Task-Specific Synthesis of 3D Porous Carbon Nitrides from the Cycloaddition Reaction and Sequential Self-Assembly Strategy toward Photocatalytic Hydrogen Evolution.

Carbon nitride has drawn widespread attention as a low-cost alternative to metal-based materials in the field of photocatalysis. However, the traditionally synthesized carbon nitrides always suffer a bulky architecture, which limits their intrinsic activities. Here, a cycloaddition reaction is proposed to synthesize a triazine-based precursor with implanted sodium and cyano groups, which are mostly retained in the resulting carbon nitride after the following polymerization. Incorporated sodium and cyano defects can not only tune the band structure of the carbon nitride but also provide more additive active sites. The optimized properties enable it an adorable photocatalytic hydrogen evolution rate of 1070 µmol h-1 g-1, varying by almost an order of magnitude from the pristine carbon nitride (79 µmol h-1 g-1). Moreover, a sequential self-assembly strategy has been adopted to further improve its architecture. As a consequence, a three-dimensional (3D) porous carbon nitride microtube cluster is constructed, indicating abundant exposed active sites and the faster separation of charge carriers. The corresponding photocatalytic hydrogen evolution rate is 1681 µmol h-1 g-1, which is very competitive compared with the reported pure carbon nitride photocatalysts. Briefly, this new approach may offer opportunities to fabricate task-specific carbon- and nitrogen-based materials from the molecular level.

Scalable synthesis of a foam-like FeS2 nanostructure by a solution combustion-sulfurization process for high-capacity sodium-ion batteries.

Pyrite-type FeS2 is regarded as a promising anode material for sodium ion batteries. The synthesis of FeS2 in large quantities accompanied by an improved cycling stability, as well as retaining high theoretical capacity, is highly desirable for its commercialization. Herein, we present a scalable and simple strategy to prepare a foam-like FeS2 (F-FeS2) nanostructure by combining solution combustion synthesis and solid-state sulfurization. The obtained F-FeS2 product is highly uniform and built from interconnected FeS2 nanoparticles (∼50 nm). The interconnected feature, small particle sizes and porous structure endow the product with high electrical conductivity, good ion diffusion kinetics, and high inhibition capacity of volume expansion. As a result, high capacity (823 mA h g-1 at 0.1 A g-1, very close to the theoretical capacity of FeS2, 894 mA h g-1), good rate capability (581 mA h g-1 at 5.0 A g-1) and cyclability (754 mA h g-1 at 0.2 A g-1 with 97% retention after 80 cycles) can be achieved. The sodium storage mechanism has been proved to be a combination of intercalation and conversion reactions based on in situ XRD. Furthermore, high pseudocapacitive contribution (i.e. ∼87.5% at 5.0 mV s-1) accounts for the outstanding electrochemical performance of F-FeS2 at high rates.

Thermal decomposition kinetics of the Pb0.25Ba0.75(TNR).H2O complex.

Studies of the non-isothermal decomposition of Pb(0.25)Ba(0.75)(TNR).H(2)O (TNR=2,4,6-trinitro-1,3-dihydroxy-benzene) were carried out by means of TG-DTA, DSC and IR techniques. The thermal decomposition mechanism and the associated kinetics have been investigated. The kinetic parameters were obtained from the analysis of the DSC curves by integral and differential methods. The most probable kinetic model function of the dehydration reaction of Pb(0.25)Ba(0.75)(TNR).H(2)O were suggested by comparison of the kinetic parameters.