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Designing high-performance cathodes is crucial for proton-conducting solid oxide fuel cells (H-SOFCs), as the cathode heavily influences cell performance. Although manganate cathodes exhibit superior stability and thermal compatibility, their poor cathode performance at intermediate temperatures renders them unsuitable for H-SOFC applications. To address this issue, Sc is utilized as a dopant to modify the traditional La0.5Sr0.5MnO3 cathode at the La site. Although the solubility of Sc at the La site is restricted to 2.5%, this modest quantity of Sc doping can improve the material's oxygen and proton transport capabilities, hence improving cathode and fuel cell performance. Furthermore, when the doping concentration exceeds 2.5%, the secondary phase ScMnO3 forms in situ, resulting in La0.475Sc0.025Sr0.5MnO3 (LScSM)+ScMnO3 nanocomposites. Although the secondary phase is often considered undesirable, the high protonation capacity of ScMnO3 can compensate for the low proton diffusion ability of LScSM. These two phases complement each other to provide high-performance cathodes. The nominal La0.4Sc0.1Sr0.5MnO3 is the optimal composition, which takes advantage of the excellent electronic conductivity and fast oxygen diffusion rates of LScSM, as well as the good proton diffusion capacity of ScMnO3, to produce a high fuel cell output of 1529 mW·cm−2 at 700 °C. Furthermore, the fuel cell exhibited good operational stability under working conditions, indicating that La0.4Sc0.1Sr0.5MnO3 is a viable cathode choice for H-SOFCs.

In this study, the electrical conductivity and electrochemical performance of Ba 3 Ca 1.18 Nb 1.82 O 9−δ were improved by substituting niobium (Nb) element with bismuth (Bi) and ytterbium (Yb) elements. Three different proton conductors, namely, Ba 3 Ca 1.18 Nb 1.82 O 9−δ (BCN), Ba 3 Ca 1.18 Nb 1.72 Bi 0.1 O 9−δ (BCNB), and Ba 3 Ca 1.18 Nb 1.72 Yb 0.1 O 9−δ (BCNYb) were prepared by solid state sintering. The electrochemical performance of BCNYb was found to be the best at 400–800 °C in the wet atmosphere. Their ion transport properties were studied by using the defect equilibrium model. The results show the improvement in proton conductivity of BCNYb. Analysis of distribution of relaxation time reveals the improvement in the grain boundary properties of BCNYb. Single cells were prepared with BCN, BCNB, and BCNYb electrolytes, and the performance of the resulting fuel cells was tested. The BCNYb-based fuel cell shows excellent electrochemical performance, indicating its promising potential as a solid-state electrolyte with excellent properties. [ABSTRACT FROM AUTHOR]

Perovskite-type proton conductors exist in two structural forms, ABO3 and A 2 B ′ B ″ O 6 . In this study, novel A-site double-perovskite proton conductors ( A ′ A ″ B 2 O 6 ) were proposed. Na1+xLa1-xZr2O6-δ (x = 0, 0.1, 0.2) perovskites were prepared by a solid-state reaction at 1200 °C. However, raising the sintering temperature to 1300 °C resulted in the Na to volatilize, converting the Na1.1La0.9Zr2O6-δ into La0.9Zr2O6-δ. The conductivities of these materials in a humid atmosphere were tested using electrochemical impedance spectroscopy, and their carrier transport numbers were measured using the defect equilibria model and concentration cell method. Na1.1La0.9Zr2O6-δ and Na1.2La0.8Zr2O6-δ are predominantly proton conductors, with Na1.1La0.9Zr2O6-δ exhibiting the highest proton transport number of 0.52 at 800 °C. In contrast, NaLaZr2O6 is predominantly an electronic conductor, while La0.9Zr2O6-δ functions as an oxide ion conductor. Due to their high protonic transport numbers, these Na1+xLa1-xZr2O6-δ A-site double-perovskite oxides present a promising avenue for the development of proton conductors. [ABSTRACT FROM AUTHOR]

