Perovskite Oxides Research Articles

Targeted Chemical Looping Materials Discovery by an Inverse Design

Chemical looping with oxygen uncoupling (CLOU) materials is actively sought for combustion of carbonaceous materials to achieve complete conversion and capture of carbon dioxide. These materials may play a vital role in reducing atmospheric carbon via negative carbon output. However, there is no one‐size‐fits‐all approach as different operating conditions and feedstocks may require different CLOU materials. As a result, the exploration and discovery of high‐performance CLOU materials can be a slow process. To address this challenge, a high‐throughput inverse machine learning workflow that identifies optimum materials from perovskite oxides for a given set of targets is developed—temperature and Gibbs free energy of oxygen formation. The model is trained on high‐throughput density functional theory calculations of CLOU materials and inverts the materials design process using a genetic algorithm to produce realistic substituted SrFeO3‐δ compositions as output. Using the inverse model, it is able to identify several interesting new families of CLOU materials: Sr1‐xAxFe1‐yByO3‐δ (e.g., A = Ca or K; B = Mg, Bi, Mn, Ni, Co, Cu, or Zn). These materials have shown promising properties, and some of them even outperform the benchmark material in terms of oxygen release kinetics under relevant CLOU operating conditions.

Valence Variability Induced in SrMoO₃ Perovskite by Mn Doping: Evaluation of a New Family of Anodes for Solid-Oxide Fuel Cells

We report on a series of SrMo1−xMnxO3−δ perovskite oxides designed as potential anode materials for solid oxide fuel cells (SOFCs). These materials were synthesized using a citrate method, yielding scheelite-type precursors with nominal SrMo1−xMnxO4 compositions, which were further reduced to obtain the active perovskite oxides. Their structural evolution was examined through X-ray diffraction (XRD) and neutron powder diffraction (NPD). These techniques provided insights into the crystallographic changes upon Mn doping, revealing key factors influencing ionic conductivity. Whereas the oxidized scheelite precursors are tetragonal, space group I41/a, the reduced perovskite specimens are cubic, space group Pm-3m, and show the conspicuous absence of oxygen vacancies, even at the highest temperature of 800 °C. The transport properties were analyzed through electrical conductivity measurements, exhibiting a metallic-like behavior. Thermogravimetric analysis (TGA) and dilatometry give insights into the thermal stability and expansion behavior, essential for SOFC operation. Test single SOFCs were built in an electrolyte-supported configuration, on LSGM pellets of 300 μm thickness, assessing the performance of the title materials as anodes. This work emphasizes the critical relationship between the crystal structure and its electrochemical behavior, providing a deeper understanding of how doping strategies can optimize fuel cell performance.

Structural, dielectric and magnetic properties of Sb/Cr-doped CaCu3Ti4O12 quadruple perovskite oxides

Driven by the miniaturization of microelectronic devices and their multifunctionalities, the development of new quadruple-perovskite oxides with high dielectric constants and high Curie temperature are highly required. Herein, we report on the structural, dielectric and magnetic properties of Sb/Cr-doped CaCu3Ti4O12(CCTO) quadruple perovskite oxides, CaCu3Ti3.9Sb0.1O12(CCTSO) and CaCu3Ti3CrO12(CCTCO). Structural Rietveld refinements demonstrated that the CCTO, CCTSO, and CCTCO ceramics adopted a cubic crystal structure (Im3¯ space group). They exhibited spherical shapes with nearly uniform particle sizes. XPS spectra clarified Cu3+ions in the CCTSO ceramics, while Cu2+and Cu+ions, and Cr3+ions in the CCTCO ceramics. All the ceramic samples displayed nearly frequency independent dielectric behaviors at low temperatures but a relaxor dielectric behavior at high temperatures. Such relaxor dielectric behavior in the CCTO and CCTSO ceramics was ascribed to the movement of doubly ionized oxygen vacancies but in the CCTCO ceramics to the movement of singly ionized oxygen vacancies. Impedance and modulus spectra reveal the significance contributions of grains and grain boundaries with non-Debye behavior. At room temperature (RT) the dielectric constant (ϵr) and dielectric loss (tanδ) of CCTO ceramics at 1 kHz were 15 922 and 0.126, respectively. An order reduction of tanδwas achieved in the CCTSO ceramics. In the CCTCO ceramics, theϵrand tanδat RT and 1 kHz were 975 and 0.453, respectively. The CCTCO powders exhibited antiferroelectric behavior at 2 K with a saturation magnetization (MS) of 1.42μB/f.u., while theMSfor the CCTSO powders was only 0.027μB/f.u. All ceramic samples exhibited semiconductor characteristics owing to their continuous decreases of resistivity from 2 K to 800 K. Our present work demonstrates an effective route to tuning the dielectric and magnetic properties of CCTO oxides via B-site non-magnetic/magnetic ion-doping.

