Interfacial Disordering and Heterojunction Enabling Fast Proton Conduction.

The interfacial disorder is a general method to change the metal-oxygen compatibility and carrier density of heterostructure materials for ionic transport modulation. Herein, to enable high proton conduction, a semiconductor heterostructure based on spinel ZnFe2 O4 (ZFO) and fluorite CeO2 is developed and investigated in terms of structural characterization, first principle calculation, and electrochemical performance. Particular attention is paid to the interfacial disordering and heterojunction effects of the material. Results show that the heterostructure induces a disordered oxygen region at the hetero-interface of ZFO-CeO2 by dislocating oxygen atoms, leading to fast proton transport. As a result, the ZFO-CeO2 exhibits a high proton conductivity of 0.21 S cm-1 and promising fuel cell power output of 1070 mW cm-2 at 510 °C. Based upon these findings, a new mechanism is proposed by focusing on the change of O-O bond length to interpret the diffusion and acceleration of protons in ZFO-CeO2 on the basis of the Grotthuss mechanism. This study provides a new strategy to customize semiconductor heterostructure to enable fast proton conduction.

Phase Evolution and Electrochemical Properties of Nanometric Samarium Oxide for Stable Protonic Ceramic Fuel Cells.

Electrochemical properties of metal oxide have a strong correlation with the crystalline structures. In this work, the effect of calcination temperature on the phase evolution and electrochemical properties of Sm2 O3 was systematically evaluated. The results demonstrate that the sample calcinated at 700 °C (SM-700) is composed of a pure cubic phase while it begins to convert into a monoclinic phase at a temperature above 800 °C and fully converts into a monoclinic phase at 1100 °C. Moreover, the evolution process causes atomic redistribution, and more oxygen vacancies are formed in cubic phase Sm2 O3 , contributing to the improved ionic conductivity. The ionic conductivity of 0.138 S cm-1 and maximum power density of 895 mW cm-2 at 520 °C are achieved using SM-700 as electrolyte for protonic ceramic fuel cell (PCFC). The cubic structure remains stable in the durability testing process and the SM-700 based fuel cell delivers enhanced stability of 140 mW cm-2 for 100 h. This research develops a calcination evolution process to improve the ionic conductivity and fuel cell performance of the Sm2 O3 electrolyte for stable PCFC.

Unveiling the role of lithium in cerium oxide based ceramic fuel cells employing lithium compounds as the anode.

Cerium oxide based ceramic fuel cells (CFCs) enable a good cell performance with high ionic conductivity when a lithium compound is utilized as the anode material. However, the mechanism of enhancement of the ionic conductivity and its effect on the fuel cell performance as well as the stability involved via the lithium effect have not been fully understood in this stage. In this paper, the role of lithium was unveiled through experimental measurements and DFT calculations in cerium oxide-based CFCs. It is found that the redistribution of lithium in cerium oxide causes gradient Li+ distribution, resulting in the diffusion of Li+ in CeO2 electrolyte to improve the cell performance. Further study discloses that the lithium at the anode is depleted and in situ doped into the cerium oxide lattice, modulating the band structure of CeO2, leading to the increased electronic conductivity and open circuit voltage (OCV) degradation. This work provides an insight into the role of lithium in cerium oxide-based CFCs, opening a new methodology for designing high performance CFCs.

Nickel-iron nanoparticles encapsulated in carbon nanotubes prepared from waste plastics for low-temperature solid oxide fuel cells.

Low-temperature solid oxide fuel cells (LT-SOFCs) are a promising next-generation fuel cell due to their low cost and rapid start-up, posing a significant challenge to electrode materials with high electrocatalytic activity. Herein, we reported the bimetallic nanoparticles encapsulated in carbon nanotubes (NiFe@CNTs) prepared by carefully controlling catalytic pyrolysis of waste plastics. Results showed that plenty of multi-walled CNTs with outer diameters (14.38 ± 3.84 nm) were observed due to the smallest crystalline size of Ni-Fe alloy nanoparticles. SOFCs with such NiFe@CNTs blended in anode exhibited remarkable performances, reaching a maximum power density of 885 mW cm-2 at 500°C. This could be attributed to the well-dispersed alloy nanoparticles and high graphitization degree of NiFe@CNTs to improve HOR activity. Our strategy could upcycle waste plastics to produce nanocomposites and demonstrate a high-performance LT-SOFCs system, addressing the challenges of sustainable waste management and guaranteeing global energy safety simultaneously.