Ba0.9Sr0.1Ce0.4Zr0.6−xYbxO3−δ(x = 0.05, 0.1, 0.15, 0.2) proton-conducting electrolyte powders were synthesized by the nitrate combustion method. The effects of co-doping of Sr and Yb on the phase composition and electrochemical performance were studied. X-ray diffraction (XRD) results indicate that Sr and Yb were successfully doped into the lattice of BaCe0.4Zr0.6O3, forming a single perovskite phase. The AC impedance technique was used to investigate the total conductivity of the materials under air and water vapor atmospheres at 400–800°C. The results show that BSCZY20 demonstrated the highest electrical conductivity of 0.033 S cm−1 at 800°C in water vapor. This suggests that the co-doping strategy can effectively enhance the conductivity of BaCe0.4Zr0.6O3 proton-conducting material, which provides valuable insight for the development of high-performance proton-conducting solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Fe-doped cobaltite Ca 3 Co 4 O 9 (CCO) is modified to enhance the efficiency of CCO cathodes in protonic ceramic fuel cells (PCFCs). The Ca 3 Co 3.8 Fe 0.2 O 9 (CCFO) material enhances the creation of oxygen vacancies, hydration, and proton migrations, as demonstrated by first-principles calculations. Subsequent investigations show that doping Fe into CCO improves the charger diffusion abilities and maintains compatible thermal expansion. A PCFC with a CCFO cathode demonstrates superior fuel cell performance, reaching 1790 mW cm−2 at 700 °C. This performance surpasses that of a cell with a CCO cathode and sets a new record for layer cobaltite in PCFCs. The composite cathode design hinders the performance of CCFO and CCO cathodes in PCFCs, indicating proton conduction in these oxides. This aligns with first-principles simulations, making them promising cathode options for PCFCs. [ABSTRACT FROM AUTHOR]

Sc is used as a dopant to tailor the traditional Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathode for protonic ceramic fuel cells (PCFCs). Experiments and first-principles calculations are used in this study to explore the influence of Sc-doping on the performance of BSCF cathodes for PCFCs. Sc can only occupy the Co or Fe sites, and doping Sc at the Ba or Sr sites results in the formation of secondary phases. The use of Sc dopant reduces the high thermal expansion of traditional BSCF. More importantly, doping Sc into BSCF reduces the formation of oxygen vacancies while improving hydration and decreasing the proton migration barrier. Doping Sc at the Fe site outperforms doping at the Co site in terms of oxygen vacancy content, hydration capability, and proton migration ability. The new Ba 0.5 Sr 0.5 Co 0.8 Fe 0.1 Sc 0.1 O 3-δ (Sc doped at Fe site) has a high fuel cell performance of 1666 mW cm−2 at 700 °C and a low polarization resistance of 0.033 Ω cm2. The fuel cell performance is superior to that of most BSCF-based PCFCs reported, indicating the efficacy of using the Sc-doping strategy to tailor BSCF and the importance of selecting the appropriate doping site. [ABSTRACT FROM AUTHOR]

Recently it was found that doped barium stannates have proton conductivity and can be used for various electrochemical applications. In this study, we investigated the effect of lutetium doping of the tin sublattice on the functional performance of oxides BaSn 1-х Lu х O 3 (х = 0, 0.05, 0.1, 0.15). Oxides with the concentration of lutetium up to 10% mol. were found to be single-phase, crystallizing in a cubic structure with a space group Pm 3 m. The lattice parameter increases linearly with the concentration of lutetium. The oxide with 15 % mol. of lutetium contains an additional phase of Lu 2 Sn 2 O 7. Electrical conductivity of the oxides was studied by the 4-probe DC method and impedance spectroscopy. Experiments were carried out in H 2 O and D 2 O - containing air atmospheres, as well as under dry air conditions. It was found that electrical conductivity of BaSnO 3 does not depend on humidity, while for Lu-doped oxides tends to decrease with increase in the humidity. Impedance data analysis has shown that change in the humidity mostly affects the grain boundary resistance. It is shown for the first time that the conductivity of BaSn 1-х Lu х O 3-δ in D 2 O-containing air is higher than in H 2 O-containing air, which was explained by the thermodynamic isotope effect. [ABSTRACT FROM AUTHOR]

The need for sustainable energy solutions is steering research towards green fuels. One promising approach involves electrocatalytic gas conversion, which requires efficient catalyst surfaces. This study focuses on developing and testing a hydrophobic octadiene (OD) coating for potential use in electrocatalytic gas conversion. The approach aims to combine a plasma-deposited hydrophobic coating with air-trapping micro- and nanotopographies to increase the yield of electrocatalytic reactions. Plasma polymerisation was used to deposit OD films, chosen for their fluorine-free non-polar properties, onto titanium substrates. We assessed the stability and charge permeability of these hydrophobic coatings under electrochemical conditions relevant to electrocatalysis. Our findings indicate that plasma-deposited OD films, combined with micro-texturing, could improve the availability of reactant gases at the catalyst surface while limiting water access. In the presence of nanotextures, however, the OD-coated catalyst did not retain its hydrophobicity. This approach holds promise to inform the future development of catalyst materials for the electrocatalytic conversion of dinitrogen (N2) and carbon dioxide (CO2) into green fuels.

