Perovskite Oxides Research Articles

Boosting the lattice oxygen reactivity of perovskite electrocatalyst via less Ru substitution

The successful deployment of efficient oxygen evolution reaction (OER) electrocatalysts is highly essential for multiple clean-energy-related conversion technologies. Perovskite oxides, with compositional diversity and elemental complexity, are a classic kind of OER electrocatalysts, whereas their activity remains insufficient under the traditional adsorbate evolution mechanism (AEM) due to limited scaling relations. Herein, taking the Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite as a model system, we find a less Ru substitution strategy to boost the lattice oxygen reactivity for improved OER. The OER behavior of BSCF is greatly ameliorated as Ru doping reaches an optimal level (BSCFR0.1), delivering a lowered overpotential by 45 mV at 10 mA cm−2. Notably, such doping remarkably triggers the generation of more surface oxygen vacancies, promotes internal charge transfer, and enlarges the surface hydrophilicity, hence facilitating more lattice oxygen to participate in the surface reaction. These results demonstrate the feasibility of Ru incorporation for ameliorating the OER behavior of perovskites, and such strategy can be further leveraged to design other remarkable perovskite-based OER catalytic materials.

Role of self-assembled molecules’ anchoring groups for surface defect passivation and dipole modulation in inverted perovskite solar cells

Abstract Inverted perovskite solar cells have gained prominence in industrial advancement due to their easy fabrication, low hysteresis effects, and high stability. Despite these advantages, their efficiency is currently limited by excessive defects and poor carrier transport at the perovskite–electrode interface, particularly at the buried interface between the perovskite and transparent conductive oxide (TCO). Recent efforts in the perovskite community have focused on designing novel self-assembled molecules (SAMs) to improve the quality of the buried interface. However, a notable gap remains in understanding the regulation of atomic-scale interfacial properties of SAMs between the perovskite and TCO interfaces. This understanding is crucial, particularly in terms of identifying chemically active anchoring groups. In this study, we used the star SAM ([2-(9H-carbazol-9-yl)ethyl] phosphonic acid) as the base structure to investigate the defect passivation effects of eight common anchoring groups at the perovskite–TCO interface. Our findings indicate that the phosphonic and boric acid groups exhibit notable advantages. These groups fulfill three key criteria: they provide the greatest potential for defect passivation, exhibit stable adsorption with defects, and exert significant regulatory effects on interface dipoles. Ionized anchoring groups exhibit enhanced passivation capabilities for defect energy levels due to their superior Lewis base properties, which effectively neutralize local charges near defects. Among various defect types, iodine vacancies are the easiest to passivate, whereas iodine-substituted lead defects are the most challenging to passivate. Our study provides comprehensive theoretical insights and inspiration for the design of anchoring groups in SAMs, contributing to the ongoing development of more efficient inverted perovskite solar cells.

In situ reconstruction of proton conductive electrolyte from self-assembled perovskite oxide-based nanocomposite for low temperature ceramic fuel cells

In the development of low temperature solid oxide fuel cells (LT-SOFCs), also called ceramic fuel cells, the lack of highly conductive and the high manufacturing cost of dense electrolyte materials severely delay their wide development. In this work, we depart from the classic substitution approach to achieve sufficient ionic conduction (0.01 S cm−2 level at temperature ≥600 °C), a superionic conductive electrolyte material was obtained from a self-assembled hybrid oxide that was derived from the perovskite oxide precursor through alkali metal ion substitution. Moreover, the hybrid oxide was further in-situ reconstructed into a nanocomposite of oxide/carbonate-hydroxide under fuel cell condition. The nanocomposite possesses dominated proton conductivity as verified by the benefited hydration effect, versatile oxygen ionic blocking cell experiment, and concentration cell investigation. Specifically, an outstanding ionic conductivity of 0.185 S cm−1 and an excellent peak power density of 1012 mW cm−2 were demonstrated at 550 °C under an typical H2/air atmosphere. This research offers a rational design strategy to achieve low temperature, high-performance semiconductor-based functional composite electrolytes for efficient and sustainable energy conversion in SOFC technology.

Ionic radius effect on structural and electrical properties of barium strontium titanate thin films

The effect of ion radius on the structural and electrical properties of the perovskite oxide Ba1-x SrxTiO3 thin film is investigated in this work. X-ray diffraction analysis confirmed the formation of phase perovskite structures. Investigations of ceramic microstructures and mechanical properties showed their dependence on the value of ratio x. X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) are used to study the crystallographic aspects of the materials. The XRD pattern changed from tetragonal to cubic as x rose. FESEM images revealed the particle size varied with the values of x increased. The results show that as the ion radius varies, the crystal structure undergoes distortions, affecting the symmetry and stability of the BaSrTiO3 thin films. Electrical properties change depending on the change in particle size.

