BiFeO₃ (BFO) and Bi_0.8La_0.1Ho_0.1FeO₃ (BLHFO) materials were prepared by a solid-state reaction method. The dynamic process of melting and solidification of the samples was observed in real time by high temperature polarizing microscopy. The phase composition, microstructure and element distribution of the solidified samples were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry. It is indicated that BFO and BLHFO samples both have polyhedral Fe₂O₃ grains precipitated along with the melting and further grow in the cooling process. Based on the results by SEM, a continuous Bi₂O₃ phase is mixed with a small amount of micron-sized Fe₂O₃ grains and a large amount of micron-sized BiFeO₃ grains. BiFeO₃ grains in the undoped samples are irregular, while La-Ho doped samples form regular cubic BiFeO₃ crystals. In addition, Fe₂O₃ grains in the co-doped sample only contain La element. La and Ho can be co-doped into BiFeO₃ polyhedral grains.

A single planar solid oxide fuel cell model considering various temperature-dependent physical and chemical properties of the materials was proposed via multi-physics coupling based on the COMSOL multiphysics simulation platform. The effects of residual stress and nickel volume fraction in the anode material on the internal thermal stress of the fuel cell were investigated. The results show that the existence of residual stress increases the maximum tensile and compressive stresses of the electrolyte and the cathode electrode under working conditions, reduces the maximum tensile stress of the anode electrode and increases its maximum compressive stress. The increase in the volume fraction of nickel in the anode electrode firstly decreases and then increases the maximum tensile stress of each component of the SOFC. The optimal percentage of nickel volume fraction in the anode electrode is 40%-60%.

Solution-based approaches are regarded as one of great potential methods for preparing Cu₂ZnSn(S,Se)₄ thin film solar cells due to the advantages of simple operation, high material utilization, and low material cost. This review systematically summarized recent development on the solution-based approaches for preparing Cu₂ZnSn(S,Se)₄ thin film solar cells, i.e., spray pyrolysis, bath-based aqueous solution, nanoparticle solution and direct solution coating methods. Recent research results on solution-based high-efficient Cu₂ZnSn(S,Se)₄ thin film solar cells based on the optimization of cation ratio, sintering conditions and selenium conditions, as well as Na, Ge and other metal elements doping were represented. This review gave the advantages and problems in the process of solution-based preparation. t In addition, the future research could also focus on membrane composition and reaction pathway, as well as some effective methods to reduce the intrinsic defects of Cu₂ZnSn(S,Se)₄ absorber layer.

A series of porous carbon based supercapacitor electrode materials (GCO600) were synthesized via simple oxidative carbonization (GCO) with K₂CO₃ activation using grapefruit peel as a resource. The optimized product GCO600-14 has massive network pores and a specific surface area of 661.7 m²/g. In the three-electrode system, the specific capacitance of GCO600-14 is 413 F/g at 1 A/g, and the specific capacitance can still reach 289 F/g when the current density increases to 30 times, which is 70% of the initial value. The cycling stability has a capacitance retention of 96% after 5 000 cycles. For GCO600-14//GCO600-14 symmetric supercapacitor, the energy density is 26 (W·h)/kg at a power density of 720 W/kg and 20.2 (W·h)/kg at a power density of 20 800 W/kg, respectively. It is indicated that GCO600-14 could have potential application prospects in environmentally friendly energy storage materials.

A composite with low crystallinity nickel manganate (NiMn₂O₄) on reduced graphene oxide (rGO) was synthesized by a solvothermal method. Velvet-like NiMn₂O₄ was deposited evenly on rGO nanosheets. The coverage of NiMn₂O₄ effectively prevents agglomeration between graphene flakes. The NiMn₂O₄/rGO composite has a large specific surface area and an excellent electrical conductivity due to the unique structure, and the specific capacitance is 1 675 F·g^-1 at 1 A·g^-1. The specific capacitance retention rate of NiMn₂O₄/rGO nanoflowers composite is 91% at 5 A·g^-1 after 2 000 cycles.

The nano-crystalline ferroelectric films composed of BiFe_0.95Mn_0.05O₃ and Bi_0.9Nd_0.1FeO₃ were fabricated on the fluorine-doped tin oxide/glass substrates via the simple and cost-effective chemical solution deposition method combined with spin-coating and the subsequent layer-by-layer annealing technique. Microstructures and ferroelectric properties of the samples were investigated. Results show that either BiFe_0.95Mn_0.05O₃ or Bi_0.9Nd_0.1FeO₃ film has a single polycrystalline perovskite phase structure with fine and homogeneous grains and smooth surface in addition to a compact and dense structure. Both film samples exhibited well-saturated polarization-electric field hysteresis loops. Especially, the BiFe_0.95Mn_0.05O₃ film showed more preferential upward polarization orientation and superior ferroelectric properties than the Bi_0.9Nd_0.1FeO₃ film, which was reflected by a high remanent polarization (P_r) of 60 μC·cm^-2 and stable ferroelectric responses to frequency and temperature in the ranges of 1 to 50 kHz and 25 to 200℃ in addition to retention capability of 1×10³ seconds and fatigue endurance over 1×10⁹ cycles.

