Hierarchical Self-assembly of Well-Defined Louver-Like P-Doped Carbon Nitride Nanowire Arrays with Highly Effcient Hydrogen Evolution

Self-assembled nanostructure arrays integrating the advantages of the intrinsic characters of nanostructure as well as the array stability are appealing in advanced materials.However,the precise bottom-up synthesis of nanostructure arrays without templates or substrates is quite challenging because of the general occurrence of homogeneous nucleation and the difficult manipulation of noncovalent interactions.Herein,we first report the precisely manipulated synthesis of well-defined louver-like P-doped carbon nitride nanowire arrays(L-PCN)via a supramolecular self-assembly method by regulating the noncovalent interactions through hydrogen bond.With this strategy,CN nanowires align in the outer frame with the separation and spatial location achieving ultrastability and outstanding photoelectricity properties.Significantly,this self-assembly L-PCN exhibits a superior visible light-driven hydrogen evolution activity of 1872.9μmol h^−1 g^−1,rendering a^25.6-fold enhancement compared to bulk CN,and high photostability.Moreover,an apparent quantum efficiency of 6.93%is achieved for hydrogen evolution at 420±15 nm.The experimental results and first-principles calculations demonstrate that the remarkable enhancement of photocatalytic activity of L-PCN can be attributed to the synergetic effect of structural topology and dopant.These findings suggest that we are able to design particular hierarchical nanostructures with desirable performance using hydrogen-bond engineering.     

Superior Pseudocapacitive Storage of a Novel Ni3Si2/ NiOOH/Graphene Nanostructure for an All‑Solid‑State Supercapacitor

Recent developments in the synthesis of graphene-based structures focus on continuous improvement of porous nanostructures,doping of thin films,and mechanisms for the construction of threedimensional architectures.Herein,we synthesize creeper-like Ni3Si2/NiOOH/graphene nanostructures via low-pressure all-solid meltingreconstruction chemical vapor deposition.In a carbon-rich atmosphere,high-energy atoms bombard the Ni and Si surface,and reduce the free energy in the thermodynamic equilibrium of solid Ni–Si particles,considerably catalyzing the growth of Ni–Si nanocrystals.By controlling the carbon source content,a Ni3Si2 single crystal with high crystallinity and good homogeneity is stably synthesized.Electrochemical measurements indicate that the nanostructures exhibit an ultrahigh specific capacity of 835.3 C g^−1(1193.28 F g^−1)at 1 A g^−1;when integrated as an all-solidstate supercapacitor,it provides a remarkable energy density as high as 25.9 Wh kg^−1 at 750 W kg^−1,which can be attributed to the freestanding Ni3Si2/graphene skeleton providing a large specific area and NiOOH inhibits insulation on the electrode surface in an alkaline solution,thereby accelerating the electron exchange rate.The growth of the high-performance composite nanostructure is simple and controllable,enabling the large-scale production and application of microenergy storage devices.     

3D Carbon Frameworks for Ultrafast Charge/Discharge Rate Supercapacitors with High Energy‑Power Density

Carbon-based electric double layer capacitors(EDLCs)hold tremendous potentials due to their high-power performance and excellent cycle stability.However,the practical use of EDLCs is limited by the low energy density in aqueous electrolyte and sluggish diffusion kinetics in organic or/and ionic liquids electrolyte.Herein,3D carbon frameworks(3DCFs)constructed by interconnected nanocages(10-20 nm)with an ultrathin wall of ca.2 nm have been fabricated,which possess high specific surface area,hierarchical porosity and good conductive network.After deoxidization,the deoxidized 3DCF(3DCFDO)exhibits a record low IR drop of 0.064 V at 100 A g^−1 and ultrafast charge/discharge rate up to 10 V s^−1.The related device can be charged up to 77.4%of its maximum capacitance in 0.65 s at 100 A g^−1 in 6 M KOH.It has been found that the 3DCF-DO has a great affinity to EMIMBF4,resulting in a high specific capacitance of 174 F g^−1 at 1 A g^−1,and a high energy density of 34 Wh kg^−1 at an ultrahigh power density of 150 kW kg^−1 at 4 V after a fast charge in 1.11 s.This work provides a facile fabrication of novel 3D carbon frameworks for supercapacitors with ultrafast charge/discharge rate and high energy-power density.     

