Energy storage and fuel cell power generation are the most important development directions for realizing the carbon neutrality goal in China. Reversible solid oxide cells (i.e., RSOCs) are promising electrochemical energy conversion devices with a high efficiency and a low emission. The polarization resistance of oxygen electrode is large, and oxygen reduction/evolution reaction (ORR/OER) is sluggish. A lower oxygen exchange rate is considered as a main rate limiting step in reactions of RSOCs, restricting the efficiency and performance. This review summarized various techniques for characterizing the oxygen surface exchange coefficient (k), and introduced the working principle, merits and research progress of optical transmission relaxation approach. Also, this review discussed the factors like defect chemistry, surface chemistry, orientation, grain boundary/grain size and the crystallinity on the oxygen exchange kinetics and catalytic activity of oxygen electrode, and gave some advices for the future research.

To provide direction and guidance for the microstructure design and development of sealing materials for high-performance intermediate-temperature solid oxide fuel cell, a Al₂O₃/BaO-CaO-B₂O₃-Al₂O₃-SiO₂ glass-ceramic (BCBAS)-based composite sealing material with superior mechanical properties and a high thermal conductivity was prepared via tape casting. According to the analysis by scanning electron microscopy and X-ray diffraction, the lamellar Al₂O₃ is regularly distributed in the BCBAS glass-ceramic matrix. The main crystallization phase of BCBAS glass transforms from Ca_0.1Ba_0.9SiO₃ into Ba_1.55Ca_0.45SiO₄ and BaAl₂Si₂O₈, and further into BaAl₂Si₂O₈ and BaAl₂O₄ phases when the lamellar Al₂O₃ content increases from 0 to 25% (in mass fraction). The thermal conductivity of biomimetic sealants increases from 0.892 W/(m·K) to 1.255 W/(m·K), and the bending strength and Vickers hardness with higher than 10 of the Weibull modulus β increase from 96 MPa to 140 MPa and 444 HV to 677 HV as the lamellar Al₂O₃ content increases from 0 to 25% (in mass fraction), indicating the mechanical properties and thermal conductivity of the sealant. The sealing tensile strength of the biomimetic sealant with the mass fraction of lamellar Al₂O₃≤20% maintains above 4 MPa. The composite with 20% Al₂O₃-80% BCBAS glass exhibits the superior comprehensive properties (i.e., thermal conductivity of 1.203 W/(m·K), bending toughness of 136 MPa, Vickers hardness of 677 and sealing strength at 4.22 MPa), thus being a potential candidate for application of intermediate- temperature solid oxide fuel cell.

Photofenton technology is one of the effective means to treat organic wastewater. Developing photofenton catalysts with a higher catalytic efficiency is always a hotspot. A BiOI/MIL-100(Fe) nanocomposite with a visible-light response was synthesized by a facile hydrothermal-co-precipitation method. The as-synthesized BiOI/MIL-100(Fe) nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, UV-vis diffuse reflectance spectroscopy and N₂ adsorption-desorption analysis, respectively. The BiOI/MIL-100(Fe) nanocomposite exhibits a better photo-Fenton activity rather than pure BiOI and MIL-100(Fe) for tetracycline degradation under visible-light irradiation. In particular, the composite (BiOI/MIL-100(Fe)-2) has the maximum efficiency when a content of MIL-100(Fe) is 5.2% (in mass fraction). The formation of BiOI/MIL-100(Fe) heterojunctions between BiOI and MIL-100(Fe) is beneficial to the transfer and separation of charge carriers. The photogenerated electrons accelerate Fe²⁺/Fe³⁺ cycle and create the reductive reaction of H₂O₂. The enhanced performance of BiOI/MIL-100(Fe) nanocomposite is ascribed to a synergic effect for photocatalysis and Fenton reaction.

Proton-conducting reversible solid oxide cells (P-RSOCs), capable of conversion of chemical energy and electrical energy with a high efficiency and a low cost due to the low activation energy for proton transport, low operating temperature and fuel flexibility, is considered as one of the most promising electrochemical devices for energy storage and conversion. This review represented recent research progress on P-RSOCs. The material systems and fabrication processes of electrolytes and electrodes were discussed. The application prospect and future direction of P-RSOCs were analyzed as well. The perovskite-based oxides are regarded as the critical materials of P-RSOCs due to the diversified composition and modification methods. The fuels flexibility, electrolyte-electrode interface, and the long-term stability are challenges for the development of P-RSOCs.

