A lightweight nitrogen/oxygen dual-doping carbon nanofiber interlayer with meso-/micropores for high-performance lithium-sulfur batteries

Lithium-sulfur(Li-S) batteries are promising energy-storage devices for future generations of portable electronics and electric vehicles because of the outstanding energy density,low cost,and nontoxic nature of S.In the past decades,various novel electrodes and electrolytes have been studied to improve the performance of Li-S batteries.However,the very limited lifespan and rate performance of Li-S batteries originating from the dissolution and diffusion of long-chain polysulfides in liquid electrolytes,and the intrinsic poor conductivity of S severely hinder their practical application.Herein,an electrospinning method was developed to fabricate a thin conductive interlayer consisting of meso-/microporous N/O dual-doping carbon nanofiber(CNF).The freestanding 3 D interwoven structure with conductive pathways for electrons and ions can enhance the contact between polysulfides and N/O atoms to realize the highly robust trapping of polysulfides via the extremely polar interaction.Consequently,combining the meso-microporous N/O dual-doping CNF interlayer with a monodispersed S nanoparticle cathode results in a superior electrochemical performance of 862.5 mAh/g after 200 cycles at 0.2 C and a cycle decay as low as 0.08% per cycle.An area specific capacity of 5.22 mAh/cm^(2) can be obtained after 100 cycles at 0.1 C with a high S loading of 7.5 mg/cm^(2).

Complementary dual-doping of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)cathode enhances ion-diffusion and stability for Li-ion batteries

The Ni-richLiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)layered cathodes endow Li-ion batteries(LIBs)with high energy density.However,they usually suffer from limited ion-diffusion and structural instability during cycling.Although doping strategy can effectively alleviate these issues,the coupling effects of multi-element doping and the corresponding performance enhancement mechanism have been yet unclear.Here,we report a Zr/Ti dual-doped NCM811 cathode material(ZT-NCM811),in which Zr-ion is doped into both transition metal(TM)layers and lithium layers and Ti-ion is only distributed in TM layers.The dual-doping can effectively enhance crystal structure stability via inhibiting the lattice collapse along c-axis and decreasing the Li/Ni disorder.Meantime,the lattice oxygen escape is also greatly reduced due to the presence of stronger Zr-O and Ti-O bonds,further mitigating the crystal surface parasitic reactions with electrolyte.The resultant ZT-NCM811 exhibits high specific capacity of 124 m Ah/g at even 10 C,much higher than undoped and single-doped NCM811,and a retention of 98.8%at 1 C after 100 cycles.The assembled ZT-NCM811/graphite full cell also delivers superior battery performances and durability.

Inside-out dual-doping effects on tubular catalysts:Structural and chemical variation for advanced oxygen reduction performance

Dual-doping of carbon,especially the combination of nitrogen and a secondary heteroatom,has been demonstrated efficient to optimize the oxygen reduction reaction(ORR)performance.However,the optimum dual-doping is still not clear due to the lack of strong experimental proofs,which rely on a reliable method to prepare carbon materials that can rule out the interference factors and then emphasize only the doping effects.In this work,an inside-out doping method is reported to prepare carbon submicrotubes(CSTs)as a material to study the principles of designing dual-doping catalysts for ORR.The interference factors including the metal impurities and doping gradient in the bulk phase are excluded,and the doping effects including the structural and chemical variation of carbon are studied.P-doping exhibited a higher pore-forming ability to perforate carbon and a lower doping content,but a higher ORR catalytic activity as compared with S-and B-doped N-CSTs,demonstrating the N,P co-doping is more efficient in making carbon-based catalysts for ORR.First-principle calculations reveal that the edge C situated around the oxidized P site nearby a graphitic N atom is the active site that shows the lowest ORR overpotential comparable to Pt-based catalysts.This study suggests that the catalytic activity of dual-heteroatoms-doped carbons not only depends on the intrinsic chemical bonding between heteroatoms and carbon,but also is affected by the structural variation generated by introducing different atoms,which can be extended to the study of other kinds of functionalization of carbon and potential reactions besides ORR.

