Perovskite Oxides for Energy and Environmental Catalysis: How Oxygen Vacancies, B-Site Metals, and the Metal–Oxygen Bond Network Regulate Reaction Performance

Introduction

Perovskite oxides are not only used in electronic ceramics, but can also serve as catalytic materials in energy- and environment-related reactions. This article mainly discusses transition-metal-containing oxide perovskites, with a focus on their catalytic behavior in thermal catalysis, electrocatalysis, and solid oxide fuel cell electrodes.

Typical perovskite oxides can be written as ABO₃ or ABO₃₋δ. In this structure, the A site is usually occupied by rare-earth or alkaline-earth metal ions, while the B site is usually occupied by transition-metal ions such as manganese, iron, cobalt, and nickel. Oxygen ions form the metal–oxygen octahedral framework. Catalytic activity is not determined by one element alone; instead, reactant adsorption, oxygen activation, electron transfer, and oxygen migration are jointly influenced by the A site, B site, oxygen site, oxygen vacancies, lattice oxygen, and surface oxygen species.

Perovskite oxides have attracted attention in the oxygen evolution reaction, oxygen reduction reaction, volatile organic compound oxidation, carbon monoxide oxidation, methane oxidation, and solid oxide fuel cell cathodes. This is because their composition is tunable, they contain abundant transition-metal sites, their oxygen non-stoichiometry can be adjusted, and their catalytic performance can be modified through doping, defect regulation, and surface engineering.

1. Basic Structure of Perovskite Oxides Used in Catalysis

Perovskite oxides used in catalysis can be understood from four levels: the A site, B site, oxygen site, and surface.

Structural position	Main role	Influence on catalytic performance
A site	Regulates lattice size, structural stability, and charge balance	Affects oxygen vacancy formation, oxygen migration, thermal stability, and the tendency toward surface segregation
B site	Provides transition-metal redox centers	Affects oxygen adsorption, electron transfer, metal valence cycling, and the binding strength of reaction intermediates
Oxygen site	Forms the metal–oxygen framework and lattice oxygen network	Affects oxygen vacancy formation, lattice oxygen migration, and the ability of oxygen to participate in reactions
Surface	Directly contacts reactants	Determines reactant adsorption, oxygen activation, product desorption, and surface reconstruction behavior

Common research systems include:

Material direction	Representative systems	Suitable research focus
Lanthanum manganite systems	LaMnO₃, La₁₋ₓSrₓMnO₃	Oxygen migration, volatile organic compound oxidation, solid oxide fuel cell cathodes
Lanthanum ferrite systems	LaFeO₃, La₁₋ₓSrₓFeO₃	Oxygen vacancy regulation, structural stability, oxidation reactions, and electrode reactions
Lanthanum cobaltite systems	LaCoO₃, La₁₋ₓSrₓCoO₃	Oxygen reduction, oxygen evolution reaction, low-temperature oxygen exchange, and oxidation activity
Lanthanum nickelate systems	LaNiO₃ and doped nickel-based perovskite oxides	B-site electronic structure, redox activity, and oxygen electrocatalysis
Cobalt–iron composite systems	La₁₋ₓSrₓCo₁₋ᵧFeᵧO₃₋δ, Ba₁₋ₓSrₓCo₁₋ᵧFeᵧO₃₋δ	Oxygen surface exchange, oxygen-ion migration, and solid oxide cell cathode reactions

It should be noted that many perovskite oxides do not necessarily operate directly through their initial surface during reaction. Especially under electrocatalytic conditions such as the oxygen evolution reaction, the surface may undergo reconstruction and form new oxide, hydroxide, or oxyhydroxide active layers. Therefore, in some cases, perovskite oxides can be regarded both as catalysts and as precursors to the active surface formed during reaction.

2. How the A Site, B Site, and Oxygen Site Jointly Affect Catalytic Performance

The catalytic performance of perovskite oxides arises from the synergistic regulation of “composition–defects–surface structure.”

Regulation method	Main influence	Points requiring attention
A-site substitution	Changes ionic radius, charge balance, lattice distortion, and the tendency toward oxygen vacancy formation	Excessive doping may lead to secondary phases, A-site segregation, or thermal expansion mismatch
B-site substitution	Changes transition-metal valence state, metal–oxygen bond strength, and electronic structure	Improved activity may be accompanied by decreased stability or metal dissolution
A-site deficiency	Increases the demand for charge compensation and may increase oxygen vacancy concentration	Excessive deficiency may damage phase stability and long-term durability
B-site compositing	Introduces two or more transition metals to tune oxygen binding strength and reaction pathways	It is necessary to confirm whether a homogeneous solid solution or locally enriched phases are formed
Oxygen non-stoichiometry	Forms oxygen vacancies or oxygen-excess states, regulating oxygen migration and conductivity	Excessive oxygen vacancies may lead to lattice instability or restricted oxygen migration
Surface regulation	Changes surface oxygen species, defect concentration, and accessible active sites	Surface modification layers must balance activity, mass transport, and stability

The A site usually does not act directly as the main reaction active center, but it can influence B-site metal valence states and oxygen vacancy formation through lattice size, charge balance, and local structure. B-site transition metals are usually the core of activity regulation because they directly participate in electron transfer, valence cycling, and reaction intermediate adsorption. The oxygen site determines whether lattice oxygen can readily migrate, be replenished, and participate in surface reactions.