Advanced oxidation technology (AOPs) is an effective technology to treat water pollution, which has attracted recent attention. The non-selective and strong oxidation properties of hydroxyl radicals (·OH) in the AOPs reaction process are efficient enough to degrade pollutants. CuFeS₂/g-C₃N₄ (CFS/CN) photofenton catalyst was synthesized by a simple hydrothermal/calcination method for degradation of Rhodamine B (RhB). The results show that CFS/CN 1∶2.5 has the optimum catalytic performance for RhB degradation at 0.10 g/L catalyst, 10 mg/L RhB concentration, 50 μL H₂O₂ addition and pH value 1. In addition, the degradation efficiency of CFS/CN for RhB is 90% at 15 min and nearly 96% at 20 min. According to the results of cyclic experiments, CFS/CN has a good cyclic stability. It is indicated that CFS/CN catalysts could provide a potential application for RhB degradation.

Hydroxyapatite (HA) is the main inorganic constituent of human hard tissue. It can effectively accelerate the repair process of hard tissue defects due to its high bioactivity and biocompatibility. Ion doping is an effective approach to enhance the bioactivity of HA materials. On this basis, dual-ion substitution can make HA materials have a higher simulation to nature bone in composition and some functional features (i.e., antitumor ability, antibacterial activity, pro-angiogenetic capacity, immunoregulatory and medical imaging capability). Dual-ion substitution greatly extends the applications of HA materials in bone tissue engineering. This review summarized the synthesis methods and their principles of dual-ion substituted HA (DIHA) materials, represented the applications of DIHA materials in hard tissue engineering, and finally proposed the future development direction of DIHA materials.

In recent years, borosilicate bioactive glass (BBG) is widely studied due to its osteoinductive activities. However, the ions accumulated in the extracts can induce cytotoxicity and hemolysis when evaluating the biological properties of the degradable materials using the extracts of the materials. In this paper, the BBGs were prepared at different ratios of B₂O₃ (0B, 1.5B, and 3.0B samples), and bone cements were fabricated by mixing the BBGs with 30% (in mass fraction) citric acid. The cytotoxic and osteogenic effects of the bone cements extracts were evaluated using human bone marrow mesenchymal stem cells (hBMSCs), and the bone healing effects of the bone cements were evaluated using a rat femoral defect model, respectively. The results show that the extracts of bone cement formed at a greatest ratio of B₂O₃ in the bioactive glass can induce a maximum inhibitive effect on the proliferation and osteogenesis of hBMSCs in vitro. However, the degradation and bone healing effect of the bone cement increase directly with the ratio of B₂O₃ in BBG upon transplantation. Also, there is a huge discrepancy with the in vivo and in vitro evaluation systems for the biodegradable biomaterials. Understanding the mechanisms of the different biological effects of BBG in vitro and in vivo will provide some guidance for the design of a more effective borate-containing bioactive materials and the construction of a better evaluation system for bioactive materials in vitro, thus facilitating the clinical applications of BBG.

In recent years, the composite hydrogels composed of micro-nano bioactive glass (MNBG) and gelatin are widely used in tissue regeneration. However, the relationship between hydrogels and MNBG in terms of mineralization and degradation is still unclear. In this paper, gelatin based composite hydrogels with different concentrations of MNBG were prepared, and the effect of MNBG on the mineralization and degradation properties of composite hydrogel was investigated by in vitro experiments. The results show that the composite hydrogel does not affect the bioactive ion release of MNBG, and the formation of negative curvature interface by a high concentration of MNBG aggregates is a necessary condition for composite hydrogels to mineralize. In addition, increasing the concentration of MNBG and quickly mineralizing to form hydroxyapatite layer can effectively reduce the degradation rate of gelatin based composite hydrogel.

Bioglass (BG) microspheres with a constitution of CaO-SiO₂-P₂O₅ demonstrate promising applications in bone repair. It has been proved that the cerium ion incorporation in bioglass structure can provide materials with additional antioxidant, anti-inflammatory and angiogenesis functions. In this study, cerium-incorporated bioglass (Ce-BG) microspheres were prepared via a spray drying process. The effects of Ce content on the phase composition, degradation performance and in vitro bioactivity of Ce-BG microspheres were investigated. The results show that all microspheres are uniform in element distribution with relatively smooth surfaces and a high degree of sphericity. The Ce incorporation introduces a small amount of CePO₄ and CeO₂ crystalline phases. Along with the increase of Ce content, the degradation rate of Ce-BG microspheres slows down, and the effect of degradation products on the increase of environmental pH value is alleviated, and the pH value was found to be the lowest after 7 d of immersion for Ce-BG microspheres with mole ratio of Ce and Ce+Ca of 0.03∶1.00 in Tris-HCl buffer. Ce-BG microspheres with different Ce content have good ability to induce apatite deposition in vitro.