CeO2 Support Research Articles

Constructing Efficient CuO-Based CO Oxidation Catalysts with Large Specific Surface Area Mesoporous CeO2 Nanosphere Support.

CeO2 is an outstanding support commonly used for the CuO-based CO oxidation catalysts due to its excellent redox property and oxygen storage-release property. However, the inherently small specific surface area of CeO2 support restricts the further enhancement of its catalytic performance. In this work, the novel mesoporous CeO2 nanosphere with a large specific surface area (~190.4 m2/g) was facilely synthesized by the improved hydrothermal method. The large specific surface area of mesoporous CeO2 nanosphere could be successfully maintained even at high temperatures up to 500 °C, exhibiting excellent thermal stability. Then, a series of CuO-based CO oxidation catalysts were prepared with the mesoporous CeO2 nanosphere as the support. The large surface area of the mesoporous CeO2 nanosphere support could greatly promote the dispersion of CuO active sites. The effects of the CuO loading amount, the calcination temperature, mesostructure, and redox property on the performances of CO oxidation were systematically investigated. It was found that high Cu+ concentration and lattice oxygen content in mesoporous CuO/CeO2 nanosphere catalysts greatly contributed to enhancing the performances of CO oxidation. Therefore, the present mesoporous CeO2 nanosphere with its large specific surface area was considered a promising support for advanced CO oxidation and even other industrial catalysts.

Studying the Structure‐Reactivity Relationship of CuO/CeO2 for Catalytic Soot Particulate Combustion: On the Monolayer Dispersion Threshold Effect

AbstractTo elucidate structure‐reactivity relationship and prepare improved catalysts for soot combustion, a series of CuO/CeO2 with different loadings have been fabricated by the impregnation method. With XRD and XPS extrapolation methods, it is disclosed that CuO disperses finely on the CeO2 support to form a monolayer with a capacity around 1.06 mmol 100 m−2, which equals to 2.9 wt. % CuO loading. Below this capacity, CuO is in a sub‐monolayer state. However, above this capacity, CuO micro‐crystallites are formed, and co‐exist with the monolayer CuO. By increasing CuO loading, soot combustion activity of the catalysts increases as well until it reaches the monolayer dispersion capacity. Further increasing the CuO loading to 5 % decreases the activity slightly, and then remains constant. Therefore, an apparent monolayer dispersion threshold effect is observed for soot combustion on CuO/CeO2 catalysts. It is found that the amount of surface‐active O2− sites plays critical role for the catalytic activity. To obtain the most active CuO/CeO2 catalyst, a monolayer amount of CuO should be loaded on the supports.

Reinforcement of methanol catalytic reforming for hydrogen production through Ru-based carbon-coated CeO2 catalyst

Methanol steam reforming for hydrogen production is a highly promising energy technology, due to the high hydrogen intensity of methanol and the appendant hydrogen capture from water. In order to reinforce the hydrogen yield in methanol steam reforming reaction, a series of Ru-based carbon-coated CeO2 catalysts were prepared in this work, using glucose, cellulose and activated carbon as different carbon sources via a hydrothermal method. The results showed that the Ru/CG-CeO2 (glucose) catalyst exhibited a superior catalytic performance at the reaction temperature of 400 °C, with a higher hydrogen production rate (0.276 mol/h) than Ru/CC-CeO2 (cellulose, 0.230 mol/h) and Ru/CA-CeO2 (activated carbon, 0.253 mol/h) catalysts. This was attributed to the synergistic effect between CeO2 and carbon, where the carbon layer formed by glucose enhanced the interaction between the active component and the CeO2 support, which also facilitated the electron transfer effects and resulted in a large amount of oxygen vacancies for Ru/CG-CeO2. This led to a strong adsorption capacity for CO and oxygen-containing species derived from the substrate, thereby improving hydrogen production. Additionally, the catalyst stability and the resistance to carbon deposition were evaluated for all the three catalysts, and Ru/CG-CeO2 catalyst also demonstrated a superior stability and anti-carbon deposition capability.

