Intermediate Temperature Solid Oxide Fuel Cells Research Articles

Structural and Electrochemical Characterisation of NBZFO Cobalt-Free Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cells: An Experimental Investigation

Compared to other energy-generating technologies and energy conversion devices, intermediate-temperature solid oxide fuel cells (IT-SOFCs) have gained significant attention from energy experts due to its high energy density, moderate operating temperature (600–800°C), low emissions and reliability. Enhancing the performance of IT-SOFCs requires suitable and excellent cathode materials. Thus, a perovskite-type Nd0.5Ba0.5Zr0.8Fe0.2O3+δ (NBZFO) material was synthesised via traditional solid-state reaction technique and analysed as a potential cathode material for IT-SOFCs. Analysis of X-ray diffraction data (XRD) revealed a single-phase perovskite material that crystallises in cubic space group (pm-3m). The thermal and electrochemical properties were analysed with the aid of thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). NBZFO has an electrical conductivity in air of 80 S cm−1 at 400°C and a polarisation resistance (Rp) of 0.106 Ω cm2 at 800°C. TGA reveals a slight loss in weight of about 0.58%, thereby suggesting a highly stable cathode material for IT-SOFC. Electrochemical investigation shows that NBZFO has good electronic and ionic conductivity and excellent oxygen stichometry. Further studies are required to understand the effects of varying B-site composition of the cathode material.

High-speed laser cladding (Fe,Cu)-dopped Ni-Co protective coatings for SOFC MICs: From long-term oxidation behavior to mechanical stability

The long-term operation of intermediate temperature-solid oxide fuel cells (IT-SOFCs) could be significantly influenced by the stability of the interconnect itself, especially, its oxidation resistance under the cathode environment. To effectively prevent Cr-volatilization and improve the interconnector performance, application of highly dense and stable protective coatings over the interconnector is indispensable. In this work, Ni-Co-based alloy protective coatings doped with Fe and Cu were applied onto the 441 interconnector via a novel high-speed laser cladding technology. The microstructure evolution, phase composition, oxidation resistance, electrical conductivity and mechanical properties of the coated steels were investigated at different oxidation stages at 800 °C. It was found that the Ni33.8Co34Fe32.2-coated steel shows the best oxidation resistance and electrical properties. The oxidation rate (kp) and ASR of Ni33.8Co34Fe32.2-coated steel is respectively 4.44 × 10−13 g2 cm−4 s−1 and 25.55 mΩ cm2, significantly lower than the uncoated steel and Ni44.6Co44.7Cu10.7-coated steel at the end of 1000-h test cycle. The resultant conductivity of the Ni44.6Co44.7Cu10.7 and Ni33.8Co34Fe32.2-coated steels is approximately 7.8 and 4.1 S cm−1, respectively, which could meet the requirement for SOFC stacks. In addition, the nano-hardness of the Ni33.8Co34Fe32.2 and Ni44.6Co44.7Cu10.7-coated steels was found to be 8.3 GPa and 8.8 GPa, respectively, through nanoindentation testing. The improved surface hardness is attributed to grain refinement and increased oxide content on the coating surface. The results indicated that the Ni-Co-based alloy coatings effectively improved the long-term stability and mechanical property of the 441 interconnector under the SOFC cathode environment.

Exploring the defect formation and ionic migration in A2Zr2O7 (A = La, Ce, Nd, and Gd) Pyrochlore solid-state electrolytes

This study investigated the potential of A2Zr2O7 pyrochlore phase oxides (A = La, Ce, Nd, and Gd) as solid oxide fuel cell (SOFC) electrolyte materials. A2Zr2O7 ceramics were synthesized using the sol-gel process, and their disordered pyrochlore structure was confirmed by X-ray Diffraction and Rietveld refinement. Field Emission Scanning Electron Microscopy (FE-SEM) was used to examine the morphology of the materials, while X-Ray Photoelectron Spectroscopy (XPS) confirmed a high oxygen ion concentration. UV–Vis Diffuse Reflectance Spectroscopy (DRS) and density of states calculations consistently showed similar bandgap patterns in all zirconate pyrochlore. Density Functional Theory (DFT) simulations provided insights into the electronic structure and migration pathways. A two-probe conductivity study confirmed the relation between the ionic conductivity and ordering degree of pyrochlore. At 750 °C, LZO, CZO, and GZO exhibited ionic conductivity values of 5.44 × 10−3 S/cm, 3.00 × 10−3 S/cm, and 2.01 × 10−3 S/cm respectively, while NZO demonstrated a conductivity of 1.27 × 10−2 S/cm at 700 °C, which is higher than that of the other samples. This study favours the use of the sol-gel route for processing zirconate pyrochlore materials, highlighting its ability to achieve high densities at lower temperatures and exhibit enhanced ionic conductivity. A2Zr2O7 has emerged as a promising oxide-ion conducting solid electrolyte for intermediate temperature SOFC applications within the 600–750 °C temperature range.