Development of a Core-Shell Heterojunction TiO2 /SrTiO3 Electrolyte with Improved Ionic Conductivity.

The front cover artwork is provided by Prof. Faze Wang's group at the Southeast University. The built-in electric field created by the semiconductor heterostructure confines the proton transport on the surface layer of the nanocomposite core-shell heterostructure imparting faster ion transport and lower activation energy. Read the full text of the Research Article at 10.1002/cphc.202200170.

Development of a Core-Shell Heterojunction TiO2 /SrTiO3 Electrolyte with Improved Ionic Conductivity.

Lately, semiconductor-membrane fuel cells (SMFCs) have attained significant interest and great attention due to the deliverance of high performance at low operational temperatures, <550 °C. This work has synthesized the nanocomposite core-shell heterostructure (TiO2 -SrTiO3 ) electrolyte powder by employing the simple hydrothermal method for the SMFC. The SrTiO3 was grown in situ on the surface of TiO2 to form a core-shell structure. A heterojunction mechanism based on the energy band structure is proposed to explain the ion transport pathway and promoted protonic conductivity. The core-shell heterostructure (TiO2 -SrTiO3 ) was utilized as an electrolyte to reach the peak power density of 951 mW cm-2 with an open-circuit voltage of 1.075 V at 550 °C. The formation of core-shell heterostructure among TiO2 and SrTiO3 causes redistribution of charges and establishes a depletion region at the interface, which confined the protons' transport on the surface layer with accelerated ion transport and lower activation energy. The current work reveals novel insights to understand enhanced proton transport and unique methodology to develop low-temperature ceramic fuel cells with high performance.

Tuning La2O3 to high ionic conductivity by Ni-doping.

Ni-doped La2O3 was developed as an ionic conducting membrane corresponding to a conductivity of 0.187 S cm-1 at 550 °C. A peak power density of 970 mW cm-2 with an open circuit voltage of 1.05 V was achieved using 10 mol% Ni-doped La2O3 (10NLO). XPS and Raman investigations reveal that the performance enhancement is due to the high concentration of oxygen vacancies. Density functional theory calculations verify that Ni doping can tune the band structure of La2O3 to enhance its electrochemical performance. A Schottky junction barrier is formed at the anode to avoid short circuit problems and facilitate the ionic transportation at the anode/electrolyte interface. This study indicates that wide-band gap semiconductors with suitable element-doping can be tuned to be promising ionic conductors for advanced fuel cell applications.

Surface-Engineered Homostructure for Enhancing Proton Transport.

Ultra-wide bandgap semiconductor samarium oxide attracts great interest because of its high stability and electronic properties. However, the ionic transport properties of Sm2 O3 have rarely been studied. In this work, Ni doping is proposed to be used for electronic structure engineering of Sm2 O3 . The formation of Ni-doping defects lowers the Fermi level to induce a local electric field, which greatly enhances the proton transport at the surface. Furthermore, ascribed to surface modification, the high concentration of vacancies and lattice disorder on the surface layer promote proton transport. A high-performance of 1438 mW cm-2 and ionic conductivity of 0.34 S cm-1 at 550 °C have been achieved using 3% mol Ni doped Sm2 O3 as electrolyte for fuel cells. The well-dispersed Ni doped surface in Sm2 O3 builds up continuous surfaces as proton channels for high-speed transport. In this work, a new methodology is presented to develop high-performance, low-temperature ceramic fuel cells.

Tunable magneto-optical and interfacial defects of Nd and Cr-doped bismuth ferrite nanoparticles for microwave absorber applications.

Tunable microwave absorption characteristics are highly desirable for industrial applications such as antenna, absorber, and biomedical diagnostics. Here, we report BiNdxCrxFe1-2xO3 (x = 0, 0.05, 0.10, 0.15) nanoparticles (NPs) with electromagnetic matching, which exhibit tunable magneto-optical and feasible microwave absorption characteristics for microwave absorber applications. The experimental results and theoretical calculations demonstrate the original bismuth ferrite (BFO) crystal structure, while Nd and Cr injection in the BFO structure may cause to minimize dielectric losses and enhance magnetization by producing interfacial defects in the spinel structure. Nd and Cr co-doping plays a key role in ordering the BFO crystal structure, resulting in improved microwave absorption characteristics. The BiNd0.10Cr0.10Fe1.8O3 (BNCF2) sample exhibits a remarkable reflection loss (RL) of -37.7 dB with a 3-mm thickness in the 10.15 GHz-10.30 GHz frequency region. Therefore, Nd and Cr doping in BFO nanoparticles opens a new pathway to construct highly efficient BFO-based materials for tunable frequency, stealth, and microwave absorber applications.