Catalytic performance of NixCoy catalysts supported on honeycomb-lantern-like CeO2 for dry reforming of methane: Synergistic effect and kinetic study

Dry reforming of methane (DRM) is considered one of the most efficient methods for carbon utilization, as it can transform greenhouse gases (CH4 and CO2) into syngas (CO and H2) which could be widely used in the production of high-value hydrocarbons. The synergistic effect between Ni and Co is leveraged to enhance the coke resistance and stability of Ni-based catalyst during the DRM process, building upon the surface spatial confinement provided by honeycomb-lantern-like CeO2 support. The enhanced catalytic performance of Ni0.9Co0.1 catalyst can be attributed primarily to the addition of cobalt, which facilitates CO2 adsorption and activation, further promotes the Boudouard reaction and aids in the elimination of coke. This phenomenon is supported by evidence from CO2-TPD, XPS, SEM, TGA, XRD, and CO2-TPO analyses. Furthermore, the kinetics of Ni0.9Co0.1 are examined using Power-Law (PL) and Langmuir-Hinshelwood (LH) mechanisms, obtaining the explicit equations for the rate constants (k and kr), reaction orders of the reactants (α and β), and adsorption equilibrium constants (KCH4 and KCO2). The comparison of the predicted CH4 consumption rates with the experimental rates suggests that the LH mechanism is notably more precise than PL mechanism for Ni0.9Co0.1 catalyst. Moreover, the relevant kinetic parameters (the activation energy and pre-exponential factor), pertinent to coke gasification process for the spent Ni0.9Co0.1 and Ni1.0, are determined and calculated through CO2-TPO characterization and the modified Wigner-Polanyi equation.

Operando Mobile Catalysis for Reverse Water Gas Shift Reaction

AbstractMetal atoms on the support serve as active sites for many heterogeneous catalysts. However, the active metal sites on the support are conventionally described as static, and the intermediates adsorbed on the support far away from the active metal sites cannot be transformed. Herein, we report the first example of operando mobile catalysis to promote catalytic efficiency by enhancing the collision probability between active sites and reactants or reaction intermediates. Specifically, ligand‐coordinated Pt single atoms (isolated MeCpPt‐ species) are bonded on CeO2 and transformed into mobile MeCpPt(H)CO complexes during the reverse water gas shift reaction for operando mobile catalysis. This strategy enables the conversion of inert carbonate intermediates on the CeO2 support. A turnover frequency (TOF) of 6358 mol CO2 molPt−1 ⋅ h−1 and 99 % CO selectivity at 300 °C is obtained for reverse water gas shift reaction, dramatically higher than those of Pt catalysts reported in the literature. Operando mobile catalysis presents a promising strategy for designing high‐efficiency heterogeneous catalysts for various chemical reactions and applications.

Identification of Direct Anchoring Sites for Monoatomic Dispersion of Precious Metals (Pt, Pd, Ag) on CeO2 Support.

Monoatomic dispersion of precious metals on the surface of CeO2 nanocrystals is a highly practical approach for dramatically reducing the usage of precious metals while exploiting the unique properties of single-atom catalysts. However, the specific atomic sites for anchoring precious metal atoms on the CeO2 support and underlying chemical mechanism remain partially unknown. Herein, we show that the terminal hydroxyls on the (100) surface are the most stable sites for anchoring Ag atoms on CeO2 , indicating that CeO2 nanocubes are the most efficient substrates to achieve monoatomic dispersion of Ag. Importantly, the newly identified chemical mechanism for single-metal-atom dispersion on CeO2 nanocubes appears to be generic and can thus be extended to other precious metals (Pt and Pd). In fact, our experiments also show that atomically dispersed Pt/Pd species exhibit morphology- and temperature-dependent CO selectivity in the catalytic CO2 hydrogenation reaction.

Identification of Direct Anchoring Sites for Monoatomic Dispersion of Precious Metals (Pt, Pd, Ag) on CeO2 Support

AbstractMonoatomic dispersion of precious metals on the surface of CeO2 nanocrystals is a highly practical approach for dramatically reducing the usage of precious metals while exploiting the unique properties of single‐atom catalysts. However, the specific atomic sites for anchoring precious metal atoms on the CeO2 support and underlying chemical mechanism remain partially unknown. Herein, we show that the terminal hydroxyls on the (100) surface are the most stable sites for anchoring Ag atoms on CeO2, indicating that CeO2 nanocubes are the most efficient substrates to achieve monoatomic dispersion of Ag. Importantly, the newly identified chemical mechanism for single‐metal‐atom dispersion on CeO2 nanocubes appears to be generic and can thus be extended to other precious metals (Pt and Pd). In fact, our experiments also show that atomically dispersed Pt/Pd species exhibit morphology‐ and temperature‐dependent CO selectivity in the catalytic CO2 hydrogenation reaction.