Facile Synthesis of FePS3 Nanosheets@MXene Composite as a High-Performance Anode Material for Sodium Storage

Searching for advanced anode materials with excellent electrochemical properties in sodium-ion battery is essential and imperative for next-generation energy storage system to solve the energy shortage problem.In this work,two-dimensional(2D)ultrathin FePS3 nanosheets,a typical ternary metal phosphosulfide,are first prepared by ultrasonic exfoliation.The novel 2D/2D heterojunction of FePS3 nanosheets@MXene composite is then successfully synthesized by in situ mixing ultrathin MXene nanosheets with FePS3 nanosheets.The resultant FePS3 nanosheets@MXene hybrids can increase the electronic conductivity and specific surface area,assuring excellent surface and interfacial charge transfer abilities.Furthermore,the unique heterojunction endows FePS3 nanosheets@MXene composite to promote the diffusion of Na^+ and alleviate the drastic change in volume in the cyclic process,enhancing the sodium storage capability.Consequently,the few-layered FePS3 nanosheets uniformly coated by ultrathin MXene provide an exceptional reversible capacity of 676.1 mAh g^−1 at the current of 100 mA g^−1 after 90 cycles,which is equivalent to around 90.6% of the second-cycle capacity(746.4 mAh g^−1).This work provides an original protocol for constructing 2D/2D material and demonstrates the FePS3@MXene composite as a potential anode material with excellent property for sodium-ion batteries.     

Hierarchical N-Doped Porous Carbons for Zn–Air Batteries and Supercapacitors

Nitrogen-doped carbon materials with a large specific surface area,high conductivity,and adjustable microstructures have many prospects for energy-related applications.This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction(ORR)and supercapacitors.Here,we report a low-cost,environmentally friendly,large-scale mechanochemical method of preparing N-doped porous carbons(NPCs)with hierarchical micro-mesopores and a large surface area via ball-milling polymerization followed by pyrolysis.The optimized NPC prepared at 1000°C(NPC-1000)offers excellent ORR activity with an onset potential(Eonset)and half-wave potential(E1/2)of 0.9 and 0.82 V,respectively(vs.a reversible hydrogen electrode),which are only approximately 30 mV lower than that of Pt/C.The rechargeable Zn–air battery assembled using NPC-1000 and the NiFe-layered double hydroxide as bifunctional ORR and oxygen evolution reaction electrodes offered superior cycling stability and comparable discharge performance to RuO2 and Pt/C.Moreover,the supercapacitor electrode equipped with NPC prepared at 800℃ exhibited a high specific capacity(431 F g^−1 at 10 mV s^−1),outstanding rate,performance,and excellent cycling stability in an aqueous 6-M KOH solution.This work demonstrates the potential of the mechanochemical preparation method of porous carbons,which are important for energy conversion and storage.     

MOF‑Derived CoSe2@N‑Doped Carbon Matrix Confined in Hollow Mesoporous Carbon Nanospheres as High‑Performance Anodes for Potassium‑Ion Batteries