Improved ionic conductivity of Ca-doped and Ca-La co-doped ceria electrolytes for intermediate temperature solid oxide fuel cells

Improved ionic conductivity of electrolytes is necessary for solid oxide fuel cells, meant for the development of efficient and clean energy devices. This study is focused on the enhancement of ionic conductivity in Ca-doped and Ca-La co-doped cerium oxide (ceria) electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The co-doped ceria electrolytes, LCDC20 (Ce0.8La0.1Ca0.1O2−δ), exhibited enhanced ionic conductivity of 1.06 ×10−1 S cm−1 at 1073 K, when compared to conventional yttria-stabilized zirconia (YSZ) electrolytes, and has lower activation energy of 1.02 eV. Also, these co-doped electrolytes showed decreased sintering temperatures, which amounts to cost-effective electrolyte materials for IT-SOFCs.

Sr0.90Ba0.10Co0.95Ti0.05O3-δ cathode as an improved electrode for IT-SOFCs

The novel perovskite Sr0.90Ba0.10Co0.95Ti0.05O3-δ has been designed as cathode material to be used in intermediate-temperature solid oxide fuel cells (IT-SOFC). To enlarge the unit-cell size and enhance oxygen diffusion, Sr atoms have been partially substituted by a 10 % of Ba. This new compound was characterized through X Ray Diffraction (XRD) unveiling a tetragonal phase at RT. An in situ Neutron Powder Diffraction (NPD) study between RT and 800 °C showed a transition to a cubic perovskite at 400 °C, which was also noticeable in the thermogravimetric analysis (TGA) and dilatometric analysis. Adequate chemical and mechanical compatibility were achieved with the components of the cell. Electrical conductivity peaked at 400 °C, with values over 200 S cm−1, where it changed its behavior from semiconductor-like to insulator. Finally, polarization resistances as low as 0.062 Ω cm−2 were obtained for the working temperature of the cell in a symmetric cell, associated with the excellent power densities of 564 and 752 mW cm−2 obtained at 850 °C using pure H2 as fuel for the conventional test fuel cell and in a Pd-infiltrated one.

Effect of Mg-doping on electrochemical performance of PrBaFe2O5+δ cathode materials for solid oxide fuel cells

PrBaFe2O5+δ (PBF) is one of the promising cathode materials for intermediate-temperature solid oxide fuel cell (IT-SOFC) technology. However, as the operating temperature decreases, the electrochemical performance of this material deteriorates rapidly. To counter this, various doping strategies have been tested and reported in order to improve the electrochemical properties of this material at intermediate-temperatures. In this study, Mg-doping to partially substitute Fe of PBF was investigated. PrBaFe2–xMgxO5+δ (PBFMgx, x=0.1, 0.15, 0.2, 0.3) materials were successfully synthesized, and their electrochemical performance as IT-SOFC cathode was evaluated. It is shown that Mg-doping enhances the conductivity of PBF between 650–800 °C, impacts little on the area-specific resistance of oxygen reduction reaction at and above 700 °C, and, most significantly, improves the power density of the Ni-SDC/SDC/PBFMg0.15 single cell by 52% compared to the un-doped PBF. This enhanced electrochemical performance is attributed to the improvement in PBF conductivity by Mg-doping.

Enhancement of redox cycling stability of Ni/GDC cermets for intermediate-temperature SOFC anodes through Ge incorporation in the ceramic phase

