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Abstract: Coral‐like, clean PtPd bimetallic nanochains with controlled composition are successfully synthesized by using carbon monoxide as reducing agent and soft‐template. The Pt74Pd26 nanochain catalyst exhibits a much more positive half‐wave potential than pure Pt nanochains (∼35 mV) and commercial Pt/C (∼30 mV) toward the oxygen reduction reaction. Meanwhile, oxygen reduction on the Pt74Pd26 electrode has only a 4 mV degradation in half‐wave potential over 5,000 cycling period, showing superior electrochemical stability. The enhanced performance could be due to the modified electronic structure (such as downshifted d‐band center and weakened bonding to oxygenated species) and the coral‐like nanochains with mesoporous structure and clean surface. This work may demonstrate a universal approach to facilitate screening of high‐efficiency catalysts for broad energy conversion/storage systems and sensing devices. [ABSTRACT FROM AUTHOR]

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]

Pr 1.85 M 0.15 NiO 4+x (M represents Ba, Sr, or Ca) materials were prepared and evaluated as cathodes for protonic ceramic fuel cells (PCFCs). Compared with the Sr and Ba doping methods, the Ca-doping approach slightly enhanced the generation of interstitial oxygen and the surface catalytic activity in Pr 2 NiO 4. Furthermore, Ca-doping decreases the distance between O atoms in the lattice compared with the Sr and Ba-doped Pr 2 NiO 4 , facilitating the movement of charge carriers. Consequently, PCFCs employing Ca-doped Pr 2 NiO 4 cathodes achieve a much greater power density of 1279 mW cm−2 at 700 °C compared to fuel cells employing Sr-doped or Ba-doped Pr 2 NiO 4 cathodes. Furthermore, a PCFC employing a Ca-doped Pr 2 NiO 4 cathode exhibited excellent long-term stability under working conditions and operated continuously for over 280 h without any discernible deterioration. These results indicate that the Ca-doped Pr 2 NiO 4 cathode is a stable and effective candidate for PCFCs. [ABSTRACT FROM AUTHOR]

Co3O4 nanocubes with exposed (001) planes were prepared and employed for use as first-generation Sr-doped LaMnO3 (LSM) cathodes in solid oxide fuel cells to improve the cell performance. Theoretical simulations suggest that the Co3O4 (001) plane has the smallest oxygen adsorption and oxygen dissociation energies compared with other planes, thus favouring cathode reactions in solid oxide fuel cells (SOFCs). Experimental studies consistently demonstrate that a cell using an LSM cathode made with Co3O4 nanocubes with selective (001) surfaces exhibits a peak power density of 500 mW cm−2 at 600 °C, while the power output for a cell using unselective (commercial) Co3O4 nanoparticles is only 179 mW cm−2 at the same temperature. The electrochemical study indicates that the use of Co3O4 nanoparticles with exposed (001) surfaces obviously accelerates the cathode reactions and thus decreases the polarisation resistance, which is the key to improving fuel cell performance. This study demonstrates the feasibility of using the crystal planes of metal oxides to improve the fuel cell performance and provides a new way to design SOFC cathodes. [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]

LaNi 0.5 Fe 0.5 O 3-δ (LNF) is a viable option for the cathode of solid oxide fuel cells (SOFCs), however, its performance in proton-conducting SOFCs (H–SOFCs) is not sufficient. In this work, an Sc-doped method to increase the cathode performance of conventional LNF for H–SOFCs is proposed. Although the Sc cation can be doped at the Ni site or the Fe site in LNF, which led to the formation of pure phase materials, first-principles calculations indicate that the formation of the LaNi 0.4 Sc 0.1 Fe 0.5 O 3-δ (LNSF) material has more advantages than the formation of the LaNi 0.5 Fe 0.4 Sc 0.1 O 3-δ (LNFS) material, even though the same Sc-doping level is employed. Compared to Sc-free LNF, LNSF provides superior fuel cell performance. At 700 °C, the LNSF cell generates a peak power density of 1534 mW cm−2, double that of the LNF cell. In addition, employing the LNSF cathode reduces the cell's polarization resistance, indicating that the Sc-doping strategy paired with selecting the doping site is an effective method for reusing LNF in high-performance H–SOFCs. • Sc cations can be doped at the Fe or Ni sites in LaNi 0.5 Fe 0.5 O 3-δ (LNF). • The site occupation at the Ni site shows advantages compared with that at the Fe site. • Sc-doped LNF shows better performance than the Sc-free one. • The performance of the cell using LaNi 0.4 Sc 0.1 Fe 0.5 O 3-δ is better. [ABSTRACT FROM AUTHOR]