Regulation of catalytic reaction performance of CO2 with ethane by metal cation substitution on CeO2 support

The catalytic reaction of CO2 with ethane balances the resourceful conversion of CO2 and the value-added utilization of shale gas. In this paper, the effects of different metal cation substitutions on CeO2 support in Fe-Ni catalysts on the regulation of CO2 and ethane directional catalytic reaction performance were studied through experiments combined with DFT calculation simulations. It was found that the Ti-substituted Fe1.5Ni0.5/CeTi-2 catalyst had the highest ethane conversion of 11.8% and CO2 conversion of 21.2%, and presented a high-value product C2H4 selectivity higher than 80%. The Ti/La species in the substituted structure are highly dispersed into the CeO2 lattice to form a Ti/LaxCe1-xO2−δ solid solution, which induces more (-111) and (110) crystal planes with high ethylene selectivity. The Ti-substituted catalyst has the highest proportion of Ce3+, which improves the formation and transfer of active oxygen, making Fe1.5Ni0.5/CeTi-C-2 exhibit higher catalytic reactivity. The substitution of metal cations weakens the adjacent Ce-O bond strength, and the Ti substitution structure facilitates the generation of Ov as a highly active center for CO2 reduction, resulting in a decrease of the energy barrier for the CO2 dissociation process from 3.87 eV on pristine CeO2(111) to 2.17 eV, and the reaction energy endotherm is 1.03 eV. Both kinetically and thermodynamically, the reduction dissociation of CO2 on Ti-CeO2(111) is more competitive than that on Zr and La-substituted CeO2(111).

The Effect of Precursor Concentration on the Crystallite Size of CeO2 to Enhance the Sulfur Resistance of Pt/CeO2 for Water Gas Shift

To develop customized sulfur–resistant catalysts for the water gas shift (WGS) reaction in the waste–to–hydrogen process, the effects of changing the nucleation conditions of the CeO2 support on catalytic performance were investigated. Supersaturation is a critical kinetic parameter for nuclei formation. The degree of supersaturation of the CeO2 precipitation solution was controlled by varying the cerium precursor concentration from 0.02 to 0.20 M. Next, 2 wt.% of Pt was impregnated on those various CeO2 supports by the incipient wetness impregnation method. The prepared samples were then evaluated in a WGS reaction using waste–derived synthesis gas containing 500 ppm H2S. The Pt catalyst supported by CeO2 prepared at the highest precursor concentration of 0.20 M exhibited the best sulfur resistance and catalytic activity regeneration. The sulfur tolerance of the catalyst demonstrated a close correlation with its oxygen storage capacity and easier reducibility. The formation of oxygen vacancies in CeO2 supports is promoted by the formation of small crystals due to a high degree of supersaturation.

Insights into direct/synergetic processes for high-efficiency steam reforming of methanol over Pt-In2O3/CeO2 catalysts: The effect of support structural properties

The addition of Pt (1 %) and In2O3 (7 %) phases into CeO2 supports exhibited an interaction, resulting in the formation of bifunctional Pt2+-In2O3-CeO2, Ptδ+-CeO2 (0 < δ < 2), In2O3-CeO2, and inactive In2O3 macroparticles., Low CO selectivity was achieved in methanol steam reforming (MSR) by sacrificing methanol conversion/catalytic stability. Two distinct reaction paths were identified, viz., the direct process over bifunctional Pt2+-In2O3-CeO2 and the synergetic process between Ptδ+-CeO2 and In2O3-CeO2. The relative ratio of these two processes played a decisive role in determining the product distribution. The direct process improved methanol conversion while maintaining low CO selectivity. However, a decrease in catalytic stability was attributed to the agglomeration and sintering of the In2O3 phase, leading to the conversion of Pt2+-In2O3-CeO2 into Ptδ+-CeO2. To address the challenge of balancing methanol conversion/catalytic stability and CO selectivity, it was crucial to enhance Pt2+-In2O3-CeO2 sites and preserve their stability. Furthermore, the structural properties of the support played a significant role in governing the distributions and states of Pt and In2O3 phases. Specifically, the use of CeO2 (0.5 °C min−1) support resulted in a substantial increase in Pt2+-In2O3-CeO2 and effectively mitigated the sintering of In2O3 phases, ensuring the stability of Pt2+-In2O3-CeO2. In conclusion, our work elucidated the intricate relationships among the structural properties of CeO2 supports, the distributions and states of Pt and In2O3 phases, and MSR performance over Pt-In2O3/CeO2 catalysts, which hold promise for advancing the development of high-performance MSR catalysts.