Constructing a medium-entropy and A-site deficient perovskite oxide for efficient electrocatalytic oxygen evolution

Electrochemical water splitting has emerged as a promising alternative to traditional fossil fuels, providing an efficient and eco-friendly pathway to generate clean hydrogen energy. While the development of high-entropy oxides (HEOs) has introduced a paradigm of integrating multiple metal elements, medium-entropy oxides (MEOs) have been recognized as a more advantageous option partly due to the more controlled entropy levels in MEOs, allowing for a finely-tuned balance between compositional complexity and functional optimization. Building on this concept, this study introduces a medium-entropy perovskite oxide (Ba0.9La0.1)0.9Co0.6Fe0.2Ni0.2O3-δ (BLCFN-0.9), with A-site deficiency for optimizing oxygen evolution reaction (OER). Comprehensive analysis reveals that BLCFN-0.9 demonstrates superior OER activity with an impressively low overpotential of 294 mV to deliver a current density of 10 mA cm−2 in an alkaline electrolyte, outperforming other state-of-the-art perovskite oxide electrocatalysts. Notably, the BLCFN-0.9 electrocatalyst achieves the robust performance stability, maintaining a consistently low potential over 30 h. This study sheds light on the potential of medium-entropy perovskite oxides for advancing OER efficiency, opening a new avenue to the evolution of electrocatalysis through strategic material design.

Optimizing oxygen transport properties in Al-substituted La0.5Sr0.5Co0.8Fe0.2-xAlxO3-δ (x = 0–0.20) perovskites

In recent years, there has been a surge in the investigation of perovskite-type complex oxides, with a particular focus on La1-xSrxCo1-yFeyO3, renowned for their exceptional mixed ionic-electronic conducting (MIEC) properties. La0.6Sr0.4Co1-yFeyO3 compositions have prominently emerged in this research domain. The hypothesis of enhancing redox stability and mitigating oxygen variations by incorporating trivalent aluminum (Al3+) into the B-site of perovskite structures has gained attention. In this study, single-phase La0.5Sr0.5Co0.8Fe0.2-xAlxO3-δ (x = 0–0.20) perovskite oxides were synthesized using the solution combustion technique. The physicochemical properties of the synthesized materials were thoroughly characterized, including their morphology, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) analysis, oxygen nonstoichiometry, and electrical transport properties. Results revealed lattice parameter variations associated with oxygen nonstoichiometry and B-site cation size, exhibiting a decline up to x = 0.10 followed by an increase. Al-substitution significantly influenced surface morphology, oxygen nonstoichiometry, and electrical conductivity. Notably, La0.5Sr0.5Co0.8Fe0.1Al0.1O3-δ displayed lower electrical conductivity (676 S cm−1 at 300 °C) among the studied oxides. Oxygen nonstoichiometry had a significant impact on oxygen transport parameters, with these perovskites demonstrating improved chemical diffusion coefficient, Dchem (5.5 × 10-5 cm2 s−1), and the oxygen surface exchange coefficient, Kchem (2.32 × 10-5 cm s−1) at 900 °C, suggesting its potential as an oxygen transport membrane. These findings underscore the promising role of Al-substituted perovskite oxides in various advanced applications.

Electrical and electrochemical properties of A-site non-stoichiometry Ca0.67La0.22□0.11Ti(1−x)CrxO3−δ electrolyte materials for solid oxide fuel cells

Due to increasing global energy demands and environmental concerns, the search for alternative and environmentally friendly energy sources is of paramount importance. Solid oxide fuel cells (SOFCs) have emerged as a promising solution thanks to their high efficiency and minimal environmental impact. In this regard, perovskite oxides, with their unique properties, have attracted significant attention. This study investigates the dielectric dispersion, electrical features, scaling behavior, and optical defects of Ca0.67La0.22Ti0.85Cr0.15O3 with x = 0.15, CLT0.85Cr0.15. The presence of a vacancy in the A-site is denoted by the square in the formula. Relaxation phenomena were analysed using dielectric and modulus formalism, while the conductivity mechanism was explored through electrical conductivity measurements. The optical defects of CLT0.85Cr0.15 were analysed using electron paramagnetic resonance (EPR) spectroscopy. The findings revealed the formation of Cr3+–VO center defects. These defects serve as sources of in-gap electron traps, thereby enhancing the optical properties of CLT0.85Cr0.15, making it as a compelling material for various optical applications. The power density increased with temperature, reaching 0.73 W/cm2 at 850 °C, suggesting that CLT0.85Cr0.15 could be a promising electrolyte for IT-SOFCs. The peak in power density correlated with temperature due to thermal effects on ion motion. However, the open circuit voltage decreased with temperature increase, due to increased oxygen vacancies and electron/hole conduction in CLT0.85Cr0.15. The findings suggest that perovskite materials could revolutionize SOFCs technology, paving the way for more efficient and environmentally friendly energy solutions.