In this study, Ge4+ was incorporated into the ceramic matrix of nickel-based anode materials, synthesizing anode materials NiO-Gd0.1Ce0.9-xGexO1.95 (x = 0.01, 0.04, 0.07) and NiO-Ce0.9Gd0.1O2–δ. Corresponding anode support samples were also prepared, designated as A-CGDC, A-C1Ge, A-C4Ge, and A-C7Ge. Additionally, single cell samples using the newly co-doped anode materials were prepared, identified as C-CGDC, C-C1Ge, C-C4Ge, and C-C7Ge. The research indicates that after doping the ceramic phase framework with Ge4+, these composite anode materials exhibit the potential to withstand more redox cycles than C-CGDC without catastrophic mechanical structural damage or degradation in electrochemical performance. Particularly, after incorporating 7mol% Ge4+ into the ceramic backbone, the issue of 86 % strain accumulation in the anode support was mitigated. Additionally, the ion doping ratio is closely linked to the stability of the single cell samples, with the A-C7Ge sample able to withstand up to 11 extreme recycling sessions at 700 °C without complete structural failure, improving structural stability by approximately 57 % compared to A-C1Ge. In terms of electrochemical output performance, the impedance of C-C1Ge prior to complete failure was nearly double that before oxidation-reduction, with a maximum power density reduction of about 26.47 %. As the co-doping concentration in the ceramic phase reached 7mol%, the impedance increase during single cell cycle testing was about four times smaller, with C-C7Ge 's impedance before mechanical failure only 37 % higher than before cycling, and a reduction in maximum power density of just 11.11 %. Moreover, during consecutive cycling tests, the average damage to the open-circuit voltage was only 0.02V, showing almost no negative impact from the cycling operations, and it maintained efficient output performance after multiple cycles. Therefore, the newly synthesized nickel-based anode materials, modified via co-doping methods within the ceramic phase, can be considered as potential composite anode materials for intermediate-temperature solid oxide fuel cells.

Prevention of morphological change for (Ba,Sr)(Co,Fe)O3 cathodes by incorporating (Ce,Gd)O2 for intermediate-temperature solid oxide fuel cells

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) generally exhibits superior cathode activity compared to La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, the chemical stability of BSCF is inferior to that of LSCF. When BSCF cathodes are sintered at a high temperature of 1050 °C, performance was compromised due to the formation of (Ba,Sr)ZrO3 between the scandia-stabilized zirconia (ScSZ) electrolyte and gadolinia-doped ceria (GDC) interlayer. The oxide ionic conductivity of (Ba,Sr)ZrO3 was low, decreasing the cathode performance. Furthermore, the BSCF grains enlarged, and cobalt oxide formed due to BSCF decomposition, decreasing the active specific surface area. However, by incorporating GDC into the BSCF cathode, the morphology remained unchanged and cobalt oxide formation was prevented, despite (Ba,Sr)ZrO3 still forming. The performance of the cell with the BSCF-GDC composite cathode surpassed that with the BSCF cathode due to decreased polarization resistance attributed to the oxygen surface exchange and diffusion processes in the cathode.

Improved electrochemical performance of high-entropy La0.8Sr0.2FeO3-based IT-SOFC cathode

It is widely accepted that solid oxide fuel cells (SOFCs) have the potential to be the most efficient and cost-effective system for the direct conversion of various fuels into electricity with low environmental pollution and high efficiency. Herein, we demonstrate a novel Fe-based high-entropy perovskite oxide as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The high-entropy perovskite La0.2Pr0.2Sm0.2Nd0.2Sr0.2FeO3-δ (HE-LSF), composed of La, Pr, Nd, Sm, and Sr is prepared by incorporating five components into the A-site of La0.8Sr0.2FeO3-δ (LSF). Doping of Pr, Nd, Sm, and Sr into the A-site significantly enhances the redox stability of LSF and restrains the surface Sr-segregation in both oxidizing and reducing conditions. The electrode polarization resistance of the anode-supported single cell with HE-LSF cathode is significantly low at intermediate temperature. Meanwhile, at 800 °C, the power density is 1029.2 mW/cm2, and the polarization resistance (Rp) is 0.101 Ω cm2, while at 700 °C, the power density is 581.52 mW/cm2 with an Rp of 0.21 Ω cm2 in humidified H2. Further, the HE-LSF cathode presents good and long-term stability at a constant voltage of 0.7 V for 100 h at 700 °C. The excellent electrochemical performance and stability results exhibit that Fe-based high-entropy perovskite oxide is a new promising candidate and cathode material for SOFCs at intermediate temperatures.

