Construction of nitrogen and phosphorus co-doped graphene quantum dots/Bi5O7I composites for accelerated charge separation and enhanced photocatalytic degradation performance

Nitrogen and phosphorus co-doped graphene quantum dot-modified Bi5O7 I(NPG/Bi5O7 I)nanorods were fabricated via a simple solvothermal method.The morphology,structure,and optical properties of the as-prepared samples were investigated by X-ray diffraction,scanning electron microscopy,high-resolution transmission electron microscopy,X-ray photoelectron spectroscopy(XPS),and diffused reflectance spectroscopy.The photocatalytic performance was estimated by degrading the broad-spectrum antibiotics tetracycline and enrofloxacin under visible light irradiation.The photodegradation activity of Bi5O7 I improved after its surface was modified with NPGs,which was attributed to an increase in the photogenerated charge transport rate and a decrease in the electron-hole pair recombination efficiency.From the electron spin resonance spectra,XPS valence band data,and free radical trapping experiment results,the main active substances involved in the photocatalytic degradation process were determined to be photogenerated holes and superoxide radicals.A possible photocatalytic degradation mechanism for NPG/Bi5O7 I nanorods was proposed.

Hierarchical sulfur and nitrogen co-doped carbon nanocages as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air battery

Exploring inexpensive and efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) is critical for rechargeable metal-air batteries. Herein, we report a new 3D hierarchical sulfur and nitrogen co-doped carbon nanocages(hSNCNC) as a promising bifunctional oxygen electrocatalyst by an in-situ MgO template method with pyridine and thiophene as the mixed precursor. The as-prepared h SNCNC exhibits a positive half-wave potential of 0.792 V(vs. reversible hydrogen electrode, RHE) for ORR, and a low operating potential of 1.640 V at a 10 mA cm-2 current density for OER. The reversible oxygen electrode index is 0.847 V, far superior to commercial Pt/C and IrO2,which reaches the top level of the reported bifunctional catalysts. Consequently, the hSNCNC as air cathodes in an assembled Zn-air battery features low charge/discharge overpotential and long lifetime. The remarkable properties arises from the introduced multiple heteroatom dopants and stable 3D hierarchical structure with multi-scale pores, which provides the abundant uniform high-active S and N species and efficient charge transfer as well as mass transportation. These results demonstrate the potential strategy in developing suitable carbon-based bi-/multi-functional catalysts to enable the next generation of the rechargeable metal-air batteries.

Ultralong nitrogen/sulfur Co-doped carbon nano-hollowsphere chains with encapsulated cobalt nanoparticles for highly efficient oxygen electrocatalysis

The development of simple and effective strategies to prepare electrocatalysts,which possess unique and stable structures comprised of metal/nonmetallic atoms for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),is currently an urgent issue.Herein,an efficient bifunctional electrocatalyst featured by ultralong N,S-doped carbon nano-hollow-sphere chains about 1300 nm with encapsulated Co nanoparticles(Co-CNHSCs)is developed.The multifunctional catalytic properties of Co together with the heteroatom-induced charge redistribution(i.e.,modulating the electronic structure of the active site)result in superior catalytic activities toward OER and ORR in alkaline media.The optimized catalyst Co-CNHSC-3 displays an outstanding electrocatalytic ability for ORR and OER,a high specific capacity of 1023.6 mAh gZn^(-1),and excellent reversibility after 80 h at 10mA cm^(-2)in a Zn-air battery system.This work presents a new strategy for the design and synthesis of efficient multifunctional carbon-based catalysts for energy storage and conversion devices.

Highly Reversible Li–Se Batteries with Ultra-Lightweight N,S-Codoped Graphene Blocking Layer

The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene(N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium–selenium(Li–Se)batteries exhibited a high reversible discharge capacity of 330.7 mAh g^(-1) at 1 C(1 C = 675 mA g^(-1)) after 500 cycles and high rate performance(over 310 mAh g^(-1) at 4 C) even at an active material loading as high as ～5 mg cm^(-2). This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li^+-ion conductivity, fast electronic transport in the conductive graphene framework, andstrong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li–Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix.