Constructing active lattice oxygen in high covalent perovskites for boosting catalytic activity

Transition-metal (TM) active centers are solely considered to probe the intrinsic origin of catalytic activity, but the interaction between metal and oxygen has been overlooked. Herein, an effective approach is demonstrated to adjust the degree of TM–O covalency, enhancing the intrinsic catalytic activity via Cu substitution and acid etching. In-situ spectroscopic investigations and theoretical calculations reveal that improved catalytic performances are attributed to enhanced TM–O covalency. Owing to the strong hybridization between TM 3d and O 2p orbitals, the intramolecular electrons are transported from oxygen to TM cations, promoting asymmetric electron redistribution and inducing oxygen holes (electrophilic O(2−δ)−) generation. Ligand oxygen holes as preactive oxygen centers achieved the initial activation of reactant molecules and lattice oxygen activation, ultimately boosting the heterogeneous catalytic activity. The findings highlight a new method to design highly covalent perovskite oxides with sufficient ligand oxygen holes to trigger lattice oxygen activation in the catalytic fields.

Chemistry and Physics of Triple Perovskite Oxides: A Topical Review

Chemistry and Physics of Triple Perovskite Oxides: A Topical Review

Eco-Friendly Mechanochemical Synthesis of Bifunctional Metal Oxide Electrocatalysts for Zn-Air Batteries.

The development of green and environmentally friendly synthesis methods of electrocatalysts is a crucial aspect in decarbonizing energy generation. In this study, eco-friendly mechanochemical synthesis of perovskite metal oxide-carbon black composites is proposed using different conditions and additives such as KOH. Furthermore, the optimization of ball milling conditions, including time and rotational speed, is studied. The mechanochemical synthesis in solid-state conditions without additives produces electrocatalysts that exhibit the highest bifunctional electrochemical activity towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Moreover, this synthesis demonstrates a lower Environmental Impact Factor (E-factor), indicating its greener nature, and due to its simplicity, it has a great potential for scalability. The obtained bifunctional electrocatalysts have been tested in a rechargeable zinc-air battery (ZAB) for 22 h with similar performance compared to the commercial catalyst (Pt/C) at significantly lower cost. These promising findings are attributed to the enhanced interaction between the perovskite metal oxide and carbon material and the improved dispersion of the perovskite metal oxide on the carbon materials.

Constructing oxygen vacancies by selective anion doping in high entropy perovskite oxide for water splitting

High entropy perovskite oxide (HEPO) is a potential electrocatalyst for the oxygen evolution reaction (OER), but insufficient activity remains a problem. Oxygen vacancies can activate the lattice oxygen to induce the lattice oxygen-mediated mechanism (LOM), which can avoid the kinetic limitation present in adsorbate evolution mechanism (AEM), thereby improving the OER activity. Herein, we select the appropriate doping element (S) through analysis of ionic radius, electronegativity, and oxygen vacancy formation energy, and report an effective two-step oxygen vacancy strategy for introducing oxygen vacancies into HEPO through electrospinning and sulfurization treatment. This strategy optimizes the eg orbital filling electron number and significantly increases the active area, oxygen vacancy content and electroconductivity. Furthermore, the apparent pH dependence and the TMA+ inhibition phenomenon suggest the involvement of the LOM. Consequently, the resulting S/LMO-E has a lower overpotential (314 mV at 10 mA cm−2) and faster kinetics, and shows excellent stability. Meanwhile, the water splitting is achieved at 1.59 V to afford 10 mA cm−2 current density for S/LMO-E⎪⎢Pt/C, which is smaller than that of RuO2⎪⎢Pt/C (1.62 V). This work provides an attractive OER electrocatalyst for efficient water splitting to produce renewable hydrogen and opens a new way for the design of effective and stable high entropy material electrocatalysts.