Synthesis and characteristics of densified GDC-LSO composite as a new apatite-based electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFC)

Developing solid-state ionic conductors with desirable charge-transport efficiency and reasonable durability is a fundamental and long-lasting challenge for solid-oxide fuel cells (SOFCs). Ceria-based electrolytes, as one of the most common types of electrolytes for intermediate-temperature solid-oxide fuel cells (IT-SOFCs), offer a high surface-exchange coefficient and faster kinetics in the triple phase boundaries (TPBs); however, they suffer to some extent of electronic conductivity in the reducing atmosphere and gradual phase transitions. Here in this work, we have reported a novel co-doped IT-SOFC electrolyte composite combining the apatite structure of Lanthanum Silicate (LSO) with the fluorite structure of Gadolinium-doped Ceria (GDC), which showed a high ionic conductivity and a minimal electronic leak. The resulting GDC-LSO composite electrolyte also achieved an OCV (open-circuit voltage) of 1 V at 800 °C, implying a significant improvement in the OCV values reported for the typical ceria-based electrolytes (∼0.75 V). The sample was prepared using 40 wt% GDC and 60 wt% LSO (40GDC-60LSO) showed a maximum electrical conductivity of 25 mS cm−1 at 800 °C with good densification properties (>95 % relative density). The cell electrochemical performance measurement was conducted using a 3.0 vol% humified H2 stream at the anode side while the cathode side was exposed to the air at 800 °C. The interdiffusion of cations between La3+ in the LSO phase and Ce4+ and Gd3+ in the GDC phase was detected by XRD and EDX results after sintering samples at 1500 °C for 4 h using 0.5 wt% PVA or 0.5 wt% Ethyl cellulose (EC) as the binder. The proposed GDC-LSO composite could help better understand the influence of compositional constituents and processing variables on the densification and electrical properties of the electrolyte materials for the IT-SOFCs.

Reconstituting the microstructural properties and ionic conductivity of copper - doped yttria-stabilized zirconia via mechanochemical synthesis for intermediate-temperature solid oxide fuel cell applications

The development of highly conductive and thermally stable solid electrolytes is crucial for the next generation of intermediate temperature solid oxide fuel cells (IT-SOFCs). This study investigates the influence of copper (Cu) doping on the microstructure and ionic conductivity of 8 mol. % yttria-stabilized zirconia (8YSZ) when sintered at lower temperatures. The mechanochemical synthesized 1, 3, and 5 wt. % Cu-doped 8YSZ compacts were extensively characterized their properties through a suite of analytical techniques like X-ray diffraction, Raman, X-ray photoelectron, UV–Vis diffused reflectance, particle size analyzer, BET surface area, Emission Scanning Electron Microscopy-Energy Dispersive X-Ray, and AC impedance. The results revealed enhanced ionic conductivity and sinterability, at reduced temperature of 1373 K, with the 5 wt. % Cu-doped 8YSZ demonstrating the highest ionic conductivity of 4.18 × 10−3 S cm−1 at 1023 K, alongside reduced activation energy of 1.14 eV. The lower sintering temperatures and consequential benefits in performance metrics suggest Cu-doping as an effective strategy for optimizing 8YSZ-based electrolytes lowering SOFC manufacturing costs without compromising performance for IT-SOFCs.

Ca-Doping Cobalt-Free Double Perovskite Oxide as a Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cell.

Mixed oxygen ion and electron-conducting materials are viable cathodes for solid oxide fuel cells due to their excellent oxygen transport kinetics and mixed electrical conductivity, which ensure highly efficient operation at low and medium temperatures. However, iron-based double perovskite oxides usually exhibit poor electrocatalytic activity due to low electron and oxygen ion conductivity. In this paper, Ca is doped in PrBaFe2O5+δ A-site to improve the electrochemical performance of PrBaFe2O5+δ. Results show that replacing Pr with Ca does not change the crystal structure, and the Ca doping effectively increases the adsorbed oxygen content and accelerates the migration and diffusion rate of O2- to the electrolyte|cathode interface. The polarization resistance of the symmetric cell PC0.15BF|CGO|PC0.15BF is 0.033 Ω·cm2 at 800 °C, which is about 56% lower than that of PBF, confirming the enhancement of the mixed conduction of oxygen ions and electrons. In addition, the anode-supported single cell has a peak power density of 512 mW·cm-2 at 800 °C.

Investigation of the properties of layered perovskite materials with varying constituent elements as SOFC cathodes

Layered perovskite materials are gaining attention as electrode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). This study explores the incorporation of various elements into the lanthanide, alkaline earth, and transition metal sites within the layered perovskite crystal structure to create diverse compositions. Structural stability and O-ion conduction performance were evaluated through simulations employing a deep learning-assisted approach. Results indicate that at the simulation temperature of 1000 K, the Sm–Sr–Co composition displays structural instability, while the La–Sr–Fe and Sm/Gd–Ba–Fe compositions exhibit decreased O-ion conductivity attributed to phase transitions, rendering them unsuitable for SOFC cathodes. Conversely, the Pr–Ba–Co and La–Sr–Co compositions demonstrate structural stability along with the highest O-ion conductivity, suggesting further exploration of these materials. Additionally, compositions such as Sm/Gd–Ba–Co, Gd–Sr–Co, La–Ba–Fe, and Sm–Sr–Fe, which exhibit structural stability and reasonable O-ion conductivity, may also merit consideration as potential candidates.

