Integration of pore structure modulation and B,N co-doping for enhanced capacitance deionization of biomass-derived carbon

Biomass-derived carbon has demonstrated great potentials as advanced electrode for capacitive deionization(CDI),owing to good electroconductivity,easy availability,intrinsic pores/channels.However,conventional simple pyrolysis of biomass always generates inadequate porosity with limited surface area.Moreover,biomass-derived carbon also suffers from poor wettability and single physical adsorption of ions,resulting in limited desalination performance.Herein,pore structure optimization and element co-doping are integrated on banana peels(BP)-derived carbon to construct hierarchically porous and B,N co-doped carbon with large ions-accessible surface area.A unique expansionactivation(EA)strategy is proposed to modulate the porosity and specific surface area of carbon.Furthermore,B,N co-doping could increase the ions-accessible sites with improved hydrophilicity,and promote ions adsorption.Benefitting from the synergistic effect of hierarchical porosity and B,N co-doping,the resultant electrode manifest enhanced CDI performance for NaCl with large desalination capacity(29.5 mg g^(-1)),high salt adsorption rate(6.2 mg g^(-1)min^(-1)),and versatile adsorption ability for other salts.Density functional theory reveals the enhanced deionization mechanism by pore and B,N co-doping.This work proposes a facile EA strategy for pore structure modulation of biomass-derived carbon,and demonstrates great potentials of integrating pore and heteroatoms-doping on constructing high-performance CDI electrode.

Inherent mass transfer engineering of a Co,N co-doped carbon material towards oxygen reduction reaction

Oxygen reduction reaction (ORR) is an important process for the conversion and utilization of a wide range of renewable energy sources, and is critical for the shape of future energy scenario [1–10]. However, ORR is a complex four-electron transfer process and is kinetically sluggish. It is urgent to develop high-efficient electrocatalysts to solve this problem [11–15]. Up to now, precious metal-based catalysts such as Pt-based electrocatalysts have been widely studied and found to be one of the most efficient electrocatalysts for ORR. However, the high price and the small reserves limit their large-scale commercialization [10,16–23]. Therefore, in order to fulfill needs for the practical applications, it is necessary to develop low-cost electrocatalysts, also with high activity and great stability [19,24–28].

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.

Boosting the polysulfide confinement in B/N–codoped hierarchically porous carbon nanosheets via Lewis acid–base interaction for stable Li–S batteries

Carbon materials have shown remarkable usefulness in facilitating the performance of insulating sulfur cathode for lithium–sulfur batteries owing to their excellent conductivity and porous structure. However,the anxiety is the poor affinity toward polar polysulfides due to the intrinsic nonpolar surface of carbon.Herein, we report a direct pyrolysis of the mixture urea and boric acid to synthesize B/N–codoped hierarchically porous carbon nanosheets(B–N–CSs) as efficient sulfur host for lithium–sulfur battery. The graphene–like B–N–CSs provides high specific surface area and porous structure with abundant micropores(1.1 nm) and low–range mesopores(2.3 nm), thereby constraining the sulfur active materials within the pores. More importantly, the codoped B/N elements can further enhance the polysulfide confinement through strong Li–N and B–S interaction based on the Lewis acid–base theory. These structural superiorities significantly suppress the shuttle effect by both physical confinement and chemical interaction, and promote the redox kinetics of polysulfide conversion. When evaluated as the cathode host, the S/B–N–CSs composite displays the excellent performance with a high reversible capacity up to 772 m A h g–1 at 0.5 C and a low fading rate of ^0.09% per cycle averaged upon 500 cycles. In particular, remarkable stability with a high capacity retention of 87.1% can be realized when augmenting the sulfur loading in the cathode up to 4.6 mg cm^(-2).

First-principles study of metallic carbon nanotubes with boron/nitrogen co-doping

Using the first-principles calculations, we investigate the electronic band structure and the quantum transport properties of metallic carbon nanotubes （MCNTs） with B/N pair co-doping. The results about formation energy show that the B/N pair co-doping configuration is a most stable structure. We find that the electronic structure and the transport properties are very sensitive to the doping concentration of the B/N pairs in MCNTs, where the energy gaps increase with doping concentration increasing both along the tube axis and around the tube, because the mirror symmetry of MCNT is broken by doping B/N pairs. In addition, we discuss conductance dips of the transmission spectrum of doped MCNTs. These unconventional doping effects could be used to design novel nanoelectronic devices.