Optimizing La₂MnXO₆ Double Perovskite for Superior Electrochemical Efficiency in Supercapacitors

ABSTRACTDouble perovskite oxides (POs) are effective electrode materials for supercapacitors (SCs). Nevertheless, adapting their unique architectures to boost the electrochemical performance remains tricky. Herein, we present exceptional La2MnXO6 (X = Co, Fe) double perovskites as SC electrode materials. The sol–gel method has prepared La2MnCoO6 (LMCO) and La2MnFeO6 (LMFO) nanorods. XRD revealed that LMCO and LMFO have monoclinic crystal structures with lattice constants of a = 5.517 Å, b = 5.528 Å, c = 7.805 Å, β = 89.926°, and a = 5.549 Å, b = 5.557 Å, c = 7.783 Å, β = 89.931°, respectively. Scanning electron microscopy indicated the existence of uniformly distributed nanorods. The bandgap using Tauc's plot was determined as 1.38 and 1.24 eV for La2MnCoO6 and La2MnFeO6, respectively. Fourier‐transform infrared spectroscopy further characterized the prepared LMCO and LMFO nanorods. X‐ray photoelectron spectroscopy investigation confirmed the existence of La3+, Mn3+, Fe3+, O2−, and La3+, Mn3+, Co3+, O2− ions on the surface of La2MnFeO6 and La2MnFeO6, respectively. The specific capacitance achieved was 333.86 and 880.5 F/g @ 2.5 A/g for La2MnCoO6 and La2MnFeO6, respectively, using 1 M KOH electrolyte. La2MnFeO6 demonstrated excellent energy and power density of 30.5 Wh/kg and 625 W/kg. The asymmetric CV curve shape proved that we have battery‐type SC behavior due to the indication of redox reactions. Furthermore, Dunn's technique evaluated the percentage contribution of capacitive and diffusion behavior. Our strategy using LMCO and LMFO nanorods material improved specific capacitance activity and significantly offered a facile guideline for targeting double perovskite electrodes for SC applications.

Surface Interactive Assembly of Ruthenium Based Janus Bimetallic Nanoparticles With Active Dual‐Function Sites for Efficient Use in CO2 Utilization

AbstractNoble bimetallic nanoparticles (NPs) are nowadays essential in various applications, like CO2 utilization by dry reforming of methane (DRM), due to their unique and potential properties. A synthesis method for Ru based Janus‐structured NPs is presented via surface interactive assembly of deposited Ru and emerged Ni species from carefully tailored perovskite oxide support. As noble‐metals typically result in the alloy, an exclusive formation mechanism is introduced by utilizing Ru energetically favorable for the Janus phase by lower ground state energy from interactions between the strongly embedded cluster and perovskite surface. Consequently, noticeable Janus NPs, controllable in size and composition with active configuration by dual‐function sites and interface strains, are well‐produced with high distribution. DRM performance highly exceeds conventional Ru over 5 times in TOFs for both CO2 and CH4 with improved stability maintaining H2/CO for 100 h without sintering at harsh reaction conditions, which comprehensively exhibits distinct advantages over recent works. Fundamental studies indicate combined electronic d‐band structures proving distinctive CO2 dissociation and CH4 activation, involving efficient dehydrogenation and CO production via surface oxygenation, considerably suppresses coking. This approach presents a potential avenue to surmount constraints on designing bimetallic NPs in any structured oxide systems for effective materials in various low carbon relevant industries.

