen evolution reaction (OER) in acid for proton exchange membrane (PEM) water splitting. Herein, P atoms were introduced into the lattice of spinel Co3O4 (P-Co3O4) to replace with octahedral coordinated Co3+ via a hydrothermal process following a thermal treatment. The formation of PO6 geometric configuration unit in Co3O4 can trigger electron rearrangement around Co ions, which resulted in the high-active Co2+ site on the surface, significantly decreasing the energy barrier of rate-determining step for OER. Moreover, the weaker covalency of the Co 3d-O 2p bond and higher formation energy of oxygen vacancy around Co2+ in P-Co3O4 inhibited the participation of lattice oxygen during OER process, enabling that P-Co3O4 can work stably in acidic media. The obtained P-Co3O4 afforded satisfying stability over 30 h in a PEM electrolysis device with an overpotential of 400 mV@10 mA/cm2 in 0.1 M HClO4.

Designing Heterovalent Substitution with Antioxidant Attribute for High‐Performance Sn‐Pb Alloyed Perovskite Solar Cells

AbstractAll‐perovskite tandem solar cells are promising for breaking through the single‐junction Shockley–Queisser limit, and that potentially raises interest in configuring efficient Sn‐Pb alloyed narrow‐bandgap perovskite solar cells (PSCs). However, the Sn‐Pb alloyed perovskites are commonly plagued by uncontrollable crystallization dynamics and severe p‐doping levels. Herein, an effective additive molecule is designed with heterovalent substitution and antioxidant functions, whereby an organic metal coordination compound of tris(2,4‐pentanedionato)gallium (TPGa) is employed to upgrade the quality of perovskite films. Ga3+ substitution obviously boosts the formation energy of Sn vacancies and heals the trap states. Meanwhile, the crystal structure evolution process is improved by the anchoring effect of 2,4‐pentanedionato. The PSCs incorporating these improvements deliver not only a power conversion efficiency of 21.5% but also outstanding stability, as demonstrated by retaining 80% of the initial efficiency for over 1500 h. In addition, 23.14%‐efficient all‐perovskite tandem solar cells are further obtained by pairing this PSC with a wide‐bandgap (1.74 eV) top cell. This study supports the feasibility of doping trivalent ions into the Sn‐Pb alloyed perovskites to compromise the self‐p‐doping effect and highlights the importance of acetylacetone for passivating defects and hindering oxidation.

Regulating the Unhybridized O 2p Orbitals of High‐Performance Li‐Rich Mn‐Based Layered Oxide Cathode by Gd‐Doping Induced Bulk Oxygen Vacancies

AbstractLi‐rich Mn‐based layered oxides (LRLOs) with ultrahigh specific capacities are promising cathode materials for high energy density lithium‐ion batteries. Nevertheless, severe irreversible oxygen release, structure degradation, capacity and voltage attenuation hinder their commercialization due to the uncontrollable oxygen redox chemistry originated from unhybridized O 2p orbitals. Herein, a strategy to generate bulk oxygen vacancies is proposed. And bulk oxygen vacancies are constructed by lowering the formation energy of oxygen vacancies in LRLOs via Gd‐doping. The energy level and the amount of unhybridized O 2p states are reduced to partly inhibit the oxygen redox activity. Surprisingly, the oxygen redox is not fully activated in the first cycle and is further activated in the second cycle. Moreover, the reduced oxygen redox activity significantly suppresses the oxygen release, lattice volume change, layered‐to‐spinel phase transition. As a result, the amount of oxygen gas release is reduced from 98.80 to ≈0 nmol mg−1 in the first cycle. Superior cycle stability of 90.4% capacity retention after 300 cycles and small voltage decay of only 1.013 mV per cycle are achieved. This study provides a valuable bulk oxygen vacancies strategy to regulate the unhybridized O 2p orbitals for designing high‐performance Li‐rich Mn‐based layered oxide cathode materials.