Turning bad into good: A medium-entropy double perovskite oxide with beneficial surface reconstruction for active and robust cathode of solid oxide fuel cells

The cathodes of solid oxide fuel cells (SOFCs) often suffer from detrimental cation segregations and associated impurities poisoning, leading to insufficient electroactivity and poor stability. Here we developed a medium-entropy double perovskite GdBa(Co1.2Mn0.2Fe0.2Ni0.2Cu0.2)O5-δ (ME-GBCO) for promising SOFC cathode. The increased configuration entropy can effectively tailor the surface composition with in situ formed active BaCoO3-δ (BCO) species, rather than inert and deleterious BaOx segregation on parent GdBaCo2O5-δ (GBCO) surface. Accordingly, the layered ME-GBCO cathode with beneficial surface reconstruction exhibited not only high oxygen reduction activity but excellent durability against CO2 impurity, enabling it a very attractive cathode for intermediate temperature SOFCs (IT-SOFCs). Our study provides a new idea for development of efficient and durable cathodes via configurational entropy induced rational surface reconstruction.

Impact of electrical conductivity and the electrochemical performance of La2NiO4+δ and La4Ni3O10±δ cathodes on symmetric cells for intermediate-temperature SOFCs

Impact of electrical conductivity and the electrochemical performance of La2NiO4+δ and La4Ni3O10±δ cathodes on symmetric cells for intermediate-temperature SOFCs

Role of charge-compensation process on the structural, microstructure and electrical properties of pure and Nb-doped Sr2SnO4

This article explores the charge compensation method by synthesising Sr2SnO4, Sr2Sn0.99Nb0.01O4, and Sr1.995Sn0.99Nb0.01O4. The synthesis of a monophasic, tetragonal sample was achieved using a typical ceramic approach and high-temperature heat treatment. The XRD followed by Rietveld refinement, confirmed the crystallization of material under the space group I4/mmm. The crystallite sizes for all samples determined to be less than 50 nm, while the micro-strain falls within the range of (1.78–2.93) × 10–3. The microstructure exhibits a cuboidal shape for all samples, and the grain size is observed to decrease with the addition of Nb. The dielectric characteristics of the samples indicate the existence of Maxwell-Wagner and Orientational polarization in the sample. The sample Sr2Sn0.99Nb0.01O4 demonstrates a greater conductivity value compared to Sr1.995Sn0.99Nb0.01O4. This is attributed to the presence of excess electrons that compensate for the overall charge, as opposed to Sr1.995Sn0.99Nb0.01O4 where the extra charge is compensated by a cationic vacancy VSr″. The time-temperature-superposition principle (TTSP) is applicable to all compositions and indicates that similar sources are responsible for both conduction and relaxation processes. The dielectric permittivity and dissipation factor are found to be in the range of 150 to 175 and 0.2 to 0.5, respectively. This suggests that they have potential for future use in millimeter-wave communication with dielectric resonator antennas (DRAs). Due to the presence of oxygen ions and the ability to conduct both ions and electrons, at temperatures above 400 °C, it is a suitable choice for electrode materials in the application of intermediate temperature solid oxide fuel cell (IT-SOFCs). Exploring the manipulation of defects using electrical and ionic charge compensation methods shows potential for enhancing materials in semiconductor technology.

Evaluation of selected Fe–Cr steels under single- and dual-atmosphere conditions for intermediate-temperature solid oxide fuel cell interconnect applications

For Intermediate-Temperature SOFC, the lower operating temperature allows for a broader range of steel grades to be used as interconnects. This work compares the oxidation performances of six Cr2O3-forming steels and one Al2O3-forming steel, under single- and dual-atmosphere conditions.Single-atmosphere exposures in combination with Cr(VI) evaporation measurements were carried out at 600 °C. Except for AISI 430 all the Cr2O3-forming steels showed protective behaviour with similar Cr(VI) evaporation values and low area specific resistance (ASR) values. Kanthal EF101 showed the lowest level of Cr(VI) vaporisation but substantially higher ASR values.Dual-atmosphere exposures were carried out at 600 °C in Ar-5%H2–3%H2O//air-3%H2O. All Cr2O3-forming steels suffered various degrees of breakaway corrosion. Therefore, operation under dual-atmosphere conditions is likely the life-time-limiting failure mode.