Charge-to-spin conversion at argon ion milled SrTiO3/NiFe hetero-interfaces

Two-dimensional electron gases (2DEGs) at perovskite oxide interfaces, such as strontium titanate (STO), have garnered significant attention due to their induced ferromagnetic (FM), spin–orbit coupling, and superconducting properties. The 2DEG, formed at the interface between STO and either insulating oxides or reactive metals, exhibits efficient charge-to-spin interconversion in STO/NM(non-magnetic)/FM structures. The insulating oxide layer at the STO interface attenuates the spin currents injected into the ferromagnet. In contrast, the metallic layers facilitate efficient spin current injection but suffer from spin current diffusion. Here, we present an approach to overcome these challenges by directly creating a 2DEG at the STO surface through Ar+ ion bombardment. This method enables efficient spin-to-charge conversion without an intermediate NM layer. Our experimental and simulation results demonstrate the generation of unconventional spin currents at the STO(Ar+)/NiFe (Permalloy) interface. Our findings may enable applications of complex oxide and ferromagnet interfaces for efficient charge-to-spin conversion, paving the way for low-power, room-temperature oxide-based spintronic devices.

Application of perovskite type oxide La x Ce1-x coo3 in lignin depolymerization and mono-phenol preparation.

This study successfully prepared La x Ce1-x CoO3 (x = 0.2, 0.4, 0.6, 0.8, 1) series perovskite oxide catalysts by co precipitation, and found that La0.6Ce0.4CoO3 can significantly improve the yield of bio-oil under specific conditions (lignin to catalyst mass ratio of 1 : 2, reaction temperature of 240 °C, time of 10 hours, using methanol and ethanol as solvents). Furthermore, NH3-TPD, GC-MS, and FTIR analyses revealed the thermal decomposition behavior of key bonding structures such as β-O-4 and C-O-C during the catalytic process, while generating various mono-phenolic products such as guaiacol and 2,6-dimethylphenol. In addition, studies have shown that the physicochemical properties of perovskite type oxide catalysts have a significant impact on the chemical properties of lignin oil. By increasing the acidity of the catalyst, not only can the yield of lignin oil and phenols be improved, but also the yield of carbon can be reduced. More importantly, the catalyst performed well in the test of lignin catalyzed hydrogenation to produce monophenols, significantly improving the conversion rate of lignin and the yield of various monophenols compared to noncatalytic processes.

Improved Ammonia Synthesis and Energy Output from Zinc-Nitrate Batteries by Spin-State Regulation in Perovskite Oxides.

Electrocatalytic nitrate reduction to ammonia (eNRA) is a promising route toward environmental sustainability and clean energy. However, its efficiency is often limited by the slow conversion of intermediates due to spin-forbidden processes. Here, we introduce a novel A-site high-entropy strategy to develop a new perovskite oxide (La0.2Pr0.2Nd0.2Ba0.2Sr0.2)CoO3-δ (LPNBSC) for eNRA. The LPNBSC possesses a higher concentration of high-spin (HS) cobalt-active centers, resulting from an increased concentration of [CoO5] structural motifs compared to conventional LaCoO3. Consequently, this material exhibits a significantly improved electrocatalytic performance toward ammonia (NH3) production, resulting in a 3-fold increase in yield rate (129 μmol h-1 mgcat.-1) and a 2-fold increase in Faradaic efficiency (FE, 76%) compared to LaCoO3 at the optimal potential. Furthermore, the LPNBSC-based Zn-nitrate battery reaches a maximum FE of 82% and an NH3 yield rate of 57 μmol h-1 cm-2. Density functional theory calculations reveal that A-site high-entropy management in perovskites facilitates nitrate activation and potentially optimizes the thermodynamic rate-determining step of the eNRA process, namely, *HNO3 + H+ + e- → *NO2 + H2O. This work presents an efficient concept for modulating the spin state of the B-site metal in perovskites and offers valuable insights for the design of high-performance eNRA catalysts.