Boron and nitrogen co-doped porous carbon derived from sodium alginate enhanced capacitive deionization for water purification

Capacitive deionization can alleviate water shortage and water environmental pollution, but performances are greatly determined by the electrochemical and desalination properties of its electrode materials. In this work, B and N co-doped porous carbon with micro-mesoporous structures is derived from sodium alginate by a carbonization, activation, and hydrothermal doping process, which exhibits large specific surface area (2587 m^(2)·g^(‒1)) and high specific capacitance (190.7 F·g^(‒1)) for adsorption of salt ions and heavy metal ions. Furthermore, the materials provide a desalination capacity of 26.9 mg·g−1 at 1.2 V in 500 mg·L^(‒1) NaCl solution as well as a high removal capacity (239.6 mg·g^(‒1)) and adsorption rate (7.99 mg·g^(‒1)·min^(‒1)) for Pb2+ with an excellent cycle stability. This work can pave the way to design low-cost porous carbon with high-performances for removal of salt ions and heavy metal ions.

Edge-enriched N, S co-doped hierarchical porous carbon for oxygen reduction reaction

The development of carbon materials with high electrochemical performance for next-generation energy device is emerging, especially N, S co-doped carbon materials have sparked intensive attention. However,the exploration of N, S co-doped carbon with well-defined active sites and hierarchical porous structures are still limited. In this study, we prepared a series of edge-enriched N, S co-doped carbon materials through pyrolysis of thiourea(TU) encapsulated in zeolitic imidazolate frameworks(TU@ZIF) composites,which delivered very good oxygen reduction reaction(ORR) performance in alkaline medium with onset potential of 0.94 V vs. reversible hydrogen electrode(RHE), good stability and methanol tolerance. Density functional theory(DFT) calculations suggested that carbon atoms adjacent to N and S are probable active sites for ORR intermediates in edge-enriched N, S co-doped carbon materials because higher electron density can enhance O_(2)adsorption, lower formation barriers of intermediates, improving the ORR performance comparing to intact N, S co-doped carbon materials. This study might provide a new pathway for improving ORR activity by the integration engineering of edge sites, and electronic structure of heteroatom doped carbon electrocatalysts.

Tuning electron delocalization and surface area in COFs derived N,B co-doped carbon materials for efficient selective hydrogenation of nitroarenes

Metal-free carbon catalysts with excellent conduction performance have drawn much research attention in reduction reactions.Herein,a N,B co-doped carbon catalyst with high pyrrolic N proportion(35.75%)and excellent surface area(1409 m^(2)/g)was successfully prepared via carbonizing covalent organic framework materials(COFs)containing N and B atoms assisted by ZnCl_(2)molten salt.The presence of ZnCl_(2)maintains the micropore structure of COFs to provide high specific surface areas and abundant lattice defects for carbon materials.In addition,electron-withdrawing B heteroatom further facilitates the formation of pyrrolic N at defect sites by modifying the electronic structure of carbon network.The tuning of surface areas and active N species in carbon catalysts successfully improve the selective hydrogenation of nitrobenzene to aniline.The optimized carbon material exhibits excellent nitrobenzene conversion(99.9%)and aniline selectivity(>99%)within 15 min,as well as excellent substrate suitability.This work provides a certain guiding for the design and application of metal-free catalysis.

