Caijin Huang

Dispersed Cu2O Octahedrons on h-BN Nanosheets for p-Nitrophenol Reduction

We demonstrate here that two-dimensional boron nitride (h-BN) nanosheets can be employed as a robust supporting substrate to incorporate function metal oxides. The Cu2O@h-BN composites are thus obtained by dispersing Cu2O octahedrons on the surfaces of h-BN nanosheets. The -OH and -NH groups on the surfaces of h-BN nanosheets are found to be beneficial for anchoring Cu2O octahedrons. Moreover, the Cu2O@h-BN composites exhibit superior activity for the reduction of p-nitrophenol to pure Cu2O crystals and h-BN nanosheets. The h-BN component in the composites plays a critical role in the formation and adsorbing of the p-nitrophenolate ions, and, at the same time, Cu2O components react with brohydride ions and transfer a surface hydrogen species and electrons, resulting in the reduction of p-nitrophenol into p-aminophenol. Our results provide a new approach for the rational design and development of metal oxides composites and open the way to a range of important applications of h-BN-based materials.

Stable colloidal boron nitride nanosheet dispersion and its potential application in catalysis

Hexagonal boron nitride (h-BN) nanosheets, a promising layered material, have drawn more and more attention in recent years. In this study, a simple method has been developed to prepare stable colloidal h-BN nanosheet dispersion with high concentration in ethylene glycol based on the matching of the surface energies of h-BN and the surface tension of the solvent. It is found that bulk h-BN can be directly exfoliated and dispersed in ethylene glycol solvent with the assistance of sonication to form stable h-BN nanosheets with a few layers. Furthermore, the stable colloidal h-BN nanosheets have been demonstrated to be good carriers to support and disperse noble metal nanoparticles such as Ag, Au, and Pt with high catalytic activity for the reduction of p-nitrophenol. Our results suggest that stable colloidal h-BN dispersion with high concentration in ethylene glycol could open the way to a range of important applications of h-BN based materials.

Boron nitride encapsulated copper nanoparticles: a facile one-step synthesis and their effect on thermal decomposition of ammonium perchlorate.

Reactivity is of great importance for metal nanoparticles used as catalysts, biomaterials and advanced sensors, but seeking for high reactivity seems to be conflict with high chemical stability required for metal nanoparticles. There is a subtle balance between reactivity and stability. This could be reached for colloidal metal nanoparticles using organic capping reagents, whereas it is challenging for powder metal nanoparticles. Here, we developed an alternative approach to encapsulate copper nanoparticles with a chemical inertness material—hexagonal boron nitride. The wrapped copper nanoparticles not only exhibit high oxidation resistance under air atmosphere, but also keep excellent promoting effect on thermal decomposition of ammonium perchlorate. This approach opens the way to design metal nanoparticles with both high stability and reactivity for nanocatalysts and their technological application.

The release of hydrogen from ammonia borane over copper/hexagonal boron nitride composites

Facile solution-phase synthesis of copper nanoparticles dispersed on h-BN via a solvothermal method is proposed for the hydrolytic dehydrogenation of ammonia borane. We found that the earth-abundant copper nanoparticles were highly stabilized on h-BN nanosheets. The resulting Cu/h-BN composites exhibited high catalytic activity and good recycling performance for hydrogen generation from the hydrolysis of ammonia borane under mild reaction conditions. Furthermore, the kinetics of the hydrolysis reaction were also investigated by varying the concentration of ammonia borane, the amount of catalyst, and the reaction temperature. An activation energy of 23.8 kJ mol−1 was measured for the hydrolysis reaction catalyzed by the 29.4 wt% Cu/h-BN sample, which is lower than most of the reported values for other catalysts. This study demonstrates that Cu/h-BN nanocomposites can act as a potential non-precious and effective catalyst for hydrogen generation from the hydrolysis of ammonia borane.

Hydrogenation of nitroarenes into aromatic amines over Ag@BCN colloidal catalysts.

