Insight of BaCe0.5Fe0.5O3−δ twin perovskite oxide composite for solid oxide electrochemical cells

One-pot synthesized twin perovskite oxide composite of BaCe_0.5Fe_0.5O_3−δ (BCF), comprising cubic and orthorhombic perovskite phases, shows triple-conducting properties for promising solid oxide electrochemical cells. Phase composition evolution of BCF under various conditions was systematically investigated, revealing that the cubic perovskite phase could be fully/partially reduced into the orthorhombic phase under certain conditions. The reduction happened between the two phases at the interface, leading to the microstructure change. As a result, the corresponding apparent conducting properties also changed due to the difference between predominant conduction properties for each phase. Based on the revealed phase composition, microstructure, and electrochemical properties changes, a deep understanding of BCF's application in different conditions (oxidizing atmospheres, reducing/oxidizing gradients, cathodic conditions, and anodic conditions) was achieved. Triple-conducting property (H⁺/O²⁻/e⁻), fast open-circuit voltage response (∼16–∼470 mV) for gradients change, and improved single-cell performance (∼31% lower polarization resistance at 600°C) were comprehensively demonstrated. Besides, the performance was analyzed under anodic conditions, which showed that the microstructure and phase change significantly affected the anodic behavior.     

Improved electrochemical performance of Bi doped La0.8Sr0.2FeO3-δ nanofiber cathode for IT-SOFCs via electrospinning

In this study, perovskite La_0.8-xBi_xSr_0.2FeO_3-δ (LBSF, x = 0.0–0.5) nanofibers with great crystallinity were prepared by electrospinning method and used as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). The symmetric cells of nanofiber-based LBSF electrode on Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte show excellent electrochemical performance. The La_0.4Bi_0.4Sr_0.2FeO_3-δ (LBSF4) cathode has the best performance with a polarization resistance (R_P) of 0.126 Ω cm² at 650 °C. The anode-supported single cell with LBSF4 as the cathode film and Ni-SDC as the anode has a maximum power density of 448 mW cm^-2 at 650 °C using wet H₂ as the fuel. In addition, the LBSF4 cathode with fibrous structure exhibits outstanding electrochemical behavior. The catalytic activity of the cathode was improved due to the incorporation of the Bi element, indicating that LBSF4 is promising as a cathode material in the field of IT-SOFCs.     

Complex Perovskite system Dy0.5-xBaxSr0.5Co0.80Fe0.20O3-δ: As cathode for IT-SOFCs

The present work is intended to study mixed conductivity of complex perovskite oxide of chemical formula Dy_0.5-xBa_xSr_0.5Co_0.8Fe_0.2O_3-δ (DBSCF-x) (0 ≤ x ≤ 0.07) to check its suitability as cathode for intermediate temperature solid oxide fuel cell (IT-SOFCs). Low-temperature sol-gel combustion route has been used to prepare DBSCF-x systems. Structures are confirmed by X-ray diffraction (XRD), exhibit single-phase perovskite structures with orthorhombic symmetry (space group Pbnm) for all compositions. Thermogravimetry (TG) results indicate lattice oxygen loss in Ba-doped DBSCF system by heat treatment in temperature interval 50-850°C, which is enhanced in N₂ atmosphere then air; in contrast to that lattice oxygen, gain is observed for DBSCF-0 system. Temperature profile of DC conductivity exhibits metallic behavior of DBSCF-x system; however, the DBSCF-0 system shows semiconductor-to-metal transition at temperature around 450°C. DBSCF-0.03 system displays maximum electronic conductivity. Electrochemical performance of electrodes is studied in three-layer symmetrical cell configuration DBSCF-x/Ce_0.85Sm_0.15O_2-δ/DBSCF-x by complex impedance spectroscopy (CIS). Impedance diagram reveals the presence of three processes mainly associated with (a) diffusion of oxide ions/oxygen intermediates through electrode/electrolyte interface, (b) atomic oxygen diffusion within the electrode, and (c) oxide ion diffusion in the crystal lattice. ASR of the DBSCF-0.05 system is found 2.21 ohm cm² at 700°C, which is lowest amongst all studied compositions. Results show that it is possible to modify the electrochemical properties of the DBSCF-x system by changing the composition, but much more work even including optimization of layer thickness and microstructure will be needed to reduce the ASR to the level of the state-of-art-electrodes and thereby better utilize the potential of the DBSCF-x system.     