Therefore, perovskite oxide catalysts should not be judged simply by saying that “a certain element is highly active.” A more reasonable approach is to examine whether the B-site metal has suitable redox capability, whether the metal–oxygen bond strength is appropriate, whether oxygen vacancies can reversibly participate in oxygen exchange, and whether the surface structure can still maintain an effective catalytic state after reaction.

3. Oxygen Vacancy Regulation: The Key Lies in Reversible Oxygen Exchange Capacity

Oxygen vacancies are defect sites formed by the absence of oxygen ions in the perovskite oxide lattice. For energy and environmental catalytic reactions, the significance of oxygen vacancies is not limited to providing defect sites; they also influence oxygen adsorption, oxygen activation, lattice oxygen migration, metal valence regulation, and surface oxygen replenishment.

In volatile organic compound oxidation, carbon monoxide oxidation, methane oxidation, the oxygen evolution reaction, the oxygen reduction reaction, and solid oxide fuel cell cathode reactions, oxygen vacancies often significantly affect oxygen adsorption, oxygen activation, lattice oxygen migration, and oxygen replenishment. However, the specific activity is also influenced by B-site electronic structure, metal–oxygen bond strength, surface reconstruction, and stability. Oxygen vacancies are a key factor connecting “structural defects” with “catalytic activity.”

Role of oxygen vacancies	Significance for catalytic reactions
Provide sites for oxygen adsorption and activation	Helps oxygen molecules, hydroxyl groups, or oxygen-containing intermediates approach surface active centers
Promote the formation of surface active oxygen	Helps form active oxygen species that participate in oxidation reactions or electrode reactions
Enhance lattice oxygen migration	Facilitates the replenishment of surface oxygen by bulk lattice oxygen and maintains the oxidation cycle
Regulate B-site metal valence states	Affects the redox states of transition metals such as manganese, iron, cobalt, and nickel through charge compensation
Influence reaction pathways	Can change the way adsorbed oxygen, surface oxygen, and lattice oxygen participate in the reaction

More oxygen vacancies are not necessarily better. When oxygen vacancies are insufficient, oxygen adsorption and oxygen migration are limited. At a moderate level, they help balance oxygen exchange and structural stability. When excessive, they may weaken lattice stability, reduce oxygen migration efficiency, and lead to irreversible structural changes or secondary phase formation. Therefore, evaluation of oxygen vacancies should focus on their reversible formation, migration, and replenishment capacity, rather than simply pursuing stronger defect signals.

Oxygen vacancy state	Catalytic behavior	Key concerns
Insufficient oxygen vacancies	Limited oxygen adsorption, oxygen activation, and lattice oxygen replenishment capacity	Low activity, difficulty initiating low-temperature reactions, slow oxygen exchange rate
Moderate oxygen vacancies	Oxygen adsorption, oxygen migration, electron transfer, and structural stability are relatively balanced	Suitable for further optimization around composition, surface structure, and reaction conditions
Excessive oxygen vacancies	Lattice stability decreases, and structural recovery after reaction becomes poor	Possible phase transformation, component segregation, abnormal conductivity, or activity decay

Therefore, the focus of oxygen vacancy regulation is not simply to increase the number of defects, but to enable oxygen vacancies to be reversibly generated, migrated, replenished, and involved in the catalytic cycle during reaction. In experimental judgment, oxygen defect characterization, metal valence changes, crystal phase before and after reaction, and stability data should be considered together, so that catalytic performance is not judged only from a single oxygen vacancy signal.

4. Why B-Site Transition Metals Are Often the Core of Activity Regulation

B-site transition metals are an important source of catalytic performance in perovskite oxides. Metals such as manganese, iron, cobalt, and nickel have variable valence states, can participate in electron transfer during reaction, and influence the binding strength between oxygen species and the surface.

B-site factor	Influence on catalytic performance
Metal valence state	Determines redox cycling capability and charge compensation mode
Metal–oxygen bond strength	Affects oxygen adsorption, intermediate stability, and product desorption
Electronic structure	Affects electron transfer rate, reaction barriers, and the activity of oxygen species
Multimetal synergy	Can regulate activity, stability, oxygen vacancy concentration, and surface reconstruction behavior
Tendency toward surface reconstruction	New active surface layers may form during reaction

The research focus differs among different B-site systems:

B-site system	Key focus
Manganese-based systems	Oxygen migration, volatile organic compound oxidation, and cathode stability in solid oxide cells
Iron-based systems	Structural stability, oxygen vacancy regulation, oxidation reactions, and electrode reactions
Cobalt-based systems	Oxygen reduction, oxygen evolution reaction, low-temperature oxygen exchange, and oxidation activity
Nickel-based systems	Redox activity, electronic structure, and reaction intermediate adsorption
Cobalt–iron composite systems	Oxygen surface exchange, oxygen-ion migration, and overall electrochemical reaction performance

The activity of B-site metals should not be understood as “the more reactive, the better.” If the metal–oxygen bond is too strong, reaction intermediates may not desorb easily. If the metal–oxygen bond is too weak, oxygen adsorption and activation may be insufficient. The key to catalyst design is to bring adsorption, reaction, electron transfer, oxygen migration, and product desorption into an appropriate balance. Especially when nickel-based and cobalt-based perovskites are used for the oxygen evolution reaction, oxide, hydroxide, or oxyhydroxide active layers may form on the surface after reaction. Therefore, activity evaluation should combine post-reaction surface structure analysis to identify the true active phase.

