Self-Assembly 3D Porous Crumpled MXene Spheres as Efficient Gas and Pressure Sensing Material for Transient All-MXene Sensors

Environmentally friendly degradable sensors with both hazardous gases and pressure efficient sensing capabilities are highly desired for various promising applications,including environmental pollution monitoring/prevention,wisdom medical,wearable smart devices,and artificial intelligence.However,the transient gas and pressure sensors based on only identical sensing material that concurrently meets the above detection needs have not been reported.Here,we present transient all-MXene NO_(2) and pressure sensors employing three-dimensional porous crumpled MXene spheres prepared by ultrasonic spray pyrolysis technology as the sensing layer,accompanied with water-soluble polyvinyl alcohol substrates embedded with patterned MXene electrodes.The gas sensor achieves a ppb-level of highly selective NO_(2) sensing,with a response of up to 12.11%at 5 ppm NO_(2) and a detection range of 50 ppb-5 ppm,while the pressure sensor has an extremely wide linear pressure detection range of 0.14-22.22 kPa and fast response time of 34 ms.In parallel,all-MXene NO_(2) and pressure sensors can be rapidly degraded in medical H_(2)O_(2) within 6 h.This work provides a new avenue toward environmental monitoring,human physiological signal monitoring,and recyclable transient electronics.

Hierarchical porous nitrogen,oxygen,and phosphorus ternary doped hollow biomass carbon spheres for high-speed and long-life potassium storage

Limited lithium resources have promoted the exploration of new battery technologies.Among them,potassium-ion batteries are considered as promising alternatives.At present,commercial graphite and other carbon-based materials have shown good prospects as anodes for potassium-ion batteries.However,the volume expansion and structural collapse caused by periodic K+insertion/extraction have severely restricted further development and application of potassium-ion batteries.A hollow biomass carbon ball(NOP-PB)ternarily doped with N,O,and P was synthesized and used as the negative electrode of a potassium-ion battery.X-ray photoelectron spectroscopy,Fourier‐transform infrared spectroscopy,and transmission electron microscopy confirmed that the hollow biomass carbon spheres were successfully doped with N,O,and P.Further analysis proved that N,O,and P ternary doping expands the interlayer distance of the graphite surface and introduces more defect sites.DFT calculations simultaneously proved that the K adsorption energy of the doped structure is greatly improved.The solid hollow hierarchical porous structure buffers the volume expansion of the potassium insertion process,maintains the original structure after a long cycle and promotes the transfer of potassium ions and electrons.Therefore,the NOP‐PB negative electrode shows extremely enhanced electrochemical performance,including high specific capacity,excellent long‐term stability,and good rate stability.

Resorcinol-formaldehyde resin-based porous carbon spheres with high CO_2 capture capacities

Porous carbon spheres are prepared by direct carbonization of potassium salt of resorcinol-formaldehyde resin spheres, and are investigated as COadsorbents. It is found that the prepared carbon materials still maintain the typical spherical shapes after the activation, and have highly developed ultra-microporosity with uniform pore size, indicating that almost the activation takes place in the interior of the polymer spheres. The narrow-distributed ultra-micropores are attributed to the "in-situ homogeneous activation"effect produced by the mono-dispersed potassium ions as a form of -OK groups in the bulk of polymer spheres. The CS-1 sample prepared under a KOH/resins weight ratio of 1 shows a very high COcapture capacity of 4.83 mmol/g and good CO/Nselectivity of7-45. We believe that the presence of a welldeveloped ultra-microporosity is responsible for excellent COsorption performance at room temperature and ambient pressure.

Nitrogen-doped hierarchically porous carbon spheres for low concentration CO_(2) capture

Synthesis of spherical carbon beads with effective CO_2 capture capability is highly desirable for large scale application of CO2 sorption, but remains challenging. Herein, a facile and efficient strategy to prepare nitrogen-doped hierarchically porous carbon spheres was developed via co-pyrolyzation of poly(vinylidene chloride) and melamine in alginate gel beads. In this approach, melamine not only serves as the nitrogen precursor, but also acts as a template for the macropores structures. The nitrogen contents in the hierarchically porous carbon spheres reach a high level, ranging from 11.8 wt% to 14.7 wt%, as the melamine amount increases. Owing to the enriched nitrogen functionalities and the special hierarchical porous structure, the carbon spheres exhibit an outstanding CO_2 capture performance, with the dynamic capacity of as much as about 7 wt% and a separation factor about 49 at 25 °C in a gas mixture of CO_2/N_2(0.5:99.5, v/v).

