Enhanced ionic conductivity has been frequently detected in the hetero-structure composites made of dissimilar structures, triggering a series of studies to develop new electrolytes for solid oxide fuel cells (SOFC) based on different structures. To verify whether such kind of enhancement exists in the composite of similar structure, a new composite electrolyte based on perovskite BaZr0.1Ce0.7Y0.1Yb0.1O3-delta (BZCYYb) and BaCo0.4Fe0.4Zr0.1Y0.1O3-delta (BCFZY) is developed and studied in this work. Micro-structural study reveals the BZCYYb and BCFZY particles form sufficient hetero-interface regions in the composite, resulting in an enrichment of oxygen vacancies. Electrical conductivity measurement detects more than two times enhancement of ionic conductivity in the composite as compared to BZCYYb, which is likely due to the strain at the hetero-interface caused by lattice mismatch. The SOFC with the 7BZCYYb-3BCFZY electrolyte exhibits a peak power density of 720 mW cm-2 at 550 degrees C, which is superior to that of the BZCYYb SOFC. Further analysis of impedance spectra and in-situ ionic conduction confirms improved ionic conductivity of the 7BZCYYb-3BCFZY electrolyte in the fuel cell. Our study indicates that the composites based on the same structures (perovskite-perovskite) can also enable enhanced interface ionic conductivity, but the enhancement is not as strong by orders of magnitude as in case of the composite made of highly dissimilar structures.

Semiconductor ionic materials (SIM) have recently gained broad attention due to their unique structural and chemical properties that enable efficient proton transport, making them promising materials for advanced fuel cell applications. This mini-review provides an overview of the proton transport phenomena in SIM and discusses their significance and future perspectives. We discuss the different types of SIMs, their proton transport mechanisms, and the factors that affect their performance. Furthermore, we emphasize the correlation between traditional perovskite oxides and SIMs and how this can be leveraged to improve the development of more advanced proton conductors for fuel cells. Also, we have highlighted the Proton-coupled electron transfer (PCET) mechanism in SIM. This mini-review provides a comprehensive overview of the current state of this emerging field, including its scientific foundations, future prospects, and applicable materials, technologies, devices, and basics for proton ceramic fuel cells (PCFCs).

Functional Sodium-doped cobalt oxide (Na0.6Co3O4, NCO) was incorporated to regulate and improve the electrochemical performance of La/Pr co-doped ceria (LCP) electrolytic materials with good operative stability, forming an p-n heterostructure electrolyte (LCP-NCO) for low-temperature solid oxide fuel cell (LTSOFC) application. LCP-NCO is a new potential semiconductor-ionic material, achieving a maximum power density of 1075 mW cm(-2) along with a high open-circuit voltage of 1.061 V at 520 degrees C. Scanning electron microscopy combined with transmission electron microscopy unveiled the crystallographic microstructure of heterostructure interface between LCP and NCO. Raman spectra and Fourier transform infrared spectroscopy spectra were analyzed to distinguish the functional groups and the vibrational properties. Ultraviolet-visible absorption and ultraviolet photoelectron spectroscopy have determined the accurate band edge positions of LCP and NCO and p-n heterojunction nature. Built-in electric field in semiconductor heterostructure and more oxygen vacancies created through the variation of Co3+/Co2+ ratio in LCP-NCO during the fuel cell test, contributed to the enhanced ionic transport. Characteristic of competent conductivity of 0.26-0.42 S cm(-1) at 400 degrees C-520 degrees C, and the improved cell duration, revealed that the LCP-NCO as a hybrid oxygen ion and protonic conductor would be a potential electrolyte for LTSOFC.