Highly Stable Perovskite Oxides for Electrocatalytic Acidic NOx− Reduction Streamlining Ammonia Synthesis from Air

AbstractElectrochemical nitrogen oxide ions reduction reaction (NOx−RR) shows great opportunity for ammonia production under ambient conditions. Yet, performing NOx−RR in strong acidic conditions remains challenging due to the corrosion effect on the catalyst and competing hydrogen evolution reactions. Here, we demonstrate a stable La1.5Sr0.5Ni0.5Fe0.5O4 perovskite oxide for the NOx−RR at pH 0, achieving a Faradaic efficiency for ammonia of approaching 100 % at a current density of 2 A cm−2 in a H‐type cell. At industrially relevant current density, the NOx−RR system shows stable cell voltage and Faradaic efficiency for >350 h in membrane electrode assembly (MEA) at pH 0. By integrating the catalyst in a stacked MEA with a series connection, we have successfully obtained a record‐breaking 2.578 g h−1 NH3 production rate at 20 A. This catalyst‘s unique acid‐operability streamlines downstream ammonia utilization for direct ammonium salt production and upstream integration with NOx sources. Techno‐economic and lifecycle assessments reveal substantial economic advantages for this ammonia production strategy, even when coupled with a plasma‐based NOx production system, presenting a sustainable complement to the conventional Haber–Bosch process.

Highly Stable Perovskite Oxides for Electrocatalytic Acidic NOx - Reduction Streamlining Ammonia Synthesis from Air.

Electrochemical nitrogen oxide ions reduction reaction (NOx -RR) shows great opportunity for ammonia production under ambient conditions. Yet, performing NOx -RR in strong acidic conditions remains challenging due to the corrosion effect on the catalyst and competing hydrogen evolution reactions. Here, we demonstrate a stable La1.5Sr0.5Ni0.5Fe0.5O4 perovskite oxide for the NOx -RR at pH 0, achieving a Faradaic efficiency for ammonia of approaching 100 % at a current density of 2 A cm-2 in a H-type cell. At industrially relevant current density, the NOx -RR system shows stable cell voltage and Faradaic efficiency for >350 h in membrane electrode assembly (MEA) at pH 0. By integrating the catalyst in a stacked MEA with a series connection, we have successfully obtained a record-breaking 2.578 g h-1 NH3 production rate at 20 A. This catalyst's unique acid-operability streamlines downstream ammonia utilization for direct ammonium salt production and upstream integration with NOx sources. Techno-economic and lifecycle assessments reveal substantial economic advantages for this ammonia production strategy, even when coupled with a plasma-based NOx production system, presenting a sustainable complement to the conventional Haber-Bosch process.

Effective magnetic moment modulated perovskite-type oxides towards peroxymonosulfate activation: A high-valent metal species and superoxide radical step-by-step oxidation route

Perovskite oxides are considered as promising catalysts in activating peroxymonosulfate (PMS) for environmental remediation, but the intrinsic properties that govern the activity of perovskites are ambiguous. Herein, a series of perovskite-type oxides La2MeO4 (LMe, where Me = Co, Mn, Cu, and Fe) were reported to activate PMS for improving organic pollutant degradation, while the LCo/PMS system showed impressive performance, achieving over 90 % removal of organic contaminants (dyes and antibiotics) under the optimized conditions of 0.05 g/L catalyst and 0.50 mM PMS. Experiments and characterizations verified a good linear correlation between the catalytic activity and effective magnetic moment (μeff) of catalysts, underlining the key role of the spin state of the metal center in governing the intrinsic activity. Additionally, two stages of oxidation pathways were evidenced to be involved in the reaction: i) high-valent cobalt-oxo species (i.e., Co(IV)) were produced from the surface reactive complexes catalyst-PMS*, afterwards ii) a portion of superoxide radicals (O2•−) were formed via the PMS reaction with Co(IV). Overall, these findings provide new insights into the mechanism of the perovskite-activated PMS system for efficient water remediation.