Compaction pressure effect on microstructure and electrochemical performance of GdBaCo2O5+δ cathode for IT-SOFCs

In order to optimize the morphology of starting powder, raw GBCO powder synthesized via solid state reaction was repeatedly compacted by uniaxial die pressing at two apparent compaction pressures of 500 and 1000 MPa. The particle size distribution curves and SEM images indicated that, with increasing compaction pressure and number of compaction times, the larger particles in the powder were gradually broken apart and the particle size became small and uniform. Then the effect of pressing treatment for the starting GBCO particles on the microstructure and performance of sintered cathode was studied. The results demonstrated that, after being sintered under the same conditions, the cathode prepared from the treated GBCO particles showed a finer microstructure compared with that prepared from the raw GBCO particles. In addition, optimizing the morphology of the starting GBCO powder by pressing treatment could improved the cathode performance and made the polarization resistance of final cathode reduce from 1.33 Ω cm² to 0.40 Ω cm² at 600 °C.     

Tuning Ba0.5Sr0.5Co0.8Fe0.2O3-δ cathode to high stability and activity via Ce-doping for ceramic fuel cells

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) fuel-cell cathode stands out because of its ultrahigh ionic conductivity and excellent electrocatalytic activity, but it is still very subject to instability. Here, a new strategy of Ce doping is proposed to boost the stability and activity of the BSCF cathode. A one-pot combustion method is employed to synthesize (Ba_0.5Sr_0.5)_1–xCe_xCo_0.8Fe_0.2O_3-δ (x=0–0.2) cathodes. Both BSCF and (Ba_0.5Sr_0.5)_0.9Ce_0.1Co_0.8Fe_0.2O_3-δ have a cubic perovskite structure. (Ba_0.5Sr_0.5)_0.8Ce_0.2Co_0.8Fe_0.2O_3-δ shows two phases of cubic perovskite and fluorite ceria. Proper Ce doping can boost the electrical conductivity of BSCF, and can dramatically reduce the polarization resistance of BSCF cathode. Ce doping significantly improved BSCF cathode long-term stability by 160 h. Moreover, ten-percent Ce doping in BSCF highly improves single-cell output performance from 516.33 mW cm^?2 to 629.75 mW cm^?2 at 750 °C. The results reveal that Ce doping as a potential strategy for enhancing the stability and activity of BSCF cathode is promising.     

Partial oxidation of methane in BaCe0.1Co0.4Fe0.5O3−δ membrane reactor

A new perovskite material, BaCe_0.1Co_0.4Fe_0.5O_3?δ used as dense oxygen permeable membrane for partial oxidation of methane (POM) reaction was investigated. In order to improve the synergetic effects between membrane and catalyst, LiLaNiO/γ-Al₂O₃ catalyst was directly packed onto the surface of the membrane to carry out POM. In BaCe_0.1Co_0.4Fe_0.5O_3?δ membrane reactor, high oxygen permeation flux, high CH₄ conversion and CO selectivity were obtained. At 950 °C, oxygen flux of 9.5 ml cm^?2 min^?1, CH₄ conversion of 99% and CO selectivity of 93% were achieved with a membrane thickness of 1.0 mm. There was an induction process at the initial stage of POM, which was related to the reduction of NiO to Ni⁰ in LiLaNiO/γ-Al₂O₃ catalyst. Experiments illustrated that higher reaction temperature would shorten the induction time. During continuously operating for 1000 h at 875 °C, no degradation of performance of the membrane reaction was observed. SEM characterization also demonstrated that the membrane disc maintained an integral structure without any cracks after long-term operation.     

Oxygen transport,thermal and electrochemical properties of NdBa0.5Sr0.5Co2O5+δ cathode for SOFCs

In this study, the crystal structure, thermal, oxygen transport, electrical conductivity and electrochemical properties of the perovskite NdBa_0.5Sr_0.5Co₂O_5+δ (NBSC55) are investigated. In the temperature range of 250 °C–350 °C, the weight loss upon heating was due to a partial loss of lattice oxygen and along with a reduction of Co⁴⁺ to Co³⁺. The tend of weight-loss slows down as temperature increased above 350 °C indicating a reduction of Co³⁺ to Co²⁺ during this stage. The oxygen migration is dominated by surface exchange process at high temperature range (650-800 °C); however, the bulk diffusion process prevails at low temperature range (500–600 °C). For long-term testing, the polarization resistance of NBSC55 increases gradually form 3.13 Ω cm² for 2 h to 3.34 Ω cm² for 96 h at 600 °C and an increasing-rate for polarization resistance is around 0.22% h^?1. The power density of the single cell with NBSC55 cathode reached 341 mW cm^?2 at 800 °C.     