Synergistic Effect of Dual-Doped Carbon on MO_(2)C Nanocrystals Facilitates Alkaline Hydrogen Evolution

Molybdenum carbide(MO_(2)C)materials are promising electrocatalysts with potential applications in hydrogen evolution reaction(HER)due to low cost and Pt-like electronic structures.Nevertheless,their HER activity is usually hindered by the strong hydrogen binding energy.Moreover,the lack of water-cleaving site's makes it difficult for the catalysts to work in alkaline solutions.Here,we designed and synthesized a B and N dual-doped carbon layer that encapsulated on MO_(2)C nanocrystals(MO_(2)C@BNC)for accelerating HER under alkaline condition.The electronic interactions between the MO_(2)C nanocrystals and the multiple-doped carbon layer endow a near-zero H adsorption Gibbs free energy on the defective C atoms over the carbon shell.Meanwhile,the introduced B atoms afford optimal H_2O adsorption sites for the water-cleaving step.Accordingly,the dual-doped MO_(2)C catalyst with synergistic effect of non-metal sites delivers superior HER performances of a low overpotential(99 mV@10 mA cm^(-2))and a small Tafel slope(58.1 mV dec^(-1))in 1 M KOH solution.Furthermore,it presents a remarkable activity that outperforming the commercial 10%Pt/C catalyst at large current density,demonstrating its applicability in industrial water splitting.This study provides a reasonable design strategy towards noble-metal-free HER catalysts with high activity.

Nitrogen/sulphur dual-doped hierarchical carbonaceous fibers boosting potassium-ion storage

The carbon materials as anode electrodes have been widely studied for potassium ion batteries(PIBs).However,the large size of potassium ions prevents their intercalation/deintercalation,resulting in poor storage behaviors.Herein,a novel design of N/S codoped hierarchical carbonaceous fibers(NSHCF)formed from nanosheets self-assembled by catalyzing Aspergillus niger with Sn is reported.The asprepared NSHCF at 600℃(NSHCF-600)exhibits a high reversible capacity of 345.4 m Ah g^(-1) at 0.1 A g^(-1) after 100 cycles and an excellent rate performance of 124.5 m Ah g^(-1) at 2 A g^(-1).The excellent potassium storage performance can be ascribed to the N/S dual-doping,which enlarges interlayer spacing(0.404 nm)and introduces more defects.The larger interlayer spacing and higher pyridinic N active sites can promote K ions diffusion and storage.In addition,the ex situ transmission electron microscopy reveals the high reversibility of potassiation/depotassiation process and structural stability.

Cu_(3)P nanoparticles confined in nitrogen/phosphorus dual-doped porous carbon nanosheets for efficient potassium storage

Immobilizing primary electroactive nanomaterials in porous carbon matrix is an effective approach for boosting the electrochemical performance of potassium-ion batteries (PIBs) because of the synergy among functional components. Herein, an integrated hybrid architecture composed of ultrathin Cu_(3)P nanoparticles (~20 nm) confined in porous carbon nanosheets (Cu_(3)P⊂NPCSs) as a new anode material for PIBs is synthesized through a rational self-designed self-templating strategy. Benefiting from the unique structural advantages including more active heterointerfacial sites, intimate and stable electrical contact, effectively relieved volume change, and rapid K^(+) ion migration, the Cu_(3)P⊂NPCSs indicate excellent potassium-storage performance involving high reversible capacity, exceptional rate capability, and cycling stability. Moreover, the strong adsorption of K^(+) ions and fast potassium-ion reaction kinetics in Cu_(3)P⊂NPCSs is verified by the theoretical calculation investigation. Noted, the intercalation mechanism of Cu_(3)P to store potassium ions is, for the first time, clearly confirmed during the electrochemical process by a series of advanced characterization techniques.

