Multi-heteroatom doped porous carbon derived from insect feces for capacitance-enhanced sodium-ion storage

The large-scale application of sodium ion batteries(SIBs)is limited by economic and environmental factors.Here,we prepare multi-heteroatom self-doped hierarchical porous carbon(HHPC)with a honeycomb-like structure by one-step carbonization method using high-yield and low-cost biomass silkworm excrement as a precursor.As an anode for SIB,HHPC-1100 exhibits a capacity of 331.7 mA h g^(-1) at 20 mA g^(-1),while it also reveals remarkable rate performance and stable long cycle capability due to its abundant pore structure and proper amount of hetero atom doping.Moreover,the synergistic effect of O,N,S,P co-doping in carbon materials on sodium ion adsorption is verified by the first-principles study,which provide a theoretical basis for the prominent electrochemical performance of the material.

Embedding amorphous MoS_(x)within hierarchical porous carbon by facile one-pot synthesis for superior sodium ion storage

The design of anode materials with a high specific capacity,high cyclic stability,and superior rate performance is required for the practical applications of sodium-ion batteries(SIBs).In this regard,we introduce in this work a facile,low-cost and scalable method for the synthesis of nanocomposites of amorphous molybdenum sulfide(a-MoS_(x))and hierarchical porous carbon and have systematically investigated their performance for sodium ion storage.In the synthesis,ammonium molybdate tetrahydrate and thioacetamide are used as molybdenum and sulfur sources,respectively,with abundant corn starch as the carbon source and KOH as an activation agent.A simple pyrolysis of their mixtures leads to the formation of nanocomposites with a-MoS_(x)embedded within a hierarchical porous carbon(MoS_(x)@HPC),which are featured with a high surface area of up to 518.4 m^(2) g^(-1)and hierarchical pores ranging from micropores to macropores.It has also been shown that the annealing of MoS_(x)@HPC results in the formation of crystalline MoS_(2)nanosheets anchored in the hierarchical porous carbon matrix(MoS_(2)@HPC).The as-prepared nanocomposite MoS_(x)@HPC1 at an optimum carbon content of 32 wt%delivers a high specific sodium storage capacity of 599 mAh g^(-1)at 0.2 A g^(-1)and a high-rate performa nce with a retained capacity of 289 mAh g^(-1)at 5 A g^(-1).A comparison of the electrochemical performances of MoS_(x)@HPC and MoS_(2)@HPC demonstrates the superior specific capacity,rate performance,and charge transfer kinetics of the former,highlighting the unique advantageous role of amorphous MoS_(x)relative to crystalline MoS_(2).

Integrated carbon nanospheres arrays as anode materials for boosted sodium ion storage

Developing cost-effective advanced carbon anode is critical for innovation of sodium ion batteries. Herein, we develop a powerful combined method for rational synthesis of free-standing binder-free carbon nanospheres arrays via chemical bath plus hydrothermal process. Impressively,carbon spheres with diameters of 150-250 nm are randomly interconnected with each other forming highly porous arrays. Positive advantages including large porosity, high surface and strong mechanical stability are combined in the carbon nanospheres arrays. The obtained carbon nanospheres arrays are tested as anode material for sodium ion batteries(SIBs) and deliver a high reversible capacity of 102 mAh g^(-1) and keep a capacity retention of 95% after 100 cycles at a current density of 0.25 A g^(-1) and good rate performance(65 mAh g^(-1) at a high current density of 2 A g^(-1)). The good electrochemical performance is attributed to the stable porous nanosphere structure with fast ion/electron transfer characteristics.

Preparation and Characterization of Nano-polymer Porous MgO

Porous carrier MgO which was aggregated by nano-particles has been firstly prepared by using a normal technology route. The MgO was rod-shaped and had large surface area. The factors which affect grain size and microstructure of MgO were explored.

3D-honeycomb carbons for high performance electrical double layer capacitors electrodes

Sodium fulvic acid based hierarchical porous carbons(SFA-HPCs) with a specific surface area of 1919 m^2·g^(–1) and total volume of 1.7 cm^3·g^(–1) has been synthesized by a simple self-template method. The carbon skeleton can be formatted by the decomposition process of sodium fulvic acid(SFA) in a N_2 atmosphere. The sodium compund in SFA is used as a self-template to create the hierarchical porous structure. The unique hierarchical structure of SFA-HPCs provides an efficient pathway for electrolyte ions to be diffused into the internal surfaces of bulk electrode particles. It results in a high charge storage capacitance of 186 F·g^(–1) at current load of 40 A·g^(–1). The capacitance of 230 F·g^(–1) at 0.05 A·g^(–1) and 186 F·g^(–1) at 40 A·g^(–1) show its good rate capability. Besides, it also achieves desirable cycling stability, 99.4% capacitance remained after 10000 cycles at 40 A·g^(–1).

Hierarchically porous carbon/red phosphorus composite for high-capacity sodium-ion battery anode

Red phosphorus has received remarkable attention as a promising anode material for sodium ion batteries(NIBs) due to its high theoretical capacity. However, its practical application has been impeded by its intrinsic low electronic conductivity and large volume variations during sodiation/desodiation process. Here, we design a composite to confine nanosized red phosphorus into the hierarchically porous carbon(HPC) walls by a vaporization-condensation strategy. The mass loading of P in the HPC/P composite is optimized to deliver a reversible specific capacity of 2,202 m Ah/gpbased on the mass of red P(836 m Ah/gcompositebased on the total composite mass), a high capacity retention over 77% after100 cycles, and excellent rate performance of 929 m Ah/gpat 2 C. The hierarchical porous carbon serves as the conductive networks, downsize the red phosphorus to nanoscale, and provide free space to accommodate the large volume expansions. The suppressed mechanical failure of the red phosphorus also enhances the stability of solid-electrolyte interface(SEI) layer, which is confirmed by the microscopy and impedance spectroscopy after the cycling tests. Our studies provide a feasible approach for potentially viable high-capacity NIB anode.