Interfacial oxygen coordination environment regulation towards high-performance Li-rich layered oxide cathode

Lithium-rich layered oxides (LLO) have drawn increasing attention as one of the most promising cathodes for next-generation high-energy–density lithium-ion batteries (LIBs). However, they are plagued by low initial Coulombic efficiency (ICE) and terrible cyclic stability due to their intrinsic irreversible oxygen release. Herein, to enhance the comprehensive electrochemical performance of LLO, an effective strategy is brought up to regulate the interfacial oxygen coordination environment via lithium deficiencies, Na+ ion doping, as well as the induced Li+/Ni2+ antisite defects and in-situ epitaxial grown spinel phase. The density functional theory calculations (DFT) confirm that the existence of lithium deficiencies and Na+ ions doping can decrease the diffusion energy barrier of Li+ ions. Meanwhile, the regulated oxygen coordination environment results in an increase in the oxygen vacancy formation energy, which is beneficial for the improvement of the lattice oxygen stability in the deeply charged state. As a result, the modified sample exhibits high initial coulombic efficiency of 91.2% and good capacity retention of 95.3% after 400 cycles at 1C (1C = 250 mA g−1). This work offers a new idea for designing advanced LLO cathodes, which could promote their practical applications in high-energy–density LIBs.

Modulating the local electronic structure via Al substitution to enhance the electrochemical performance of Li-rich Mn-based cathode materials

The performance degradation caused by irreversible O2 release and structural collapse has seriously hindered the commercialization of Li-rich Mn-based oxide cathode materials (LMOs). Herein, a Li-rich Mn-based cathode material Li1.2Ni0.2Mn0.6−xAlxO2 (x = 0.02, 0.04, 0.06) via the substitution of Mn by Al was designed. By introducing additional strong Al-O bonds into the local atomic coordination around O and transition metal (TM) to modulate the local electronic structure, the TM 3d-O 2p and non-bonding O-2p band are transferred to lower energy, thus increasing the redox reaction potential. The substitution of Al also enhances the interaction with oxygen and increases the oxygen vacancy formation energy, which stabilizes the lattice oxygen framework and ultimately further inhibits the structural transition (layered → spinel phase) caused by the reduction of TM ions during the cycling process and improves the stability of the layered structure. The results show that the voltage decay of the Al-doped sample is only 0.349 V after 300 cycles, which is much lower than the 0.578 V of the pristine sample. Assembled as a full cell using LMNA2 as the cathode and commercial graphite as the anode, it exhibited a specific energy density of 454.3 Wh kg−1 at 0.1 C, with a capacity retention rate of over 86% after 100 cycles. This research provides a novel idea for the future development of LMOs for high voltage and energy density applications.

Accurate prediction of oxygen vacancy concentration with disordered A-site cations in high-entropy perovskite oxides

Entropic stabilized ABO3 perovskite oxides promise many applications, including the two-step solar thermochemical hydrogen (STCH) production. Using binary and quaternary A-site mixed {A}FeO3 as a model system, we reveal that as more cation types, especially above four, are mixed on the A-site, the cell lattice becomes more cubic-like but the local Fe–O octahedrons are more distorted. By comparing four different Density Functional Theory-informed statistical models with experiments, we show that the oxygen vacancy formation energies ({E}_{V}^{f}) distribution and the vacancy interactions must be considered to predict the oxygen non-stoichiometry (δ) accurately. For STCH applications, the {E}_{V}^{f} distribution, including both the average and the spread, can be optimized jointly to improve Δδ (difference of δ between the two-step conditions) in some hydrogen production levels. This model can be used to predict the range of water splitting that can be thermodynamically improved by mixing cations in {A}FeO3 perovskites.

Does Zn mimic diffusion of Al in the HCP Al-Sc-Hf-Ti-Zr high entropy alloys?

The presence of Al in the hexagonal close-packed (HCP) Al-Sc-Hf-Ti-Zr high-entropy-alloy system was previously found to be a primary reason for partial D019 ordering. Since tracer measurements of Al self-diffusion are extremely challenging due to the absence of a suitable radioisotope, in this work, diffusion of Zn as a solute element is investigated for two HCP Al-Sc-Hf-Ti-Zr alloys. The experimental results on diffusion of the 65Zn radioisotope are benchmarked against Al diffusion rates predicted by kinetic Monte Carlo simulations using ab initio-informed calculations of the vacancy formation and migration energies. Furthermore, the partitioning of Zn and the mechanism of Zn diffusion are evaluated. Similarities between Zn and Al diffusion in the investigated HCP Al-Sc-Hf-Ti-Zr alloys are traced back to correlations between the corresponding chemically resolved site substitution energies and migration barriers.

A Gradient Doping Strategy toward Superior Electrochemical Performance for Li-Rich Mn-Based Cathode Materials.