Realization of solid-state red fluorescence and concentration-induced multicolor emission from N,B co-doped carbon dots

As a new type of luminescent material,carbon dots(CDs)have attracted increased attention for their superior optical properties in recent years.However,solidstate fluorescent CDs,especially with red emission,are still a major challenge.Here,CDs with solid-state red emission were synthesized by co-doping of N and B using the one-step microwave method.The CD powder exhibits excitation-independent solid-state red fluorescence without any dispersion matrices,with optimum solid-state fluorescence wavelength of 623 nm.The hydrogen bonding interaction in CDs is helpful for solid-state fluorescence of CDs.The IG/ID value of CDs reaches up to 3.49,suggesting their very high graphitization degree,which is responsible for their red emission.In addition,CDs show the concentration-induced multicolor emission,which is attributed to the decreased energy gap in the high concentrated CD solution.To exploit their concentration-dependent emission,CDs with changing ratio in matrices are applied as a color-converting layer on ultraviolet chip to fabricate multicolor light-emitting diodes with light coordinates of(0.33,0.38),(0.41,0.48),(0.49,0.44),and(0.67,0.33),which belong to green,yellow,orange,and red light,respectively.

Highly N/O co-doped ultramicroporous carbons derived from nonporous metal-organic framework for high performance supercapacitors

A new nonporous Zn-based metal-organic framework(NPMOF) synthesized from a high nitrogencontaining rigid ligand was converted into porous carbon materials by direct carbonization without adding additional carbon sources.A series of NPMOF-derived porous carbons with very high N/O contents(24.1% for NPMOF-700,20.2% for NPMOF-800,15.1% for NPMOF-900) were prepared by adjusting the pyrolysis temperatures.The NPMOF-800 fabrica ted electrode exhibits a high capacitance of220 F/g and extremely large surface area normalized capacitance of 57.7 μF/cm~2 compared to other reported MOF-derived porous carbon electrodes,which could be attributed to the abundant ultramicroporosity and high N/O co-doping.More importantly,symmetric supercapacitor assembled with the MOF-derived carbon manifests prominent stability,i.e.,99.1 % capacitance retention after 10,000 cycles at 1.0 A/g.This simple preparation of MOF-derived porous carbon materials not only finds an application direction for a variety of porous or even nonporous MOFs,but also opens a way for the production of porous carbon materials for superior energy storage.

Self-sacrificial template synthesis of Fe, N co-doped porous carbon as efficient oxygen reduction electrocatalysts towards Zn-air battery application

Designing highly efficient non-precious based electrocatalysts for oxygen reduction reaction(ORR) is of significance for the rapid development of metal-air batteries.Herein,a hydrothermal-pyrolysis method is employed to fabricate Fe,N co-doped porous carbon materials as effective ORR electrocatalyst through adopting graphitic carbon nitride(g-C_(3)N_(4)) as both the self-sacrificial templates and N sources.The gC_(3)N_(4)provides a high concentration of unsaturated pyridine-type N to coordinate with iron to form Fe-N active sites.Through adjusting the Fe doping amounts,it is proved that appropriate Fe doping content is conducive to the construction of abundant defects and active sites of Fe-N.The as-prepared catalyst exhibits superior electrocatalytic ORR performance in alkaline media with half-wave potential(E_(1/2)=0.82 V) and onset potential(E_(onset)=0.95 V),equivalent to the commercial Pt/C catalyst.Moreover,there is almost no activity loss after 10 k continuous cyclic voltammetry cycles and methanol tolerance,indicating the excellent durability and superior methanol tolerance.Remarkably,when assembled as the cathode in a Zn-air battery,the device displays a power density of 99 mW/cm^(2),an open-circuit potential of 1.48 V and long-term discharge-charge cycling stability,indicating the promising potential to substitute the Pt catalyst for practical application.

N,O co-doped porous carbon with rich pseudocapacitive groups exhibiting superior energy density in an acidic 2.4 V Li_(2)SO_(4)electrolyte