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole （Fe-N/C） catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid （TsOH）, by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction （ORR） in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry （CV） and rotating disk electrode （RDE） are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of -1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction （XRD）, scanning electron microscope （SEM） and X-ray photoelectron spectroscopy （XPS） are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C-Sn-C, an additional beneficial factor for the ORR.

Regulated adsorption-diffusion and enhanced charge transfer in expanded graphite cohered with N,B bridge-doping carbon patches to boost K-ion storage

The great challenges are remained in constructing graphite-based anode with well built-in structures to accelerate kinetics and enhance stability in the advanced K-ion batteries(KIBs).Here,we firstly report the design of expanded graphite cohered by N,B bridge-doping carbon patches(NBEG)for efficient K-ion adsorption/diffusion and long-term durability.It is the B co-doping that plays a crucial role in maximizing doping-site utilization of N atoms,balancing the adsorption-diffusion kinetics,and promoting the charge transfer between NBEG and K ions.Especially,the robust lamellar structure,suitable interlayer distance,and rich active sites of the designed NBEG favor the rapid ion/electron transfer pathways and high K-ion storage capacity.Consequently,even at a low N,B doping concentration(4.36 at%,2.07 at%),NBEG anode shows prominent electrochemical performance for KIBs,surpassing most of the advanced carbon-based anodes.Kinetic studies,density functional theory simulations,and in-situ Raman spectroscopy are further performed to reveal the K-ion storage mechanism and confirm the critical actions of co-doping B.This work offers the new methods for graphite-electrode design and the deeper insights into their energy storage mechanisms in KIBs.

A combination therapy for androgenic alopecia based on quercetin and zinc/copper dual-doped mesoporous silica nanocomposite microneedle patch

A nanocomposite microneedle(ZCQ/MN)patch containing copper/zinc dual-doped mesoporous silica nanoparticles loaded with quercetin(ZCQ)was developed as a combination therapy for androgenic alopecia(AGA).The degradable microneedle gradually dissolves after penetration into the skin and releases the ZCQ nanoparticles.ZCQ nanoparticles release quercetin(Qu),copper(Cu^(2+))and zinc ions(Zn^(2+))subcutaneously to synergistically promote hair follicle regeneration.The mechanism of promoting hair follicle regeneration mainly includes the regulation of the main pathophysiological phenomena of AGA such as inhibition of dihydrotestosterone,inhibition of inflammation,promotion of angiogenesis and activation of hair follicle stem cells by the combination of Cu^(2+)and Zn^(2+)ions and Qu.This study demonstrates that the systematic intervention targeting different pathophysiological links of AGA by the combination of organic drug and bioactive metal ions is an effective treatment strategy for hair loss,which provides a theoretical basis for development of biomaterial based anti-hair loss therapy.

3D nitrogen and boron dual-doped carbon quantum dots/reduced graphene oxide aerogel for advanced aqueous and flexible quasi-solid-state zinc-ion hybrid capacitors

As prospective energy storage devices,zinc-ion hybrid capacitors(ZHCs)still suffer from unsatisfactory cathode materials.Herein,the three dimensional(3D)N,B dual-doped carbon quantum dots/reduced graphene oxide(N,B-CQDs/rGO)composite aerogel is prepared via a onepot hydrothermal method.Thanks to the synergism of CQDs modification and N,B dual-doping,the resultant N,B-CQDs/rGO composite aerogel delivers superior electrochemical properties.Furthermore,the as-obtained N,B-CQDs/rGO composite aerogel is served as a cathode for aqueous and flexible quasi-solid-state ZHCs for the first time.Impressively,the aqueous N,B-CQDs/rGO//Zn ZHC manifests a large energy density of 96.2 Wh·kg^(-1)at80 W·kg^(-1)and still remains a high energy density of 54.7Wh·kg^(-1)at a superb power density of 80 kW·kg^(-1).Meanwhile,kinetic analyses are employed to elucidate the prominent power performance,and various ex situ tests are undertaken to explore the energy storage mechanism of aqueous ZHC.More notably,the flexible quasi-solid-state N,B-CQDs/rGO//Zn ZHC displays a desirable energy density(89.1μWh·cm^(-2)),a superior power density(96,000μW·cm^(-2))and exceptional flexible performance.The present study offers a valuable reference for designing and developing advanced cathode materials for aqueous and flexible quasi-solid-state ZHCs.

