NiSe2 nanoparticles embedded in CNT networks: Scalable synthesis and superior electrocatalytic activity for the hydrogen evolution reaction

For the first time, NiSe₂ nanoparticles embedded in CNT networks have been synthesized via spray-drying followed by a selenization process. The NiSe₂/CNTs hybrid (NCH) delivers superior electrocatalytic performance for HER. It has a low onset potential of ~ 159 mV and a cathode current density of 35.6 mA cm^− 2 at − 250 mV vs RHE; more importantly, the Tafel slope has a very low value of 29 mV dec^− 1, which is comparable to a platinum (Pt) catalyst; in addition, it is stable even after 1000 cycles. The superior HER performance of NCH is attributed to its unique structure, which is composed of ultrathin NiSe₂ nanoparticles homogenously embedded in highly conductive and porous CNT networks. This not only provides abundant HER active sites, but also guarantees robust contact between the NiSe₂ nanoparticles and the CNT networks. The present study provides new insights into the large-scale and low-cost synthesis of a highly effective and stable NiSe₂-based electrocatalyst which could be extended to large-scale production of other non-precious metal hybrid catalysts with low cost, high efficiency and excellent stability.     

用于高性能锂-硫电池的氮化硼纳米片/碳纤维改性隔膜

通过静电纺丝、热亚胺化和碳化过程,将氮化硼纳米片(BNNSs)负载在碳纤维(CFs)表面,组成用于修饰商业聚丙烯(PP)隔膜的氮化硼纳米片/碳复合纤维(BNNSs/CFs)复合材料。BNNSs和CFs的协同作用为电池提供了额外的导电路径,并将可溶性多硫化锂固定在正极区域。结果表明,采用10BNNSs/CFs-PP隔膜的电池在0.05C下的初始放电容量高达1 295.7 mAh·g^-1,当电流密度增加到1C时,以10BNNSs/CFs-PP为隔膜的电池也具有良好的长期循环稳定性,在400次循环后最终容量高达568.1mAh·g^-1,每次循环容量衰减0.073%。     

Carbon dioxide-controlled assembly based on conjugated polymer and boron nitride

C02-controlled assembly of conjugated polymer and boron nitride(BN)was fabricated via electrostatic and hydrophobic interactions between the BN fiber and conjugated polymer of PFBT containing fluorene units and 2,1,3-benzothiadiazole units.C02,an effective and green stimulus for regulating the assembly of PFBT and BN fibers,leads to an obvious fluorescence variation.Moreover,PFBT enables the assembly with the signal amplification and light-harvesting properties.This work provides a new triggering method to construct intelligent conjugated polymer-based platform,and offers fluorescence monitoring strategy for carbon dioxide capture.     

用于高性能锂-硫电池的氮化硼纳米片/碳纤维改性隔膜

通过静电纺丝、热亚胺化和碳化过程,将氮化硼纳米片(BNNSs)负载在碳纤维(CFs)表面,组成用于修饰商业聚丙烯(PP)隔膜的氮化硼纳米片/碳复合纤维(BNNSs/CFs)复合材料。BNNSs和CFs的协同作用为电池提供了额外的导电路径,并将可溶性多硫化锂固定在正极区域。结果表明,采用10BNNSs/CFs-PP隔膜的电池在0.05C下的初始放电容量高达1 295.7 mAh·g^-1,当电流密度增加到1C时,以10BNNSs/CFs-PP为隔膜的电池也具有良好的长期循环稳定性,在400次循环后最终容量高达568.1mAh·g^-1,每次循环容量衰减0.073%。     

Photochemical Synthesis of Ultrafine Cubic Boron Nitride Nanoparticles under Ambient Conditions

Cubic boron nitride (c‐BN) is a super‐hard material whose hardness increases dramatically with decreasing size. However, c‐BN nanoparticles (NPs) with sizes less than 10 nm have never been obtained. Herein we report a simple strategy towards the synthesis of ultrafine c‐BN NPs with an average size of 3.5 nm. The method, under ambient conditions, exploits a laser‐induced photochemical effect and employs dioxane solution of ammonia borane (AB) as a liquid target. Meanwhile, total dehydrogenation of AB is realized by laser irradiation. Therefore, this approach shows great potential for the preparation of super‐hard NPs as well as controllable dehydrogenation.     