Tuning interface mechanism of FeCo alloy embedded N,S-codoped carbon substrate for rechargeable Zn-air battery

The interface mechanism between catalyst and carbon substrate has been the focus of research.In this paper,the FeCo alloy embedded N,S co-doped carbon substrate bifunctional catalyst(FeCo/S-NC)is obtained by a simple one-step pyrolysis strategy.The experimental results and density functional theory(DFT)calculation show that the formation of FeCo alloy is conducive to promoting electron transfer,and the introduction of S atom can enhance the interaction between FeCo alloy and carbon substrate,thus inhibiting the migration and agglomeration of particles on the surface of carbon material.The FeCo/SNC catalysts show outstanding performance for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).FeCo/S-NC shows a high half-wave potential(E_(1/2)=0.8823 V)for ORR and a low overpotential at 10 mA cm^(-2)(E_(j=10)=299 mV)for OER.In addition,compared with Pt/C+RuO_(2) assembled Zn-air battery(ZAB),the FeCo/S-NC assembled ZAB exhibits a larger power density(198.8 mW cm^(-2)),a higher specific capacity(786.1 mA h g_(zn)~(-1)),and ultra-stable cycle performance.These results confirm that the optimized composition and the interfacial interaction between catalyst and carbon substrate synergistically enhance the electrochemical performance.

Interconnected carbon nanocapsules with high N/S co-doping as stable and high-capacity potassium-ion battery anode

Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g^(−1) at 0.05 A g^(−1)), outstanding rate capability (149 mAh g^(−1) at 5 A g^(−1)) and favorable cycle stability (150m Ah g^(−1) at 2 A g^(−1) after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.

Flexible Conductive Anodes Based on 3D Hierarchical Sn/NS-CNFs@rGO Network for Sodium-Ion Batteries

Metallic Sn has provoked tremendous progress as an anode material for sodium-ion batteries(SIBs).However,Sn anodes suffer from a dramatic capacity fading,owing to pulverization induced by drastic volume expansion during cycling.Herein,a flexible three-dimensional(3D)hierarchical conductive network electrode is designed by constructing Sn quantum dots(QDs)encapsulated in one-dimensional N,S codoped carbon nanofibers(NS-CNFs)sheathed within two-dimensional(2D)reduced graphene oxide(rGO)scrolls.In this ingenious strategy,1D NS-CNFs are regarded as building blocks to prevent the aggregation and pulverization of Sn QDs during sodiation/desodiation,2D rGO acts as electrical roads and“bridges”among NS-CNFs to improve the conductivity of the electrode and enlarge the contact area with electrolyte.Because of the unique structural merits,the flexible 3D hierarchical conductive network was directly used as binder-and current collectorfree anode for SIBs,exhibiting ultra-long cycling life(373 mAh g?1 after 5000 cycles at 1 A g?1),and excellent high-rate capability(189 mAh g?1 at 10 A g?1).This work provides a facile and efficient engineering method to construct 3D hierarchical conductive electrodes for other flexible energy storage devices.

Sulfur–nitrogen co-doped graphene supported cobalt–nickel sulfide rGO@SN-CoNi_(2)S_(4) as highly efficient bifunctional catalysts for hydrogen/oxygen evolution reactions

Designing highly active and stable electrocata-lysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is a challenge for energy con-version and storage technology.In this work,a S and N co-doped graphene supported cobalt–nickel sulfide composite catalyst(rGO@SN-CoNi_(2)S_(4))was synthesized simply via a one-step hydrothermal method.The as-synthesized CoNi_(2)S_(4)particles grew in a mosaic manner inside GO lamellae and were encapsulated with graphene.As a bifunctional catalyst,the r GO@SN-CoNi_(2)S_(4)exhibits excellent electrocatalytic performance under alkaline con-ditions,which only required the overpotential of 142.6 mV(vs.RHE)and 310 m V(vs.RHE)to deliver a current density of 10 mA·cm^(-2) for HER and OER,respectively.The good hydrophilicity of the r GO@SN,the pure phase of bimetallic structure,and the chemical coupling/interaction between the CoNi_(2)S_(4)and the rGO@SN are attributable to be the possible reasons responsible for the higher HER and OER catalytic activities.Additionally,the rGO@SN-CoNi_(2)S_(4)also shows a great potential for serving as an excellent cathode and anode electrolyzer during the water splitting process.