B-site nickel tuned high active Sr and Co-free Ba0.8Ca0.2Fe0.8Ni0.2O3-δ air electrode for reversible solid oxide cells

Reversible solid oxide cells (RSOCs) have aroused wide concern as a promising technology in conversion between chemical energy and electrical power. However, the double conducting (O2−/e−) air electrode with high electrocatalytic activity and thermomechanical stability keeps a significant challenge for practical application. Herein, a perovskite Ba0.8Ca0.2Fe0.8Ni0.2O3-δ (BCFNi) oxide is synthesized and used as the air electrode material, which is experimentally and theoretically demonstrated to have excellent oxygen reduction/evolution reactions (ORR/OER) activity. The density functional theory (DFT) calculations indicate that BCFNi oxide accelerates the oxygen desorption/desorption, thus promoting the OER/ORR kinetics. The cell with BCFNi air electrode achieves a peak power density of 1.29 W cm−2 in the fuel cell (FC) mode and an electrolysis current density of 1.47 A cm−2 with 50 % H2O-H2 at 1.3 V applied voltage in the electrolysis cell (EC) mode at 800 °C. Moreover, it maintains favorable durability of 225 h in the FC, reversible, and EC modes at 750 °C, respectively. The results suggest that the Ni doping in B-site of perovskite oxide is beneficial to improve the ORR/OER activity and BCFNi material has great potential as an air electrode for RSOCs.

(Invited) Probing Oxygen Intercalation, Oxidation and Chemo-Mechanical Coupling in OER Electrocatalysts

I will discuss how intercalation of O2- under OER conditions can lead to lattice oxygen redox and chemo-mechanical coupling inside the crystal lattice of a perovskite electrocatalyst. Specifically, I will show that high-resolution resonant inelastic X-ray scattering (RIXS) can detect the oxidation state of oxygen in a perovskite oxide. The emergence of oxidized oxygen depends on the transition metal and the amount of intercalated oxygen. At the same time, oxygen dimerization has a direct relevance to the stress-induced structural disorder that takes place inside the electrocatalyst. At the end, I will also discuss our recent finding in which oxygen can intercalate spontaneously following a catalytic O2 splitting at the surface and induce substantial transformations in the bulk of the perovskite.

(Invited) Two-Dimensional Organic-Perovskite Hybrid Materials and Heterostructures

Epitaxial heterostructures based on oxide perovskites and III–V, II–VI and transition metal dichalcogenide semiconductors form the foundation of modern electronics and optoelectronics. Halide perovskites—an emerging family of tunable semiconductors with desirable properties—are attractive for applications such as solution-processed solar cells, light-emitting diodes, detectors and lasers. Their inherently soft crystal lattice allows greater tolerance to lattice mismatch, making them promising for heterostructure formation and semiconductor integration. Atomically sharp epitaxial interfaces are necessary to improve performance and for device miniaturization. However, epitaxial growth of atomically sharp heterostructures of halide perovskites has not yet been achieved, owing to their high intrinsic ion mobility and their poor chemical stability. Therefore, understanding the origins of this instability and identifying effective approaches to suppress ion diffusion are of great importance. In this talk I will present an effective strategy to substantially inhibit in-plane ion diffusion in two-dimensional halide perovskites by incorporating rigid π-conjugated organic ligands. Highly stable and tunable lateral and vertical epitaxial heterostructures, multiheterostructures and superlattices will be demonstrated. Furthermore, using these 2D heterostructures as a new platform, I will present our recent efforts in 1) quantitatively understanding the anion inter-diffusions and migrations, and 2) controlling and manipulating exciton transport and light-emission in halide perovskites.

(Invited) Novel High Entropy Perovskite Oxides for High-Performance Protonic Ceramic Electrochemical Cells

Due to the intermediate operating temperatures (400-600oC), protonic ceramic electrochemical cells have attracted significant attention in the last 10 years because of the demonstration of potential applications of fuel-flexible fuel cells, water electrolysis to produce hydrogen, solid-state ammonia synthesis, electrochemical reduction of carbon dioxide to fuels, and fuel processing (e.g., natural gas to liquids). In addition to developing specific fuel electrodes for different electrocatalytic reactions, we need to discover new electrolyte and oxygen electrode materials generically for all the protonic ceramic electrochemical cells to further decrease the operating temperatures, increase performance, and prolong the long-term stability. The recently emerging materials of high entropy perovskite oxides have been reported to be able to serve as promising electrolyte and oxygen electrode materials. In this talk, we will summarize what Clemson University has done about developing, characterizing, understanding, and demonstrating high entropy perovskite oxides as high-performance and stable electrolyte and oxygen electrode materials for protonic ceramic electrochemical cells.