As a cathode material for proton-conducting SOFCs (H–SOFCs), a novel MnCo 1.9 Sb 0.1 O 4 (MCSO) spinel material was suggested. The MCSO material was effectively produced, and it demonstrated excellent phase stability at elevated temperatures and chemical stability against CO 2 and H 2 O. Doping Sb into the MnCo 2 O 4 (MCO) allowed for enhanced proton diffusion and surface exchange, as evidenced by electrical conductivity relaxation tests. In addition, an oxygen-vacancy-rich surface was developed for the MCSO material, resulting in the possibility of a high cathode oxygen reduction reaction activity. The MCSO material was examined in the H–SOFC application, and the fuel cell with an MCSO cathode attained a high power density of 1380 mW cm−2 at 700 °C. At 700 °C, the cell employing the Sb-free MCO cathode, which had a comparable cell microstructure to the MCSO cell, only obtained a peak power density of 836 mW cm−2. The higher cell performance resulted from the Sb-modified MCO cathode's increased catalytic activity. In addition, the MCSO cell displayed excellent operational stability under fuel cell operating conditions, indicating that MCSO is a novel and effective spinel cathode for H–SOFCs. • A new MnCo 1.9 Sb 0.1 O 4 (MCSO) spinel was proposed for H–SOFCs. • Doping Sb into MnCo 2 O 4 (MCO) enhanced proton diffusion and surface exchange. • MCSO improved the cathode activity compared with Sb-free MCO. • A high performance was obtained for the fuel cell using MCSO cathode. [ABSTRACT FROM AUTHOR]

In this study, both cathode powder preparations and fuel cell fabrications for proton-conducting solid oxide fuel cells (H–SOFCs) were performed using the microwave sintering technique. The microwave sintering approach produced Sr 2 Fe 1.5 Mo 0.25 Sc 0.25 O 6-δ (SFMS) cathode particles with a lower phase formation temperature and smaller grain size than the standard muffle furnace sintering method. The advantages of microwave sintering were also recognized during the fuel cell manufacturing process. Using the same electrolyte and anode, conventional sintering and microwave sintering were used to produce SFMS cathodes, resulting in varied fuel cell performance. The fuel cell output of the conventionally sintered cell was 1312 mW cm−2 at 700 °C, whereas the power density of the microwave-prepared cell achieved 1452 mW cm−2 under the same testing conditions, which was also higher than the performance of a number of recently reported H–SOFCs. Surface chemistry research revealed that microwave sintering generated more oxygen vacancies (Vo). Calculations based on first-principles indicated that the greater surface abundance of Vo increased the oxygen reduction reaction (ORR) activity. The benefits of microwave sintering can be discovered in both the powder preparation and cell construction stages, making it an intriguing and simple way to enhance the performance of H–SOFCs. [ABSTRACT FROM AUTHOR]

Electrospinning is the most common and promising method to prepare nanofibers. The nanofibers produced have the advantages of a small average diameter, high specific surface area, and high porosity. In recent years, fibers have been used as cathodes and anodes in solid oxide fuel cells (SOFCs). Owing to the unique microstructure and electron and ion conduction properties of nanofiber electrodes, the electrocatalytic activity is significantly increased, and as a consequence, the electrochemical performance of the fuel cell is substantially improved. This paper mainly reviews the research progress of electrospinning technology in the SOFCs field. In addition, the effects of various processing parameters on the fiber structure are summarized from the perspective of processing variables. The electrodes prepared by the electrospinning method in recent years are primarily introduced. [Display omitted] [ABSTRACT FROM AUTHOR]

• DFT calculations used for H-SOFCs are briefly reviewed. • The advantages of using DFT calculations are clarified. • Limitations and future developments are discussed. Density functional theory (DFT) calculations have been widely used to investigate insights for electrochemical materials, but its application in proton-conducting solid oxide fuel cells has just started a few years ago. Despite the limited time, the DFT calculation is regarded as a powerful tool to anticipate the properties of the proton-conducting oxides with success, bring insights into the material design that promotes the electrochemical performance of the cells. Furthermore, the DFT calculation provides a solution to reveal the potential proton conduction in the cathode materials for proton-conducting solid oxide fuel cells that is difficult to achieve by experimental approaches. However, some limitation for the current DFT application has also been observed. This mini-review briefly documents the application of DFT calculations for the cathodes of proton-conducting solid oxide fuel cells, focusing on the exploration of new cathode materials with high electrochemical performance. Both success stories and the current limitations have been presented, aiming to arouse the attention of the community for this interesting method. [ABSTRACT FROM AUTHOR]