Advances in Oxygen Evolution Reaction Electrocatalysts via Direct Oxygen-Oxygen Radical Coupling Pathway.

Oxygen evolution reaction (OER) is a cornerstone of various electrochemical energy conversion and storage systems, including water splitting, CO2/N2 reduction, reversible fuel cells, and rechargeable metal-air batteries. OER typically proceeds through three primary mechanisms: adsorbate evolution mechanism (AEM), lattice oxygen oxidation mechanism (LOM), and oxide path mechanism (OPM). Unlike AEM and LOM, the OPM proceeds via direct oxygen-oxygen radical coupling that can bypass linear scaling relationships of reaction intermediates in AEM and avoid catalyst structural collapse in LOM, thereby enabling enhanced catalytic activity and stability. Despite its unique advantage, electrocatalysts that can drive OER via OPM remain nascent and are increasingly recognized as critical. This review discusses recent advances in OPM-based OER electrocatalysts. It starts by analyzing three reaction mechanisms that guide the design of electrocatalysts. Then, several types of novel materials, including atomic ensembles, metal oxides, perovskite oxides, and molecular complexes, are highlighted. Afterward, operando characterization techniques used to monitor the dynamic evolution of active sites and reaction intermediates are examined. The review concludes by discussing several research directions to advance OPM-based OER electrocatalysts toward practical applications.

Suppressing surface segregation by introducing lanthanides to enhance high-temperature oxygen evolution reaction activity and durability

Abstract Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is a conventional anode material for solid oxide electrolysis cells (SOECs) to catalyze oxygen evolution reactions (OERs). However, the inferior chemical stability of BSCF results in severe surface segregation and performance degradation under high temperatures. A critical challenge lies in alleviating surface segregation and preserving the high OER performance of BSCF anodes. Herein, lanthanides are introduced to substitute the Ba in BSCF, labeled as Ln0.5Sr0.5Co0.8Fe0.2O3−δ (LnSCF, Ln = La, Pr, Nd, Sm), to regulate its stability and performance. The introduction of La and Pr effectively enhances stability, suppresses surface segregation and maintains high OER activity. Continuous lattice oxygen loss and Co ion oxidation of LnSCF are demonstrated upon annealing in oxidizing atmosphere; thus, we propose that surface segregation is a self-regulation mechanism of perovskite lattice to tolerant oxidizing atmosphere. Perovskite oxides maintain structurally stable via decreasing A-site valence state and forming surface segregation. SOECs with La0.5Sr0.5Co0.8Fe0.2O3−δ anodes deliver an optimal current density of 1.69 A cm−2 at 1.6 V and stability for CO2 electrolysis at 800 °C, shedding light on designing advanced catalysts for high-temperature OER.

Catalytic decomposition of methane: Ni-promoted perovskite oxide catalysts for turquoise hydrogen and carbon nanomaterials Co-production