Hierarchical porous Co_(3)O_(4) spheres fabricated by modified solvothermal method as anode material in Li-ion batteries

Hierarchical porous Co_(3)O_(4)spheres were synthesized by a solvothermal method followed by high-temperature calcination.XRD,SEM,TEM and electrochemical tests were used to study the structure and performance of the hierarchical porous Co_(3)O_(4)spheres.The results show that the Co_(3)O_(4)synthesized at a calcination temperature of 700°C(Co_(3)O_(4)-700)is micro-sized spheres(1-2μm)consisting of plentiful nanoparticles(50-200 nm)and numerous pores(~100 nm).Due to its numerous porous morphology,the Co_(3)O_(4)-700 anode exhibits the highest cycling performance with excellent reversible discharge and charge specific capacities of 745 and 755 m A·h/g at the current density of 100 m A/g after 100 charge-discharge cycles,respectively.

Pomegranate-like porous NiCo_(2)Se_(4) spheres with N-doped carbon as advanced anode materials for Li/Na-ion batteries

Design and preparation of dual-role anode materials with extraordinary performance for rechargeable Li/Na-ion batteries (LIBs/NIBs) remains highly challenging.Herein,three-dimensional (3D) pomegranate-like porous bimetallic NiCo_(2)Se_(4) spheres with N-doped carbon (termed as NC@NiCo_(2)Se_(4)) are synthesized by solvothermal method and annealing.Microstructure investigations reveal that the NC@NiCo_(2)Se_(4) spheres include nano-sized NiCo_(2)Se_(4) particles as inner core and NiCo_(2)Se_(4) with the modification of thin-walled N-doped carbon layer as inner/outer shell.The bimetallic NC@NiCo_(2)Se_(4) spheres possess synergistic interaction of Ni/Co atoms to enhance intrinsic conductivity and electrochemical activity,unique pomegranate-like structure with an inner void space and robust shell to mitigation volume expansion,and intimate contact of N-doped carbon layer to improve interface effect and accelerate conversion kinetics.As anode materials,the NC@NiCo_(2)Se_(4) exhibits superior lithium/sodium storage performances (1401.6 and 794.8 mA h g^(-1)at current density of 0.5 and 5 A g^(-1)after 500 cycles for LIBs as well as 433.9 mA h g^(-1)at 3 A g^(-1)after 1000 cycles and a high capability of 306.6 mA h g^(-1)at 20 A g^(-1)for NIBs).This work represents an impressive strategy for future research of bimetallic selenides as anode materials for advanced high-performance LIBs/NIBs.

Preparation of V2O5 Porous Hollow Spheres and Study on Excellent Cycling Stability of Lithium Battery

Through one-step simple polyol-assisted (ethylene glycol) process, V2O5 hollow mi-cro-spheres about 3 micrometres in size were successfully synthesized. The structure is neat, the outer wall were porous. Testing its electrochemical properties with V2O5 hollow materials as cathode materia of lithium ion battery, the results showed that under the ratio of 1 C, the initial charge and discharge specific capacity were 236.8 mAh g^-1, 213 mAh g^-1, even if after 100 cycles, the charge and discharge specific capacity were still 220 mAh g^-1 and 219.7 mAh g^-1 respectively. Relative to the charge and discharge capacity of the second cycle, the keep rate were 93.2%, 92.9% respectively, has good cycle stability.

Preparation of Porous U_(3)O_(8) Ceramic Microspheres for ^(99)mTc Production

^(99)mTc is a pure Beta-decay nuclide,with a half-life of 6.01 h and β-energy of 140.5 keV.It is widely used in clinic diagnosis of various diseases.^(99)mTc is obtained from its parent nuclide^(99)Mo(T1/2=65.95 h)via β-decay.