Evaluation of GdBaCuCo0.5Fe0.5O5+δ as cathode material for intermediate temperature solid oxide fuel cells

The GdBaCuCo_0.5Fe_0.5O_5+δ (GBCCF) layered perovskite oxide was evaluated as novel cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Its electrical conductivity was 9–13 S cm^?1 at 650–800 °C in air. The average thermal expansion coefficient (TEC) of GBCCF was 14.4 × 10^?6 K^?1, which was close to that of the typical electrolyte material. The cathode polarization resistance of GBCCF was 0.650 Ω cm² at 750 °C and it decreases to 0.118 Ω cm² when Ce_0.9Gd_0.1O_1.95 (GDC) was added to form a GBCCF–GDC composite cathode. Preliminary results indicated that layered perovskite GBCCF was a promising alternative cathode material for IT-SOFCs.     

A novel BaCe0.5Fe0.3Bi0.2O3–δ perovskite-type cathode for proton-conducting solid oxide fuel cells

A perovskite-type BaCe_0.5Fe_0.3Bi_0.2O_3-δ (BCFB) was employed as a novel cathode material for proton-conducting solid oxide fuel cells (SOFCs). The single cells with the structure of NiO-BaZr_0.1Ce_0.7Y_0.2O_3-δ (BZCY7) anode substrate|NiO-BZCY7 anode functional layer|BZCY7 electrolyte membrane|BCFB cathode layer were fabricated by a dry-pressing method and investigated from 550 to 700 °C with humidified hydrogen (~3% H₂O) as the fuel and the static air as the oxidant. The low interfacial polarization resistance of 0.098 Ω cm² and the maximum power density of 736 mW cm⁻² are achieved at 700 °C. The excellent electrochemical performance indicates that BCFB may be a promising cathode material for proton-conducting SOFCs.     

Improved oxygen reduction reaction activity by in-situ synthesizing Sr3Fe1.8Nb0.2O7-δ coating on SrFe0.9Nb0.1O3-δ cathode via the microwave water bath heating method

The sluggish oxygen reduction kinetics remains to be the main obstacle to the development of low temperature proton ceramic fuel cells which limits its commercial application. This phenomenon has driven the exploration of the oxide electrode materials which both possess high oxygen reduction reaction activity and heterogeneous structure. In this work, mixed ionic and electronic conductor SrFe_0.9Nb_0.1O_3-δ (SFN113) is partially transformed into the triple-phase conductor Sr₃Fe_1.8Nb_0.2O_7-δ (SFN327) by in-situ reaction with uniformly coated SrO layer using a microwave water bath heating method. The introduction of the second phase SFN327 significantly improves the oxygen surface exchange kinetics of SFN113 investigated by the electrical conductivity relaxation method. The present work not only remarkably improves the electrocatalytic reduction activity of SFN113 by the introduction of the second phase SFN327 and the construction of the heterogeneous interface, but also provides a valuable route for the further optimization of the exiting electrode materials.     

Modeling of U-shaped Ba0.5Sr0.5Co0.8Fe0.2O3-δ hollow-fiber membrane for oxygen permeation

A mathematic model is developed for the perovskite-type mixed ionic-electronic conducting (MIEC) membrane,which makes it possible to simulate the process of oxygen separation in the U-shaped Ba0.5Sr0.5Co0.8Fe0.2O3-δ hollow-fiber membrane.The model correlates the oxygen permeation flux to the measurable variables.The trends of calculated results for purge operation coincide well with the experimental data,therefore the model is considerable for flux prediction under vacuum operation.Higher oxygen separation efficiency can be achieved with vacuum operation than purge operation.Parameter study with vacuum operation reveals that oxygen permeation flux increases with higher vacuum levels,and vacuum pressure of around 1.013 × 103 Pa is the optimal.Also,vacuum operation on the lumen side is much more efficient to achieve higher oxygen permeation flux compared with compression mode on the shell side.     