Self-dispersed bimetallic NiRu nanoparticles on CeO2 for CO2 methanation

Redispersing bimetallic active nanoparticles in a heterogeneous catalyst can significantly improve metal utilization and catalytic performance, but it is very challenging. In this work, we report a feasible method to redisperse large bimetallic NiRu particles (30–40 nm) on the CeO2 support into small alloyed NiRu nanoparticles (3–5 nm) in an Ar gas atmosphere (NiRu/CeO2-Ar). During the high-temperature treatment, Ru metal in big bimetallic NiRu particles migrated to the surface of small alloyed nanoparticles because of the metal-phase separation, forming more Ni−Ru metal interfaces. As a result, NiRu/CeO2-Ar showed much better catalytic performance in CO2 methanation than the pristine catalyst (NiRu/CeO2) and the catalysts treated in air, H2, and reactant gases, respectively. Experimental and theoretical calculation results reveal that the newly generated Ni−Ru metal interfaces are conducive to the adsorption of CO2 and further direct dissociation into CO*, thus enhancing the catalytic performance. This work provides a reliable strategy to redisperse bimetallic NiRu nanoparticles into small ones with more intermetallic interfaces.

Effect of CeO2 support structure on the catalytic performance of ammonia synthesis in an electric field at low temperatures.

Ammonia is an extremely important storage and transport medium for renewable energy, and technology is expected to produce it on demand and onsite using renewable energy. Applying a DC (direct current) to a solid catalyst layer with semiconducting properties makes ammonia synthesis highly efficient, even at low temperatures (approximately 400 K). In this process, oxide supports with semiconducting properties play important roles as metal supports and conduction fields for electrons and protons. The influence of the degree of particle aggregation on the support properties and ammonia synthesis using an electric field was evaluated for CeO2, which is the best material for this purpose because of its semiconducting properties. The results showed that controlling the aggregation structure of the crystalline particles could significantly influence the surface conductivity of protons and electrons; thus, the activity could be largely controlled. The Ru-CeO2 interaction could also be controlled by changing the crystallinity, which suppressed the aggregation of the supported Ru and significantly improved the ammonia synthesis activity using an electric field at low temperatures.

Highly Stable Pt/CeO2 Catalyst with Embedding Structure toward Water-Gas Shift Reaction.

Strong metal-support interaction (SMSI) has been extensively studied in heterogeneous catalysis because of its significance in stabilizing active metals and tuning catalytic performance, but the origin of SMSI is not fully revealed. Herein, by using Pt/CeO2 as a model catalyst, we report an embedding structure at the interface between Pt and (110) plane of CeO2, where Pt clusters (∼1.6 nm) are embedded into the lattice of ceria within 3-4 atomic layers. In contrast, this phenomenon is absent in the CeO2(100) support. This unique geometric structure, as an effective motivator, triggers more significant electron transfer from Pt clusters to CeO2(110) support accompanied by the formation of interfacial structure (Ptδ+-Ov-Ce3+), which plays a crucial role in stabilizing Pt nanoclusters. A comprehensive investigation based on experimental studies and theoretical calculations substantiates that the interfacial sites serve as the intrinsic active center toward water-gas shift reaction (WGSR), featuring a moderate strength CO activation adsorption and largely decreased energy barrier of H2O dissociation, accounting for the prominent catalytic activity of Pt/CeO2(110) (a reaction rate of 15.76 molCO gPt-1 h-1 and a turnover frequency value of 2.19 s-1 at 250 °C). In addition, the Pt/CeO2(110) catalyst shows a prominent durability within a 120 h time-on-stream test, far outperforming the Pt/CeO2(100) one, which demonstrates the advantages of this embedding structure for improving catalyst stability.