A Sr-deficiency approach is utilized to adjust the composition of the standard Sr 2-x Fe 1.5 Mo 0.25 Sc 0.25 O 6 (SFMS) material, with the goal of improving the performance of the SFMS cathode in proton-conducting solid oxide fuel cells (H–SOFCs). The Sr-deficiency concentration is restricted to 10% at the Sr site, and an increase in Sr-deficiency leads to the formation of more oxygen vacancies. However, the presence of increased oxygen vacancies does not consistently enhance the diffusion capabilities of charge carriers. The excess of oxygen vacancies impedes the movement of oxygen and protons. The optimal oxygen and proton transport capabilities are achieved when the Sr-deficiency level is set at 5%. Specifically, this is observed in the compound Sr 1.9 Fe 1.5 Mo 0.25 Sc 0.25 O 6 (S1.9FMS). The enhanced oxygen and proton diffusion kinetics enable H–SOFCs to achieve exceptional performance when employing the S1.9FMS cathode, reaching a power density of 1709 mW cm−2 at 700 °C with a low polarization resistance of 0.023 Ω cm2. The fuel cell's output exceeds that of many previously reported H–SOFCs. Furthermore, the fuel cell utilizing the S1.9FMS cathode not only exhibits excellent fuel cell performance but also maintains reliable operational stability. This indicates that employing the Sr-deficiency technique with an appropriate level of deficiency is a successful approach to enhance the cathode performance for H–SOFCs. • A Sr-deficiency approach was used to tailor Sr 2-x Fe 1.5 Mo 0.25 Sc 0.25 O 6 (SFMS). • The Sr-deficient SFMS showed improved oxygen and proton diffusion kinetics. • A high fuel cell performance was obtained with the Sr 1.9 Fe 1.5 Mo 0.25 Sc 0.25 O 6 cathode. • Good stability was retained for the Sr 1.9 Fe 1.5 Mo 0.25 Sc 0.25 O 6 cathode. [ABSTRACT FROM AUTHOR]

One current research direction in proton-conducting solid oxide fuel cells (H–SOFCs) focuses on developing triple-phase conducting cathodes. By optimizing the cerium and indium ratio and adjusting the phase composition of barium ferrate cathode materials, improved power density is achieved in single cells with BaCe 0.21 Fe 0.64 In 0.15 O 3-δ (BCFI15) as the cathode, reaching a peak power density of 1473 mW cm−2 at 700 °C. Density functional theory calculations (DFT) further support that the incorporation of indium through doping effectively reduces the energy barrier for proton transition, thereby enhancing proton absorption capability and electrochemical reactivity. • Self-assembled composite cathodes are obtained by traditional sol-gel method. • Indium doping reduces proton migration barrier energy and improves cathode activation capacity. • Enhanced cell performance is achieved by regulating cathode chemical composition. [ABSTRACT FROM AUTHOR]

Fuel cells can efficiently convert the chemical energy in fuels like hydrogen and methane into electricity and are an important component for the forthcoming hydrogen society. Compared with conventional solid oxide fuel cells (SOFCs) and proton exchange membrane fuel cells (PEMFCs), protonic ceramic fuel cells (PCFCs) using proton conducting solid oxides as the electrolyte operate at intermediate temperature (400–700 °C), enabling the reduction in cost by using inexpensive catalysts and structural materials. In the last couple of decades, the development of electrolyte and electrode materials for PCFCs has seen significant advances, including fabrication of large‐size cells, promoting PCFCs to step out of the lab toward real applications. This review provides a historic overview of the development of proton conducting oxides, summarizes recent progress on the development of electrolyte and electrode materials and large‐size cells, and discusses present problems and challenges ahead. [ABSTRACT FROM AUTHOR]

Hierarchically oriented macroporous NiO–BaZr0.1Ce0.7Y0.2O3−δ (BZCY7) anode‐supporting layer (ASL) was developed using the freeze casting technique. The resulting freeze‐cast structure was analyzed through scanning electron microscopy and X‐ray computed tomography. A thin layer of BZCY7 was utilized as a proton‐conducting electrolyte, whereas La1.9Sr0.1Ni0.7Cu0.3O3−δ –gadolinium‐doped ceria 10% Gd (LSNC–GDC10) was employed and evaluated as cathode layer. The performance of the cell was assessed by means of electrochemical impedance spectroscopy and I–V–P curves at various temperatures. Furthermore, as a point of comparison, a cell with an ASL was prepared using the dry pressing method, incorporating 20 wt.% graphite as a pore‐forming agent. The freeze‐cast anode‐supported cell demonstrated a polarization resistance of 1.45 Ω cm2 at 550°C and 0.29 Ω cm2 at 750°C. Maximum achieved power densities were 0.189 and 0.429 W cm−2 at 550 and 750°C, respectively. For the cell fabricated by the dry pressing method, the maximum power densities were 0.158 and 0.397 W cm−2 at 550 and 750°C, respectively. Additionally, the tortuosity factor of the anode layer and the gas diffusion streamline in the direction of solidification were determined by using 3D X‐ray tomography imaging and subsequent image processing. [ABSTRACT FROM AUTHOR]