La/Pr co-doped ceria (LCP) is processed to fabricate low-temperature ceramic fuel cell based on industrial-grade rare-earth carbonate electrolyte that is reached above a maximum power density of 750 mW/cm² at 520 °C. The charge carriers are investigated through LCP fuel cell having symmetric NCAL (Ni<inf>0.8</inf>Co<inf>0.15</inf>Al<inf>0.05</inf>LiO<inf>2-δ</inf>) electrodes using proton conductor BCZY (BaCe<inf>0.7</inf>Zr<inf>0.1</inf>Y<inf>0.2</inf>O<inf>3-δ</inf>) as a blocking layer and are found protons that dominate during the cell operation. The results of associated characterizations for HCC (hydrogen concentration cell) and the OCC (oxygen concentration cell) reveal that LCP material is mixed conductor of both protons and oxygen ions simultaneously. Transmission electron microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analysis before and after the electrochemical testing of the cell are performed which show an amorphous layer of LiOH/Li<inf>2</inf>CO<inf>3</inf> mixture that is formed after the tests on the surface of LCP structure. Conceptually, it looks that LiOH/Li<inf>2</inf>CO<inf>3</inf> mixture in molten state in the interface region of two-phase material promotes the proton conduction through LCP electrolyte, with negligible oxygen ion conduction.

Semiconductor ionic electrolytes are attracting growing interest for developing low-temperature solid oxide fuel cells (LT-SOFCs). Our recent study has proposed a p-n heterostructure electrolyte based on perovskite oxide BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) and ZnO, achieving promising fuel cell performance. Herein, to further improve the performance of the heterostructure electrolyte, an A-site-deficiency strategy is used to solely modify BCFZY for regulating the ionic conduction and catalytic activity of the heterostructure. Two new electrolytes, B0.9CFZY-ZnO and B0.8CFZY-ZnO, were developed and systematically studied. The results show that the two samples gain improved ionic conductivity and auxiliary catalytic activity after A-site deficiency as a result of the increment of the surface and interface oxygen vacancies. The single cells with B0.9CFZY-ZnO and B0.8CFZY-ZnO exhibit enhanced peak power outputs at 450-550 °C compared to the cell based on B1.0CFZY-ZnO (typically, 745 and 795 vs 542 mW cm-2 at 550 °C). Particular attention is paid to the impact of A-site deficiency on the interface energy band alignment between BxCFZY and ZnO, which suggests that the p-n heterojunction effect of BxCFZY-ZnO for charge carrier regulation can be tuned by A-site deficiency to enable high proton transport while avoiding fuel cell current leakage. This study thus confirms the feasibility of A-site-deficiency engineering to optimize the performance of the heterostructure electrolyte for developing LT-SOFCs.

Developing highly effective catalysts for oxygen reduction reaction (ORR) is crucial to enable the low-temperature operation of solid oxide fuel cells (SOFCs). Recent studies have proposed a promising O2-/H+/e- conducting oxide, LiNi0.8Co0.15Al0.05O2-delta (LNCA) with good ORR catalytic activity for SOFC cathode uses. Herein, to further optimize the cathode functionality of LNCA, a fluorine anion (F-) doping strategy is ap-plied to develop highly active LNCAF0.1 and LNCAF0.2 cathodes for Sm-doped ceria (SDC) electrolyte-based SOFCs. It is found the successful doping of F- in the oxygen site of LNCA leads to improved oxygen ionic conductivity and facilitated surface exchange and bulk diffusion of oxygen in LNCAF0.1 and LNCAF0.2, which thus gain distinctly promoted ORR catalytic activity at 450-550 degrees C, as confirmed by the decreased area specific resistances (ASR) and activation energy on symmetrical cells. The as-fabricated two SDC-based SOFCs with LNCAF0.1 and LNCAF0.2 cathodes exhibit peak power densities of 497 and 591 mW cm-2 at 550 degrees C, respectively, which are higher than that of the cell with LNCA cathode. Furthermore, the single cell with the best-performing LNCAF0.2 cathode demonstrates a good stability for 110 h at 550 degrees C. The present study thus provides a feasible strategy of F anion doping to promote the ORR catalytic activity of LNCA cathode for developing low-temperature SOFCs.