5. Which Energy and Environmental Reactions Perovskite Oxides Participate In

The catalytic reactions suitable for discussion with perovskite oxides are mostly related to oxygen adsorption, oxygen activation, lattice oxygen migration, or oxygen-ion conduction. Different reactions have different core controlling steps, so they should not be judged by the same material selection logic.

Reaction direction	Reaction essence	Key role of perovskite oxides	Key indicators
Oxygen evolution reaction	Water or hydroxide is converted into oxygen	B-site metals regulate oxygen-containing intermediate adsorption, while surface reconstruction and oxygen vacancies influence reaction rate	Overpotential, current density, Tafel slope, Faradaic efficiency, stability
Aqueous oxygen reduction reaction	Oxygen is reduced to water or hydroxide in an aqueous electrolyte	Surface oxygen adsorption, electron transfer, and oxygen intermediate stability determine activity	Onset potential, half-wave potential, electron transfer number, peroxide yield, stability
Volatile organic compound oxidation	The goal is usually to deeply oxidize volatile organic compounds into carbon dioxide and water while controlling partially oxidized by-products	Surface active oxygen and lattice oxygen jointly participate in the oxidation cycle	Light-off temperature, half-conversion temperature, complete-conversion temperature, carbon dioxide selectivity, resistance to water and poisoning
Carbon monoxide oxidation	Carbon monoxide is converted into carbon dioxide	Oxygen vacancies promote oxygen adsorption and activation, and lattice oxygen can participate in the oxidation process	Conversion temperature, reaction rate, moisture resistance, carbonate coverage
Complete methane oxidation	Strong C–H bonds are activated and oxidized	Surface oxygen species, lattice oxygen activity, and thermal stability jointly influence conversion	Conversion, carbon dioxide selectivity, sintering resistance, water resistance
Solid oxide fuel cell cathode reaction	Oxygen is adsorbed, dissociated, reduced, and converted into oxygen ions	Oxygen surface exchange, oxygen-ion migration, electronic conduction, and electrode structure jointly determine performance	Polarization resistance, area-specific resistance, power density, thermal expansion matching, long-term stability

The oxygen evolution reaction and oxygen reduction reaction are key sluggish reactions in water splitting, fuel cells, and metal–air batteries. Because of their tunable composition and abundant transition-metal sites, perovskite oxides are widely studied as non-noble-metal oxygen electrocatalysts. Volatile organic compound oxidation, carbon monoxide oxidation, and methane oxidation place greater emphasis on surface oxygen species, lattice oxygen replenishment capacity, low-temperature activity, and long-term resistance to deactivation. Solid oxide fuel cell cathodes also require simultaneous consideration of oxygen exchange, oxygen-ion migration, electronic conduction, thermal expansion matching, and electrode–electrolyte compatibility.

6. From Performance Data to Structural Evidence: How to Judge Catalytic Results

Evaluation of perovskite oxide catalysts should not rely only on single-run activity. High conversion, low overpotential, or low polarization resistance only indicates good performance under the current testing conditions. To determine whether the material design is valid, performance data must be analyzed together with crystal phase, metal valence state, oxygen vacancies, surface structure, specific surface area, and post-reaction stability.

Question to be answered	Evidence to focus on	Judgment points
Whether the target perovskite phase has formed	Crystal phase analysis, elemental ratio analysis	Confirm whether impurities, unreacted precursors, or composition deviations exist, and avoid mistaking impurity-phase activity for the intrinsic role of the perovskite
Whether activity enhancement comes from B-site metal regulation	Surface valence analysis, absorption spectroscopy, comparison of valence states before and after reaction	Determine whether B-site metals such as manganese, iron, cobalt, and nickel participate in redox cycling and electron transfer
Whether oxygen vacancies truly participate in catalysis	Multi-method oxygen defect analysis, oxygen temperature-programmed desorption, hydrogen temperature-programmed reduction, electron paramagnetic resonance, thermogravimetric analysis	Determine whether oxygen vacancy changes correspond to oxygen adsorption, oxygen migration, lattice oxygen replenishment, or activity changes
Whether activity differences are only caused by specific surface area	Specific surface area and pore structure testing	Distinguish apparent activity enhancement caused by increased surface area from structural activity enhancement caused by regulation of the metal–oxygen network
Whether the structure remains after reaction	Comparison of crystal phase, morphology, elemental distribution, and surface valence before and after reaction	Determine whether sintering, phase transformation, component segregation, metal dissolution, or surface coverage has occurred
Whether lattice oxygen participates in the reaction	Isotope labeling, in situ spectroscopy, temperature-programmed reaction analysis	Determine whether the reaction involves lattice oxygen consumption, oxygen vacancy formation, and oxygen replenishment cycles
Whether electrode performance is affected by interfaces	Impedance analysis, symmetric cell testing, observation of interfacial microstructure	Determine whether the limiting step originates from the material itself, interfacial contact, electrode pore structure, or ion conduction
Whether the results are reproducible	Parallel samples, batch-to-batch reproducibility, records of reaction precursors and calcination conditions	Determine whether performance changes are reliable and avoid misjudgment caused by differences in synthesis batch, particle size, or testing conditions