Junction and energy band on novel semiconductor-based fuel cells.

Fuel cells are highly efficient and green power sources. The typical membrane electrode assembly is necessary for common electrochemical devices. Recent research and development in solid oxide fuel cells have opened up many new opportunities based on the semiconductor or its heterostructure materials. Semiconductor-based fuel cells (SBFCs) realize the fuel cell functionality in a much more straightforward way. This work aims to discuss new strategies and scientific principles of SBFCs by reviewing various novel junction types/interfaces, i.e., bulk and planar p-n junction, Schottky junction, and n-i type interface contact. New designing methodologies of SBFCs from energy band/alignment and built-in electric field (BIEF), which block the internal electronic transport while assisting interfacial superionic transport and subsequently enhance device performance, are comprehensively reviewed. This work highlights the recent advances of SBFCs and provides new methodology and understanding with significant importance for both fundamental and applied R&D on new-generation fuel cell materials and technologies.

Superionic Conductivity in Ceria-Based Heterostructure Composites for Low-Temperature Solid Oxide Fuel Cells.

Ceria-based heterostructure composite (CHC) has become a new stream to develop advanced low-temperature (300-600 °C) solid oxide fuel cells (LTSOFCs) with excellent power outputs at 1000 mW cm-2 level. The state-of-the-art ceria-carbonate or ceria-semiconductor heterostructure composites have made the CHC systems significantly contribute to both fundamental and applied science researches of LTSOFCs; however, a deep scientific understanding to achieve excellent fuel cell performance and high superionic conduction is still missing, which may hinder its wide application and commercialization. This review aims to establish a new fundamental strategy for superionic conduction of the CHC materials and relevant LTSOFCs. This involves energy band and built-in-field assisting superionic conduction, highlighting coupling effect among the ionic transfer, band structure and alignment impact. Furthermore, theories of ceria-carbonate, e.g., space charge and multi-ion conduction, as well as new scientific understanding are discussed and presented for functional CHC materials.

[Intervention effect of Modified Dahuang Zhechong Granule on epididymal morphological changes in experimental varicocele rats].

OBJECTIVE: To explore the effect of Modified Dahuang Zhechong Granule (MDZG) on the development and maturation of epididymal sperm in experimental varicocele (VC) rats. METHODS: Sixty SD male rats were randomly divided into six groups of equal number, sham operation, VC model, Aescuven forte, and low-, medium- and high-dose MDZG. The model of left VC was made by the Turner method in all the rats except those of the sham operation group, followed by treatment with 0.9% normal saline for the animals in the sham operation and VC model groups, Aescuven forte tablets at 54 mg per kg of the body weight for those in the Aescuven forte group, and MDZG at 0.6, 1.2 and 2.4 g/ml for those in the low-, medium- and high-dose MDZG groups, all administered intragastrically qd for 8 successive weeks. Then, all the rats were sacrificed and their left epididymides harvested for examination of the quality of the epididymal sperm and the local microscopic and ultrastructural changes of the epididymal tissue. RESULTS: The VC model rats showed significant apoptosis of the epididymal sperm cells, interstitial edema, microvascular dilatation, degeneration and degeneration of the epithelial cells, degeneration of some principal cells and basal cell vacuoles, and immature spermatids in the lumen. Sperm motility was significantly increased in the Aescuven forte and low-, medium- and high-dose MDZG groups as compared with the VC models (P <0.01). Both sperm concentration and motility were markedly higher in the high-dose MDZG than in the Aescuven forte group (P <0.05). Remarkable apoptosis of epididymal sperm cells was observed in the microenvironment of sperm development in the VC models, which exhibited no statistically significant difference from that in the rats of the medium- and high-dose MDZG groups. CONCLUSIONS: Experimental varicocele induced local apoptosis of epididymal sperm cells, interstitial edema and microvascular dilatation in the rat epididymis, while Modified Dahuang Zhechong Granule could improve the stability of epididymal sperm maturation and contribute to their development.