This study investigates the effectiveness of catalytic decomposition of methane for producing turquoise hydrogen and solid carbon nanomaterials. The focus is on developing cost-effective and high-performance Nickel (Ni)-promoted perovskite oxide catalysts. A series of transition metal, Ni-promoted (La0.75Ca0.25)(Cr0.5Mn0.5)O3-δ (LCCM) catalysts have been successfully prepared using water-based gel-casting technology. These catalysts are designed to decompose methane into turquoise hydrogen and carbon nanomaterials, achieving negligible CO2 emissions. X-ray diffraction results indicate that the solubility of Ni at the B-site of LCCM perovskite is limited, x ≤ 0.2. Field Emission Scanning Electron Microscopy analysis of xNi-LCCM, calcined at 1050 °C for ten h in the air, confirms severe catalyst sintering with excess nickel oxide distributed around the LCCM particles. At a 750 °C operating temperature, a Ni to LCCM molar ratio of 1.5 yields a maximum carbon output of 17.04 gC/gNi. Increasing the molar ratios to 2.0 and 2.5 results in carbon yields of 17.17 gC/gNi and 17.63 gC/gNi, respectively, showing minor changes. The morphology of the carbon nanomaterials is unaffected by the molar ratio of NiO promoter to LCCM and remains nearly the same within the scope of this study.

Creation of Piezoelectricity in Quadruple Perovskite Oxides by Harnessing Cation Defects and Their Application in Piezo-Photocatalysis.

Quadruple perovskite oxides have received extensive attention in electronics and catalysis, owing to their cation-ordering structure and intriguing physical properties. However, their repertoires still remain limited. In particular, piezoelectricity from quadruple perovskites has been rarely reported due to the frustrated symmetry-breaking transition in A-site-ordered perovskite structures, disabling their piezoelectric applications. Herein, we report a feasible strategy to achieve piezoelectricity in CaCu3Ti4O12 (CCTO) quadruple perovskite via cation defect engineering, specifically through a thermal-driven selective cation exsolution strategy to introduce Cu vacancies. The introduction of Cu point defects in CCTO locally destabilizes the constrained tilted TiO6 octahedra framework, relaxing the octahedral tilting and inducing structural heterogeneity which, in turn, disrupts the high symmetry of the pristine cubic phase. As a result, the defective CCTO with localized asymmetry exhibits intense polarization and a robust piezoelectricity of 7 pC N-1. The created piezoelectricity is further validated by its application as a piezo-photocatalyst, enabling efficient charge separation and transfer with a 2.5-times increment in the lifetime of photoexcitations. This enhancement leads to a 3.86- and 31-fold increase in the production of hydrogen peroxide and reactive oxygen species compared with individual piezocatalysis and photocatalysis, respectively. This study establishes a pathway to engineer piezoelectricity in quadruple perovskites, potentially unlocking a wide range of applications in modern microelectronics beyond the demonstrated piezo-photocatalysis.

Self-powered ultraviolet position-sensitive detectors based on PrNiO3/Nb-doped SrTiO3 p–n junctions

Position-sensitive detectors based on the lateral photovoltaic effect have been widely used in optical engineering for the measurement of position, distance, and angles. However, self-powered ultraviolet position-sensitive detectors with high sensitivity and fast response are still lacking due to the difficulty associated with the fabrication of p-type wide bandgap semiconductors, which hinders their further design and enhancement. Here, the influence of band structures and interfacial transport properties on the performance of self-powered ultraviolet position-sensitive detectors based on PrNiO3/Nb:SrTiO3p–n junctions is systematically investigated. Large position sensitivity and fast relaxation time of the lateral photovoltaic effect were observed up to 400 K in the perovskite-based ultraviolet position-sensitive detectors. Hall effect measurements revealed that the transport of photoexcited carriers occurs mainly through the interface of the PrNiO3/Nb:SrTiO3 junctions, resulting in a fast response and a stable photovoltaic effect. This study presents insights and avenues for designing self-powered perovskite oxide ultraviolet position-sensitive detectors with enhanced photoelectric performance.