Lithium-rich layered oxides (LLOs) are concerned as promising cathode materials for next-generation lithium-ion batteries due to their high reversible capacities (larger than 250mA h g-1 ). However, LLOs suffer from critical drawbacks, such as irreversible oxygen release, structural degradation, and poor reaction kinetics, which hinder their commercialization. Herein, the local electronic structure is tuned to improve the capacity energy density retention and rate performance of LLOs via gradient Ta5+ doping. As a result, the capacity retention elevates from 73% to above 93%, and the energy density rises from 65% to above 87% for LLO with modification at 1 C after 200 cycles. Besides, the discharge capacity for the Ta5+ doped LLO at 5 C is 155mA h g-1 , while it is only 122mA h g-1 for bare LLO. Theoretical calculations reveal that Ta5+ doping can effectively increase oxygen vacancy formation energy, thus guaranteeing the structure stability during the electrochemical process, and the density of states results indicate that the electronic conductivity of the LLOs can be boosted significantly at the same time. This strategy of gradient doping provides a new avenue to improve the electrochemical performance of the LLOs by modulating the local structure at the surface.

Point defect properties in high entropy MAX phases from first-principles calculations

MAX phase materials exhibit both metal and ceramic properties due to their unique laminated atomic structures, making them promising candidates in advanced nuclear energy systems. Recently, high entropy MAX (HE-MAX) phases have been developed and attracted much attention due to their unique properties. However, the role of chemical disorder in HE-MAX phases in their point defects properties is still not clear. In this work, we investigated the point defect properties in (TiVNb)2SnC, (TiZrHf)2SnC, (TiVNbZrHf)2SnC, and five corresponding single-component M2SnC phases (M=Ti, V, Nb, Zr, Hf) using first-principles calculations. The average vacancy (VM, VSn, VC) formation energies in the HE-MAX phases are (TiZrHf)2SnC > (TiVNbZrHf)2SnC > (TiVNb)2SnC. With the addition of Zr and Hf atoms, the charge transfer between atoms in the HE-MAX phase increases, hindering the formation of these vacancies. Meanwhile, the obtained migration energies show that the migration barrier of VM through Ti is lower than that of V, Nb, Zr, or Hf, while Zr and Hf atoms increase the VC migration barrier due to their large atomic sizes. Additionally, the formation energies of antisite defects in all three HE-MAX phases are lower than the single-component M2SnC phases, indicating that the HE-MAX phases are more resistant to radiation-induced amorphization. This work provides a fundamental understanding of the effect of chemical disorder on point defect properties in MAX phases and proposes a new strategy for designing novel HE-MAX phases with better performance in nuclear applications.

Spatial inhomogeneity of point defect properties in refractory multi-principal element alloy with short-range order: A first-principles study

Short-range order can be developed in multi-principal element alloys and influences the point defect behavior due to the large variation of the local chemical environment. The effect of short-range order on vacancy and interstitial formation energy and migration behavior was studied in body-centered cubic multi-principal element alloy NbZrTi by first-principles calculations. Two short-range order structures created by density functional theory and Monte Carlo method at 500 and 800 K were compared with the structure of random solid solution. Both vacancy and interstitial formation energies increase with the degree of short-range order. Point defect formation energies tend to be higher in regions enriched in Nb and lower in regions enriched in Zr and Ti. Both vacancies and interstitials prefer to migrate toward Zr,Ti-rich regions and away from Nb-rich regions, suggesting that Zr,Ti-rich regions can potentially act as recombination centers for point defect annihilation. Compared to an ideal random solid solution, the short-range order increases the spatial inhomogeneity of point defect energy landscape. Tuning the degree of short-range order by different processing techniques can be a viable strategy to optimize the point defect behavior to achieve enhanced radiation resistance in multi-principal element alloys.

Incorporation and migration of xenon in uranium-plutonium mixed nitride; A density functional theory study

Actinide nitride materials are promising candidates for advanced nuclear fuels. In this work, we investigate the bulk properties of the mixed nitrides U0.75Pu0.25N and U0.5Pu0.5N, and study the incorporation and migration behaviour of the fission gas Xe. The disordered U0.75Pu0.25N and U0.5Pu0.5N structures are constructed using the special quasi-random structure method. Their lattice parameters are closer to the experimentally determined values than the corresponding ordered structures. The density of states show that Pu f states are located at lower energy than U f, consistent with the trend of increasing f orbital stability across the actinide series. The actinide vacancy formation energy (Ef) in disordered and ordered U0.5Pu0.5N is highly dependent on the chemical environment around the vacancy: it increases as the number of U atoms in the first nearest-neighbour shell (NU(1NN)) increases, but decreases as the number of U atoms in the second nearest-neighbour shell (NU(2NN)) increases. The Xe incorporation energy (Ei) is found to be independent of vacancy species, depending only on the chemical environment of the vacancy. As does Ef, Ei increases with increasing NU(1NN), while decreases with increasing NU(2NN), because the smaller the NU(1NN) and the larger the NU(2NN), the larger the vacancy steric space. The Ei of Xe and Kr are calculated to be within the ranges 4.47–6.01 eV and 3.30–4.64 eV, respectively. The Xe migration energy barrier in ordered U0.5Pu0.5N allows us to set the energy range for Xe diffusion in disordered U0.5Pu0.5N as 0.50–1.75 eV. A lower range of 0.30–1.25 eV is found for Kr diffusion.