In this work,a novel vacuum-assisted strategy is proposed to homogenously form Metal-organic frameworks within hollow mesoporous carbon nanospheres(HMCSs)via a solid-state reaction.The method is applied to synthesize an ultrafine CoSe2 nanocrystal@N-doped carbon matrix confined within HMCSs(denoted as CoSe2@NC/HMCS)for use as advanced anodes in highperformance potassium-ion batteries(KIBs).The approach involves a solvent-free thermal treatment to form a Co-based zeolitic imidazolate framework(ZIF-67)within the HMCS templates under vacuum conditions and the subsequent selenization.Thermal treatment under vacuum facilitates the infiltration of the cobalt precursor and organic linker into the HMCS and simultaneously transforms them into stable ZIF-67 particles without any solvents.During the subsequent selenization process,the“dual confinement system”,composed of both the N-doped carbon matrix derived from the organic linker and the small-sized pores of HMCS,can effectively suppress the overgrowth of CoSe2 nanocrystals.Thus,the resulting uniquely structured composite exhibits a stable cycling performance(442 mAh g^−1 at 0.1 A g^−1 after 120 cycles)and excellent rate capability(263 mAh g^−1 at 2.0 A g^−1)as the anode material for KIBs.     

Cu3(PO4)2: Novel Anion Convertor for Aqueous Dual‑Ion Battery

Electrode materials which can reversibly react with anions are of interest for aqueous dual-ion batteries.Herein,we propose a novel anion electrode,Cu3(PO4)2,for constructing an aqueous dual-ion cell.The Cu3(PO4)2 electrode can operate in a quasi-neutral condition and deliver a reversible capacity of 115.6 mAh g^−1 with a well-defined plateau at−0.17 V versus Ag/AgCl.Its reaction mechanism shows that Cu3(PO4)2 decomposes into Cu2O and subsequently is converted into Cu during the initial discharge process.In the following charge process,Cu is oxidized into Cu2O.It suggests Cu3(PO4)2 reacts with OH−ions instead of PO43−ions after the initial discharge process and its potential thereby depends upon the OH−ions concentration in electrolyte.Additionally,an aqueous dual-ion cell is built by using pretreated Cu3(PO4)2 and Na0.44MnO2 as anode and cathode,respectively.During cycling,OH−ions and Na^+ions in electrolyte can be stored and released.Such a cell can provide a discharge capacity of 52.6 mAh g^−1 with plateaus at 0.70 and 0.45 V,exhibiting the potential of application.This work presents an available aqueous dual-ion cell and provides new insights into renewable energy storage and adjustment of the OH−ions concentration in aqueous buffer solution.     

Homologous Strategy to Construct High‑Performance Coupling Electrodes for Advanced Potassium‑Ion Hybrid Capacitors

Potassium-ion hybrid capacitors(PIHCs)have been considered as promising potentials in mid-to large-scale storage system applications owing to their high energy and power density.However,the process involving the intercalation of K+into the carbonaceous anode is a sluggish reaction,while the adsorption of anions onto the cathode surface is relatively faster,resulting in an inability to exploit the advantage of high energy.To achieve a high-performance PIHC,it is critical to promote the K^+insertion/desertion in anodic materials and design suitable cathodic materials matching the anodes.In this study,we propose a facile“homologous strategy”to construct suitable anode and cathode for high-performance PIHCs,that is,unique multichannel carbon fiber(MCCF)-based anode and cathode materials are firstly prepared by electrospinning,and then followed by sulfur doping and KOH activation treatment,respectively.Owing to a multichannel structure with a large interlayer spacing for introducing S in the sulfur-doped multichannel carbon fiber(S-MCCF)composite,it presents high capacity,super rate capability,and long cycle stability as an anode in potassium-ion cells.The cathode composite of activated multichannel carbon fiber(aMCCF)has a considerably high specific surface area of 1445 m^2 g^−1 and exhibits outstanding capacitive performance.In particular,benefiting from advantages of the fabricated S-MCCF anode and aMCCF cathode by homologous strategy,PIHCs assembled with the unique MCCF-based anode and cathode show outstanding electrochemical performance,which can deliver high energy and power densities(100 Wh kg^−1 at 200 W kg^−1,and 58.3 Wh kg^−1 at 10,000 W kg^−1)and simultaneously exhibit superior cycling stability(90%capacity retention over 7000 cycles at 1.0 A g^−1).The excellent electrochemical performance of the MCCF-based composites for PIHC electrodes combined with their simple construction renders such materials attractive for further in-depth investigations of alkali-ion battery and capacitor applications.     