Designing a high‐performance cathode is essential for the development of proton‐conducting solid oxide fuel cells (H‐SOFCs), and nanocomposite cathodes have proven to be an effective means of achieving this. However, the mechanism behind the nanocomposite cathodes' remarkable performance remains unknown. Doping the Co element into BaZrO3 can result in the development of BaCoO3 and BaZr0.7Co0.3O3 nanocomposites when the doping concentration exceeds 30%, according to the present study. The construction of the BaCoO3/BaZr0.7Co0.3O3 interface is essential for the enhancement of the cathode catalytic activity, as demonstrated by thin‐film studies using pulsed laser deposition to simulate the interface of the BCO and BZCO individual particles and first‐principles calculations to predict the oxygen reduction reaction steps. Eventually, the H‐SOFC with a BaZr0.4Co0.6O3 cathode produces a record‐breaking power density of 2253 mW cm−2 at 700°C. [ABSTRACT FROM AUTHOR]

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By modifying the proton conductor BaTbO 3 with the element Co, it is discovered that the solubility of Co in BaTbO 3 is restricted to 20 mol.%, and phase segregations happen for high Co doping concentrations in BaTbO 3. The fabrication of nominal BaTb 0.5 Co 0.5 O 3 results in the in-situ development of the heterostructure cathode composed of BaTb 0.8 Co 0.2 O 3 +BaCoO 3. The critical role of the interface between BaTb 0.8 Co 0.2 O 3 and BaCoO 3 in enhancing fuel cell performance is to accelerate charge transfer kinetics, thereby enabling proton-conducting solid oxide fuel cells (H-SOFCs) to operate at higher performance levels than cells employing BaTb 0.8 Co 0.2 O 3 or BaCoO 3 cathodes alone. Furthermore, the favorable chemical stability of the BaTb 0.8 Co 0.2 O 3 +BaCoO 3 nanocomposite is maintained, thereby enhancing the fuel cell's operational stability. This research suggests that unanticipated phase segregation may occasionally improve the performance of the cathode, thereby presenting an interesting approach to cathode design in H-SOFCs. [ABSTRACT FROM AUTHOR]

Nb-doped SrFeO3−δ (SFO) is used as a cathode in proton-conducting solid oxide fuel cells (H-SOFCs). First-principles calculations show that the SrFe0.9Nb0.1O3−δ (SFNO) cathode has a lower energy barrier in the cathode reaction for H-SOFCs than the Nb-free SrFeO3−δ cathode. Subsequent experimental studies show that Nb doping substantially enhances the performance of the SrFeO3−δ cathode. Then, oxygen vacancies (VO) were introduced into SFNO using the microwave sintering method, further improving the performance of the SFNO cathode. The mechanism behind the performance improvement owing to VO was revealed using first-principles calculations, with further optimization of the SFNO cathode achieved by developing a suitable wet chemical synthesis route to prepare nanosized SFNO materials. This method significantly reduces the grain size of SFNO compared with the conventional solid-state reaction method, although the solid-state reaction method is generally used for preparing Nb-containing oxides. As a result of defect engineering and synthesis approaches, the SFNO cathode achieved an attractive fuel cell performance, attaining an output of 1764 mW·cm−2 at 700 °C and operating for more than 200 h. The manipulation of Nb-doped SrFeO3−δ can be seen as a “one stone, two birds” strategy, enhancing cathode performance while retaining good stability, thus providing an interesting approach for constructing high-performance cathodes for H-SOFCs.

Different transition metals are employed to tune the Y-doped BaZrO 3 proton conductor, resulting in the new BaZr 0.125 Y 0.125 M 0.75 O 3 (M = Cu, Mn, Ni, Zn, Co, and Fe) compositions as cathodes for proton-conducting solid oxide fuel cells. Only Co and Fe dopants can yield pure phases, whereas the use of other dopants results in impurities. Further experimental studies and first-principles calculations show that using Fe dopant has some advantages over Co-doped material, such as increased oxygen vacancies, lower proton migration energy barriers, and faster proton and oxygen diffusion kinetics. The fuel cell employing the BaZr 0.125 Y 0.125 Fe 0.75 O 3 (BZYFe) cathode has a larger fuel cell output than the fuel cell using the BaZr 0.125 Y 0.125 Co 0.75 O 3 (BZYCo) cathode. Furthermore, the CO 2 adsorption energy on the BZYFe surface is larger than that at the BZYCo surface, indicating that BZYFe has significantly better chemical stability than BZYCo. The long-term stability of the fuel cell demonstrates that the fuel cell with the BZYCo cathode is degrading. In contrast, the BZYFe cell has good operating stability. Given its phase purity, fuel cell performance, and stability, the Fe element is an appropriate dopant for altering BZY and creating a new cathode. • BaZr 0.125 Y 0.125 M 0.75 O 3 (M = Cu, Mn, Ni, Zn, Co, and Fe) were prepared. • Only Co and Fe dopants can generate pure phases. • BaZr 0.125 Y 0.125 Co 0.75 O 3 and BaZr 0.125 Y 0.125 Fe 0.75 O 3 cathodes yielded similar cell performance. • The cell using BaZr 0.125 Y 0.125 Fe 0.75 O 3 cathode showed better operational stability. [ABSTRACT FROM AUTHOR]