Effect of microstructure on oxygen permeation of Ba0.5Sr0.5Co0.8Fe0.2O3−δ and SrCo0.8Fe0.2O3−δ membranes

The effect of grain size on oxygen permeation properties of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCF) and SrCo_0.8Fe_0.2O_3?δ (SCF) membranes was investigated by variation of the dwell time. The membrane microstructure was examined by field-emission scanning microscopy (FE-SEM) and then evaluated using a statistical approach. With longer dwell times the grain growth was stimulated and leaded to grains with a narrower size distribution. The grains of SCF (average size from 11.3 to 19.9 μm) were found to be smaller than those of BSCF (average size from 13.9 to 41.3 μm). The oxygen permeation flux of BSCF membranes was found to be independent of grain size in the range from 24 to 42 μm. However, membranes with smaller grains (13.9 μm) show a decreased oxygen permeation flux. For the SCF membranes a decrease in permeation flux with larger grains was observed for average grain sizes between 11.3 and 19.9 μm. By transmission electron microscopy (TEM) formation of an oxygen ordered SrCo_0.8Fe_0.2O_2.5 brownmillerite by-phase could be observed at the oxygen-depleted sweep side of the membrane.     

Evaluation of (Ba0.5Sr0.5)0.85Gd0.15Co0.8Fe0.2O3−δ cathode for intermediate temperature solid oxide fuel cell

A perovskite-type (Ba_0.5Sr_0.5)_0.85Gd_0.15Co_0.8Fe_0.2O_3?δ (BSGCF) oxide has been investigated as the cathode of intermediate temperature solid oxide fuel cells (IT-SOFCs). Coulometric titration, thermogravimetry analysis, thermal expansion and four-probe DC resistance measurements indicate that the introduction of Gd³⁺ ions into the A-site of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCF) leads to the increase in both oxygen nonstoichiometry at room temperature and electrical conductivity. For example, the conductivity of BSGCF is 148 S cm^?1 at 507 °C, over 4 times as large as that of BSCF. Furthermore, the electrochemical activity toward the oxygen reduction reaction is also enhanced by the Gd doping. Impedance spectra conducted on symmetrical half cells show that the interfacial polarization resistance of the BSGCF cathode is 0.171 Ω cm² at 600 °C, smaller than 0.297 Ω cm² of the BSCF cathode. A Ni/Sm_0.2Ce_0.8O_1.9 anode-supported single cell based on the BSGCF cathode exhibits a peak power density of 551 mW cm^?2 at 600 °C.     

Ca and Pr substitution promoted the cell performance in LnSr3Fe3O10-δ cathode for solid oxide fuel cells

The substitution of Ca for Sr in the LnSr_3-xCa_xFe₃O_10-δ (x = 0–1.5, Ln = La, Pr, and Sm), Ruddlesden-Popper (RP) intergrowth structure was investigated to determine how the physical and electrochemical properties of this potential cathode material in solid oxide fuel cells (SOFCs) are impacted. A small amount of Ca incorporated into the structure reduced the thermal expansion coefficient, improved the electrical conductivity, and increased power density by up to 30% of a La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ electrolyte-supported single cell. The microstructure and oxygen permeability of the materials were independent of Ca substitution. A phase transformation of LaSr_3-xCa_xFe₃O_10-δ to perovskite was observed when the Ca composition of x > 1.0. Among the substitution of Pr and Sm for La in LaSr_2.7Ca_0.3Fe₃O_10-δ, only PrSr_2.7Ca_0.3Fe₃O_10-δ was pure with no phase transformation found. The co-substitution of Pr and Ca promoted the reduction of Fe, enhanced the oxygen permeation and active surface, and diminished the contact resistance at the cathode-electrolyte interlayer. The co-substitution of Ca and Pr delivered good electrochemical performance of approximately 354 mWcm⁻² at 800 °C on a 0.3 mm thick La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ electrolyte-supported cell and the lowest area specific resistance (ASR).     

