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Constructing direct Z-scheme heterojunction is an effective approach to separating photogenerated charge carriers and improving the activity of semiconductor photocatalysts. Herein, a composite of bismuth(III) oxide (Bi 2 O 3 ) and graphitic carbon nitride (g-C 3 N 4 ) was in situ fabricated at room temperature by photoreductive deposition of Bi 3+ and subsequent air-oxidation of the resultant metallic Bi. Quantum-sized ω-Bi 2 O 3 nanoparticles approximately 6 nm in diameter were uniformly distributed on the surface of mesoporous g-C 3 N 4 . The as-prepared Bi 2 O 3 /g-C 3 N 4 composite exhibited higher photocatalytic activity than pure Bi 2 O 3 and g-C 3 N 4 for photocatalytic degradation of phenol under visible light. Reactive species trapping experiments revealed that superoxide radicals and photogenerated holes played important roles in the photocatalytic degradation of phenol. The enhanced photocatalytic activity, identification of reactive species and higher rate of charge carrier recombination (as indicated by stronger photoluminescence intensity) collectively suggest that the charge migration within the Bi 2 O 3 /g-C 3 N 4 composite followed a Z-scheme mechanism. Photogenerated electrons on the conduction band of Bi 2 O 3 migrate to the valence band of g-C 3 N 4 and combine with photogenerated holes therein. At the cost of these less reactive charge carriers, the Z-scheme heterojunction enables efficient charge separation, while preserving the photogenerated electrons and holes with stronger redox abilities, which is beneficial for enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: Porous SiC y (core)/C (shell) composite fibres have been fabricated using a simple KOH controlled-activation of SiC x fibres, which were pyrolyzed from polycarbosilane-pitch blend fibres. Effects of activation conditions and pyrolysis temperatures were studied. There are distinctive interfaces observed on the cross-sections of the co-axial fibres, where Si content varies gradually from the core to the shell. The etching of Si follows a slow “core-reducing” process in N2, while in CO2, cracks are frequently observed on the shells due to the accelerated activations. V-shaped Si-free carbon fibres could be obtained when a lower pyrolysis temperature was used to produce the SiC x fibres. [Copyright &y& Elsevier]

Abstract: In an effort to prepare new hydrogen storage materials, we successfully obtained three types of polymer-derived nanoporous SiC x (x =5–7) fibers, whose specific surface areas (SSAs) are larger than 580m2/g. Their hydrogen adsorption properties were studied with a comparison of multi-walled carbon nanotubes (MWCNTs). The results reveal that micropores play a predominant role in hydrogen adsorptions at 77K and at pressures below 0.5MPa, and mesopores begin to take greater effect when the pressure increases beyond 0.5MPa. The maximum hydrogen storage capacity (HSC), 0.33wt% at 302K and 4MPa, was achieved for SiC x -KN fibers with SSA of 990m2/g, while the HSC of the MWCNTs is 0.09wt% at the same conditions. For these new materials, this work demonstrates that small pore size, large micropore volume and large SSA are all beneficial for the high hydrogen uptake. It can also be deduced from the work that the HSC of the SiC x fibers could be further increased if the crystallinity and the composition are better controlled. [Copyright &y& Elsevier]

Photocatalysis opens a new door to H 2 O 2 formation via a low-cost, clean, mild, and sustainable process, which holds great promise for the next generation of massive H 2 O 2 production. However, fast photogenerated electron-hole recombination and slow reaction kinetics are the main obstacles for its practical application. An effective solution is to construct the step-scheme (S-scheme) heterojunction, which remarkably promotes carrier separation and boosts the redox power for efficient photocatalytic H 2 O 2 production. Considering the superiority of S-scheme heterojunctions, this Perspective summarizes the recent advances of S-scheme photocatalysts for H 2 O 2 production, including photocatalysts for building S-scheme heterojunctions, H 2 O 2 -production performance, and S-scheme photocatalytic mechanisms. Lastly, some prospects are given to motivate future research in this promising field, other promising strategies are provided to further improve H 2 O 2 yields, and future research directions are suggested.