[Display omitted] • The diffusion of Ni from the anode to the electrolyte is revealded for H-SOFC. • The diffused Ni has significnalty influeced the performance of fuel cells. • Microwave sintering can mitigate the Ni diffusion at the interface. • Better performance is obtained with the microwave sintered fuel cell. Although Ni-based anodes are commonly employed in proton-conducting solid oxide fuel cells (H-SOFCs), interfacial diffusion of Ni from the anode to the electrolyte is difficult to avoid, resulting in lower electrolyte and fuel cell performance. In this study, the electrolyte/anode half-cells are co-sintered using a microwave sintering process, providing a lower co-sintering temperature than the standard sintering approach. The lower co-sintering temperature minimizes Ba-evaporation at the electrolyte and mitigates anode/electrolyte interfacial Ni diffusion, resulting in decreased electrolyte and interfacial polarization resistance. The microwave-sintered cell outperforms the traditionally sintered cell in electrochemical performance, with higher fuel cell performance and lower cell resistances. Furthermore, the improved interfacial condition improves the fuel cell's long-term durability, allowing the cell to operate for 200 h without detectable degradation. This study presents an intriguing and simple way to reduce anode/electrolyte interfacial Ni diffusion, which improves fuel cell output and operational stability. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Twisted PdCu nanochains are synthesized successfully via a staged thermal treatment route, offering rich twin boundaries as catalytic "active sites" and modified electronic effects. Toward formic acid oxidation, the twisted PdCu nanochains hold the highest catalytic peak current density (1108.2 mA mg−1 Pd) over previous reported PdCu alloy catalysts, and also much higher catalytic activity and durability comparing with Pd nanochains and commercial Pd/C. The catalytic enhancement mechanism to PdCu nanochains is proposed and discussed. Additionally, we found that the formation of PdCu nanochains follows a typical anisotropic growth approach, and the multiple steps of staged thermal treatment route displays a vital role in fabricating the unique PdCu nanochains while the introduced Cu precursors might affect the reduction rate of Pd species and act as deposition or nucleation sites for twisted structure in terms of rich twin boundaries. This work describes an efficient, low-Pd loading catalyst for electrooxidation of formic acid, and also demonstrates a universal method to fabricate other defect-rich catalysts for broad applications in energy conversion and storage systems and sensing devices. [ABSTRACT FROM AUTHOR]

Unique and novel Pd 4 Sn nanochain networks were successfully synthesized with an average diameter of 5 nm, rendering a modified Pd electronic structure with rich defects such as atomic corners, steps or ledges as catalytic active sites for great enhancement of charge transfer and electrode kinetics. The prepared Pd 4 Sn nanochain networks held an electrochemically active surface area as high as 119.40 m 2  g −1 , and exhibited higher catalytic activity and stability toward formic acid oxidation compared with Pd 3 Sn nanochain networks, Pd 5 Sn nanochain networks, Pd 4 Sn dendrites and Pd/C. The fundamental insight of the enhancement mechanism is discussed, and this work offers a novel, less expensive but highly active catalyst for direct formic acid fuel cells. [ABSTRACT FROM AUTHOR]

Abstract Protonic ceramic fuel cells answer the call for lowering the operation temperature for traditional solid oxide fuel cells, with relevant research flourishing in the past decade. This review presents a brief introduction of the history and recent development of protonic ceramic fuel cells with stable electrolyte, focusing on their electrochemical performance and the challenges that need to be addressed. Highlights • Recent work on protonic ceramic fuel cells with stable electrolyte are summarized. • Focus is paid on BaZrO 3 -based cells and their electrochemical performance. • Challenges and prospects are discussed. [ABSTRACT FROM AUTHOR]

A strategy of tailoring the ceramic cathode composite is presented to improve the performance of proton-conducting solid oxide fuel cells (SOFCs) prepared by a one-step co-firing process. Comparing to the conventional way of using BaCe 0.7 Zr 0.1 Y 0.2 O 3- δ (BCZY) in the composite cathode for BCZY-electrolyte based cells, the replacement of BCZY by BaZr 0.8 Y 0.2 O 3- δ (BZY) mitigates the reaction between the two ceramic phases in the composite cathode during the co-firing process and also keeps the cathode with sufficient porosity for ample gas diffusion which could assist in adequate cathode reactions. As a result, the BCZY-electrolyte based cell with Sm 0.5 Sr 0.5 CoO 3- δ (SSC)-BZY composite cathode shows a power output of 300 mW cm −2 at 600 °C, which is the largest ever reported for proton-conducting SOFCs prepared by a one-step co-firing process. The strategy of tailoring the composite cathode offers both small ohmic resistance and polarization resistance, providing a promising way to develop single-step co-fired proton-conducting SOFCs. [ABSTRACT FROM AUTHOR]