High-yield production of porous carbon spheres derived from enzymatic hydrolysis lignin for zinc ion hybrid capacitors

The widespread implementation of supercapacitors is hindered by the limited energy density and the pricey porous carbon electrode materials.The cost of porous carbon is a significant factor in the overall cost of supercapacitors,therefore a high carbon yield could effectively mitigate the production cost of porous carbon.This study proposes a method to produce porous carbon spheres through a spray drying technique combined with a carbonization process,utilizing renewable enzymatic hydrolysis lignin as the carbon source and KOH as the activation agent.The purpose of this study is to examine the relationship between the quantity of activation agent and the development of morphology,pore structure,and specific surface area of the obtained porous carbon materials.We demonstrate that this approach significantly enhances the carbon yield of porous carbon,achieving a yield of 22%in contrast to the conventional carbonization-activation method(9%).The samples acquired through this method were found to contain a substantial amount of mesopores,with an average pore size of 1.59 to 1.85 nm and a mesopore ratio of 25.6%.Additionally,these samples showed high specific surface areas,ranging from 1051 to 1831 m2·g^(−1).Zinc ion hybrid capacitors with lignin-derived porous carbon cathode exhibited a high capacitance of 279 F·g^(−1) at 0.1 A·g^(−1) and an energy density of 99.1 Wh·kg^(−1) when the power density was 80 kW·kg^(−1).This research presents a novel approach for producing porous carbons with high yield through the utilization of a spray drying approach.

Steady rotation of a composite sphere in a concentric spherical cavity

The problem of steady rotation of a composite sphere located at the centre of a spherical container has been investigated. A composite particle referred to in this paper is a spherical solid core covered with a permeable spherical shell. The Brinkman＇s model for the flow inside the compos- ite sphere and the Stokes equation for the flow in the spheri- cal container were used to study the motion. The torque ex- perienced by the porous spherical particle in the presence of cavity is obtained. The wall correction factor is calculated. In the limiting cases, the analytical solution describing the torque for a porous sphere and for a solid sphere in an un- bounded medium are obtained from the present analysis.

Cobalt-nitrogen co-doped porous carbon sphere as highly efficient catalyst for liquid-phase cyclohexane oxidation with molecular oxygen and the active sites investigation

The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol(KA oil)is a challenging issue in the chemical industry.At present the industrial conversion of cyclohexane to cyclohexanone and cyclohexanol is normally controlled at less than 5%selectivity.Thus,the development of highly active and stable catalysts for the aerobic oxidation of cyclohexane is necessary to overcome this low-efficiency process.Therefore,we have developed a cobalt-nitrogen co-doped porous sphere catalyst,Co-NC-x(x is the Zn/Co molar ratio,where x=0,0.5,1,2,and 4)by pyrolyzing resorcinol-formaldehyde resin microspheres.It achieved 88.28%cyclohexanone and cyclohexanol selectivity and a cyclohexane conversion of 8.88%under Co-NC-2.The results showed that the introduction of zinc effectively alleviated the aggregation of Co nanoparticles and optimized the structural properties of the material.In addition,Co0 and pyridinic-N are proposed to be the possible active species,and their proportion efficiently increased in the presence of Zn^(2+)species.In this study,we developed a novel strategy to design highly active catalysts for cyclohexane oxidation.

Synthesis of porous carbon spheres derived from lignin through a facile method for high performance supercapacitors

Porous carbon spheres（PCS） derived from lignin have been prepared through a facile method and fabricated as electrodes for electric double-layer capacitors. Spherical shaped mixtures of lignosulfonate and crystalized KOH are formed by spray drying of a solution of lignosulfonate and KOH. Activation by KOH is performed at high temperatures along with lignosulfonate carbonization. With an appropriate pore structure, the obtained PCS have a specific surface area of 1372.87 m^2 g^-1 and show a capacitance of 340 F g^-1 in 3 M KOH at a current density of 0.5 A g^-1. Moreover, a symmetric supercapacitor fabricated using the PCS as electrodes show a maximum capacitance of 68.5 F g^-1, and an energy density of 9.7 W h kg^-1 at a power density of 250 W kg^-1. The capacity retention is more than 94.5% after 5000 galvanostatic chargedischarge cycles. The excellent characteristics seem to be ascribed to the pore structures of PCS that have a large specific surface area and a low electrical resistance.