Enhancing kinetics of Li-S batteries by graphene-like N,S-codoped biochar fabricated in NaCl non-aqueous ionic liquid

Graphene-like N,S-codoped bio-carbon nanosheets(GNSCS) were prepared by a facile and environment-friendly NaCl non-aqueous ionic liquid route to house sulfur for lithium-sulfur battery. The natural nori powder was calcined at 900°C for 3 h under Ar, in which NaCl non-aqueous ionic liquid can exfoliate carbon aggregates into nanosheets. The structural characterization of GNSCS by a series of techniques demonstrates the graphene-like feature.When evaluated as the matrix for sulfur cathode, GNSCS/S exhibits more prominent cycling stability and rate capability.A discharge capacity of 548 mA h g-1 at a current density of 1.6 A g-1 after 400 cycles was delivered with a capacity fade rate of only 0.13% per cycle and an initial Coulombic efficiency(CE) as high as 99.7%. When increasing the areal sulfur loading up to 3 mg cm-2, the discharge capacity can still be retained at 647 mA h g-1 after more than 100 cycles with a low capacity degradation of only ~0.30% per cycle. The features of N/S dual-doping and the graphene-like structure are propitious to the electron transportation, lithium-ion diffusion and more active sites for chemically adsorbing polysulfides. It is anticipated that other functional biochar carbon can also be attained via the low-cost, sustainable and green method.

Self-assembled three-dimensional carbon networks with accessorial Lewis base sites and variational electron characteristics as efficient oxygen reduction reaction catalysts for alkaline metal-air batteries

Heteroatom-doped carbon has been demonstrated to be one of the most promising non-noble metal catalysts with high catalytic activity and stability through the modification of the electronic and geometric structures.In this study,we develop a novel solvent method to prepare interconnected N,S co-doped three-dimensional（3D）carbon networks with tunable nanopores derived from an asso-ciated complex based on melamine and sodium dodecylbenzene sulfonate（SDBS）.After the intro-duction of silica templates and calcination,the catalyst exhibits 3D networks with interconnected 50-nm pores and partial graphitization.With the increase of the number of Lewis base sites caused by the N doping and change of the carbon charge and spin densities caused by the S doping,the designed N,S co-doped catalyst exhibits a similar electrochemical activity to that of the commercial 20-wt%Pt/C as an oxygen reduction reaction catalyst.In addition,in an aluminum-air battery,the proposed catalyst even outperforms the commercial 5-wt%Pt/C catalyst.Both interconnected porous structures and synergistic effects of N and S contribute to the superior catalytic perfor-mance.This study paves the way for the synthesis of various other N-doped and co-doped carbon materials as efficient catalysts in electrochemical energy applications.

Revisiting N,S co-doped carbon materials with boosted electrochemical performance in sodium-ion capacitors:The manipulation of internal electric field

Heteroatom doping has emerged as a prevailing strategy to enhance the storage of sodium ions in carbon materials.However,the underlying mechanism governing the performance enhancement remains undisclosed.Herein,we fabricated N/S co-doped carbon beaded fibers(S-N-CBFs),which exhibited glorious rate performance and durableness in Na+storage,showcasing no obvious capacity decay even after 3500 cycles.Furthermore,when used as anodes in sodium-ion capacitors,the S-N-CBFs delivered exceptional results,boasting a high energy density of 225 Wh·kg^(-1),superior power output of 22500 W·kg^(-1),and outstanding cycling stability with a capacity attenuation of merely 0.014%per cycle after 4000 cycles at 2 A·g^(-1).Mechanistic investigations revealed that the incorporation of both pyridinic N and pyrrolic N into the carbon matrix of S-N-CBFs induced internal electric fields(IEFs),with the former IEF being stronger than the latter,in conjunction with the doped S atom.Density functional theory calculations further unveiled that the intensity of the IEF directly influenced the adsorption of Na+,thereby resulting in the exceptional performances of S-N-CBFs as sodium-ion storage materials.This work uncovers the pivotal role of IEF in regulating the electronic structure of carbon materials and enhancing their Na^(+)storage capabilities,providing valuable insights for the development of more advanced electrode materials.