Two-dimensional titanium carbide (Ti₃C₂T_x) material with an organ-like morphology was prepared by a selective etching reaction strategy, and the surface-treated Ti₃C₂T_x samples were obtained by O₂-Ar microwave plasma technology under different temperatures to regulate the terminal functional groups. The microstructure evolution and surface oxygen functional group changes of Ti₃C₂T_x were investigated at different plasma treatment temperatures. The effect of activated Ti₃C₂T_x on gaseous formaldehyde, benzene, toluene and xylene were analyzed. A possible gas-sensing mechanism was discussed based on the perspective of the variation of the surface oxygen functional groups. The results show that O₂-Ar plasma treatment can increase the content of surface oxygen functional groups of activated Ti₃C₂T_x. The gas sensitive response of a sample treated by plasma at 500℃ can reach 169 for 0.01% formaldehyde at an optimal operating temperature, and this sample also exhibits a good selectivity to gaseous formaldehyde.

In order to improve the photocatalytic oxidative desulfurization (PODS) activity of TiO₂, a composite of TiO₂ and g-C₃N₄ was supported on bimodal mesoporous silica (BMMS) to synthesize TiO₂-g-C₃N₄/BMMS. The dodecane solution of dibenzothiophene (DBT) was used as a simulated oil to evaluate the catalytic performance of the samples. The reaction conditions were optimized and the catalytic reaction mechanism was proposed. The results show that TiO₂-g-C₃N₄/BMMS has a bimodal mesoporous structure. As an active composite, TiO₂-g-C₃N₄ can be dispersed on BMMS. Compared to pure TiO₂, the light absorption ability of TiO₂-g-C₃N₄/BMMS is enhanced and the catalytic activity is improved. The desulfurization rate of TiO₂-g-C₃N₄/BMMS obtained under optimized reaction conditions (i.e., the catalyst amount of 3% (in mass fraction), the molar ratio of O∶S of 10∶1, and the volume ratio of solvent to oil of 1∶1) can reach 96.6%, and the desulfurization rate remains more than 85% after 8-run repeated reactions. The main active species in the PODS process are ·O₂^- and h⁺.

Titanium dioxide based organic-inorganic hybrid film containing azobenzene was prepared by a sol-gel technique and a spin-coating method. The surface morphology, transmission mode, refractive index, thickness and photochemical structural properties of the hybrid film were characterized at different heat-treatment temperatures. The results show that the hybrid film is a good optical waveguide material with the smooth and dense surface. Also, the refractive index is adjustable when the heat-treatment temperature is lower than 300℃. The absorbance of the sample irradiated by a ultraviolet light at 365 nm and a visible light at 450 nm was examined to investigate the optical switching property of the hybrid film. It is indicated that the hybrid film has good optical switching properties. In addition, the hybrid film with a fatigue resistance also has promising application prospects in photonics.

Zinc oxide (ZnO) is widely used as a photocatalyst in the treatment of organic pollutants in wastewater due to its wide bandgap, high photocatalytic efficiency, and stable chemical properties. Based on the results by X-ray diffraction and transmission electric microscopy, synthesized ZnO remains a highly disordered structure because the crystallization of ZnO is suppressed by ultrasonic atomization. Amorphous ZnO nanoparticles were synthesized by a ultrasonic atomization-assisted microwave sintering method. Amorphous ZnO nanoparticles with a highly disordered structure enhance the absorption at a wavelength of 300 nm. The UV absorption of amorphous ZnO nanoparticles shifts to the lower energy side and is greater than that of crystal ZnO nanoparticles. The forbidden bandwidth of amorphous ZnO nanoparticles reduces to 3.17 eV. The photocatalytic efficiency of amorphous ZnO nanoparticles is improved, and the photocatalytic degradation efficiency of amorphous ZnO nanoparticles on Rhodamine B (RB) is 37% greater than that of crystal ZnO nanoparticles. Ultrasonic atomization-assisted microwave sintering method could be an effective method for preparing amorphous ZnO nanoparticles at a low temperature and a low energy consumption. Amorphous ZnO nanoparticles are a highly efficient photocatalyst. However, since the photocatalytic efficiency of amorphous ZnO nanoparticles could decrease with increasing the catalytic cycles, the stability and dispersion of amorphous ZnO nanoparticles should be thus further improved.