Novel Sr1.95Fe1.4Co0.1Mo0.5O6-δ anode heterostructure for efficient electrochemical oxidative dehydrogenation of ethane to ethylene by solid oxide electrolysis cells

The electrocatalytic conversion of ethane to ethylene is an important industrial process since ethylene is useful for the production of various chemical intermediates and polymers. However, this process often requires high temperatures. Metal-oxide heterogeneous interfaces constructed by in-situ exsolved process under reducing conditions would be favorable for promoting the catalyst activity, selectivity, and stability of ethane conversion to ethylene. Herein, Sr_1.95Fe_1.4Co_0.1Mo_0.5O_6-δ (abbreviated as SFCoM) was prepared as a novel anode material of solid oxide electrolysis cells (SOECs) for green ethylene production by electrochemical oxidative dehydrogenation of ethane. After reduction, nano CoFe particles were in-situ exsolved on SFCoM oxides to form a nano alloy-oxide heterostructure (CoFe@SFCoM) with large numbers of reactive sites, relevant for improving the conversion rate of ethane and the yield of ethylene. At 800 °C, the single cell based on CoFe@SFCoM anode exhibited a current density of 1.89 A cm⁻² at 1.6 V with an ethane conversion rate of 36.4% and corresponding ethylene selectivity of 94.5%. After 50 h of testing, the electrolysis current density(∼0.5 A cm⁻²) and ethylene yield(∼18.43%) of the single cell did not change significantly, showing good stability. In sum, CoFe@SFCoM looks very promising for future use as a SOECs anode for the electro-catalytic conversion of ethane to ethylene.     

Conductivity and electrochemical performance of (Ba0.5Sr0.5)0.8La0.2CoO3−δ cathode for intermediate-temperature solid oxide fuel cell

This study reports the successful preparation of a single-phase cubic (Ba_0.5Sr_0.5)_0.8La_0.2CoO_3?δ perovskite by the citrate–EDTA complexing method. Its crystal structure, thermogravimetry, coefficient of thermal expansion, electric conductivity, and electrochemical performance were investigated to determine its suitability as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Its coefficient of thermal expansion shows abnormal expansion at 300 °C, which is associated with the loss of lattice oxygen. The maximum conductivity of a (Ba_0.5Sr_0.5)_0.8La_0.2CoO_3?δ electrode is 689 S/cm at 300 °C. Above 300 °C, the electronic conductivity of (Ba_0.5Sr_0.5)_0.8La_0.2CoO_3?δ decreases due to the formation of oxygen vacancies. The charge-transfer resistance and gas phase diffusion resistance of a (Ba_0.5Sr_0.5)_0.8La_0.2CoO_3?δ–Ce_0.8Sm_0.2O_1.9 composite cathode are 0.045 Ω cm² and 0.28 Ω cm², respectively, at 750 °C.     

Assessment of cobalt–free ferrite–based perovskite Ln0.5Sr0.5Fe0.9Mo0.1O3–δ (Ln = lanthanide) as cathodes for IT-SOFCs

Cobalt–free perovskites Ln_0.5Sr_0.5Fe_0.9Mo_0.1O_3–δ (Ln = lanthanide; LnSFM) were prepared via a sol–gel process. Pure rhombohedral phases were still not obtained for the samples (Ln = Sm and Gd) even sintered at 1300 °C. Thus, only the LaSFM, PrSFM and NdSFM compositions were assessed as IT–SOFC cathodes in terms of their thermal, electrical and electrochemical properties. Thermal expansion of the LnSFM was well compatible with that of Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte. Both conductivity and electrochemical performances of the LnSFM followed the same sequence of La > Nd > Pr. For the LaSFM, NdSFM and PrSFM cathodes, peak conductivities reached 73, 63 and 59 S·cm^–1 at 650 °C; polarization resistances attained 0.211, 0.446 and 0.469 Ω·cm² at 700 °C; peak power densities of the LnSFM cells with 300–μm–thick SDC electrolyte achieved 269, 261 and 233 mW·cm^–2 at 700 °C without cell degradation for operating 100 h. By comprehensive comparison, the LaSFM is assessed as a preferred cobalt–free ceramic cathode for IT–SOFC.     