The present work reports that two-dimension layered ternary boron carbon nitrogen nanosheets can serve as good carriers to support and disperse noble metal nanoparticles. The Ag@BCN colloids have thus been prepared by attaching Ag nanoparticles on the surfaces of BCN nanosheets. The detailed structures of the Ag@BCN samples were investigated by X-ray diffraction, transmission electron microscopy, atomic force microscope, infrared, and X-ray photoelectron spectroscopy. It is found that the surface NH groups of BCN nanosheets are beneficial for the attachment of Ag nanopaprticles. Compared with the conventional organic capping compounds, the two dimensional planar BCN nanosheets endow the attached nanoparticle with the high active surfaces. Moreover, the hydrogenation of nitroarenes into the corresponding aromatic amines can be highly achieved over Ag@BCN colloids by NaBH4. In particular, the apparent activation energy of the conversion reaction of p-nitroaniline to p-phenylenediamine was found to be 76.0kJ/mol over the Ag@BCN colloids with 3wt% Ag content. Our results may provide a new approach for the design noble metal based composites and find the practical application for the hydrogenation of nitroarenes.

One-step synthesis of magnetically recyclable Co@BN core–shell nanocatalysts for catalytic reduction of nitroarenes

We present a facile one-step synthesis of chemically stable and magnetic Co@BN core–shell nanoparticles. We found that Co@BN nanoparticles acted as excellent catalysts with high stability and magnetic recyclability for reduction of nitroarenes to aminoarenes under mild reaction conditions. The sample 13.6 wt% Co@BN showed the best catalytic activity for reduction of 4-nitrophenol (4-NP). In addition, a significant synergistic effect of the h-BN support was observed during the catalytic reaction by effectively adsorbing/concentrating and ionizing the reactant nitroaromatics. Moreover, the kinetics of the catalytic reaction were investigated at different reaction temperatures, 4-nitrophenol concentrations, sodium borohydride concentrations, metal loadings and catalyst amounts. The activation energy of the catalytic reduction of 4-nitrophenol for 13.6 wt% Co@BN was determined to be 102.93 kJ mol−1. This work provides a clear example of Co@BN core–shell nanoparticles as nanocatalysts.

Solvothermal fabrication of thin Ag nanowires assisted with AAO

Single crystalline thin silver nanowires with a diameter of ∼45 nm were synthesized using a solvothermal method assisted with an anodic aluminum oxide (AAO) template. AAO here is not playing a role as a hard template but as a heterogeneous medium whose porous structure can promote PVP molecules to form into a one dimensional template. This soft template can effectively guide the growth of Ag nanowires and thus reduce the reaction time considerably. We further investigated the influences of reaction time, temperature and ratio of PVP to AgNO3 on the formation of Ag nanowires by SEM and UV-Vis absorption spectra characterization. The reaction mechanism was also demonstrated by TEM analysis. Our work may provide a better way to control the synthesis of metallic nanostructures in chemical solution.

Constructing hierarchical sulfur-doped nitrogenous carbon nanosheets for sodium-ion storage

Hierarchical sulfur-doped nitrogenous carbon (S/NC) and nitrogenous carbon (NC) nanosheets are successfully fabricated by carbonization of their corresponding precursor polymers which are synthesized through the polymerization reaction of dianhydride and multi-amine compounds. Hierarchical S/NC nanosheets deliver greatly enhanced reversible capacity, compared with hierarchical NC nanosheets, of 280 mAh g-1 at a current density of 100 mA g-1 after 300 cycles. It is found that the introduction of sulfur species in carbon skeleton results in increasing the turbostratic structures, rather than enlarging the interlayer distances, for boosting the specific capacity of sodium-ion storage. The turbostratic structures and sulfur dopant existed in the carbon can offer more active sites for the sodium-ion storage. Carbon-based materials doped with sulfur are capable of improving the sodium-ion storage property, which can broaden the horizon of designing a string of outstanding carbon materials for the future energy storage technologies.

Fluorine Modified Boron Carbon Nitride Semiconductors for Improved Photocatalytic CO2 Reduction under Visible Light

Photocatalytic conversion of CO2 to usable fuel precursors is one of the most important renewable paths to mitigate energy shortages and greenhouse gas emissions. Photocatalysts for this transformation are typically based on precious metals to obtain high yield and selectivity. Currently, metal‐free graphitic conjugated materials (such as g‐C3N4, ternary boron carbon nitride) are promising and emerging photocatalysts to offset the above issues. Here we further modulated photocatalytic performance of ternary boron carbon nitride (BCN) by introducing fluorine into its graphitic‐like framework. As a result, the fluorination of the BCN productively increases the CO yield by three times under visible light. It was found that fluorine doping can remarkably accelerate migration‐separation efficiency of photogenerated charge carriers, prolong lifetime of the excited state and optimize electronic properties of BCN.