Direct insight into sulfiphilicity-lithiophilicity design of bifunctional heteroatom-doped graphene mediator toward durable Li-S batteries

The practical applications of lithium-sulfur(Li-S)battery have been greatly hindered by the severe polysulfide shuttle at the cathode and rampant lithium dendrite growth at the anode.One of the effective solutions deals with concurrent management of both electrodes.Nevertheless,this direction remains in a nascent stage due to a lack of material selection and mechanism exploration.Herein,we devise a temperature-mediated direct chemical vapor deposition strategy to realize the controllable synthesis of three-dimensional boron/nitrogen dual-doped graphene(BNG)particulated architectures,which is employed as a light-weighted and multi-functional mediator for both electrodes in Li-S batteries.Benefiting from the“sulfiphilic”and“lithiophilic”features,the BNG modified separator not only enables boosted kinetics of polysulfide transformation to mitigate the shuttle effect but also endows uniform lithium deposition to suppress the dendritic growth.Theoretical calculations in combination with electro-kinetic tests and operando Raman analysis further elucidate the favorable sulfur and lithium electrochemistry of BNG at a molecular level.This work offers direct insight into the mediator design via controllable synthesis of graphene materials to tackle the fundamental challenges of Li-S batteries.

Facile synthesis of Co and Ce dual-doped Ni3S2 nanosheets on Ni foam for enhanced oxygen evolution reaction

Nano Research volume 13,pages2130–2135(2020)Cite this article 376 Accesses 2 Citations Metrics details Abstract Developing efficient and stable oxygen evolution reaction(OER)electrocatalysts via doping strategy has well-documented for electrochemical water splitting.Herein,a homogeneous structure(denoted as Co/Ce-Ni3S2/NF)composed of Co and Ce dual doped Ni3S2 nanosheets on nickel foam was synthesized by a facile one-step hydrothermal method.Co and Ce dopants are distributed inside the host sulfide,thereby raising the active sites and the electrical conductivity.Besides,the CeOx nanoparticles generated by part of the Ce dopants as a cocatalyst further improve the catalytic activity by adding defective sites and enhancing the electron transfer.As a consequence,the obtained Co/Ce-Ni3S2/NF electrode exhibits better electrocatalytic activity than single Co or Ce doped Ni3S2 and pure Ni3S2,with low overpotential(286 mV)at 20 mA-cm^−2,a small Tafel slope and excellent long-term durability in strong alkaline solution.These results presented here not only offer a novel platform for designing transition metal and lanthanide dual-doped catalysts,but also supply some guidelines for constructing catalysts in other catalytic applications.

Pulse-potential electrochemistry to boost real-life application of pseudocapacitive dual-doped polypyrrole

Polypyrrole(PPy)is a very promising pseudocapacitive electrode material for supercapacitors.However,the poor electrochemical performances and cycling stability caused by volumetric change and counterion drain severely limited its practical application and commercialization.Herein,we present a pulsepotential polymerization strategy for uniformly depositing a dual-doped PPy with ordered and shorter molecular structure by balancing the concentration polarization.Such a strategy ensures more homogeneous stress distribution of PPy during ultralong cycling tests and improves the cycle stability.Moreover,the pulse-potential polymerized PPy with dual anion doping behavior induces enhanced protonation level and improved electrical conductivity,which boosting the charge transfer kinetics.Therefore,the as-synthesized PPy exhibits a remarkable capacitance performance(7250 mF/cm^(2)@3 mA/cm^(2)),outstanding rate capability(3073 mF/cm^(2)@200 mA/cm^(2))and a long cycle life.The assembled symmetric and asymmetric supercapacitors(ASC)exhibit good energy densities(0.8 mWh/cm^(2) for ASC and 0.5 mWh/cm^(2) for symmetric supercapacitor),and excellent durability with zero capacitive loss after 35,000 cycles.In addition,we have fabricated small pouch devices,which can effectively operate a variety of electronic products(including the high-voltage 5 V smartphone,and tablet)and well withstand the external extreme tests during operation,demonstrating the quantitative investigation of the real-life application of aqueous supercapacitors.