Correlation Between Conductivity and Oxygen Evolution Reaction Activity in Perovskite Oxides CaMnO3-δ, Ca0.5Sr0.5MnO3-δ and SrMnO3-δ

The perovskite oxides CaMnO3-δ, Ca0.5Sr0.5MnO3-δ, and SrMnO3-δ were synthesized in air using a solid-state method, and their structural, electrical, and electrocatalytic properties were studied in relation to their oxygen evolution reaction (OER) performance. Iodometric titration showed δ values of 0.05, 0.05, and 0.0, respectively, indicating that Mn is predominantly in the 4+ oxidation state across all materials, consistent with prior reports. Detailed characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), iodometric titration, and variable-temperature conductivity measurements. Four-point probe DC measurements revealed that CaMnO3-δ (δ = 0.05) has a semiconductive behavior over a temperature range from 25 °C to 300 °C, with its highest conductivity attributed to polaron activity. Cyclic voltammetry (CV) in 0.1 M KOH was employed to assess OER catalytic performance, which correlated with room-temperature conductivity. CaMnO3-δ exhibited superior catalytic activity, followed by Ca0.5Sr0.5MnO3-δ and SrMnO3-δ, demonstrating that increased conductivity enhances OER performance. The conductivity trend, CaMnO3-δ > Ca0.5Sr0.5MnO3-δ > SrMnO3-δ, aligns with OER activity, underscoring a direct link between electronic transport properties and catalytic efficiency within this series.

Large Manipulation of Ferrimagnetic Curie Temperature by A-Site Chemical Substitution in ACu3Fe2Re2O12 (A = Na, Ca, and La) Half Metals.

CaCu3Fe2Re2O12 and LaCu3Fe2Re2O12 quadruple perovskite oxides are well known for their high ferrimagnetic Curie temperatures and half-metallic electronic structures. By A-site chemical substitution with lower valence state Na+, an isostructural compound NaCu3Fe2Re2O12 with both A- and B-site ordered quadruple perovskite structures in Pn-3 symmetry was prepared using high-pressure and high-temperature techniques. The X-ray absorption study demonstrates the valence states to be Cu2+, Fe3+, and Re5.5+. A ferrimagnetic phase transition is found to take place at the Curie temperature TC ≈ 240 K, which is much less than that observed in A = Ca (560 K) and La (710 K) analogues. NaCu3Fe2Re2O12 possesses a larger saturated magnetic moment up to 9.4 μB/f.u. as well as a remarkably reduced coercive field less than 10 Oe at 2 K. Theoretical calculations suggest that NaCu3Fe2Re2O12 displays a half-metallic electronic band structure with complete spin polarization of conduction electrons in the minority-spin bands. The magnetic properties and electronic structures of the ACu3Fe2Re2O12 family are compared and discussed.

Large enhancement of ferroelectric properties of perovskite oxides via nitrogen incorporation.

Perovskite oxides have a wide variety of physical properties that make them promising candidates for versatile technological applications including nonvolatile memory and logic devices. Chemical tuning of those properties has been achieved, to the greatest extent, by cation-site substitution, while anion substitution is much less explored due to the difficulty in synthesizing high-quality, mixed-anion compounds. Here, nitrogen-incorporated BaTiO3 thin films have been synthesized by reactive pulsed-laser deposition in a nitrogen growth atmosphere. The enhanced hybridization between titanium and nitrogen induces a large ferroelectric polarization of 70 μC/cm2 and high Curie temperature of ~1213 K, which are ~2.8 times larger and ~810 K higher than in bulk BaTiO3, respectively. These results suggest great potential for anion-substituted perovskite oxides in producing emergent functionalities and device applications.

Enhancing performance of proton ceramic fuel cells through fluorine-doped perovskite oxides

Enhancing performance of proton ceramic fuel cells through fluorine-doped perovskite oxides

Precise Regulation of In Situ Exsolution Components of Nanoparticles for Constructing Active Interfaces toward Carbon Dioxide Reduction.