Hollow Bio-derived Polymer Nanospheres with Ordered Mesopores for Sodium-Ion Battery

Bio-inspired hierarchical self-assembly provides elegant and powerful bottom-up strategies for the creation of complex materials.However,the current self-assembly approaches for natural bio-compounds often result in materials with limited diversity and complexity in architecture as well as microstructure.Here,we develop a novel coordination polymerization-driven hierarchical assembly of micelle strategy,using phytic acid-based natural compounds as an example,for the spatially controlled fabrication of metal coordination bio-derived polymers.The resultant ferric phytate polymer nanospheres feature hollow architecture,ordered meso-channels of^12 nm,high surface area of 401 m2 g−1,and large pore volume of 0.53 cm3 g−1.As an advanced anode material,this bio-derivative polymer delivers a remarkable reversible capacity of 540 mAh g−1 at 50 mA g−1,good rate capability,and cycling stability for sodium-ion batteries.This study holds great potential of the design of new complex bio-materials with supramolecular chemistry.     

Experimental and DFT Studies of Au Deposition Over WO3/g-C3N4 Z-Scheme Heterojunction

A typical Z-scheme system is composed of two photocatalysts which generate two sets of charge carriers and split water into H2 and O2 at different locations.Scientists are struggling to enhance the efficiencies of these systems by maximizing their light absorption,engineering more stable redox couples,and discovering new O2 and H2 evolutions co-catalysts.In this work,Au decorated WO3/g-C3N4 Z-scheme nanocomposites are fabricated via wet-chemical and photo-deposition methods.The nanocomposites are utilized in photocatalysis for H2 production and 2,4-dichlorophenol(2,4-DCP)degradation.It is investigated that the optimized 4Au/6%WO3/CN nanocomposite is highly efficient for production of 69.9 and 307.3μmol h−1 g−1 H2 gas,respectively,under visible-light(λ>420 nm)and UV–visible illumination.Further,the fabricated 4Au/6%WO3/CN nanocomposite is significant(i.e.,100%degradation in 2 h)for 2,4-DCP degradation under visible light and highly stable in photocatalysis.A significant 4.17%quantum efficiency is recorded for H2 production at wavelength 420 nm.This enhanced performance is attributed to the improved charge separation and the surface plasmon resonance effect of Au nanoparticles.Solid-state density functional theory simulations are performed to countercheck and validate our experimental data.Positive surface formation energy,high charge transfer,and strong non-bonding interaction via electrostatic forces confirm the stability of 4Au/6%WO3/CN interface.     

g-C_3N_4-CdS异质结的合成及其光催化性能研究

以尿素为前驱体,550℃热聚合反应5 h,制备了块状g-C_3N_4。然后将块状g-C_3N_4超声剥离得到片状g-C_3N_4,在g-C_3N_4纳米片上原位生长Cd S(直径约130 nm),从而制备了g-C_3N_4-Cd S异质结。g-C_3N_4-Cd S异质结的吸收边约505 nm处,与g-C_3N_4(约460 nm)相比具有明显的红移,可吸收更多的可见光。此外,g-C_3N_4-Cd S异质结可降解99%的罗丹明B,具有较高的光催化活性。     

Increasingπ-electron availability in benzene ring incorporated graphitic carbon nitride for increased photocatalytic hydrogen generation

