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The slow reaction kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during the charging and discharging process result in inferior cycle life and low-energy conversion efficiency of commercial zinc-air batteries (ZABs). Stannic oxide (SnO2) has received increasing attention for its unique advantages such as low cost, good stability, and high catalytic activity. In present work, mesoporous nanosphere carbon@stannic oxide (C@SnO2) core–shell structures with C as the inner layer and SnO2 as the outer shell are successfully prepared. When C@SnO2 serves as the cathode for ZABs, its specific surface area (245 m2 g−1) provides amounts of chemically active sites for ORR and OER. Similarly, carbon can not only increase the electrical conductivity of electrocatalyst, but also act as a support body for the core–shell structure which gives the material a robust structure and distinctive morphology. When C@SnO2 are employed as cathode in ZABs, it exhibits excellent electrocatalytic activity with half-wave potential (0.88 V) for ORR and onset potential (1.45 V) for OER. In addition, it shows a superior charging-discharging cycle stability. This work offers an insight for the selection and preparation of high-performance electrocatalysts. [ABSTRACT FROM AUTHOR]

Photocatalytic degradation has received considerable emphasis since it shows significant possibilities in environmental pollution. In this work, ternary Z-scheme heterojunction g-C3N4/TiO2/Ti3C2 photocatalysts are designed and fabricated. The Z-scheme heterojunctions formed on the surfaces of g-C3N4 and TiO2 dramatically modify the photocatalytic performances of the compound under illumination. Meanwhile, in this process, multilayer Ti3C2, as the transport medium of Z-scheme heterojunction, is tightly bonded to TiO2 generated by hydrothermal oxidation and g-C3N4 with large specific surface area, which effectively facilitates the space charge separation and depresses the charge recombination. When the addition amount of TiO2/Ti3C2 is 80 mg and calcined at 450 ℃ for 4 h, g-C3N4/TiO2/Ti3C2 has the greatest photocatalytic performance, and the kinetic constant for degradation methyl orange (MO) was about 3.62 times that of g-C3N4 and 14.55 times that of Ti3C2, respectively. This work illustrates that g-C3N4/TiO2/Ti3C2 has outstanding potential and offers novel insights for designing and synthesizing new ternary heterojunction materials. [ABSTRACT FROM AUTHOR]

The excellent photoresponse of semiconductors enables them as a promising photocatalyst for photocatalytic degradation of organic pollutants and antibiotics, but their practical applications are limited by photogenerated carrier recombination, instability, and fixed energy band positions. Herein, we designed and synthesized a dual Z-scheme flower-like spherical Ag3PO4/MoS2/g-C3N4 (AMN) photocatalyst loaded with different mass of g-C3N4 (3, 5 and 7 mg). Under visible light irradiation, MoS2 enhanced the light absorption range of AMN composite. The holes concentrated in the valence band of Ag3PO4 provide strong oxidation capacity, and the electrons retained in conduction band of g-C3N4 provide strong reduction ability in the photocatalytic system. It is helpful to improve the separation efficiency of photogenerated carriers and enhance the photocatalytic activity of AMN composite. The AMN photocatalyst loaded with 5 mg g-C3N4 (AMN-5) has the optimal photocatalytic activity. The photocatalytic degradation efficiency of the photocatalyst for methylene blue (MB) within 24 min is 3.98, 1.85, and 1.17 times that of g-C3N4, Ag3PO4, and Ag3PO4/MoS2, respectively. After three cycles, the degradation efficiency of AMN-5 for MB decreased from 99.44% to 90%, about 3.79 times of Ag3PO4 (23.77%). In addition, the optimal AMN-5 photocatalyst also has excellent photocatalytic degradation efficiency for Rhodamine B (RhB) and tetracycline (TC). This design and concept provide a promising insight for the photocatalytic degradation of pollutants. [ABSTRACT FROM AUTHOR]