The focus of experimental evaluation is not to perform every characterization method, but to ensure that performance data and structural evidence can correspond to each other. If activity enhancement is accompanied by reasonable B-site metal valence changes, explainable oxygen vacancy regulation, a stable crystal structure, or a controllable surface active layer, then the structure–performance relationship becomes more convincing.

Conversely, if activity enhancement is accompanied by obvious phase transformation, metal dissolution, particle sintering, surface carbonate coverage, or excessive batch-to-batch variation, then it is necessary to judge cautiously whether this direction is worth further optimization. At this point, one should first return to material composition, synthesis route, calcination conditions, and testing environment to confirm whether the performance change comes from controllable structural regulation rather than an accidental surface state or irreversible damage.

7. Deactivation Mechanisms and Troubleshooting Priorities: Changes in Structure, Surface, and Reaction Environment

Deactivation of perovskite oxide catalysts is usually not caused by a single factor, but by the combined changes in structural stability, surface state, and reaction environment. During reaction, the surface may undergo reconstruction, lattice oxygen may be continuously consumed, oxygen vacancies may undergo irreversible changes, particles may sinter and grow, and A-site or B-site elements may segregate, dissolve, or react with the reaction atmosphere.

Deactivation source	Typical manifestation	Priority checks
High-temperature sintering	Particles grow, specific surface area decreases, and active sites decrease	Particle size, pore structure, specific surface area, and morphology before and after reaction
Uncontrolled surface reconstruction	Unexpected new phases form on the surface, and the active layer structure becomes unstable	Surface valence, crystal phase, and local structure before and after reaction
A-site element segregation	Elements such as strontium and barium become enriched on the surface and may form carbonates or sulfates	Surface elemental composition and surface species after exposure to carbon dioxide or sulfur-containing atmospheres
B-site metal dissolution	Active metals such as manganese, iron, cobalt, and nickel are lost, and electrocatalytic stability decreases	Metal content in the electrolyte, post-reaction surface composition, and crystal phase changes
Carbonate or strongly adsorbed species coverage	Surface active sites are covered, and low-temperature oxidation activity decreases	In situ infrared spectroscopy, temperature-programmed desorption, and carbon dioxide influence experiments
Irreversible oxygen vacancy changes	Oxygen migration and lattice oxygen replenishment capacity decrease, and activity becomes difficult to recover	Oxygen defect characterization, oxygen species changes, and reduction behavior before and after reaction
Water vapor or impurity poisoning	Reactant adsorption and oxygen activation are hindered, and long-term activity decays	Water resistance, sulfur resistance, chlorine resistance, and impurity tolerance
Structural phase transformation or secondary phase formation	The perovskite framework is damaged, and post-reaction performance decreases irreversibly	Post-reaction crystal phase, elemental distribution, and local structure
Electrode interface degradation	Cathode impedance increases in solid oxide fuel cells, and interfacial reactions become restricted	Electrode–electrolyte interface, thermal expansion matching, and long-term impedance changes

It should be noted that surface reconstruction is not necessarily always a cause of deactivation. In some oxygen evolution and oxygen reduction reactions, the surface of perovskite oxides may form new active layers that actually participate in the catalytic process. The key is whether such reconstruction is controllable and stable, and whether it is accompanied by severe metal dissolution, lattice collapse, or irreversible phase transformation.

To determine whether a perovskite oxide catalyst has deactivated, one should not look only at the activity decrease itself. It is also necessary to consider the crystal phase, surface valence state, elemental composition, oxygen vacancy state, specific surface area, and morphology changes before and after reaction. Only by correlating performance decay with structural changes can one determine whether deactivation arises from sintering, surface coverage, metal dissolution, oxygen defect imbalance, or mismatch between the reaction environment and the material itself.

8. Material Selection Logic: Matching Metal Sites, Oxygen Defects, and Stability According to the Reaction Task

The selection of perovskite oxide catalysts should begin with the reaction task. Different reactions have different requirements for metal valence states, metal–oxygen bond strength, oxygen vacancies, lattice oxygen migration, surface stability, and electrode interfaces.