Increasing the availability ofπ-electron in graphitic carbon nitride(g-C₃N₄)can reduce the band gap and thus enhance the photocatalytic hydrogen(H₂)generation activity upon exposure to visible light,However,such strategy has not yet been largely applied to increase the H₂generation of g-C₃N₄.Herein,we succes s fully increased the amount ofπ-electron in g-C₃N₄by incorporatingπ-electron-rich benzene rings through copolymerization of melamine and trimesic acid in air.The incorporation of benzene rings not only extends the light absorption of g-C₃N₄to 650 nm,but also improves the electrical conductivity due to delocalization ofπelectrons in benzene rings.As a result,a 3.4 times enhancement of photocatalytic H₂generation was achieved from the g-C₃N₄with benzene ring incorporation in comparing with that of pristine g-C₃N₄.More interestingly,H₂generation still occurs under irradiation of the light ofλ≥490 nm,above the absorption edge of pristine g-C₃N₄(~460 nm),illustrating the positive effectiveness of incorporated benzene rings on enhancing the H₂generation capacity of g-C₃N₄.The present work manifests the advantages of increasingπ-conjugated electrons on designing highly active g-C₃N₄photocatalysts.     

Significantly enhanced photocatalytic hydrogen production performance of g-C3N4/CNTs/CdZnS with carbon nanotubes as the electron mediators

The electron mediator can effectively improve the performance of the direct Z-scheme heterojunction photocatalysts.However,it is still a great challenge to select cheap and efficient electron mediators and to design them into the Z-scheme photocatalytic system.In the present paper,the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst was prepared using carbon nanotubes (CNTs) as the electron mediators,and its photocatalytic hydrogen production performance was studied.Compared with single-phase g-C3N4,CdZnS and biphasic g-C3 N4/CdZnS photocatalysts,the photocatalytic hydrogen production performance of the prepared g-C3N4/CNTs/CdZnS has been significantly enhanced.Meanwhile,g-C3N4/CNTs/CdZnS possesses very good photocatalytic hydrogen production stability.The enhanced photocatalytic hydrogen production performance of g-C3 N4/CNTs/CdZnS is attributed to the fact that CNTs,as an electron mediator,can accelerate the recombination of the photogenerated holes in the valence band of g-C3N4 and the photogenerated electrons in the conduction band of CdZnS,which makes the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst be easier to escape the photogenerated electrons,increases the concentration of the photogenerated carriers and prolongs the lifetime of the photogenerated carriers.This work provides a theoretical basis for the further development and design of CNTs as the intermediate electron mediator of the Z-scheme heterojunction photocatalyst.     

三维大孔g-C3N4吸附和光催化还原U(VI)性能研究

将易溶的U(VI)还原为微溶的U(IV)是治理放射性铀污染的有效方法。本研究以SiO₂纳米球作为硬模板, 通过热聚合-刻蚀制备具有连续贯通的三维大孔g-C₃N₄光催化剂, 用于吸附-光催化还原U(VI)。材料表征结果显示: 三维大孔g-C₃N₄比表面积显著增加, 对可见光的吸收明显增强; 同时具有三维有序大孔结构, 并呈规则的紧密堆积结构, 孔壁完整多孔, 整个结构具有良好的三维连通性。吸附实验表明: 三维大孔g-C₃N₄对U(VI)最大吸附容量可达~30.5 mg/g, 该过程更符合Langmuir吸附模型, 与块体g-C₃N₄相比吸附容量提高了~1.83倍。光催化还原实验表明: 三维大孔g-C₃N₄具有高的光催化活性和良好的稳定性, 其还原反应速率常数为~0.0142 min ^-1, 是块体g-C₃N₄ (~0.0024 min ^-1)的~5.9倍。鉴于三维大孔g-C₃N₄具有较优异的吸附-催化还原性能, 该材料有望应用于放射性废水中U(VI)的快速高效清除。     