Barium-doped Sr2Fe1.5Mo0.5O6-δ perovskite anode materials for protonic ceramic fuel cells for ethane conversion

Protonic ceramic ethane fuel cells fed by hydrocarbon fuels are demonstrated to be effective energy conversion devices. However, their practical application is impeded by a lack of anode materials combining excellent catalytic activity with good chemical stability and anti-carbon deposition properties. In this work, in which Sr₂Fe_1.5Mo_0.5O_6-δ (SFM) double perovskite oxide is used as the matrix framework, catalytic activity toward H₂ and C₂H₆ oxidation is systematically investigated using Ba-doping. It is found that the concentration of the oxygen vacancy is gradually improved with increased Ba content to significantly enhance catalytic activity toward H₂ and C₂H₆ oxidation. From the series studied, Ba_0.6Sr_1.4Fe_1.5Mo_0.5O_6-δ exhibits the highest catalytic activity, while the power densities of the electrolyte-supported Ba_0.6SFM/BaCe_0.7Zr_0.1Y_0.2O_3-δ (BCZY)/La_0.58Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF)-Sm_0.2Ce_0.8O_2-δ (SDC) single cell reach 205 and 138 mW cm^–2 at 750°C in H₂ and C₂H₆, respectively. The ethane conversion rate of the experimental cell is shown to reach 38.4%, while simultaneously maintaining ethylene selectivity at 95%. Furthermore, the single cell exhibits no significant attenuation during stable operation for 20 h, as well as demonstrating excellent anti-coking performance. The proposed results suggest that Ba_0.6Sr_1.4Fe_1.5Mo_0.5O_6-δ represents a promising anode material for efficient hydrocarbon-related electrochemical conversion to realize the coproduction of ethylene and power in protonic ceramic ethane fuel cells.     

Improved electrochemical activity of Bi0.5Sr0.5FeO3-δ–Ce0.9Gd0.1O1.95composite cathode electrocatalyst for solid oxide fuel cells

Developing MIEC materials with high electrocatalytic performance for the ORR and good thermal/chemical/structural stability is of paramount importance to the success of solid oxide fuel cells (SOFCs). In this work, high-activity Bi_0.5Sr_0.5FeO_3-δ-xCe_0.9Gd_0.1O_1.95 (BSFO-xGDC, x = 10, 20, 30 and 40 wt%) oxygen electrodes are synthesized, and confirmed by XRD, SEM and EIS, respectively. The crystal structure, microstructure, electrochemical property and performance stability of the promising BSFO-xGDC composite cathodes are systematically evaluated. It is found that introducing GDC nanoparticles can obviously improve the electrochemical property of the porous composite electrode. Among all these composite cathodes, BSFO-30GDC composite cathode shows the best ORR activity. The peak power density of anode supported single cells employing BSFO-30GDC composite cathode reaches 709 mW cm^?2 and the electrode polarization resistance (R_p) of the BSFO-30GDC is about 0.14 Ω cm² at 700 °C. The analysis of the oxygen reduction kinetic indicates that the major electrochemical process of the GDC-decorated composite cathode is oxygen adsorption-dissociation. These preliminary results demonstrated that BSFO-30GDC is a prospective composite cathode catalyst for SOFCs because of its outstanding ORR activity.     

Enhanced catalytic oxidation via nano Cu0.5Mg0.5Fe2O4 embedded in CNTs for adsorption–reduction of hexavalent chromium

A catalyst consisting of Cu_0.5Mg_0.5Fe₂O₄ (CMF) supported on carbon nanotubes (CNTs) which exhibits great potential as an adsorbent for treating Cr(VI)-contaminated wastewater has been successfully prepared. The ferrite possesses excellent magnetic properties, while CNTs have the advantage of a large surface area. This composite material not only prevents the aggregation of magnetic materials and enhances the exposure of active sites but also effectively solves the recycling problem of CNTs. Our results show that the adsorption capacity of Cu_0.5Mg_0.5Fe₂O₄–carbon nanotubes (CMF-CNTs) for Cr(VI) wastewater (45.60 mg/g) is 1.49 times higher than that of Cu_0.5Mg_0.5Fe₂O₄ (30.48 mg/g). Compared to a single catalyst, CMF-CNTs not only improve the dispersibility of magnetic materials but also exhibit synergistic effects between the composite materials, enhancing the chemical adsorption capacity. After five consecutive adsorption and desorption experiments, the adsorption capacity of CMF-CNTs remains at 88% of its initial value. Furthermore, the study of the catalyst before and after adsorption by XPS reveals that the valence state transition of Fe³⁺/Fe²⁺ and Cu²⁺/Cu⁺ plays a crucial role in the adsorption process. The results of this study demonstrate the potential of using waste materials for effective wastewater treatment and provide insights into the development of new adsorbents for pollutant removal.