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• Cost-effective 3D porous diatomite biomass is used to fabricate conductive networks. • The CNTs/graphene hybrid can enhance the electric conductivity and surface area. • The MnO 2 @CNTs/G/diatomite shows high specific capacitance and good cyclic stability. • The ASC exhibits high energy density (64.4 W h kg−1) and power density (19.8 kW kg−1). Natural abundant and industrial available biomass diatomite is act as the porous template to in-situ grown graphene layer (G), while the carbon nanotubes (CNTs) arrays are subsequently grown on the graphene surface. The seamless anchored 1D CNTs arrays together with 3D interconnected graphene networks can construct conductive hierarchical framework to enhance the electric conductivity. Furthermore, the enlarged effective surface area of the CNTs/G/diatomite can increase the active material loading amount and facilitate the electrolyte infiltration. Therefore, the MnO 2 @CNTs/G/diatomite hybrid exhibits a highest specific capacitance of 264.0 F g−1 (based on the MnO 2 , the value is ~880.0 F g−1), good rate capability and excellent cyclic stability. Moreover, the asymmetric supercapacitor assembled by MnO 2 @CNTs/G/diatomite and microwave exfoliated graphite oxide reveals a highest energy density of 64.3 W h kg−1 and maximum power density of 19.8 kW kg−1, respectively. [ABSTRACT FROM AUTHOR]

Four silver chalcogen compounds, Ag 2 O, Ag 2 S, Ag 2 Se and Ag 2 Te, can be utilized as visible-light-driven photocatalysts. In this research, the electronic structures of these compounds were analyzed by simulation and experiments to systematically reveal the relationship between photocatalytic performance and energetic structure. All four chalcogenides exhibited interesting photocatalytic activities under ultraviolet, visible and near-infrared light. However, their photocatalytic performances and stability significantly depended on the band gap width, and the valence band and conduct band position, which was determined by their composition. Increasing the X atomic number from O to Te resulted in the upward movement of the valence band top and the conduct band bottom, which resulted in narrower band gaps, a wider absorption spectrum, a weaker photo-oxidization capacity, a higher recombination probability of hole and electron pairs, lower quantum efficiency, and worse stability. Among them, Ag 2 O has the highest photocatalytic performance and stability due to its widest band gap and lowest position of VB and CB. The combined action of photogenerated holes and different radicals, depending on the different electronic structures, including anion ozone radical, hydroxide radical, and superoxide radical, was observed and understood. The results of experimental observations and simulations of the four silver chalcogen compounds suggested that a proper electronic structure is necessary to obtain a balance between photocatalytic performance and absorbable light region in the development of new photocatalysts. [ABSTRACT FROM AUTHOR]

• The graphene-like g-C 3 N 4 was coated successfully on the surface of porous ZnO. • PNS-ZnO@g-CN exhibited higher photocatalytic activity for CO 2 reduction. • G-CN content has great influence on the photocatalytic performance of composites. • The loading of g-CN nanofilms can improve the chemisorption of CO 2 on the surface of ZnO. • Formation of heterojunction in composites can depress the recombination of photo-carriers. Porous ZnO nanosheets (PNS-ZnO) were prepared by calcining ZnS(en) 0.5 (en = ethylenediamine) nanosheets in air, and g-C 3 N 4 (g-CN) nanofilms were coated on the surface of PNS-ZnO by thermal deposition using bulk g-C 3 N 4 as precursor. Experimental results showed that the graphene-like g-C 3 N 4 could be deposited on the surface of ZnO to form nanocomposites with core/shell structure. After the loading of g-CN, the light absorption and chemical adsorption of CO 2 over PNS-ZnO were improved obviously and the recombination of photogenerated electron and hole was greatly depressed due to the formation of heterojunction between PNS-ZnO and g-CN. All PNS-ZnO@g-CN nanocomposites exhibited much higher photocatalytic activity for CO 2 reduction with H 2 O vapor when compared to pure PNS-ZnO and bulk g-CN. The loading amount of g-CN had significant influence on the light absorption and photocatalytic activity, and PNS-ZnO@g-CN-0.4 exhibited the best photocatalytic performance, for which H 2 , CH 4 and CO production rates of 22.7, 30.5 and 16.8 μmol/g cat /h can be obtained, respectively. [ABSTRACT FROM AUTHOR]