Progress in Solid State Chemistry最新文献

Perovskite-type oxynitrides are a new class of inorganic materials that have potential applications as photocatalysts, inorganic pigments and dielectrics. Design of the morphology in conjunction with new synthesis methods is essential for their practical use. In this review, we present the formation of fine particles via a low temperature and ammonia-free synthesis method, the morphology of the oxynitride perovskites obtained using metal carbodiimide, and the toughness of the sintered ceramics in relation to their microstructure.

Making highly efficient and stable perovskite solar cells (PSCs) are often based on the processing techniques, band gap of the material and effective interface charge separation. The efficiency of PSCs can be enhanced through several methods including the utilization of a solar-friendly absorber, interface passivation and the implementation of multi-junction spectrally matched absorbers or bilayered phase homojunction (BPHJ) consisting of identical absorbers. Here, we demonstrated BPHJ concept by stacking identical compositions of highly efficient and stable FA_0.15MA_0.85PbI₃ perovskite absorbers adopting solution process (SP) and thermal evaporation (TEV) techniques. We successfully achieved FA_0.15MA_0.85PbI₃ (SP)/FA_0.15MA_0.85PbI₃-(TEV) based BPHJ normal n-i-p devices, which significantly crossing 22.

% PCE. These improvement stems from effective deposition method for achieving high-quality FA_0.15MA_0.85PbI₃-based BPHJ enabling smooth charge transfer at the interfaces. The resulting BPHJ-based champion device achieve a 22.13 % PCE and retain >95 % its original efficiency over 1000 hours.

Lithium-rich manganese-based transition metal oxide Li_1.2Ni_0.2Mn_0.6O₂ (LNMO) can achieve high energy density due to the interaction of anionic redox kinetics in Li₂MnO₃. However, the irreversible release of oxygen and migration of Mn ions during deep de-lithiation disrupts the layer structure of LNMO, leading to a decrease in voltage and capacity. Herein, we confine oxygen anion through Zr and Al co-doping. Combined analysis of structure refinement, XPS and XAS, the co-doped strategy effectively prohibits cation disordering of Li/Ni, inhibits the Jahn-Teller effect and reduces the transition metal (TM) and oxygen hybridization. As a result, the Zr and Al co-doping LNMO sample (ZA-LNMO) possesses a capacity retention of 92% after 100 cycles and 86% after 200 long-term cycles, much higher than the value of the undoped sample (79% for 100 cycles and 58% for 200 cycles). Even at the harsh conditions such as ultra-high current rate (10 C) or high temperature (60 °C), ZA-LNMO also maintains 70% retention after 200 cycles. Our findings provide an insight into the synergistic effect of cation co-doping and help to design layered oxides for future applications.

Perovskite-type oxynitrides ACa_0.2M_0.8O_2.6N_0.4 (A = Sr, Ba; M = Nb, Ta) were synthesized via the ammonolytic reaction between A₅M₄O₁₅ and CaCl₂, where the Ca²⁺ insertion and O²⁻/N³⁻ substitution occurred cooperatively. In terms of the average structure, SrCa_0.2Nb_0.8O_2.6N_0.4 and SrCa_0.2Ta_0.8O_2.6N_0.4 belong to the orthorhombic Pnma space group, and BaCa_0.2Nb_0.8O_2.6N_0.4 and BaCa_0.2Ta_0.8O_2.6N_0.4, the primitive cubic Pm $\bar{3}$ m group. The comparison between the experimental lattice volume and the summed ionic volume suggested that ACa_0.2M_0.8O_2.6N_0.4 have higher degrees of ionicity than AM'_0.2M_0.8O_3−xN_x (M′ = Li, Mg, Mn), but are more covalent than ANa_0.2M_0.8O_2.8N_0.2. Despite the significant mismatches of size and charge between Ca²⁺ and Nb⁵⁺ (or Ta⁵⁺), no cation ordering was detected on the octahedral site. On the other hand, the O/N distribution appeared to depend on the bonding geometry around the anion sites in a way N favors the straighter bonding connectivity of M−N−M. The band gap energies of ACa_0.2M_0.8O_2.6N_0.4 were estimated to be 1.9–2.25 eV depending on A and M. The band gaps and color properties of AMO₂N and AM'_0.2M_0.8O_3−xN_x (A = Sr, Ba; M = Nb, Ta; M′ = Li, Na, Mg, Ca, Mn) are compared. Thermogravimetry and differential scanning calorimetry were conducted in the air to assess the oxynitride stability. The electrical behaviors were studied by the equivalent circuit analysis of the impedance spectrum using compacted polycrystalline specimens, where BaCa_0.2Ta_0.8O_2.6N_0.4 was found to possess a bulk dielectric constant of 4550 along with an electrical conductivity of ≈10⁻⁶ S/cm at 27 °C. It remains, however, necessary to assess the extrinsic effects arising from the non-ideal sintering to interpret thoroughly the electrical property of BaCa_0.2Ta_0.8O_2.6N_0.4.