Thermal catalytic oxidation reactions usually focus on oxygen adsorption, lattice oxygen replenishment, low-temperature activity, and resistance to water and poisoning. Electrocatalytic oxygen evolution and oxygen reduction reactions focus on B-site metal electronic structure, oxygen-containing intermediate adsorption, surface reconstruction, and metal dissolution. Solid oxide fuel cell cathodes require simultaneous consideration of oxygen surface exchange, oxygen-ion conduction, electronic conduction, thermal expansion matching, and interfacial stability.

Research objective	Material selection direction	Key focus
Volatile organic compound oxidation	Manganese-based, cobalt-based, iron-based perovskite oxides and composite systems	Low-temperature activity, lattice oxygen activity, carbon dioxide selectivity, water resistance
Carbon monoxide oxidation	Cobalt-based, manganese-based, or oxygen-vacancy-rich perovskite oxides	Oxygen adsorption, oxygen activation, surface carbonate coverage
Complete methane oxidation	Thermally stable manganese-based, cobalt-based, and iron-based perovskite oxides	C–H bond activation, high-temperature stability, sintering resistance
Oxygen evolution reaction	Cobalt-based, nickel-based, iron-based, or composite B-site systems	Overpotential, surface reconstruction, metal dissolution, long-term stability
Oxygen reduction reaction	Lanthanum manganites, lanthanum cobaltites, lanthanum nickelates, and doped systems	Oxygen adsorption strength, electron transfer, reaction pathway, and stability
Solid oxide fuel cell cathode	Strontium-doped lanthanum manganites, strontium-doped lanthanum cobalt ferrites, barium–strontium cobalt ferrites	Oxygen surface exchange, oxygen-ion conduction, thermal expansion matching, and interfacial stability
High-temperature oxidation reactions	Thermally stable perovskite oxides and composite structures	Sintering resistance, phase stability, and lattice oxygen replenishment capacity

Material selection can be judged in the following order:

1. Whether the reaction is mainly controlled by oxygen adsorption, oxygen activation, oxygen migration, or oxygen release;

2. Whether the B-site metal has suitable redox capability;

3. Whether the metal–oxygen bond strength is favorable for reaction intermediate adsorption and product desorption;

4. Whether oxygen vacancies can be reversibly generated, migrated, and replenished during the reaction;

5. Whether surface oxygen species are favorable for the target selectivity;

6. Whether the perovskite structure or the active surface layer remains stable after reaction;

7. Whether the catalyst has a basis for reproducible synthesis and stable operation.

9. Product Selection Guide for Perovskite Oxides in Energy and Environmental Catalysis (Tables 1–5)

Research or experimental objective	Recommended table to start with	Why start with this table	Tables to consult together	Selection guidance
Establish a basic formulation for lanthanum-based perovskite oxides	Table 1	Table 1 focuses on A-site metal sources such as lanthanum, strontium, barium, and calcium, helping first define the main perovskite oxide framework and the direction of A-site doping	Tables 2 and 4	First determine the A-site composition, then select B-site manganese, iron, cobalt, or nickel sources, and combine them with synthesis aids to establish a precursor preparation route
Compare the effects of A-site regulation by strontium, barium, calcium, and related elements on oxygen vacancies and structural stability	Table 1	A-site ionic radius, charge balance, and doping ratio influence lattice distortion, oxygen vacancy formation, and high-temperature stability	Tables 2 and 3	Comparative experiments can be designed around strontium doping, barium–strontium compositing, or calcium-based systems, followed by analysis of structure–performance relationships using oxygen-defect and oxygen-ion-conducting materials
Select B-site transition metals to regulate catalytic activity	Table 2	Table 2 focuses on manganese, iron, cobalt, and nickel sources. B-site metals directly affect valence cycling, metal–oxygen bond strength, oxygen adsorption, and electron transfer	Tables 1 and 3	Manganese-based, iron-based, cobalt-based, nickel-based, or composite B-site systems can be selected according to the target reaction, followed by activity and stability regulation through A-site doping and oxygen-defect-related materials
Study volatile organic compound oxidation, carbon monoxide oxidation, or methane oxidation	Table 2	These reactions focus on oxygen activation, lattice oxygen replenishment, and metal valence cycling. B-site manganese, cobalt, and iron systems are usually starting points for experimental screening	Tables 1 and 3	First determine the oxidation catalysis direction based on the B-site metal, then improve oxygen migration and resistance to deactivation through A-site regulation with strontium, barium, calcium, and composite materials such as ceria
Conduct electrocatalytic research on the oxygen evolution reaction or oxygen reduction reaction	Table 2	The oxygen evolution and oxygen reduction reactions are sensitive to B-site electronic structure, metal valence states, and oxygen-containing intermediate adsorption, so the B-site metal combination should be clarified first	Tables 1 and 5	First determine cobalt-based, nickel-based, iron-based, or composite B-site systems, then complete electrode evaluation by combining A-site doping design with electrolytes and conductive auxiliary materials
Construct solid oxide fuel cell cathodes or composite electrode materials	Table 3	Table 3 includes yttria-stabilized zirconia, ceria, and rare-earth oxides, as well as precursors for zirconia-based composite or interfacial materials, which are suitable for oxygen-ion conduction, interface stabilization, and composite electrode studies	Tables 1 and 2	Oxygen-ion-conducting or composite electrode materials can be identified first, then combined with A-site and B-site precursors to construct strontium-doped lanthanum manganite, lanthanum cobalt ferrite, or barium–strontium cobalt ferrite systems
Study oxygen vacancies, lattice oxygen replenishment, and oxygen storage/release behavior	Table 3	Cerium oxide, gadolinium oxide, samarium oxide, zirconium oxide, and yttria-stabilized zirconia can be used for oxygen-defect regulation, oxygen-ion conduction, and composite interface regulation	Tables 1 and 2	Suitable for analyzing how composites of perovskite oxides with ceria-based or zirconia-based materials influence oxygen migration and catalytic cycling
Prepare multimetal oxides by sol–gel, complexation combustion, or polymeric complexation methods	Table 4	Table 4 lists citric acid, ethylene glycol, ethylenediaminetetraacetic acid, glycine, and urea, which are suitable for uniform dispersion of multiple metal ions, precursor gel formation, combustion, or precipitation control	Tables 1 and 2	Select complexing agents, fuels, or precipitation-control aids according to the synthesis method, then match them with A-site and B-site metal salts to reduce compositional segregation and secondary phase formation
Compare the effects of solid-state synthesis and wet-chemical methods on phase formation and particle structure	Tables 1 and 2	Tables 1 and 2 include oxides, carbonates, nitrates, and acetates, which can be used to establish comparative experiments with different precursor routes	Table 4	Solid-state synthesis can start from oxides or carbonates, while wet-chemical methods can start from nitrates and complexing aids, with emphasis on comparing phase purity, particle size, specific surface area, and oxygen-defect state
Evaluate the electrocatalytic performance of perovskite oxide electrodes	Table 5	Table 5 includes alkaline test electrolytes and conductive auxiliary materials, which can be used to establish electrocatalytic evaluation systems for oxygen evolution, oxygen reduction, and related reactions	Tables 2 and 3	First build the test system using potassium hydroxide and conductive carbon materials, then analyze activity, stability, and electron-transport effects together with B-site metal composition and oxygen-defect-related materials
Troubleshoot low catalytic activity, poor stability, or large batch-to-batch variation	Tables 1, 2, and 4	A-site components, B-site components, and synthesis aids jointly influence phase purity, elemental distribution, oxygen vacancies, and particle structure, making them the main entry points for troubleshooting experimental differences	Tables 3 and 5	If the issue is concentrated in oxygen migration or electrode performance, Tables 3 and 5 can be consulted to examine oxygen-ion conduction, composite interfaces, and the electrode conductive network