Enhanced Adsorption of Polysulfides on Carbon Nanotubes/Boron Nitride Fibers for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are one of the most promising high-energy-density storage systems. However, serious capacity attenuation and poor cycling stability induced by the shuttle effect of polysulfide intermediates can impede the practical application of Li-S batteries. Herein we report a novel sulfur cathode by intertwining multi-walled carbon nanotubes (CNTs) and porous boron nitride fibers (BNFs) for the subsequent loading of sulfur. This structural design enables trapping of active sulfur and serves to localize the soluble polysulfide within the cathode region, leading to low active material loss. Compared with CNTs/S, CNTs/BNFs/S cathodes deliver a high initial capacity of 1222 mAh g⁻¹ at 0.1 C. Upon increasing the current density to 4 C, the cell retained a capacity of 482 mAh g⁻¹ after 500 cycles with a capacity decay of only 0.044 % per cycle. The design of CNTs/BNFs/S gives new insight on how to optimize cathodes for Li-S batteries.     

Structure,electronic and magnetic properties of hexagonal boron nitride sheets doped by 5d transition metal atoms: First-principles calculations and molecular orbital analysis

A first-principles calculation based on density functional theory is carried out to reveal the geometry, electronic structures and magnetic properties of hexagonal boron nitride sheets (h-BNSs) doped by 5d transitional mental atoms (Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg) at boron-site (B_5d) and nitrogen-site (N_5d). Results of pure h-BNS, h-BNS with B vacancy (V_B) and N vacancy (V_N) are also given for comparison. It is shown that all the h-BNSs doped with 5d atoms possess a C_3v local symmetry except for N_Lu and N_Hg which have a clear deviation. For the same 5d dopant, the binding energy of B_5d is larger than that of N_5d, which indicates the substitution of a 5d atom for B is preferred. The total densities of states are presented, where impurity energy levels exist. Besides, the total magnetic moments (TMMs) change regularly with the increment of the 5d atomic number. Theoretical analyses by molecular orbital under C_3v symmetry explain the impurity energy levels and TMMs.     

Synthesis and properties of a novel high temperature pyridine‐containing phthalonitrile polymer

A novel pyridine‐containing aromatic phthalonitrile monomer, 2,6‐bis[4‐(3,4‐dicyanophenoxy)benzoyl]pyridine (BCBP) was synthesized from the nitro displacement of 4‐nitrophthalonitrile by the phenoxide of 2,6‐bis (4‐hydroxybenzoyl)pyridine (BHBP). 4‐(Aminophenoxy) phthalonitrile (APPH) was selected to promote the curing reaction, and the curing behavior has been investigated by differential scanning calorimetric (DSC), suggesting a wide processing window about 64 °C. Different curing additive concentrations resulted in polymers with different crosslinking degrees and subsequently influenced the performance of resins. The resulting BCBP polymer exhibited high glass transition temperatures exceeding 400 °C, outstanding thermo‐oxidative stability with weight retention of 95% at 530 °C, indicating a significant improvement in thermal properties endowed by pyridine units. Additionally, it also showed a lower overall water absorption after submersion in boiling water for 50 hours. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3819–3825     

用于高性能锂-硫电池的氮化硼纳米片/碳纤维改性隔膜

通过静电纺丝、热亚胺化和碳化过程,将氮化硼纳米片(BNNSs)负载在碳纤维(CFs)表面,组成用于修饰商业聚丙烯(PP)隔膜的氮化硼纳米片/碳复合纤维(BNNSs/CFs)复合材料。BNNSs和CFs的协同作用为电池提供了额外的导电路径,并将可溶性多硫化锂固定在正极区域。结果表明,采用10BNNSs/CFs-PP隔膜的电池在0.05C下的初始放电容量高达1 295.7 mAh·g^-1,当电流密度增加到1C时,以10BNNSs/CFs-PP为隔膜的电池也具有良好的长期循环稳定性,在400次循环后最终容量高达583.1mAh·g^-1,每次循环容量衰减0.069%。