Covalent Triazine Frameworks-derived N,P Dual-doped Porous Carbons for Highly Efficient Electrochemical Reduction of CO_(2)

Electroreduction of CO_(2)into chemicals is of great importance in the global carbon balance.Although noble-metal based catalysts and single-atom catalysts(SACs)are known to be active for CO_(2)electroreduction reaction(CO_(2)RR),the high cost of noble-metal and the lack of effective synthesis approaches to prepare SACs have tremendously hindered the application.Non-metal doped carbon materials have attracted great interest because of their reasonable cost,chemical stability and excellent electrical conductivity.Nevertheless,the design and fabrication of highly efficient non-metal doped carbon electrocatalysts for CO_(2)RR to meet industry demands still remains a big challenge.Herein,triphenylphosphine@covalent triazine frameworks(CTFs)composites were employed as precursors to fabricate N,P dual-doped porous carbon catalysts PCTF-X-Y(X represents the carbonization temperature,and Y represents the mass ratio of CTF to triphenylphosphine)for CO_(2)RR.Due to the high specific surface areas and synergistic effect between N and P,the obtained PCTF-1000-5 exhibited high selectivity for CO production up to 84.3%at–0.7 V versus the reversible hydrogen electrode(vs.RHE)and long-term durability over 16 h,which are better than the reported N,P dual-doped carbon catalysts in aqueous media.This work provides a new way to design and fabricate non-metal catalysts for electrocatalysis.

Porous nitrogen/halogen dual-doped nanocarbons derived from imidazolium functionalized cationic metal-organic frameworks for highly efficient oxygen reduction reaction

Heteroatom-doped carbon materials as alternative catalysts for oxygen reduction reaction(ORR)have drawn increasing attention due to their tunable chemical and electronic structures for achieving high activity and stability. However, there still remains a great challenge to fabricate porous heteroatoms dual-doped carbons with uniformly doping in a facile and controllable way. Herein,imidazole/imidazolium-functionalized metal-organic frameworks(MOFs) are employed as precursors and templates to achieve porous nitrogen and halogen dual-doped nanocarbons. Among these carbon materials, the as-prepared nitrogen/bromine dual-doped catalyst BrNC-800 exhibits the best ORR performance with a positive half-wave potential at 0.80 V(vs. RHE) in 0.1 mol L-1 KOH, which is comparable to the benchmark commercial 20 wt% Pt/C catalyst. BrNC-800 shows excellent long term stability and methanol tolerance.This work provides a facile approach to fabricate highly efficient heteroatoms dual-doped carbon catalysts for energy conversion.

Boron and nitrogen dual-doped carbon as a novel cathode for high performance hybrid ion capacitors

Hybrid ion capacitors have been considered as a very attractive energy source with high energy density and power density since it combines both merits of lithium ion batteries and supercapacitors. However,their commercial application has been limited by the mismatch of charge-storage capacity and electrode kinetics between the capacitor-type cathode and battery-type anode. Herein, B and N dual-doped 3D superstructure carbon cathode is prepared through a facile template method. It delivers a high specific capacity, excellent rate capability and good cycling stability due to the B, N dual-doping, which has a profound effect in control the porosity, functional groups, and electronic conductivity for the carbon cathode. The hybrid ion capacitors using B, N dual-doping carbon cathode and prelithiated graphite anode show a high energy density of 115.5 Wh/kg at 250 W/kg and remain about 53.6 Wh/kg even at a high power density of 10 kW/kg. Additionally, the novel hybrid device achieves 76.3% capacity retention after 2000 cycles tested at 1250 W/kg power density. Significantly, the simultaneous manipulation of heteroatoms in carbon materials provides new opportunities to boost the energy and power density for hybrid ion capacitors.