Table 1 | A-Site Metal Sources: Lanthanum, Strontium, Barium, and Calcium Precursors

Category	CAS No.	Aladdin Catalog No.	Name	Specification or purity	Product features and applications
A-site lanthanum source	10277-43-7	L106051	Lanthanum nitrate hexahydrate	PrimorTrace™, ≥99.999% metals basis	Commonly used to prepare lanthanum-based perovskite oxides through sol–gel, complexation combustion, and coprecipitation routes; can serve as an A-site precursor for lanthanum manganite, lanthanum ferrite, lanthanum cobaltite, and lanthanum nickelate systems
A-site lanthanum source	1312-81-8	L431805	Lanthanum(III) oxide	Basic-grade reagent, for preparation	Can be used in solid-state or high-temperature sintering routes to prepare lanthanum-based perovskite oxides; suitable for studying A-site lanthanum content, phase formation, and high-temperature structural stability
A-site strontium source	10042-76-9	S431181	Strontium nitrate	Anhydrous grade, PrimorTrace™, ultrapure grade, ≥99.99% metals basis	Can serve as a soluble A-site precursor for strontium-doped perovskite oxides, used to regulate charge balance, oxygen vacancy formation, and oxygen surface exchange capability
A-site strontium source	1633-05-2	S102043	Strontium Carbonate	Electronic grade, ≥99.5%, 0–1 μm	Can be used in solid-state synthesis of strontium-doped lanthanum manganite, lanthanum cobaltite, and lanthanum cobalt ferrite systems; suitable for studying the influence of strontium doping on oxygen vacancies, conductivity, and cathode reactions
A-site barium source	10022-31-8	B431112	Barium nitrate	Suitable for analysis, ACS, premium grade	Can serve as a soluble A-site precursor for barium-based or barium–strontium composite perovskite oxides, used to study the effects of barium incorporation on lattice size, oxygen non-stoichiometry, and oxygen migration behavior
A-site barium source	513-77-9	B1519978	Barium carbonate	Electronic grade, ≥99.8% metals basis	Can be used in solid-state synthesis of barium-based or barium–strontium cobalt ferrite materials; suitable for studying phase formation in high-temperature oxidation reactions and solid oxide fuel cell cathode materials
A-site calcium source	13477-34-4	B431112	Calcium nitrate tetrahydrate	BioReagent, ≥99%	Can be used in the wet-chemical synthesis of calcium-based perovskite oxides such as calcium manganite and calcium ferrite; suitable for studying the effects of calcium-site incorporation on lattice stability and oxygen migration
A-site calcium source	471-34-1	C432735	Calcium carbonate	≥99.995% metals basis	Can be used in solid-state synthesis of calcium-based perovskite oxides or composite oxides; suitable for studying high-temperature sintering, phase stability, and alkaline-earth-metal regulation in oxidation catalysis