Steam Treatment Promotion on the Performance of Pt/CeO2 Three-Way Catalysts for Emission Control of Natural Gas-Fueled Vehicles

Three-way catalyst (TWC) is the mainstream technology for stoichiometric natural gas vehicle gas emission purification to meet the China VI emission standard for heavy-duty vehicles. Due to the high price of Pd-Rh TWC widely used at present, it is of great significance to develop cheaper Pt-only catalysts as substitutes. However, there are few studies on Pt-only TWC, especially for natural gas vehicles. It remains a formidable challenge to develop Pt-only TWC with excellent activity and stability. In this study, we significantly improved the catalytic performance of Pt/CeO2 TWC through thermal treatment, especially steam treatment at 800 °C, and used XRD, TEM, H2-TPR, and XPS techniques to investigate how Pt/CeO2 can be activated via these treatments. Our results suggested that after these treatments, CeO2 crystallites sintered slightly, while platinum particles remained highly dispersed. Moreover, these treatments also weakened the Pt-CeO2 interaction, promoted the formation of oxygen vacancies in CeO2 support, and generated a new type of active surface oxygen in the vicinity of Ptδ+, thus improving the activity of the catalyst. After 800 °C steam treatment, the T50 of CH4 and NO decreased by 31 and 36 °C, respectively. The results obtained in this study provide implications for the synthesis of efficient Pt-based catalysts.

Hydroxyls on CeO2 Support Promoting CuO/CeO2 Catalyst for Efficient CO Oxidation and NO Reduction by CO.

Transition metal catalysts, such as copper oxide, are more attractive alternatives to noble metal catalysts for emission control due to their higher abundance, lower cost, and excellent catalytic activity. In this study, we report the preparation and application of a novel CuO/CeO2 catalyst using a hydroxyl-rich Ce(OH)x support for CO oxidation and NO reduction by CO. Compared to the catalyst prepared from a regular CeO2 support, the new CuO/CeO2 catalyst prepared from the OH-rich Ce(OH)x (CuO/CeO2-OH) showed significantly higher catalytic activity under different testing conditions. The effect of OH species in the CeO2 support on the catalytic performance and physicochemical properties of the CuO/CeO2 catalyst was characterized in detail. It is demonstrated that the abundant OH species enhanced the CuOx dispersion on CeO2, increased the CuOx-CeO2 interfaces and surface defects, promoted the oxygen activation and mobility, and boosted the NO adsorption and dissociation on CuO/CeO2-OH, thus contributing to its superior catalytic activity for both CO oxidation and NO reduction by CO. These results suggest that the OH-rich Ce(OH)x is a superior support for the preparation of highly efficient metal catalysts for different applications.

Effect of silica on generation and stability of Cu+ cations in CuO/CeO2 catalysts for CO oxidation in H2-rich atmosphere

Developing efficient CuO/CeO2 catalysts for CO preferential oxidation in H2-rich atmosphere (CO PROX) is essential for removing residual CO in the reformate gas. However, achieving robust performance in a wide working temperature window is still a great challenge. Herein, SiO2 was introduced to modify the CuO/CeO2 catalysts and the best catalyst exhibited 100 % of CO conversion and >50 % of CO2 selectivity from 120 to 220 °C over CO PROX reaction. Combined characterization techniques demonstrate the enhanced interaction between copper species and CeO2 support after deposition of SiO2, promoting the generation of active Cu+ sites as well as the reactivity of lattice oxygen in CeO2 for CO conversion. Besides, in presence of SiO2, the main intermediates changed from carbonates to formate species. More importantly, the active Cu+ sites were stabilized by SiO2 due to formation of Cu+-O-SiOx interface, retarding the competitive H2 oxidation at high temperatures.

Shape dependency of CO2 hydrogenation on ceria supported singly dispersed Ru catalysts

Harnessing the selectivity in catalytic hydrogenation of CO2 is important for producing valuable chemicals. Herein, the shape dependency of the CO2 hydrogenation on singly dispersed Ru/CeO2 catalysts is investigated. CeO2 of three shapes, including nanocube, nanooctahedron and nanorod, are prepared as the catalyst supports and assigned to the surface of (100), (111) and (110) crystal plane, respectively. The Ru/CeO2 (nanorod) exhibits the highest selectivity to CO (97.6 %) at 350 °C, while the Ru/CeO2 (nanocube) exhibits a mediocre selectivity to CO (41.4 %) but the highest CO2 conversion. The shape of the CeO2 support determines the electronic state of supported Ru atoms through the electronic metal-support interaction. The low CO affinity on cationic Ruβ sites leads to the higher selectivity to CO on the Ru/CeO2 (nanorod) and Ru/CeO2 (nanooctahedron) catalysts, while the strong dissociation ability of H2 on low valence Ruα sites results in the high activity on the Ru/CeO2 (nanocube) catalyst.