Biological proton channels have perfect selectivity in aqueous environment against almost all ions and molecules, a property that differs itself from other biological channels and a feature that remains challenging to realize for bulk artificial materials. The biological perfect selectivity originates from the fact that the channel has almost no free space for ion or water transport but generates a hydrogen bonded wire in the presence of protons to allow the proton hopping. Inspired by this, we used the interlayer spacings of covalent organic framework materials consisting of hydrophilic functional groups as perfectly selective artificial proton channels. The interlayer spacings are so narrow that no atoms or molecules can diffuse through. However, protons exhibit a diffusivity in the same order of magnitude as that in bulk water. Density functional theory calculations show that water molecules and the COF material form hydrogen bonded wires, allowing the proton hopping. We further demonstrate that the proton transport rate can be tuned by adjusting the acidity of the functional groups. [ABSTRACT FROM AUTHOR]

The present study explores a nano-grained perovskite material for use in an intermediate-temperature solid oxide fuel cell. Electrolytes with the formula Ba1−xCaxCe0.8Nd0.2O3−δ (BCCN), where x = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05, were synthesized through the sol–gel auto-combustion process. Structural, surface morphology and vibrational analyses were conducted through XRD, SEM, FTIR, and Raman studies. Scherer's formula revealed predicted crystallite sizes for the electrolyte materials ranging from 25.13 to 38.69 nm. Morphological assessments determined grain diameters between 1 to 3 µm. Raman spectroscopy identified the 355 cm−1 vibrational mode associated with CeO6 octahedra, while FT-IR identified bands corresponding to M–O vibrations. Electrical impedance spectroscopy results indicated ionic behavior conducive to electrolytes, with overall conductivities increasing with measurement temperature. Notably, bulk conductivity surpassed grain boundary conductivity, with the highest overall conductivity observed in x = 0.05 compositions among the examined perovskite oxides. [ABSTRACT FROM AUTHOR]

To study the electrochemical properties of Yb-doped CaZrO3 in more detail, the CaZr1−xYbxO3−δ (x = 0.000, 0.025, 0.050, 0.075, and 0.100) solid electrolyte specimens were prepared by high-temperature solid-state method at the temperatures of 1523 K and 1873 K for 8 h. XRD, SEM, EDS, and electrochemical workstation were used to test the micromorphology and electrochemical performance of the electrolyte samples. When the doping amount of Yb is 0.05, the electrolyte sample has excellent electrical properties. The total conductivity of electrolyte CaZr0.95Yb0.5O3−δ is 1.13 × 10−5 to 1.28 × 10−3 S/cm and the conductivity activation energy falls in 0.69–1.34 eV in hydrogen and oxygen atmosphere at 973–1173 K. The chemical diffusion coefficient of hydrogen in CaZr0.95Yb0.05O3−δ electrolyte is between 1.55 × 10−6 and 5.82 × 10−6 cm2/s in the temperature range of 973 to 1373 K, and the diffusion activation energy is 12,278 kJ/mol. [ABSTRACT FROM AUTHOR]

Abstract Designing a high‐performance cathode is essential for the development of proton‐conducting solid oxide fuel cells (H‐SOFCs), and nanocomposite cathodes have proven to be an effective means of achieving this. However, the mechanism behind the nanocomposite cathodes' remarkable performance remains unknown. Doping the Co element into BaZrO3 can result in the development of BaCoO3 and BaZr0.7Co0.3O3 nanocomposites when the doping concentration exceeds 30%, according to the present study. The construction of the BaCoO3/BaZr0.7Co0.3O3 interface is essential for the enhancement of the cathode catalytic activity, as demonstrated by thin‐film studies using pulsed laser deposition to simulate the interface of the BCO and BZCO individual particles and first‐principles calculations to predict the oxygen reduction reaction steps. Eventually, the H‐SOFC with a BaZr0.4Co0.6O3 cathode produces a record‐breaking power density of 2253 mW cm−2 at 700°C.