CO2-tolerant and cobalt-free La4Ni3-xCuxO10±δ (x = 0, 0.3, 0.5 and 0.7) cathodes for intermediate-temperature solid oxide fuel cells

Cu is doped to La4Ni3O10±δ to improve its electrochemical performance as a potential intermediate-temperature solid oxide fuel cell (IT-SOFC) cathode material. A new higher-order Ruddlesden-Popper (R-P) phase composition La4Ni3-xCuxO10±δ, (L4N3-xCx, 0.0 ≤ x ≤ 0.7) is synthesized using an EDTA-citrate process. The L4N3-xCx cathode has a good chemical compatibility with the La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte. A thermodynamic stability test shows that L4N3-xCx is stable after 72 h exposure to 600, 700, and 800 °C in air. The L4N3-xCx cathode shows chemical stability against CO2, and a stable structure over 12 h in CO2 has been demonstrated. The thermal expansion coefficients (TECs) have been determined to be in the range of 14.1–14.6 × 10−6 K−1, close to that of the LSGM electrolyte. The Cu content (x) significantly affects the electrical conductivity and sinter density of L4N3-xCx. La4Ni2.7Cu0.3O10 (L4N2.7C0.3) displays the highest electrical conductivity value of which reaches about 383 to 319 S cm−1 at 600–800 °C. In addition, Cu doping improves the electrochemical performance of L4N3-xCx. The area specific resistance (ASR) of the La4Ni2.5Cu0.5O10 (L4N2.5C0.5) cathode was found to be 0.045 Ω cm2 at 800 °C, which is significantly better than that of L4N3. The peak power density of a single cell using the L4N2.5C0.5 cathode is 526 mW cm−2 at 800 °C, and a 200 h long-term test demonstrates good stability. These results indicate that La4Ni3-xCuxO10±δ cathode is a promising cathode material for IT-SOFCs.

Novel spinel based high entropy oxide as electrode for symmetric SOFCs

Fabrication of symmetric electrodes for intermediate temperature SOFCs can significantly reduce fuel cell production costs without compromising efficiency. Herein, we report a novel spinel based high entropy oxide (CuLiFeCoNi)1.4Mn1.6O4-δ (CM-HEO) that exhibit better symmetric electrode properties than the parent spinel oxide, Cu1.4Mn1.6O4-δ (CM). The prepared HEO exhibited good structural and thermal stability up to 800 °C as inferred from the XRD, Raman and TGA-DSC results. Temperature-programmed reduction and desorption profiles of CM-HEO outperformed CM by exhibiting hydrogen adsorption and lower CO2 desorption across different temperature ranges. The enhancement of Lewis acid-base sites is evident from the XPS analysis validating the observed increase in HOR and ORR activity. The high electrocatalytic activity of the material arise from its lower activation energies (0.27 eV in air, 0.09 eV in dry H2 and 0.03 eV in dry CH4) with a polarisation resistances of 0.152 Ωcm2 under ambient atmosphere and 0.044 Ωcm2 under dry H2. These findings exalt CM-HEO as an efficient symmetric SOFC electrode material.

Structural, thermal, surface, and electrical properties of Bi2O3 ceramics co–doped with Er–Ho–Tb rare earths

Face–centered cubic–Bi2O3 (δ–phase) material is a better ion conductor when compared to other types of solid electrolytes that have been declared in the literature due to its anion–defective crystal configuration, and hence it can be a promising solid electrolyte choice for intermediate temperature SOFC applications. In this research, Er–Ho–Tb co–doped Bi2O3 compounds were successfully synthesized by the solid–state reaction method and characterized using the XRD, TG & DTA, FPPT, and FE–SEM techniques. Apart from sample 4Er4Ho4Tb, each sample became stable with a cubic δ–phase at room temperature, according to XRD patterns. The DTA curves revealed no exothermic or endothermic peaks, implying a phase change in the constant heating cycle. The conductivity of Ho–rich compositions was higher than that of others, confirming the impact of cation polarizability on conductivity. In addition, at 700 °C, the sample 4Er8Ho4Tb with 1:2:1 content ratios had the highest conductivity of 0.29 S/cm. The porosity on the grain boundaries increased with doping, leading to higher grain boundary resistance, which could be responsible for the conductivity drop.