Nanocellulose/nitrogen and fluorine co-doped graphene composite hydrogels for high-performance supercapacitors

Three-dimensional graphene materials have been studied as typical supercapacitors electrode materials by virtue of their ultrahigh specific surface area and good ion transport capacity.However,improvement of the poor volumetric electrochemical performance of these graphene materials has been required although they have high gravimetric energy density.In this work,nanocellulose/nitrogen and fluorine co-doped graphene composite hydrogels(NC-NFGHs)were prepared through a convenient hydrothermal approach utilizing ammonium fluoride as the heteroatom source.Nanocellulose(NC)and high concentration of graphene oxide(GO)were utilized to adjust the structure of NC-NFGHs and increase their packing density.Subsequently,the aqueous symmetric supercapacitor based on NC-NFGH-80 exhibits remarkable gravimetric(286.6 F·g^(-1))and volumetric(421.3 F·cm^(-3))specific capacitance at 0.3 A·g^(-1),good rate performance,and remarkable cycle stability up to 10,000 cycles.Besides,the all-solid-state flexible symmetric supercapacitors(ASSC)fabricated by NC-NFGH-80 also delivered a large specific capacitance of 117.1 F·g^(-1)at 0.3 A·g^(-1)and long service life over 10,000 cycles at 10 A·g^(-1).This compact porous structure and heteroatom co-doped graphene material supply a favorable strategy for high-performance supercapacitors.

Fabrication of N,S co-doped porous carbon nanofibers as anode material for sodium-ion batteries with high performance

The N,S co-doped porous carbon nanofibers were fabricated by the carbonization of[Zn_(2)(tdc)_(2)(MA)]n MOFs/polyacrylonitrile nanofibers composite,which was produced by the electrospinning technology.The electrochemical results show that the N,S co-doped porous carbon nanofibers can achieve capacity of 201.2 mAh·g^(-1)at the current density of 0.05 A·g^(-1).Furthermore,the reversible capacity still has 161.3 mAh·g^(-1)even at a high current density of 1 A·g^(-1)after 600 cycles.The superior electrochemical performance shows that the N,S co-doped porous carbon nanofibers electrode material can be used as an ideal anode material for sodium-ion batteries.

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.

Cubic S/N co-doped TiO_(2) with rich oxygen vacancies from Ti-MOFs for efficient elimination of formaldehyde

The cubic S/N co-doped TiO_(2)(TNSx,x is the calcination temperature)photocatalysts with rich oxygen vacancies were obtained by high temperature calcination of sulfur powder and titanium-based MOFs NH_(2)-MIL-125 for the photocatalytic removal of gaseous formaldehyde(a volatile organic compound).Among the obtained catalysts,the presence of oxygen vacancies restricted photogenerated electron and holes recombination.98.00%removal of gaseous formaldehyde in 150 min could be achieved over TNS600 by xenon lamp.The removal efficiency for formaldehyde was well retained for five cycle experiment.The results from PL,TRPL and EIS revealed that TNS600 had the best separation efficiency of photogenerated electrons and holes,and the enhanced charge separation led to a significant increase in photocatalytic activity.The photocatalytic oxidation mechanism indicated that the ^(•)OH and ^(•)O_(2)−radicals were mainly involved in the efficient elimination of gaseous formaldehyde and were able to mineralize formaldehyde to H_(2)O and CO_(2).

Peroxymonosulfate activation by Fe-N-S co-doped tremella-like carbocatalyst for degradation of bisphenol A: Synergistic effect of pyridine N, Fe-Nx, thiophene S

Bisphenol A(BPA)has received increasing attention due to its long-term industrial application and persistence in environmental pollution.Iron-based carbon catalyst activation of peroxymonosulfate(PMS)shows a good prospect for effective elimination of recalcitrant contaminants in water.Herein,considering the problem about the leaching of iron ions and the optimization of heteroatoms doping,the iron,nitrogen and sulfur co-doped tremellalike carbon catalyst(Fe-NS@C)was rationally designed using very little iron,S-C_(3)N_(4) and low-cost chitosan(CS)via the impregnation-calcination method.The as-prepared Fe-NS@C exhibited excellent performance for complete removal of BPA(20 mg/L)by activating PMS with the high kinetic constant(1.492 min^(−1))in 15 min.Besides,the Fe-NS@C/PMS system not only possessed wide pH adaptation and high resistance to environmental interference,but also maintained an excellent degradation efficiency on different pollutants.Impressively,increased S-C_(3)N_(4) doping amount modulated the contents of different N species in Fe-NS@C,and the catalytic activity of Fe-NS@C-1-x was visibly enhanced with increasing SC_(3)N_(4) contents,verifying pyridine N and Fe-Nx as main active sites in the system.Meanwhile,thiophene sulfur(C-S-C)as active sites played an auxiliary role.Furthermore,quenching experiment,EPR analysis and electrochemical test proved that surface-bound radicals(·OH and SO_(4)^(·−))and non-radical pathways worked in the BPA degradation(the former played a dominant role).Finally,possible BPA degradation route were proposed.This work provided a promising way to synthesize the novel Fe,N and S co-doping carbon catalyst for degrading organic pollutants with low metal leaching and high catalytic ability.