Mechanism investigation of enhanced electrochemical H_(2)O_(2) production performance on oxygen-rich hollow porous carbon spheres

Electrochemical oxygen reduction is a promising approach for the sustainable decentralized production of H_(2)O_(2),but its viable commercialization is hindered by the insufficient development of efficient electrocatalysts.Here,we demonstrate a promising carbon-based catalyst,consisting of oxygen-rich hollow mesoporous carbon spheres(HMCSs),for selective oxygen reduction to H_(2)O_(2).The as-prepared HMCS exhibits high onset potential(0.82 V)and half-wave potential(0.76 V),delivering a significant positive shift compared with its oxygen-scarce counterparts and commercial Vulcan carbon.Moreover,excellent H2O2 selectivity(above 95%)and electrochemical stability(7%attenuation after 10 h operation)make this material a state-of-the-art catalyst for electrochemical H_(2)O_(2) production.The outstanding performance arises from a combination of several aspects,such as porous structure-facilitation of mass transport,large surface area,and proper distribution of oxygen-containing functional groups modification on the surface.Furthermore,the proposed oxygen reduction reaction(ORR)mechanism on HMCS surface reveals that-OH functional groups help promote the first electron transfer process while other oxygen modification facilitate the second electron transfer.

Preparation of porous polyimide microspheres by thermal degradation of block copolymers

A new preparation method has been developed for thermally stable porous polyimide microspheres. Porous polyimide microspheres were prepared using trib]ock copolymers that consisted of a thermally stable polyimide derived from pyromellitic dianhydride/4,4＇-oxydianiline as the continuous phase and a thermally labile polyether as the dispersed phase. Spheres of copolymers were generated in a nonaqueous emulsion and then gradually heated to complete the imidization to form a microphase-separated structure. Subsequently, thermal treatment at a slightly reduced pressure removed the labile blocks and produced pores. Under suitable decomposition conditions, the pore size of the porous polyimide was in the range of 200-400nm.

Direct synthesis of tin spheres/nitrogen-doped porous carbon composite by self-formed template method for enhanced lithium storage

To inhibit the agglomeration of tin-based nanomaterials and simplify the complicated synthesis process,a facile and eco-friendly self-formed template method is reported to synthesize tin submicron spheres dispersed in nitrogen-doped porous carbon(Sn/NPC)by pyrolysis of a mixture of disodium stannous citrate and urea.The vital point of this strategy is the formation of Na_(2)CO_(3)templates during pyrolysis.This self-formed Na_(2)CO_(3)acts as porous templates to support the formation of NPC.The obtained NPC provides good electronic conductivity,ample defects,and more active sites.Serving as anode for Li-ion batteries,the Sn/NPC electrode obtains a stable discharge capacity of 674.1 mAh/g after 150 cycles at 0.1 A/g.Especially,a high discharge capacity of 331.2 mAh/g can be achieved after 1100 cycles at 3 A/g.Additionally,a full cell coupled with LiCoO_(2)as cathode yields a discharge capacity of 524.8 mAh/g after 150 cycles at 0.1 A/g.In-situ XRD is implemented to investigate the alloying/dealloying reaction mechanisms.Density functional theory calculation ulteriorly explicates that NPC heightens intrinsic electronic conductivity,and NPC especially pyrrolic-N and pyridinic-N doping facilitates the Li-adsorption ability.Climbing image nudged elastic band method reveals low Li~+diffusion energy barrier in presence of N atoms,which accounts for the terrific electrochemical properties of Sn/NPC electrode.

Porous carbon spheres anode with the stable output of low delithiation plateau and constant delithiation ratio for lithium ion hybrid capacitor

Porous carbon spheres derived from the facile hydrothermal treatment associated with the calcination process exhibit the good spherical morphology and unique porous structure.For the Li-based half-cell test,porous carbon spheres electrode not only exhibits larger reversible capacities and better compatibility as compared to the widely-used graphite,but also provides stable delithiation plateaus under different current density.Additionally,the delithiation ratio below 1 V almost accounts for a constant value(around 70%)with the increase of current density,evidencing that Li intercalation storage is the dominant model and Li insertion/extraction processes are propitious.The lithium ion hybrid capacitor configured with S-doped mesoporous graphene and porous carbon spheres as cathode and anode,delivers satisfied energy and power densities(up to 177 Wh kg^(−1) and 12,303 W kg^(−1),respectively)as well as long-term cyclability,which is superior to the corresponding S-doped mesoporous graphene//graphite and activated carbon//porous carbon spheres.In addition,the developed synthesis strategy is in favor of the realization of the scalable production of porous carbon spheres.

