A novel high-efficient P/N/Si-containing APP-based flame retardant with a silane coupling agent in its molecular structure for epoxy resin

A flame retardant containing multiple antiflaming elements usually exhibits high-efficient flame retardancy. Here, a novel P/N/Si-containing ammonium polyphosphate derivative(APTES-APP) is synthesized from ammonium polyphosphate(APP) and silane coupling agent(3-aminopropyl)triethoxysilane(APTES)via cation exchange, which is quite different in the chemical structure from APTES-modified APP for retaining silicon hydroxyls. APTES-APP is highly efficient for the epoxy resin. 8%(mass) APTES-APP imparts excellent flame retardancy to the epoxy resin, with a V-0 rating at the UL-94 test(1.6 mm)and an LOI value of 26%(vol). The peak heat release rate and total smoke production of the flameretardant epoxy resin are decreased by 68.1% and 31.3%, respectively. The synergy of P/N/Si contributes to the well-expanded char residue with a strong and dense surface layer, which is a very good barrier against heat and mass transfer. Besides, there is no significant deterioration in the mechanical properties of flame-retardant epoxy resin thanks to silicon hydroxyls forming hydrogen bonds with epoxy molecules. Meanwhile, other molecules can be grafted onto APTES-APP via these silicon hydroxyls, if needed.Briefly, this work has developed a new strategy for amino silane as flame retardants. In conjunction with a low-cost and simple preparation method, APTES-APP has a promising prospect in the high-performance flame-retardant epoxy.

In situ growth of 3D walnut-like nano-architecture Mo-Ni2P@NiFeLDH/NF arrays for synergistically enhanced overall water splitting

The in situ growth of nano-array on material structure is a novel and high-efficient strategy to design catalysts,however,it still remains a challenge to fabricate unique nano-architecture electrocatalyst with prominent activity and superior durability for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).Herein,a unique nano-architecture catalyst is successfully synthesized by using NiFe LDH nanosheets as framework to the in situ growth Mo-doped Ni2 P ultrafine nanosheets(marked as Mo-Ni2 P@NiFe LDH/NF).The unique 3 D core-shell nano-architecture is favorable for enhancing electron transfer/mass diffusion,providing abundant active sites,prompting O2/H2 gas release,and creating the synergistic effect between Mo-Ni2 P and NiFe LDH.Therefore,comparing with pure NiFe LDH/NF and MoNi2 P/NF electrodes,walnut-like Mo-Ni2 P@Ni Fe LDH/NF catalyst exhibits significantly improved electrocatalytic activities and durability towards OER(269 m V@40 m A cm^-2),HER(82 mV@10 mA cm^-2),and overall water splitting(1.46 V@10 m A cm^-2),respectively.Such electrocatalytic activity of Mo-Ni2 P@NiFe LDH/NF is comparable with that of majority reported non-precious metal catalysts and even precious catalysts(IrO2 and Pt/C).This work presents a new perspective strategy to fabricate ingeniously bifunctional electrocatalysts with well-designed structure and superior performance for clean energy conversion technologies or storage devices.

Rhodium-catalyzed enantio-and diastereoselective carboamidation of bicyclic olefins toward construction of remote chiral centers and axis

The precise control of multiple chiral elements through a single step catalytic process remains a significant challenge in asymmetric catalysis.Reported herein is rhodium-catalyzed three-component asymmetric carboamidation between aryl boronic acid,achiral strain-activated symmetric bicyclic olefins bearing a prochiral C-N or N-N axis,and dioxazolones.The reaction proceeded effectively in excellent enantio-and diastereoselectivity under mild conditions to produce the bicyclic framework with six contiguous chiral centers as well as a N-N or C-N chiral axis.The reaction featured excellent functional group tolerance,chemoselectivity,and stereoselectivity.Mechanistic studies indicated that the coupling system proceeded via initial transmetalation,followed by stereo-determining migratory insertion into the olefin and electrophilic amidation.

Tuning the electronic structure of NiCoP arrays through V doping for pH-universal hydrogen evolution reaction electrocatalyst

The exploration of cost-effective,high-performance,and stable electrocatalysts for the hydrogen evolution reaction(HER)over wide pH range(0–14)is of paramount importance for future renewable energy conversion technologies.Regulation of electronic structure through doping vanadium atoms is a feasible construction strategy to enhance catalytic activities,electron transfer capability,and stability of the HER electrode.Herein,V-doped NiCoP nanosheets on carbon fiber paper(CFP)(denoted as Vx-NiCoP/CFP)were constructed by doping V modulation on NiCoP nanosheets on CFP and used for pH-universal HER.Benefiting from the abundant catalytic sites and optimized hydrogen binding thermodynamics,the resultant V15-NiCoP/CFP demonstrates a significantly improved HER catalytic activity,requiring overpotentials of 46.5,52.4,and 85.3 mV to reach a current density of 10 mA·cm^(−2)in 1 mol·L^(−1) KOH,0.5 mol·L^(−1) H_(2)SO_(4),and 1 mol·L^(−1) phosphate buffer solution(PBS)electrolytes,respectively.This proposed cation-doping strategy provides a new inspiration to rationally enhance or design new-type nonprecious metal-based,highly efficient,and pH-universal electrocatalysts for various energy conversion systems.