B,N,S共掺杂石墨烯量子点的制备及对Fe3+和H2PO4-的荧光检测

利用水热法制备了一种可在纯水体系中连续"OFF-ON-OFF"荧光识别Fe^3+和H2PO4^-的B,N,S共掺杂的石墨烯量子点探针材料(BNS-GQDs),并对其形貌和结构进行了表征,结果表明,BNS-GQDs粒径分布均匀,平均粒径为4nm,具有类似石墨烯的结构,且成功掺杂了B,N,S原子.光谱表征结果表明,其在纯水体系中可以实现对Fe^3+的荧光猝灭识别;同时,BNS-GQDs+Fe^3+体系能够专一性地荧光增强识别H2PO4^-.识别机理研究表明,BNS-GQDs可与Fe^3+通过静电作用形成配合物并向Fe^3+转移电子,从而引起荧光猝灭;H2PO4^-可从上述配合物中置换出Fe^3+,引起体系荧光恢复.BNS-GQDs识别Fe3+和H2PO4-具有较好的可逆性,可应用于Hela细胞和实际水样中Fe^3+和H2PO4^-的检测.

氮掺杂Stone-Wales缺陷石墨烯吸附H_(2)S的密度泛函理论研究

利用密度泛函理论研究H_(2)S分子在氮掺杂Stone-Wales(SW)缺陷石墨烯上的吸附行为,通过吸附能、差分电荷密度、Bader电荷和电子态密度等分析了H_(2)S分子在SW缺陷石墨烯及氮掺杂SW缺陷石墨烯上的吸附差异。计算结果表明氮原子掺杂可以有效提升H_(2)S分子与石墨烯表面的相互作用,并加强二者之间的电荷转移。其中,氮原子主要作为电子传递的桥梁参与H_(2)S与石墨烯表面之间的电荷转移。H_(2)S分子被选择性吸附在SW缺陷及氮掺杂SW缺陷石墨烯的五元碳环中心处,这说明五元碳环的电荷分布促进H_(2)S分子的吸附行为。

Robust self-supported anode by integrating Sb2S3 nanoparticles with S,N-codoped graphene to enhance K-storage performance

Developing high-performance anode materials for potassium-ion batteries is significantly urgent. We here demonstrate Sb_2S_3 nanoparticles(~20 nm) homogeneously dispersed in porous S,N-codoped graphene framework(Sb_2S_3-SNG) as a self-supported anode material for potassium-ion batteries. The rational structure design of integrating Sb_2S_3 nanoparticles with S,N-codoped graphene contributes to high reactivity, strong affinity, good electric conductivity, and robust stability of the composite, enabling superior K-storage performance. Moreover, the self-supported architecture significantly decreases the inactive weight of the battery, resulting in a high energy density of a Sb_2S_3-SNG/KVPO_4 F-C full cell to ~166.3 W h kg^(-1).

氮硫共掺杂石墨烯/SnS2纳米复合材料的制备及储锂性能

锡基负极材料的理论储锂容量高,但循环稳定性和倍率性能差,难以满足实际应用的需要。我们以四氯化锡、二硫化碳、氨水、石墨烯为原料,采用水热-热处理相结合的方法,合成了氮硫共掺杂石墨烯/硫化锡复合材料(SnS_2@N,S-RGO)。该材料中,硫化锡纳米粒子均匀地生长在石墨烯上,增大了其比表面积,提高了其稳定性和导电性。因此,该复合材料的储锂容量高、倍率性能和循环稳定性好,有望用于高性能锂离子电池。