Accelerating the Development of Oxygen Electrodes for Solid Oxide Cells Using Two-Stage Machine Learning

Reversible Solid Oxide Cells (RSOCs) stand out as highly efficient and cost-effective devices for energy storage and conversion. However, the pursuit of high-performance and durable RSOCs is impeded by the lack of efficient and stable oxygen electrodes. The conventional trial-and-error approach used for the development of oxygen electrodes is resources and time-consuming. In this presentation, we introduce a novel "two-stage machine learning" approach designed to expedite the discovery of optimal oxygen electrodes for efficient oxygen reduction/evolution reaction (ORR/OER) in SOCs. In the initial stage, we employed a high-throughput calculation approach to generate four ORR/OER related descriptors (energy above the convex hull, p-band center, d-band center, and vacancy formation energy) for a set of 4455 perovskite oxide candidates. Subsequently, we successfully predicted these descriptors using machine learning techniques based on the fundamental physico-chemical features of the candidates. Moving to the second stage, we measured the polarization resistances - directly related to ORR/OER activity - of 142 oxygen electrodes and employed them as prediction targets. Through our machine learning method, we accurately predicted experimental results based on the fundamental physico-chemical features of the candidate materials. Notably, among the 4455 candidates studied, a specific oxygen electrode material is predicted to exhibit both high activity and stability. When applied to an RSOC based on a proton-conducting electrolyte operated at 600 °C, a high peak power density of >1.5 W cm−2 is demonstrated in the fuel cell mode, and a high current density of >2.5 A cm−2 is achieved at a cell voltage of 1.3 V in the water electrolysis mode while maintaining stable operation for 500 hours.

Electronic Structure Investigation of BSCF Catalysts during Electrochemical Water Electrolysis by Using Time Zero Analysis and Advanced Operando X-Ray Absorption Spectroscopy

The rapid increase in global energy demands and environmental awareness regarding the excessive use of fossil fuel has spurred significant academic interest in the development of alternative energy conversion and storage technologies that prioritize both efficiency and environmental sustainability. Among all kinds of renewable energy, hydrogen energy holds the potential to create a carbon free clean society, and a possible solution to the environmental issues.1 Electrochemical water splitting is considered as a greener approach for pure H2, which involved cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER). The anodic OER is kinetically sluggish and considered as a rate determining step of the water splitting reaction. Therefore, it is necessary to develop OER catalysts with high activities.Perovskite oxides knows as a promising oxygen electrode catalyst due to their low cost, flexibility, and tailorable properties. However, most perovskite oxides possess poor electrical conductivity at room temperatures, and this limits their oxygen catalytic activity. In our work Ba0.5Sr0.5CoxFe1-xO3-δ (BSCF) catalysts with different cobalt and iron amounts where X=0, 0.2, 0.8, 1 were synthesized and investigated by time zero analysis and flow rate infinitization analysis which are electrochemical testing method that uses pressure to remove generated oxygen gas bubbles and provides accurate activity of the catalyst.2We find the volcano plot of the Fe amount and the OER activities, showing samples with X=0.8 have the best OER activities as Figure 1. Electronic structure of B-Site transition metal elements, oxygen vacancies, crystal structures and electrical conductivity are the key factors for determining the activities of Perovskite catalysts in OER.3Also it is quite important to determine the real active sites during the OER process by using advance operando techniques.Therefore, in order to investigate the in-depth mechanism of OER activities of Perovskite catalysts, the newly designed operando soft X-ray Absorption Spectroscopy (XAS) cells was utilized to analyze the subtle change as shown in Figure 2 on the oxygen K-edge (531 eV - 532 eV). Ba0.5Sr0.5Co0.8Fe0.2O3-δ has the most obvious changes in integral surface area at the O K-edge pre-edge region, which leads to the best activity among other BSCF samples. According to the Energy Dispersive X-ray Spectroscopy and Lattice Oxygen Evolution Mechanism, ions on the A sites (Ba2+,Sr2+) tend to dissolve and ions on the B sites (Co, Fe) are forming hydroxides (BOOH).Keywords: oxygen evolution reaction, BSCF catalysts, Time zero analysis, operando X-ray absorption spectroscopy Acknowledgements This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. Reference: (1) Rose, P. K.; Neumann, F. Hydrogen refueling station networks for heavy-duty vehicles in future power systems. Transportation Research Part D: Transport and Environment 2020, 83, 102358.(2) Nagasawa, K.; Matsuura, I.; Kuroda, Y.; Mitsushima, S. A Novel Evaluation Method of Powder Electrocatalyst for Gas Evolution Reaction. Electrochemistry 2022, 90 (1), 017012-017012.(3) Zhu, Y.; Zhou, W.; Shao, Z. Perovskite/carbon composites: applications in oxygen electrocatalysis. Small 2017, 13 (12), 1603793. Figure 1