Vacancy Formation Energy as an Effective Descriptor for the Catalytic Oxidation of CO by Au Nanoparticles

Gold nanoparticles (AuNPs) have attracted wide attention in the field of catalysis because of their excellent stability and electrical properties. Herein, an accurate vacancy formation energy model based on nanothermodynamics theory is developed, the intrinsic correlation between vacancy formation energy and CO oxidation activity is investigated in detail, and the relationship between vacancy formation energy and activity-influencing factors such as particle size, temperature, and crystal surface is analyzed. The results show an excellent linear relationship between vacancy formation energy and CO oxidation activity, with an accuracy of up to 95%. In addition, the vacancy formation energy also corresponds well to the influencing factors of size, temperature, and crystal surface, and its correspondence is particularly accurate when the size is below 20 nm and the temperature is below 500 K. It can serve as a normalized expression of the three influencing factors. Moreover, the present research reveals that the essence of the vacancy formation energy descriptor is the chemical bond energy, and gives its correspondence with the coordination number, diffusion activation energy, and adsorption energy (with a decrease in vacancy formation energy, the adsorption effect of AuNPs is stronger), further demonstrating the feasibility and accuracy of the vacancy formation energy as a descriptor. This research not only overcomes the problem that traditional single-influence descriptors are difficult to apply in complex environments but also has considerable potential for defect modulation.

Simulation of bulk and grain boundary diffusion phenomena in a high entropy CoCrFeMnNi alloy by molecular dynamics

A series of calculations on the self-diffusion behavior of high entropy CoCrFeMnNi alloy were carried out using molecular dynamics methods. By computing both vacancy formation energy and atomic migration energy of the constituent elements in the alloy, the diffusional activation energy of each element is obtained, and the self-diffusion coefficients for bulk diffusion were calculated, with the values exhibiting close to of experiments. A model for structures of symmetrically tilted grain boundary is established, with Σ9 and Σ27 grain boundaries studied based on the coincidence site lattice theory. Measured by the full width at half maxima of the radial distribution function, it is found that the grain boundaries with low index are more ordered than those with high plane index, and the atom fluctuation occurred in the low-indexed grain boundaries is less intensively and sensitively to temperature change. Meanwhile, the diffusion coefficients of ordered grain boundaries are generally smaller than those of disordered grain boundaries. Compared with the experimental values of grain boundary diffusion, the diffusion activation energy of configured grain boundaries from coincidence site lattice is smaller than that of normal large-angle grain boundaries.

Contrasting thermoelectric properties in cubic SnSe-NaSbSe2 and SnSe-NaSbTe2: High performance achieved via increasing cation vacancies and charge densities

Cubic SnSe has been recognized as one of the most promising mid-temperature thermoelectric candidates. Herein, the cubic-phase SnSe has been stabilized at room temperature by alloying NaSbSe2 and NaSbTe2, respectively, and the contrasting thermoelectric properties of SnSe-NaSbSe2 and SnSe-NaSbTe2 were systematically investigated. NaSbTe2-alloyed SnSe demonstrates better performance with especially higher electrical properties. According to the DFT calculations, the introduction of NaSbTe2 can bring the lattice parameter of cubic-phase SnSe closer to SnTe, leading to a lower cation vacancy formation energy and producing an ultra-high hole carrier concentration. Meanwhile, Te has a more developed charge density compared with that of Se, providing additional channels for charge transport when bonded to Sn atoms in cubic lattice. Limited by the electrical transport properties, the ZTmax for SnSe-NaSbSe2 only reaches ∼ 0.50 at 773 K, while the ZTmax for SnSe-NaSbTe2 approaches ∼ 0.95. Furthermore, sodium doping was utilized to tune the carrier mobility and carrier concentration of SnSe-NaSbTe2. Resultantly, the PFmax and ZTmax values reach ∼ 11 μW cm−1 K−2 and ∼ 1.20 at 773 K in sodium-doped SnSe-NaSbTe2, 4.4 and 3.0 times higher than those of pure SnSe, respectively. Our study further promotes cubic-phase SnSe thermoelectrics for mid-temperature energy harvesting applications.