A new medium entropy material LiCo0.25Fe0.25Mn0.25Ni0.25O2 (LCFMN) is proposed as a cathode for proton-conducting solid oxide fuel cells (H-SOFCs). Unlike traditional LiXO2 (X = Co, Fe, Mn, Ni) lithiated oxides, which have issues like phase impurity, poor chemical compatibility, or poor fuel cell performance, the new LCFMN material mitigates these problems, allowing for the successful preparation of pure phase LCFMN with good chemical and thermal compatibility to the electrolyte. Furthermore, the entropy engineering strategy is found to weaken the covalence bond between the metal and oxygen in the LCFMN lattice, favoring the creation of oxygen vacancies and increasing cathode activity. As a result, the H-SOFC with the LCFMN cathode achieves an unprecedented fuel cell output of 1803 mW·cm−2 at 700 ℃, the highest ever reported for H-SOFCs with lithiated oxide cathodes. In addition to high fuel cell performance, the LCFMN cathode permits stable fuel cell operation for more than 450 h without visible degradation, demonstrating that LCFMN is a suitable cathode choice for H-SOFCs that combining high performance and good stability.

BaCe0.65Zr0.2Y0.15O3-δ (BCZ20Y15) has raised great interest due to its good protonic conductivity and chemical stability. However, the sintering of the material is considerably challenged by its refractory nature. In the current work, almost fully densified single-phase BCZ20Y15 with grain sizes exceeding 10 μm was successfully fabricated by sintering at 1500 °C by using calcined powders consisting of naturally separated perovskite phases and 0.5 wt% NiO. The role of NiO as sintering aid was elucidated by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Atom Probe Tomography (APT) methods, concerning global and local material composition. Furthermore, the mechanism leading to the promoted densification and grain growth is elucidated based on current experimental results and a comprehensive review of the literature.

As the third generation of fuel cells, solid oxide fuel cell (SOFC) provides a clean and low-pollution technology. Electrolyte material, which often plays a vital role in SOFC, has always been the focus and difficulty of research. Y-doped barium cerate-based proton conductor electrolyte, BaCe1–xYxO3–δ (x = 0, 0.05, 0.1, 0.15), were prepared using the nitrate-citrate-glycine combustion method. A series of tests and characterizations were performed to examine the structural, morphological, and electrical properties. X-ray diffraction (XRD) analysis proved that the BCY powders with pure cubic perovskite structure were formed after calcined at 1100 °C. SEM results showed that the BCY ceramics sintered at 1350 °C were dense and well-developed grains. The electrochemical performance of BCY proton conductor electrolyte was determined using the electrochemical impedance spectroscopy in dry air and wet air atmosphere at 400–800 °C. Results showed that Y-doped BaCeO3-based material had superior conductivity in air and the conductivity of proton conductor was significantly improved under wet air environment. Furthermore, the electrical conductivity of BCY samples was related to the amount of Y3+ doping. The conductivity in a water vapor environment achieved a maximal value of 0.039 S cm−1 at 800 °C when x = 0.15. So BaCe1–xYxO3-based materials can be used as a proton conductor electrolyte for SOFC in the medium temperature range. [ABSTRACT FROM AUTHOR]

This study proposes a new Pr 0.25 Nd 0.25 Ca 0.5 MnO 3-δ (PNCM) cathode material for protonic ceramic fuel cells (PCFCs). As demonstrated by first-principles calculations, the Ca-doping strategy can promote oxygen vacancy formation and accelerate the oxygen reduction reaction (ORR) compared to the conventional Sr-doping method. Additional experiments reveal the doping of Ca can enhance the proton and oxygen diffusion abilities compared with the traditional Sr-doped material. Consequently, the PCFC with single-phase PNCM cathode produces a high peak power density of 1232 mW cm-2 at 700 °C, which is significantly greater than the cell with Sr-doped cathode, which only produces 749 mW cm-2 under the same testing conditions. The PNCM cathode inherits the excellent stability of manganate cathodes, allowing the fuel cell to exhibit good stability under operational conditions. PNCM is a new and promising cathode material for PCFCs due to its excellent fuel cell performance and stability. [ABSTRACT FROM AUTHOR]

Previous studies have found that in ceramic fuel cells using Ni 0·8 Co 0·15 Al 0·05 LiO 2 (NCAL) as the electrode, lithium compounds such as LiOH generated by reduction of NCAL anode by H 2 diffuse into oxide electrolyte membranes such as Gd 0.1 Ce 0·9 O 2 (GDC), and the "GDC-lithium compounds" composite electrolyte formed online is an excellent proton conductor. In this paper, the low-temperature electrolysis performance of proton conductor type solid oxide electrolysis cell (P-SOEC) with GDC as electrolyte and NCAL as electrode for direct electrochemical conversion of H 2 O into H 2 was investigated. It is found that at operation temperature of 550 °C, the current density of the SOEC prepared in this paper can reach 2.263 A cm−2 at 1.6 V. The composite electrolyte in the electrolysis cell reaches an ionic conductivity of 0.572 S cm−1 in the SOEC mode. The excellent hydrogen production performance proves that this new type of electrolysis cell with lithium compounds as electrodes is a promising and potential proton conductive low-temperature SOEC. • SOEC with NCAL electrodes was fabricated. • Proton conductivity of the composite electrolyte reaches 0.572 S cm−1 at 550 °C. • The electrolytic current density of the SOEC reaches 2.263 A·cm−2 at 1.6 V. • Provided a new type of SOEC and related electrolytic cell material. [ABSTRACT FROM AUTHOR]