Ru complex and N,P-containing polymers confined within mesoporous hollow carbon spheres for hydrogenation of CO_(2)to formate

The development of reliable catalysts with both excellent activity and recyclability for carbon dioxide(CO_(2))hydrogenation is challenging.Herein,a ternary hybrid heterogeneous catalyst,involving mononuclear Ru complex,N,P-containing porous organic polymers(POPs),and mesoporous hollow carbon spheres(Ru^(3+)-POPs@MHCS)is reported for CO_(2)hydrogenation to formate.Based on comprehensive structural analyses,we demonstrated that Ru^(3+)-POPs were successfully immobilized within MHCS.The optimized Ru^(3+)-0.5POPs@MHCS catalyst,which was obtained with about 5 wt.%Ru^(3+)and 0.5 mmol POPs polymers confined into 0.3 g MHCS,exhibited high catalytic activity for CO_(2)hydrogenation to formate(turnover number(TON)>1,200 for 24 h under mild reaction conditions(4.0 MPa,120℃))and improved durability,compared to Ru^(3+)catalysts without POPs polymers(Ru^(3+)-MHCS)and unencapsulated MHCS(Ru^(3+)-0.5POPs)catalysts.The improved catalytic performance is attributed to the high surface area and large pore volume of MHCS which favors dispersion and stabilization of Ru^(3+)-POPs.Furthermore,the MHCS and POPs showed high CO_(2)adsorption ability.Ru^(3+)-POPs encapsulated into MHCS reduces the activation energy barrier for CO_(2)hydrogenation to formate.

Sandwich-like chitosan porous carbon Spheres/MXene composite with high specific capacitance and rate performance for supercapacitors

The application of porous carbon microspheres derived from pure biomass in supercapacitors is restricted due to their limited reactive groups.MXene owns a combination of redox Faradic surface with good metallic conductivity and hydrophilicity,which assists to obtain high pseudocapaci-tance and energy density.Herein,Ti_(3)C_(2)T_(x)MXene was introduced to chitosan-based porous carbon microsphere(CPCM)to fabricated sandwich-like structure(CPCM/MXene)through electrostatic interaction.The Ti_(3)C_(2)T_(x)protected the spherical structure of CPCM.Meanwhile,CPCM hindered the reaggregation of Ti_(3)C_(2)T_(x)by inserting in the Ti_(3)C_(2)T_(x)layers,promoting the electrolyte migra-tion kinetics.The synergistic effect endowed CPCM/MXene high specific capacitance of 362 F/g at current density of 0.5 A/g and acceptable cycling stability with 93.87%capacitance retention at a high current density of 10 A/g after 10,000 cycles.Furthermore,CPCM/MXene displayed a high energy density of 27.8 W/(h•kg)at 500.0 W/kg of power density.These satisfactory perfor-mances prove that combining Ti_(3)C_(2)T_(x)MXene nanosheets with porous carbon microspheres is a considering method to construct a new generation electrode material of supercapacitor.

Preparation of porous silica spheres with self-dispersing properties

A sol-gel procedure in a water/oil emulsion was introduced for the synthesis of porous silica spheres. Tetraethoxysilane was used as the silica source. The specific surface area and total pore volume of the product reached 772.3 m2/g and 0.663 cm3/g, respectively. The electrolyte washing process conferred a surface charge to the product, which displayed self-dispersal properties in water. The porous spheres have potential applications in the fields of drug delivery, controlled release capsules, indoor air pollutant scavengers, and hydrogen storage agents. The oil phase, which accounts for over 8O% of the chemical cost of the procedure, could largely be recycled by filtering, standing, and layering. The whole procedure is suitable for application as an industrial process.

Hollow-in-hollow carbon spheres with hollow foam-like cores for lithium-sulfur batteries

Lithium-sulfur batteries have attracted increasing attention because of their high theoretical capadty. Using sulfur/carbon composites as the cathode materials has been demonstrated as an effective strategy to optimize sulfur utilization and enhance cycle stability as well. In this work hollow-in-hollow carbon spheres with hollow foam-like cores （HCSF@C） are prepared to improve both capability and cycling stability of lithium-sulfur batteries. With high surface area and large pore volumes, the loading of sulfur in HCSF@C reaches up to 70 wt.%. In the resulting S/HCSF@C composites, the outer carbon shell serves as an effective protection layer to trap the soluble polysulfide intermediates derived from the inner component. Consequently, the S/HCSF@C cathode retains a high capacity of 780 mAh/g after 300 cycles at a high charge/discharge rate of 1 A/g.