Sodium carbonate-assisted synthesis of hierarchically porous single-crystalline nanosized zeolites

Hierarchically porous single-crystalline nanosized zeolites as heterogeneous catalysts show great poten- tial in fine chemistry because they offer more rich hierarchically porous channels for the mass transfer and molecular diffusion. However, the synthesis of hierarchically porous nanosized zeolites generally requires the assistance of templates acting as the mesoporogens, which limits its popularity. Herein, we report a one-pot and template-free synthesis of hierarchically porous single-crystalline nanosized zeolite beta only by introducing sodium carbonate in precursor solution. The resulted sample features the extraordinary properties, including the uniform nanocrystal （200-300 nm）, high pore volume （0.65 cm3g 1） and the hierarchical pore-size distribution （e.g., 2-8 and 90-150 nm）. After slicing pro- cessing, it is interestingly found that a large number of interconnected mesopores penetrate throughout whole material, which enables the hierarchically porous nanosized zeolite beta remarkably superior cat- alytic activity than the conventional zeolite beta in condensation of henzaldehyde with ethanol at room temperature. More importantly, this one-pot sodium carbonate-assisted synthetic strategy is highly ver- satile, which has also been successfully developed to synthesize hierarchically porous nanosized single- crystalline zeolites ZSM-5 and TS.

Facile construction of honeycomb-shaped porous carbon electrode materials using recyclable sodium chloride template for efficient lithium storage

Carbon materials are the preferred anode materials for Li-ion batteries.Here,we propose an easy and sustainable strategy to prepare honeycomb-shaped porous carbon(HPC)electrode materials through a process involving simple calcination and subsequent water washing by using polyvinyl-pyrrolidone(PVP)as carbon source and NaCl as pore-forming agent.A controllable cavity size and distribution of the carbon materials can be readily obtained solely by adjusting the NaCl amount.Results showed that the optimized HPC sample had a relatively uniform cavity distribution and a highly porous structure.Moreover,the special honeycomb-shaped structure was conducive to the electronic conductivity of the electrode materials,provided a short path for Li-ion transport and a wide interface with the electrolyte,and buffered the volume change of active materials.The special honeycomb-shaped structure was also maintained well after long cycles,which improved electrode stability.When used as anode materials for Li-ion batteries(LIBs),the sample demonstrated excellent cycling stability and rate performance,with a high specific capacity of 230 mA hg^-1 and a reversible capacity of 197 mA hg^-1,after 1200 cycles at 2 C.Overall,we introduced a simple strategy for the potential mass production of porous carbon materials for LIBs.

3D uniform nitrogen-doped carbon skeleton for ultra-stable sodium metal anode

Sodium metal batteries are arousing extensive interest owing to their high energy density,low cost and wide resource.However,the practical development of sodium metal batteries is inherently plagued by the severe volume expansion and the dendrite growth of sodium metal anode during long cycles under high current density.Herein,a simple electrospinning method is applied to construct the uniformly nitrogen-doped porous carbon fiber skeleton and used as three-dimensional(3D)current collector for sodium metal anode,which has high specific surface area(1,098 m^2/g)and strong binding to sodium metal.As a result,nitrogen-doped carbon fiber current collector shows a low sodium deposition overpotential and a highly stable cyclability for 3,500 h with a high coulombic effciency of 99.9%at 2 mA/cm^2 and 2 mAh/cm^2.Moreover,the full cells using carbon coated sodium vanadium phosphate as cathode and sodium pre-plated nitrogen-doped carbon fiber skeleton as hybrid anode can stably cycle for 300 times.These results illustrate an effective strategy to construct a 3D uniformly nitrogen-doped carbon skeleton based sodium metal hybrid anode without the formation of dendrites,which provide a prospect for further development and research of high performance sodium metal batteries.

A simple method to fabricate N-doped hierarchical porous carbon for supercapacitors

Direct carbonization of nitrogen-containing precursors combined with activation is an effective way to prepare nitrogen-doped hierarchical porous carbon.The most common activation agents being used such as KOH and NaOH may cause serious corrosion to the manufacturing equipment.To resolve this problem,a facile approach has been developed to prepare phenolic resin-derived nitrogen-doped hierarchical porous carbon using sodium acetate as the activation agent and hexamethylenetetramine as the nitrogen source.Acting as an in situ activation agent,sodium acetate is less corrosive.The results show that the sample obtained at 900℃(PHS-900)reaches a maximum specific surface area(S_(BET))of 1591 m^(2)g^(−1).Benefiting from the optimum balance between high nitrogen content(5.41 at.%)and relatively large surface area(827 m^(2)g^(−1)),the optimal sample PHS-700 exhibits a high specific capacitance of 352 Fg^(−1) when it is used as an electrode in 7 M KOH aqueous electrolyte with a three-electrode system.Furthermore,it also shows excellent long-term stability in a two-electrode cell(95.3%retention after 10000 cycles).The good electrochemical performance of the samples and the low corrosion,template-free preparation make it a promising strategy to fabricate nitrogen-doped hierarchical porous carbon for supercapacitor electrode materials.