In order to improve the properties, alkaline earth element doped La 1.95 M 0.05 Hf 2 O 7-δ (M = Ca, Sr, Ba) are prepared by high-temperature solid state method. The experimental results indicate that Ca is a suitable doping element. The prepared La 2-x Ca x Hf 2 O 7-δ (x = 0, 0.025, 0.05, 0.1) series samples are of pure pyrochlore structures. Among them, La 1.95 Ca 0.05 Hf 2 O 7-δ has the densest structure, the highest conductivity, which is 2.86 × 10−3 S cm−1 in humid air at 800 °C, and outstanding chemical stability in H 2 O, CO 2 , H 2 and 300 ppm H 2 S. The hydrogen separation performance of La 1.95 Ca 0.05 Hf 2 O 7-δ membrane is tested using the external short-circuit method. The hydrogen permeation flux of 1.25 mm thick La 1.95 Ca 0.05 Hf 2 O 7-δ membrane is 0.15 mL·min−1·cm−2 in 70% H 2 /He feed gas at 900 °C. Humidification increases the hydrogen permeation flux and CO 2 or H 2 S reduces the hydrogen permeation flux. Hydrogen separation performance of La 1.95 Ca 0.05 Hf 2 O 7-δ material under external short circuit. [Display omitted] • Ca, Sr or Ba doping improves the sinter ability and conductivity of La 2 Hf 2 O 7. • All the samples display excellent chemical stability under the test conditions. • The Pt/La 1.95 Ca 0.05 Hf 2 O 7-δ /Pt membrane was utilized for hydrogen separation. • The membrane showed excellent resistance to CO 2 and H 2 S interference in utilization. [ABSTRACT FROM AUTHOR]

For the sake of enhance the sinter ability and electrical conductivity of BaZr0.1Ce0.7Y0.2O3‐δ (BZCY) electrolytes, a modified aqueous gel‐casting method was applied to synthesize high sintering active and high conductive BZCY nano‐powders. The new approach makes it easy to obtain pure perovskite. The highly sintering active purity‐phase of BZCY nano‐powder (particle size of 50∼100 nm) was obtained by calcining at 1100°C for 2 h. Nano‐powders effectively reduce the sintering densification temperature and successfully prepare BZCY electrolyte with relative density > 96 % at 1450°C, and promote grain growth with an average grain size of 2.36 μm. Benefiting from this, improved electrical conductivities (e.g., 12.4×10−3 S cm−1 at 700°C, in wet air) are obtained. The NiO‐BZCY/BZCY/LSCF‐BZCY anode‐supporting single cell shows a peak power density of 0.75 W cm−2 at 700°C while taking ambient air as oxidants and wet H2 (∼3 vol.% H2O) as fuels. [ABSTRACT FROM AUTHOR]

Proton‐conducting solid oxide fuel cells (H‐SOFCs) have the potential to be a promising technology for energy conversion and storage. To achieve high chemical compatibility and catalytic activity, nickel‐doped barium ferrate with triple conducting ability is developed as cathodes for H‐SOFCs, presenting an impressive electrochemical performance at intermediate temperatures. The cell performance with the optimized BaCe0.26Ni0.1Fe0.64O3–δ (BCNF10) composite cathode reaches an outstanding performance of 1.04 W cm−2 at 600 °C. The high electrocatalytic capacity of the nickel‐doped barium ferrate cathode can be attributed to its significant proton conductivity which is confirmed through hydrogen permeation experiments. Density functional theory (DFT) calculations are further conducted to reveal that the presence of nickel can enhance processes of hydration formation and proton migration, leading to improve proton conductivity and electro‐catalytic activity. [ABSTRACT FROM AUTHOR]

