In light of the depletion of conventional energy sources, it is imperative to conduct research and development on sustainable alternative energy sources. Currently, electrochemical energy storage and conversion technologies such as fuel cells and metal-air batteries rely heavily on precious metal catalysts like Pt/C and IrO₂, which hinders their sustainable commercial development. Therefore, researchers have devoted significant attention to non-precious metal-based catalysts that exhibit high efficiency, low cost, and environmental friendliness. Among them, perovskite oxides possess low-cost and abundant reserves, as well as flexible oxidation valence states and a multi-defect surface. Due to their advantageous structural characteristics and easily adjustable physicochemical properties, extensive research has been conducted on perovskite-based oxides. However, these materials also exhibit drawbacks such as poor intrinsic activity, limited specific surface area, and relatively low apparent catalytic activity compared to precious metal catalysts. To address these limitations, current research is focused on enhancing the physicochemical properties of perovskite-based oxides. The catalytic activity and stability of perovskite-based oxides in Oxygen Reduction Reaction/Oxygen Evolution Reaction (ORR/OER) can be enhanced using crystallographic structure tuning, cationic regulation, anionic regulation, and nano-processing. Furthermore, extensive research has been conducted on the composite processing of perovskite oxides with other materials, which has demonstrated enhanced catalytic performance. Based on these different ORR/OER modification strategies, the future challenges of perovskite-based bifunctional oxygen electrocatalysts are discussed alongside their development prospects.

A new approach was developed to prepare NaZr2(PO4)3 (NZP) powders at low temperature of 330?C. The effect of different molar ratios of ZrO(NO3)2 ? xH2O to NaH2PO4 ? 2H2O on the synthesis of NZP powders was systematically investigated by XRD, FE-SEM, TEM, EDS and Raman spectroscopy. The mineralizer NaNO3 was formed in situ due to the mechanochemical reaction between raw materials ZrO(NO3)2 ? xH2O and NaH2PO4 ? 2H2O during the grinding process. When the optimal molar ratio of Zr:P = 2:6 was used, the NZP powders with high crystallinity, good dispersity and particle sizes in the range of 500-700 nm were obtained. The dense NZP ceramics was obtained by sintering at 1100 ?C for 3 h with 2 wt.% ZnO as the sintering aid. The relative density and Vickers hardness of the sintered ceramics reached 93.4% and 704MPa, respectively.

With reducing diamond grain size to nano-grade, the increase of grain boundaries and non-diamond phase will result in the change of the optical properties of chemical vapor deposition (CVD) diamond films. In this paper, the structure, morphology and optical properties of nanocrystalline diamond (NCD) films, deposited by hot-filament chemical vapor deposition (HFCVD) method under different carbon concentration, are investigated by SEM, Raman scattering spectroscopy, as well as optical transmission spectra and spectroscopic ellipsometry. With increasing the carbon concentration during the film deposition, the diamond grain size is reduced and thus a smooth diamond film can be obtained. According to the data on the absorption coefficient in the wavelength range from 200 to 1100 nm, the optical gap of the NCD films decreases from 4.3 eV to 3.2 eV with increasing the carbon concentration from 2.0% to 3.0%. From the fitting results on the spectroscopic ellipsometric data with a four-layer model in the photon energy range of 0.75–1.5 eV, we can find the diamond film has a lower refractive index (n) and a higher extinction coefficient (k) when the carbon concentration increases.

The free-standing diamond films with a smooth and high quality nucleation side were prepared by hot filament chemical vapor deposition (HFCVD) method. The nucleation side of the films had a mean surface roughness of 1.6nm.AlN films were then deposited on the nucleation side of the above diamond films by radio-frequency (RF) reactive magnetron sputtering method. The structure characteristics of AlN films deposited under different working pressure (p), sputtering power (w) and sputtering plasma composition were studied. The optimized parameters for the growth of high c-axis orientation AlN films were obtained: p=0.2Pa,w=600w and Ar/N₂=3:1.Surface morphologies of AlN films deposited under these parameter, tested by means of atomic force microscope (AFM), showed that the mean surface roughness was about 4.1nm.It also had a strong c-axis orientation structure investigated by X-ray diffraction (XRD). All results above suggested that the AlN/diamond structure prepared in this work was ideal for the application of high frequency surface acoustic wave devices (SAW) device.