Table 2 | B-Site Transition Metal Sources: Manganese, Iron, Cobalt, and Nickel Precursors

Category	CAS No.	Aladdin Catalog No.	Name	Specification or purity	Product features and applications
B-site manganese source	20694-39-7	M191978	Manganese(II) nitrate tetrahydrate	≥98%	Can serve as a wet-chemical synthesis precursor for manganese-based perovskite oxides, used to prepare oxidation catalytic materials such as lanthanum manganite, strontium-doped lanthanum manganite, and calcium manganite
B-site manganese source	6156-78-1	M110795	Manganese acetate	PrimorTrace™, ≥99.99% metals basis	Can be used in complexation sol–gel and low-temperature precursor routes to prepare manganese-based composite oxides; suitable for studying manganese valence changes, oxygen vacancies, and lattice oxygen activity
B-site manganese source	1313-13-9	M101140	Manganese dioxide	≥99.95% metals basis	Can serve as a manganese source for solid-state synthesis or as an oxidizing manganese component, used in the preparation of manganese-based perovskite oxides and composite oxides; suitable for volatile organic compound oxidation and carbon monoxide oxidation studies
B-site iron source	7782-61-8	I434042	Iron(III) nitrate nonahydrate	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade	Can serve as a soluble B-site precursor for iron-based perovskite oxides, used in the wet-chemical synthesis of lanthanum ferrite, strontium-doped lanthanum ferrite, and cobalt–iron composite systems
B-site iron source	1309-37-1	F108317	Ferric sesquioxide	AR, ≥99%	Can serve as an iron source for solid-state synthesis, used to prepare iron-based perovskite oxides and cobalt–iron composite oxides; suitable for studying structural stability, redox behavior, and durability in high-temperature reactions
B-site cobalt source	10026-22-9	C431137	Cobalt(II) nitrate hexahydrate	Suitable for analysis, premium grade	Can serve as a wet-chemical synthesis precursor for cobalt-based perovskite oxides, used for compositional regulation of lanthanum cobaltite, strontium-doped lanthanum cobaltite, and cobalt–iron composite systems
B-site cobalt source	1307-96-6	C104343	Cobalt(II)oxide	Reagent grade	Can serve as a cobalt source for solid-state synthesis, used to prepare cobalt-based perovskite oxides and composite oxides; suitable for studying cobalt valence states, metal–oxygen bond strength, and low-temperature oxidation activity
B-site cobalt source	1308-06-1	C431733	Cobalt(II,III) oxide	Powder, <10 μm	Can serve as a B-site source for cobalt-based composite oxides and cobalt–iron perovskite materials; suitable for studying the effects of multivalent cobalt on oxygen adsorption, oxygen exchange, and electrocatalytic reactions
B-site nickel source	13478-00-7	N108888	Nickel nitrate hexahydrate	PrimorTrace™, ≥99.999% metals basis	Can serve as a wet-chemical synthesis precursor for nickel-based perovskite oxides, used to study the electronic structure and redox activity of lanthanum nickelate and composite B-site systems
B-site nickel source	1313-99-1	N431816	Nickel(II) oxide	Nanowires, diameter × length ~20 nm × 10 μm	Can serve as a nickel source or composite oxide component, used in nickel-based perovskite oxides, redox catalysis, and electrode material studies; the nanowire morphology is useful for constructing contact interfaces

Table 3 | Oxygen-Defect Regulation, Oxygen-Ion Conductor Precursors, and Composite Electrode-Related Materials

Category	CAS No.	Aladdin Catalog No.	Name	Specification or purity	Product features and applications
Oxygen-defect and oxygen storage/release regulation material	1306-38-3	C431729	Cerium(IV) oxide	Nanopowder, particle size <25 nm	Has oxygen storage/release and cerium valence cycling characteristics; can be used for composite modification of perovskite oxides and to support studies of oxygen vacancies, lattice oxygen replenishment, and low-temperature oxidation activity
Oxygen-defect and composite electrolyte component	12064-62-9	G105875	Gadolinium oxide	PrimorTrace™, ≥99.99% metals basis	Can be used to prepare oxygen-ion-conducting materials such as gadolinium-doped ceria, and can also serve as an ion-conduction-regulating component in composite electrodes
Oxygen-defect and composite electrolyte component	12060-58-1	S118883	Samarium oxide	PrimorTrace™, ≥99.999% metals basis	Can be used to prepare composite ion conductors such as samarium-doped ceria; suitable for studying oxygen-ion conduction and interfacial reactions in solid oxide cell electrodes
Zirconia-based composite and interface-stabilizing material	1314-23-4	Z431833	Zirconium(IV) oxide	Nanoparticle dispersion, <100 nm particle size (BET), 5 wt.% in H₂O	Can be used in zirconia-based composite materials, electrode coatings, and interface stabilization studies; the nano-dispersion form facilitates the construction of uniform composite structures
Oxygen-ion conduction stabilizer	1314-36-9	Y431838	Yttrium oxide 99+	Suitable for analysis, premium reagent, ≥99%	Can serve as a zirconia stabilizer and a component of solid oxide cell-related materials, used to regulate oxygen-ion conduction, thermal stability, and electrode–electrolyte compatibility
Oxygen-ion conductor and electrode composite material	114168-16-0	Z477814	Zirconium(IV) oxide-yttria stabilized	Nanopowder	Can serve as a solid oxide cell electrolyte or composite cathode component, used to study oxygen-ion conduction, electrode interfaces, and thermal expansion matching