A DFT study of elementary reaction steps of dry reforming of methane catalyzed by Ni: Explaining the difference between Ni particles supported on CeO2 and MnO[formula omitted]-doped CeO2

With the aid of DFT calculations, we investigate the elementary reaction steps of dry reforming of methane (DRM) on Ni(111) and NiO(100) as simple models of metallic and oxidized Ni catalysts. The reaction-path calculations reveal that DRM is feasible on metallic Ni at elevated temperatures. However, a notable problem with metallic Ni catalysts is the coke formation because the activation barrier for the C* formation is not considerably higher than those of the competing reactions that lead to the DRM products. In contrast, NiO does not encounter issues with coke formation, but it is not an effective catalyst due to too high activation energies and slow surface diffusion of H*. We also explain the experimentally observed difference between the DRM catalysts consisting of Ni particles supported on undoped and MnOx-doped CeO2 supports (designated as Ni/CeO2 and Ni/MnxCeO2, respectively). Specifically, we explain the absence of the 2020 cm−1 vibrational peak on the Ni/MnxCeO2 catalyst. Calculations univocally attribute the experimentally observed 2020 cm−1 peak to CO adsorbed on a top site of metallic Ni because all other sites and involved species display considerably different frequencies. The CO stretching frequency increases as Ni oxidizes, and on NiO(100), it is similar to the vibration of CO on the CeO2(111) support, about 2100 cm−1. Current results thus provide a sound explanation of why Ni/MnxCeO2 is a superior DRM catalyst to Ni/CeO2. In particular, the presence of the 2020 cm−1 peak on the Ni/CeO2 catalyst signals that Ni particles are sufficiently metallic and thus susceptible to carbon poisoning. In contrast, the absence of the 2020 cm−1 peak on the Ni/MnxCeO2 catalyst indicates that Ni particles are oxidized, i.e., the Ni oxidation is low enough to allow the DRM reaction but high enough to reduce the catalyst’s carbon poisoning.

Binder effect on CeO2-based technical catalyst performance: insights and implications

Cerium oxide has earned recognition as a valuable support material in heterogeneous catalysis due to its exceptional catalytic properties. Ensuring the mechanical stability of CeO2-based technical catalysts is crucial for reliable industrial performance. This study reports two primary approaches for enhancing the mechanical resistance of these catalysts. Firstly, thermal treatment was explored, applying various calcination temperatures and heating rates, which highlighted the balance between mechanical strength and porosity in catalyst supports. Secondly, the influence of inorganic binders ―boehmite, bentonite, and kaolinite― on the physicochemical properties and catalytic performance of CeO2-based supports in the context of CO2 methanation was systematically evaluated. Binder-modified CeO2-based technical supports (with a CeO2-to-binder ratio of 10:1) were fabricated, impregnated with nickel salts, characterized using N2-physisorption, compression assays, XRD, TGA, SEM-EDX, and H2-TPR, and their activity in the methanation of CO2 was assessed. Bentonite demonstrated remarkable strength enhancement, doubling the mechanical resistance compared to the pure CeO2 support. However, employing clay-altered supports as catalysts led to unfavorable results for application in practical cases. Boehmite emerged as a highly promising binder, demonstrating exceptional chemical and mechanical stability and minimal disruption to the activity of the catalyst in CO2 methanation thus establishing its practical suitability for catalyst development. This research highlights the nuanced influence of different binders on catalyst performance, providing valuable insights into the design and optimization of CeO2-based catalysts for applied catalytic technologies.

Enhancing the electrocatalytic oxygen evolution performance of iridium oxide in acidic media by inducing a lower valence state using CeO2 support

In this study, a composite catalyst consisting of IrOx nanoparticles dispersed in CeO2 support (IrOx/CeO2) was prepared for oxygen evolution reaction (OER) using a simple polyol method. The oxygen transfer from IrOx to oxygen defects in CeO2 induced a high ratio of lower-valence Ir3+ species, which are known to be an active phase for OER. The prepared IrOx/CeO2 catalyst exhibited excellent OER performance with a small overpotential of 263.4 mV at 10 mA/cm2, and good stability for 10 h under acidic condition, outperforming IrOx/C and commercial IrO2 catalysts. The lower-valence Ir3+ species near the catalyst surface functioned as possible active site ensembles, promoting the chemical and electrochemical steps during OER process and improving the OER activity. Additionally, the metal-support interaction between IrOx and CeO2 enhanced the durability of the catalyst.