A perovskite-structured proton conductor, CaHf 0.9 In 0.1 O 2.95 , was synthesized via solid-state reaction, and proton conductivity and transport number of its grain interior were determined by using the defect equilibria model. The results reveal that the total conductivity of grain interior and the entire sample (grains and grain boundaries) of CaHf 0.9 In 0.1 O 2.95 , respectively, reaches 7.26 × 10−4 S∙cm−1 and 3.03 × 10−4 S∙cm−1 in a humid atmosphere at 800 °C. Moreover, it was observed that the conductivities of the grain interior exhibited higher values than those of the entire sample within the temperature range of 400–800 °C. The activation energy of the entire sample was higher than that of the grain interior; and for the charge carriers of CaHf 0.9 In 0.1 O 2.95 , the activation energy of oxygen vacancies and holes was higher than that of the proton. At 400–800 °C, transport properties of CaHf 0.9 In 0.1 O 2.95 were dominated by proton conduction under the atmosphere containing oxygen and water vapor, where the transport numbers of proton in the grain interior and the entire sample were estimated to be 0.541 and 0.497, respectively, at a temperature of 800 °C. Thus, the proton transport number of grain interior was found to be higher than that of the entire sample. Therefore, the grain interior of CaHf 0.9 In 0.1 O 2.95 can provide better proton conduction than grain boundary. In summary, these results exhibit that CaHf 0.9 In 0.1 O 2.95 possesses certain application prospects in electrochemical sensors. [ABSTRACT FROM AUTHOR]

Dopamine plays a significant role in the proper functioning of the central nervous system. Hence, the ability to sense levels of dopamine is pivotal in diagnosis and treatment procedures. For sensing dopamine, a mixed metal oxide nanocomposite (NC) of copper oxide‐nickel oxide/reduced graphene oxide (CuO‐NiO/rGO) is fabricated by the sol–gel method, and it is used to modify the glassy carbon electrode. The structural and morphological characterizations are done by X‐ray diffraction (XRD), Energy dispersive X‐ray (EDAX), Raman, and Scanning electron microscopy (SEM). XRD results exhibit monoclinic CuO, cubic NiO, and hexagonal rGO structures. The Raman studies confirm the D and G bands for rGO. Different electrochemical techniques are used to examine the efficacy of nanocomposite in detecting dopamine. The CuO‐NiO metal oxide NC response compared with the CuO‐NiO/rGO NC shows a better response by rGO containing nanocomposite. Further, the chronoamperometric method is employed, and the diffusion coefficient is calculated as 1.04 × 10−6 cm2 s−1. The differential pulse voltammetry is carried out to measure the nanocomposite's sensitivity and detection limit (LOD). The catalyst exhibits a sensitivity of 7.2 µA cm−2 mM−1 and a LOD of 0.006 µM. The composite can be used as a flexible skin patch sensor to predict abnormal dopamine levels such as Parkinson's disease. [ABSTRACT FROM AUTHOR]

By synthesizing the nominal Pr x Sr 0.5 MnO 3-δ materials (x = 0.5, 0.6, 0.7, 0.8), new Pr 0.5 Sr 0.5 MnO 3-δ (PSM50)+PrO 2−x composite cathodes for proton-conducting solid oxide fuel cells (SOFCs) were developed. The structure analysis and morphology observations verified the exsolution of PrO 2−x particles, and the amount of exsolved PrO 2−x increased with the amount of Pr in Pr x Sr 0.5 MnO 3-δ. An H-SOFC with a Pr 0.7 Sr 0.5 MnO 3-δ (PSM70) cathode enabled the highest reported fuel cell output for H-SOFCs with manganate cathodes. The construction of a PSM50/PrO 2 heterostructure interface can reduce the formation energy of oxygen vacancies, hence accelerating the cathode oxygen reduction reaction (ORR) kinetics, as confirmed by oxygen diffusion and surface exchange experiments. The excellent electrochemical performance was combined with its good chemical stability against CO 2 and H 2 O, allowing a stable operation of the cell for over 100 h, indicating that PSM70, which was in fact PSM50 +PrO 2−x , was a highly efficient and durable cathode material for H-SOFCs. [ABSTRACT FROM AUTHOR]

The effect of Sr deficiency on the hydration process and ionic and electronic conductivity of Yb-doped SrZrO3 proton conductors with a perovskite-type structure was investigated. Dense SrxZr0.95Yb0.05O3-δ (x = 0.94–1.00) ceramics were prepared using solution combustion synthesis. Thermogravimetry and Raman spectroscopy methods were used to determine the concentration of bulk protonic species. Sr deficiency was found to enhance the hydration ability of the zirconate; however, lowering of Sr content to x = 0.94 deteriorated the proton uptake. The conductivity of the SrxZr0.95Yb0.05O3-δ series depending on the oxygen partial pressure at different humidities was studied by the four-probe direct current technique. Sr-deficient ceramics with x = 0.96 and 0.98 were shown to become purely protonic conductors in humid atmospheres at a temperature close to 500 °C. The ionic conductivity reaches its highest value at a Sr content of x = 0.98 (2 × 10−4 S cm−1 at 500 °C and pH2O = 3.17 kPa). The hydration behavior and transport properties of SrxZr0.95Yb0.05O3-δ are discussed in terms of the defect chemistry model that assumes the distribution of Yb ions over Sr and Zr sites at a large Sr deficiency. [ABSTRACT FROM AUTHOR]