High performance of Mg3Bi1.5Sb0.5 based materials for power generation: Revealing the counter-intuitive effect of tuning Bi content on the thermoelectric properties

Recently, Mg3Sb2-xBix alloys have attracted intensive attention, with the aim of maximizing the electrical transport performance via donor element doping, increasing the grain size, as well as electronic band structure engineering. However, less attention has been paid to other significant factors, like how these intrinsic point defects and accompanied secondary phases influence thermoelectric properties. In this study, the microstructure and thermoelectric transport properties of Mg3.2Sb0.5Bi1.495-xTe0.005 (x = 0 ∼ 0.2) compounds were systematically investigated, where tuning the Bi content shows the counter-intuitive impact on the thermoelectric properties. It was found that the Bi-poor environment associated with Bi impurities facilitated the increment of cation vacancy formation energy and then increased the carrier concentration, leading to the enhancement of power factor. Simultaneously, the reduction of Bi-rich second phase content weakened the carrier scattering by grain boundaries whereas high carrier mobility was maintained. Moreover, the bipolar thermal conductivity decreased obviously due to the increased majority carrier concentration to suppress the intrinsic excitation. The synergistic optimization pushes the average ZT value (300–573 K) up to 0.95 in the Mg3.2Sb0.5Bi1.295Te0.005 sample. Moreover, the calculated single-leg conversion efficiency is increased up to 9.7% with the hot-side temperature of 573 K, as the record-high value in this system.

Preparation of a novel iron oxychloride (FeOCl) auxiliary electrode in promoting electrokinetic remediation of Cr(VI) contaminated soil: An experimental and DFT calculation analysis.

The utilization of auxiliary electrode can improve substantially the electrokinetic remediation efficiency of heavy metal contaminated soil. The increase in the auxiliary electrode performance is the key to further promote the electrokinetic remediation efficiency. In this study, two kinds of auxiliary electrodes, pure FeOCl and doped FeOCl with W and S, were prepared and used in the electrokinetic remediation of Cr(VI) contaminated soil. The system equipped with the auxiliary electrode doped FeOCl brought more stable system current (202mA) and more uniform electric field than blank group (130mA). The reduction rate of Cr(VI) was increased by 50% due to the presence of Fe2+ and S2-. The accelerating migration of ions by auxiliary electrode was responsible for the improvement in electrokinetic remediation efficiency. Density functional theory (DFT) calculation showed that Cl vacancy formation energies of pure FeOCl, S-doped FeOCl (S/FeOCl) and W-doped FeOCl (W/FeOCl) were 1.29, 1.15 and 1.49eV respectively, and the ion diffusion barriers were 0.093, 0.099 and 0.148eV respectively. Calculation results indicated that the doping of S was conducive to the diffusion of Cl ions, and the bonding of W-Cl was stronger than Fe-Cl. The charging and discharging process of auxiliary electrode became easier due to the formation of lower vacancy in S-doped FeOCl, which could bring a higher current for the electrokinetic remediation system. The electrochemical performance of FeOCl doped with W and S was improved obviously. This study provided a further explanation for the positive role of auxiliary electrode in electrokinetic remediation system.

Understanding thermochemical energy storage performance of Ba1-xSrxCoO3-δ perovskite system: A computational and experimental study

Concentrated solar power coupled with thermochemical energy storage (TCES) has emerged as an effective approach for renewable energy utilization. TCES based on perovskites attracts much attention because of temperature tunability and high flexibility. In this work, the electronic structures are simulated by the density functional theory (DFT) method, revealing the reduction temperatures is related to the formation energy of oxygen vacancy (Evac). The compounds of Ba1-xSrxCoO3-δ with x = 0–1 are synthesized and investigated by experimental methods. According to the results, Ba content improves the redox capacities and reaction kinetics, while Sr content expands the reaction temperatures and enhances the micro morphologies. In addition, all the samples present a greater reversibility after 150 cycles, because the extended pores are beneficial to the oxygen diffusion. Overall, Ba0.5Sr0.5CoO3-δ is suggested as a suitable TCES material with a reaction enthalpy of 202.20 kJ kg−1. This study provides a design principle of composite perovskites for thermochemical energy storage.