Today, carbon dioxide (CO₂) is one of the most pervasive greenhouse gases in the atmosphere, mainly because of the burning of fossil fuels. The carbon dioxide reduction reaction by photocatalysis and electrocatalysis is one approach that holds a lot of promise for easing the global crisis on the environmental and energy fronts. Developing and constructing high-performance photo- and electrocatalysts is a challenge that is being studied. The class of anionic metal-oxo clusters known as polyoxometalates (POMs) brings diverse and interesting chemical and physical characteristics that can be modified easily. The studies reveal that POMs are emerging to be distinctive photo/electrocatalysts for these reactions because of their unmatched advantages, like thermal and redox stability, light-absorbing capacity, quasi-semiconductor properties, etc. Numerous studies have demonstrated the capability of tungsten and molybdenum-based photo- and electrocatalysts for CO₂ reduction and conversion into value-added products. This review has covered the most recent developments in tungsten and molybdenum-based POMs that convert CO₂ into multiple products (CO, H₂, HCOOH, HCHO, CH₃OH, etc.). Perspectives for designing and constructing different kinds of POM-based catalytic systems have been offered.

Ferroelectric ceramics, which exhibit the phenomenon of reversible spontaneous polarization, have been utilized in multiple conventional applications including sensors, actuators, nano-generators, micro-electromechanical systems (MEMS), memory storage systems, energy harvesting devices, etc. Recently, ferroelectric ceramics have been employed for catalysis-induced applications. One of such catalysis process is known as ‘pyrocatalysis’, which makes use of pyroelectric materials to execute catalysis reactions using temperature fluctuation-derived waste thermal energy/heat. This new and evolving pyrocatalysis process has shown promising potential in new and exciting applications including water-cleaning, water-splitting, bacterial disinfection, tooth whitening, carbon-dioxide reduction, tumor therapy, etc. In principle, ferroelectric ceramics are always pyroelectric in nature, which enables them to be utilized for pyrocatalytic applications. High pyrocatalytic performances of ferroelectric ceramics have been reported by various reports in multiple applications. This review starts with the basic introduction to ferroelectric ceramics, pyroelectric effect, and pyrocatalysis process. Further, it provides the review of recent studies utilizing ferroelectric ceramics for pyrocatalytic applications. The strategies to improve pyrocatalytic performance of ferroelectric ceramics are discussed in detail. At last, this review provides insights to new future directions for researchers working on ferroelectric pyrocatalysts.

Being a highly proficient material for electrochemical energy storage systems, MXene is gaining popularity. MXene pseudocapacitive charge storage system with electric double layer behaviour has improved the efficiency of supercapacitors. Furthermore, the proper interlayer spacing and distinct chemistry have enabled batteries to attain high capacity while enabling quick charge-discharge. Such breakthroughs are a result of MXene inherent characteristics, including its strong electrical conductivity, well defined layered structure, and capacity for modification, which allows it to customize electrodes to a particular purpose. Additionally, MXenes have shown their value by allowing supercapacitors and batteries to defy convention and explore the world of hybrid capacitors, micro-supercapacitors (MSCs), and batteries other than Li-ion. This article covers the MXene-based supercapcitor electrodes and difficulties associated with them. By using logical analysis, we also present several important directions for future study that could assist in resolving these issues and enabling the family of MXene materials to reach its full potential.

This comprehensive review paper offers an extensive overview of recent developments in doping strategies to enhance the applications of M-type hexaferrites. These distinctive materials have gained considerable attention across a range of technological fields. The paper focuses on structural attributes of M-type hexaferrites, delves into their diverse applications—such as permanent magnets, high-density storage media, EMI shielding, photocatalysis for wastewater treatment, and potential for hydrogen storage—and underscores their suitability for these uses. The review also investigates the influence of doping on the performance of M-type hexaferrites in various applications. The insights presented herein not only provide a deeper understanding of the potential of M-type hexaferrites but also pave the way for future advancements in this dynamic field.

CuAl₂-type VN₂, which is synthesized under high pressure, is a recoverable material at ambient conditions and has a high bulk modulus. In this study, we investigated the thermal expansion behavior of CuAl₂-type VN₂ by low-temperature X-ray diffraction measurements between 109.3(5) K and 298.3(8) K. The axial thermal expansion coefficient of VN₂ was determined to be α_a = 2.7(9) × 10⁻⁶ K⁻¹ and α_c = 17.8(12) × 10⁻⁶ K⁻¹ at 298.3(8) K, which has large anisotropy similar to that of compression behavior. It is found that the small coefficient of thermal expansion of the a-axis is due to the negative and positive effects on the a-axis length with increasing temperature of the bond angles and bond lengths of VN₂, respectively. As a result, VN₂ exhibits very large anisotropic thermal expansion behavior.