Effect of doping order on metal-free heteroatoms dual-doped carbon as oxygen reduction electrocatalyst

Metal-free heteroatoms dual-doped carbon has been recognized as one of the most promising Pt/C-substitutes for oxygen reduction reaction(ORR).Herein,we optimize the preparation process by doping order of metal-free heteroatoms to obtain the best electrocatalytic performance through three types of dual-doped carbon,including XC-N(first X doping then N doping),NC-X(first N doping then X doping) and NXC(N and X doping)(X=P,S and F).XC-N has more defect than the other two indicated by Raman spectra.X-ray photoelectron spectrom(XPS) measurements indicate that N and X have been dual-doped into the carbon matrix with different doping contents and modes,Electrocatalytic results,including the potential of ORR peak(Ep),the half-wave potential,the diffusion-limiting current density mainly follows the order of XC-N>NC-X> NXC,Furthermore,the synergistic effect of second atom doping are also compared with the single doped carbon(NC,PC,SC and FC).The differences in electronegativity and atomic radius of these metal-free heteroatoms can affect the defect degree,the doping content and mode of hete roatoms on carbon matrix,induce polarization effect and space effect to affect O2 adsorption and product desorption,ultimately to the ORR electrocatalytic performance.

Realizing high thermoelectric performance via selective resonant doping in oxyselenide BiCuSeO

Tuning the charge carrier concentration is imperative to optimize the thermoelectric(TE)performance of a material.For BiCuSeO based oxyselenides,doping efforts have been limited to optimizing the carrier concentration.In the present work,dual-doping of In and Pb at Bi site is introduced for p-type BiCuSeO to realize the electric transport channels with intricate band characteristics to improve the power factor(PF).Herein,the impurity resonant state is realized via doping of resonant dopant In over Pb,where Pb comes forward to optimize the Fermi energy in the dual-doped BiCuSeO system to divulge the significance of complex electronic structure.The manifold roles of dual-doping are used to adjust the elevation of the PF due to the significant enhancement in electrical properties.Thus,the combined experimental and theoretical study shows that the In/Pb dual doping at Bi sites gently reduces bandgap,introduces resonant doping states with shifting down the Fermi level into valence band(VB)with a larger density of state,and thus causes to increase the carrier concentration and effective mass(m*),which are favorable to enhance the electronic transport significantly.As a result,both improved ZTmax=0.87(at 873 K)and high ZTave=0.5(at 300–873 K)are realized for InyBi(1−x)−yPbxCuSeO(where x=0.06 and y=0.04)system.The obtained results successfully demonstrate the effectiveness of the selective dual doping with resonant dopant inducing band manipulation and carrier engineering that can unlock new prospects to develop high TE materials.

N,P-dual doped carbon with trace Co and rich edge sites as highly efficient electrocatalyst for oxygen reduction reaction

Oxygen reduction reaction （ORR） is key to fuel cells and metal-air batteries which are considered as the al- ternative clean energy. Various carbon materials have been widely researched as ORR electrocatalysts. It has been ac- cepted that heteroatom doping and exposure of the edge sites can effectively improve the activity of carbon materials. In this work, we used a simple method to prepare a novel N, P-dual doped carbon-based catalyst with many holes on the surface. In addition, trace level Co doping in the carbon material forming Co-N-C active species can further enhance the ORR performance. On one hand, the doping can adjust the elec- tronic structure of carbon atoms, which would induce more active sites for ORR. And on the other hand, the holes formed on the surface of carbon nanosheets would expose more edge sites and can improve the intrinsic activity of carbon. Due to the heteroatom doping and the exposed edge sites, the pre- pared carbon materials showed highly excellent ORR perfor- mance, dose to that of commercial Pt/C.