The use of ceramic semiconductors to serve as an efficient proton conductor is an evolving approach in the novel emerging field of semiconductor protonic fuel cells (SPFCs). One of the most critical challenges in SPFCs is to design a sufficient proton-conductivity of 0.1 S cm(-1) below <600 degrees C. Here we report to tune the perovskite BaSnO3 (BSO), a semi-conductor single-phase material, to be applied as a proton-conducting electrolyte for SPFC. It was found that the oxygen vacancies play a vital role to promote proton transport while the electronic short-circuiting issue of BSO semiconductor has been justified by the Schottky junction mechanism at the anode/electrolyte interface. We have demonstrated a SPFC device to deliver a maximum power density of 843 mW cm(-2) with an ionic conductivity of 0.23 S cm(-1) for BSO at 550 degrees C. The oxygen vacancy formation by increasing the annealing temperature helps to understand the proton transport mechanism in BSO and such novel low-temperature SPFC (LT-SPFC).

Rare earth element doping is a popular methodology for improving the electrical and electrochemical properties of materials. Inspired by this ideology, garnet ferrite material Sm3Fe5O12 (SFO) doped by rare earth (Yb, La) metal ions to form Sm3-0.5Yb0.5Fe5O12 (SYFO) and Sm3-0.5La0·5Fe5O12 (SLFO). The samples are synthesized by sol gel auto combustion and have been applied as electrolyte membrane for the first time in low temperature solid oxide fuel cell (LT-SOFC). The results indicate that the as-prepared materials have triple charge transport (H+/O−2/e−) carrier which promotes the hydrogen oxidation reaction (HOR) and oxygen reduction reactions (ORR) in SOFC at triple phase boundary region (TPB). Electrochemical impedance spectroscopy (EIS) reveals that the polarization resistance of SLFO membrane significantly reduces from 0.92 Ω-cm2 to 0.45 Ω-cm2 and the power output improve from 310 mW/cm2 to 650 mW/cm2 at 550 °C temperature in comparison with that of SYFO and SFO electrolyte supported cells. UV-vis diffused spectroscopy explains the semiconducting nature of the prepared materials due to the existence of optical bandgap in the semiconductor region. The further investigation also verifies the protonic conduction of SLFO membrane by constructing oxygen ion blocking fuel cell with configuration of Ni-NCAL/BZCY/SLFO/BZCY/Ni-NCAL having 427.94 mW/Cm2 fuel cell performance with 1.03 OCV at 550 °C temperature. 

Inertia properties of several medium speed large diesel engines are evaluated using the Inertia Restrain Method (IRM). This method requires measuring frequency response functions (FRFs) at several well-chosen locations and under dynamic loading in different directions that stimulate rigid body movements. The mass line values of the measured FRFs are then evaluated and, together with the sensor locations, are used by IRM to determine center of gravity, mass and mass moments of inertia. The aim of the study is to investigate the accuracy and robustness of the IRM for extracting the inertia properties of complex structures. Therefore, several line- and V-engines were measured. The experimental results are compared with finite element models and result obtained from weighing tests. Different types of excitation source such as hammer and shaker are used to excite the structure. The result obtained from two excitation sources are compared and discussed. The effect of measurement point locations and driving point accelerometers on the FRFs and inertia properties are investigated. The extracted inertia properties in all cases are considered sufficiently accurate. This indicates that the IRM is a robust tool for identifying the inertia properties of large and complex structures and can be employed at an industrial level. 

Semiconductors are well known as excellent materials in the field of exploring novel avenues which combine various fields in electronics, electrochemistry, etc for new functional device concepts. Lithium silicon carbide (LiSiC) is a well-known electrode material for Lithium ion batteries but relatively new for solid oxide fuel cells (SOFCs) and electrolyte-layer free fuel cells (EFFCs). In the present work, we have explored three categories of fuel cells based on mixed LiSiC-SDC (samarium doped ceria) in SOFC and LiSiC as a single component material with type (I) and without coating of a layer of 3C-SiC as EFFC type (II). All of three cells are sandwiched between Ni foams coated with NCAL (Ni0.8Co0.15Al0.05Li-oxide). The electrochemical performances of as prepared fuel cells are tested at 550 degrees C, which is substantially lower than in conventional fuel cell materials. The LiSiC based EFFC type (II) demonstrates better performance because of less ohmic resistance as compared to type (I) have more layers. This indicates that the LiSiC-SDC system has potential for fuel cell development in accordance with energy band structure and alignment.