Designing a carbon material with a unique composition and surface functional groups for offering high specific capacity in a wide voltage window is of great significance to improve the energy density for the supercapacitor in a cheap and eco-friendly aqueous electrolyte.Herein,we develop an efficient strategy to synthesize a N,O co-doped hierarchically porous carbon(NODPC-1.0)with moderate specific surface area and pore volume as well as rich heteroatoms using a deep eutectic solvent(DES)as an activator.It is found that NODPC-1.0 with a large proportion of pseudocapacitive functional groups(pyrrole-N,pyridineN and carbonyl-quinone)can work stable in an acidic 2 mol/L Li_(2)SO_(4)(pH 2.5)electrolyte,exhibiting specific capacities of 375 and 186 F/g at the current densities of 1.0 and 100 A/g,respectively.Also,the assembled symmetric capacitor using the NODPC-1.0 as the active material and 2 mol/L acidic Li_(2)SO_(4)(pH 2.5)as the electrolyte shows an outstanding energy density of 74.4 Wh/kg at a high power density of 1.44 k W/kg under a broad voltage window(2.4 V).Relevant comparative experiments indicate that H+of the acidic aqueous electrolyte plays a crucial part in enhancement the specific capacity,and the abundant pseudocapacitive functional groups on the surface of the NODPC-1.0 sample play the key role in the improvement of electrochemical cycle stability under a broad voltage window.

A high-performance potassium-ion capacitor based on a porous carbon cathode originated from the Aldol reaction product

Potassium-ion capacitors(KICs) emerge as a promising substitute for the well-developed lithium-ion capacitors(LICs),however,the energy density of KICs is below expectations because of lacking a suitable electrical double-layer positive electrode.Using chemical activation of the Aldol reaction product of acetone with KOH,we synthesized a porous ca rbon with a Brunauer-Emmett-Teller surface area of up to 2947 m2/g and a narrow pore size distribution ranging from 1 nm to 3 nm.Half-cell(versus potassium metal) test demonstrates that this porous carbon has high capacitive performance in K+ based organic electrolytes.Furthermore,a novel KIC fabricated by this porous carbon as the cathode,yields high values of energy density and power density.The processes used to make this porous carbon are readily low-cost to fabricate metal-ion capacitors.

B-incorporated,N-doped hierarchically porous carbon nanosheets as anodes for boosted potassium storage capability

Carbonaceous nanomaterials with porous structure have become the highly promising anode materials for potassium-ion batteries(PIBs)due to their abundant resources,low-cost,and excellent conductivity.Nevertheless,the sluggish reaction kinetics and inferior cycling life caused by the large radius of K ions severely restrict their commercial development.Herein,B,N co-doped hierarchically porous carbon nanosheets(BNPC)are achieved via a facile template-assisted route,followed by a simple one-step carbonization process.The resultant BNPC possesses a unique porous structure,large surface area,and high-level B,N co-doping.The structural features endows it with remarkable potassium storage performances,which delivers a high reversible capacity(242.2 mA h/g at100 m A/g after 100 cycles),and long cycling stability(123.1 m Ah/g at 2000 m A/g and 62.9 m Ah/g at5000 mA/g after 2000 cycles,respectively).Theoretical simulations further validate that the rich B doping into N-modified carbon configuration can greatly boost the potassium storage capability of the BNPC anode.

Binary doping of nitrogen and phosphorus into porous carbon: A novel di-functional material for enhancing CO_(2) capture and super-capacitance

Designing of hetero-atomic doped carbon-based systems through pyrolysis of abundant element organic precursors is a novel approach to construct rational porous carbon materials.Herein,a highly-cross-linked triazine polymer is employed to fabricate N,P co-doped porous carbon(A-TDP-12)with tunable active nitrogen in the carbon framework for simultaneous enhancement of CO_(2) capture capability and Supercapacitance(SC).The synthesized A-TDP-12 possesses a typical hierarchically porous framework(micro-pores and meso-pores)with a large surface area(1332 m^(2) g^(-1))and a rich content of N(7.89 at.%)and P(0.74 at.%).It delivers a CO_(2) adsorption capacity of 1.52 and 5.68 mmol g^(-1) at 1 and 5 bar,respectively,with almost no decay after successive 8 recycles.In 6 M KOH aqueous electrolyte,A-TDP-12 exhibits a superior specific capacitance of 172.7 F g^(-1) at a current density of 1 A g^(-1).Even at a high current density of 10 A g^(-1),80%of its initial capacity still remains.This work not only offers a novel strategy for fabricating promising adsorbents and electrodes for CO_(2) uptake and SCs,but also provides new insights into design of porous carbon material for related applications.