Table 4 | Complexation, Sol–Gel, and Combustion Synthesis Aids

Category	CAS No.	Aladdin Catalog No.	Name	Specification or purity	Product features and applications
Complexation sol–gel synthesis aid	77-92-9	C434173	Citric acid	Moligand™, anhydrous grade, ACS, ≥99.5%	Can serve as a metal-ion complexing agent for preparing compositionally uniform perovskite oxide precursors; suitable for homogenizing composition in multimetal systems
Complexation sol–gel synthesis aid	5949-29-1	C112632	Citric acid monohydrate	AR, ≥99.5%	Can be used in citric acid complexation methods to prepare precursors for lanthanum manganite, lanthanum ferrite, lanthanum cobaltite, and cobalt–iron composite perovskite oxides
Polymeric complexation synthesis aid	107-21-1	E1522420	Ethylene glycol	USP, electronic grade, ≥99.5%	Can be used together with citric acid in polymeric complexation routes to help form uniform gel precursors; suitable for low-temperature synthesis studies of multimetal perovskite oxides
Complexation regulation aid	60-00-4	E112487	Ethylenediaminetetraacetic acid	AR, ≥99.5%	Can complex various metal ions and regulate precursor solution stability and metal-ion distribution; suitable for the synthesis of complex doped perovskite oxides
Combustion synthesis aid	56-40-6	A110749	Glycine	Moligand™, ≥99%	Can serve as both a complexing agent and a fuel in combustion synthesis, used for rapid preparation of multimetal oxide precursors; suitable for screening perovskite phase formation conditions
Combustion synthesis and precipitation regulation aid	57-13-6	U111897	Urea	AR, ≥99%	Can be used in combustion synthesis, homogeneous precipitation, and precursor acid–base regulation; suitable for preparing composite oxide powders with good dispersibility

Table 5 | Electrocatalytic Testing Electrolyte, Conductive Auxiliary Material, and Control Variables

Category	CAS No.	Aladdin Catalog No.	Name	Specification or purity	Product features and applications
Electrocatalytic testing electrolyte	1310-58-3	P112287	Potassium hydroxide	Electronic grade, ≥99.999% metals basis, excludes sodium content	Can be used in alkaline oxygen evolution reaction and oxygen reduction reaction testing systems; suitable for evaluating the electrocatalytic activity, stability, and reaction pathways of perovskite oxides
Electrode conductive auxiliary material	1333-86-4	C431910	Carbon, mesoporous	≥99.95% metals basis, nanopowder, graphitized, <500 nm particle size (DLS)	Can be used to construct conductive networks in electrocatalytic electrode preparation and improve electronic contact between perovskite oxide particles and the current collector; it should also be treated as a testing control variable, especially in oxygen evolution reaction evaluation, where carbon oxidation and its influence on apparent activity need to be considered

Note: The products listed above are representative Aladdin products. Additional product specifications can be searched on the Aladdin website using the product name, CAS number, or catalog number.

References

[1] Suntivich J., May K. J., Gasteiger H. A., Goodenough J. B., Shao-Horn Y. A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles. Science, 2011, 334: 1383–1385.

[2] Suntivich J., Gasteiger H. A., Yabuuchi N., Nakanishi H., Goodenough J. B., Shao-Horn Y. Design Principles for Oxygen-Reduction Activity on Perovskite Oxide Catalysts for Fuel Cells and Metal–Air Batteries. Nature Chemistry, 2011, 3: 546–550.

[3] Liu L. B., Yi C., et al. Perovskite Oxides Toward Oxygen Evolution Reaction: Intellectual Design Strategies, Properties and Perspectives. Electrochemical Energy Reviews, 2024, 7: 14.

[4] Li Z., Mao X., Feng D., et al. Prediction of Perovskite Oxygen Vacancies for Oxygen Electrocatalysis at Different Temperatures. Nature Communications, 2024, 15: 9318.

[5] Yang L., et al. Perovskite Oxides in Catalytic Combustion of Volatile Organic Compounds: Recent Advances and Future Prospects. Energy & Environmental Materials, 2022, 5(3): 751–776.

[6] Jiang Y., Feng Y., Rastegarpanah A., et al. Perovskite-type Oxide Catalysts for VOC Removal: Recent Advances and Future Prospects. Environmental Science: Nano, 2025, 12: 4491–4514. DOI: 10.1039/D5EN00680E.

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