Metal nanocatalysts supported on oxide scaffolds have been widely used in energy storage and conversion reactions. So far, the main research is still focused on the growth, density, size, and activity enhancement of exsolved nanoparticles (NPs). However, the lack of precise regulation of the type and composition of NPs elements under reduction conditions has restricted the architectural development of in situ exsolution systems. Herein, we propose a strategy to attain a regulated distribution of exsolved transition metals (Cu, Ni, and Fe) on Sr2Fe1.2Ni0.2Cu0.2Mo0.4O6-δ medium-entropy perovskite oxides by varying the oxygen partial pressure (pO2) gradient in the mixture. At 800 °C, the unitary Cu, binary Cu-Ni, and ternary Cu-Ni-Fe NPs are exsolved as pO2 decreases from high to low. Combining experimental and theoretical simulations, we further corroborate that solid oxide electrolysis cells with ternary alloy clusters at the CNF@SFO interface exhibit superior CO2 electrolytic performance. Our results provide tailored strategies for nanostructures and nanointerfaces for studying metal oxide exsolution systems, including fuel electrode materials.

Stabilization of oxygen vacancy ordering and electrochemical-proton-insertion-and-extraction-induced large resistance modulation in strontium iron cobalt oxides Sr(Fe,Co)Oy

Electrochemically inserting and extracting hydrogen into and from solids are promising ways to explore materials’ phases and properties. However, it is still challenging to identify the structural factors that promote hydrogen insertion and extraction and to develop materials whose functional properties can be largely modulated by inserting and extracting hydrogen through solid-state reactions at room temperature. In this study, guided by theoretical calculations on the energies of oxygen reduction and hydrogen insertion reactions with oxygen-deficient perovskite oxides, we demonstrated that the oxygen vacancy ordering in Sr(Fe1−xCox)Oy (SFCO) epitaxial films can be stabilized by increasing the Co content (x ≥ 0.3) and revealed that it plays a key role in promoting proton accommodation into the SFCO lattice. We also show that the electrical resistance of SFCO films can be reversibly modulated by electrochemical proton insertion and extraction, and the modulation exceeds three orders of magnitude for Sr(Fe0.5Co0.5)O2.5 epitaxial films. Our results provide guidelines for controlling material properties through the insertion and extraction of hydrogen and for designing and exploring hydrogen-insertion materials.

Sulfonated reduced graphene oxide encapsulated perovskite-type ErCoFe oxide nanoparticles for efficient electrochemical water oxidation.

Perovskite oxides play a vital role as electrocatalysts in water oxidation due to their flexible and unique electronic structures. In this work, Er-based perovskites ErCo1-xFexO3-δ (x = 0.0, 0.1, 0.3, 0.5, 0.7, and 1.0) denoted as EC, ECF-0.9, ECF-0.7, ECF-0.5, ECF-0.3, and EF, respectively, are synthesized by the sol-gel method. Then, ECF-0.9 is supported on sulfonated reduced graphene oxide (S-rGO) by a hydrothermal method, with weight ratios of 1 : 1 and 3 : 1 of ECF/0.9 to S-rGO (shown as ECF-0.9/S-rGO(50%) and ECF-0.9/S-rGO(75%), respectively). The structural properties and the morphology of the synthesized materials are studied using a series of different techniques. The prepared perovskites are then used as electrode materials for electrochemical water oxidation. ECF-0.9 reveals better activity than pure EF, EC, and other perovskite oxides in terms of overpotential, Tafel slope, electrochemically active surface area (ECSA), and charge transfer resistance (Rct) values. Interestingly, when the optimized perovskite oxide catalyst ECF-0.9 is decorated on S-rGO sheets, the water oxidation activity is significantly improved. ECF-0.9/S-rGO(75%) exhibits superior activity for water oxidation with an overpotential of 290 mV@10 mA cm-2 and a Tafel slope of 41 mV dec-1. Finally, overall water splitting with ECF-0.9/S-rGO(75%) as the anode electrode shows a low electrolysis voltage of 1.60 V, alongside excellent stability for 20 h.