类石墨相氮化碳二维纳米片的制备及可见光催化性能研究

以三聚氰胺为原料制备类石墨相氮化碳(g-C3N4),采用球磨与超声联用技术制备g-C3N4二维纳米片. 利用X 射线衍射光谱(XRD)、紫外-可见漫反射(UV-Vis)光谱、扫描电镜(SEM)、透射电镜(TEM)、原子力显微镜(AFM)、荧光(PL)光谱等分析手段对制备的催化剂进行了表征. 结果表明: g-C3N4二维纳米片具有与体相g-C3N4相同的晶体结构,片层结构仅有5个原子层厚.g-C3N4二维纳米片增加了对可见光的吸收,提高了光生电子-空穴对的分离效率.以染料罗丹明B的降解反应研究了g-C3N4二维纳米片在可见光下的催化性能. 结果表明,球磨超声1 h后制备的g-C3N4二维纳米片表现出最佳的光催化性能, 150 min 内对罗丹明B的降解率高达94%,是体相g-C3N4的2 倍.     

Confined reaction inside nanotubes: New approach to mesoporous g-C3N4 photocatalysts

Mesoporous g-C3N4 nanorods (NRs) are synthesized through the nano-confined thermal condensation of cyanamide in silica nanotubes (NTs) with porous shells.The gas bubbles retained during condensation and the limited cyanamide precursor inside the silica NTs lead to the formation of mesoporous g-C3N4.This nano-confined reaction is an alternative method to the traditional templating process for the synthesis of mesoporous materials.The as-prepared mesoporous g-C3N4 NRs exhibit remarkably improved photocatalytic activity and high stability in water splitting and degradation of Rhodamine B compared with bulk g-C3N4.     

具有三维网状结构的石墨相氮化碳/还原氧化石墨烯/钯复合材料的合成及可见光催化性能

石墨相氮化碳(g-C_3N_4)已经被认为是一种高效的非金属半导体光催化剂。为进一步优化其光催化性能,通过热解-水热两步法制备了三维网状结构的g-C_3N_4/还原氧化石墨烯(rGO)/钯纳米颗粒(Pd NPs)复合材料。该复合材料由大量超薄片组成,而且薄片上有大量直径约为10nm的Pd NPs。g-C_3N_4/rGO/Pd NPs复合材料展现了一个宽的可见光吸收(边~460nm),其在460~800nm波长范围内还有一个随波长增加的光吸收。经可见光(λ400nm)照射140 min后,g-C_3N_4/rGO/Pd NPs复合材料可降解90%罗丹明B(RhB)。此外,循环实验表明g-C_3N_4/rGO/Pd NPs复合材料具有良好的稳定性。因此,g-C_3N_4/rGO/Pd NPs复合材料有望成为一种高效稳定的光催化剂,在水污染处理领域具有潜在的应用价值。     

Electrogenerated chemiluminescence behavior of graphite-like carbon nitride and its application in selective sensing Cu2+

This paper reports for the first time the electrogenerated chemiluminescence (ECL) behavior of graphite-like carbon nitride (g-C(3)N(4)) with K(2)S(2)O(8) as the coreactant. The possible ECL reaction mechanisms are proposed. The spectral features of the ECL emission and photoluminescence (PL) of g-C(3)N(4) are compared, and their resemblance demonstrates that the excited states of g-C(3)N(4) from both ECL and photoexcitation are the same. The effects of K(2)S(2)O(8) concentration, pH, g-C(3)N(4)/carbon powder ratio, and scan rate on the ECL intensity have been studied in detail. Furthermore, it is observed that the ECL intensity is efficiently quenched by trace amounts of Cu(2+). g-C(3)N(4) is thus employed to fabricate an ECL sensor which shows high selectivity to Cu(2+) determination. The limit of detection is determined as 0.9 nM. It is anticipated that g-C(3)N(4) could be a new class of promising material for fabricating ECL sensors.     

High visible light photocatalytic activities obtained by integrating g-C3N4 with ferroelectric PbTiO3

Graphitic carbon nitride (g-C3 N4) with the merits of high visible light absorption,proper electronic band structure with high conduction band edge and variable modulation,is viewed as a promising photocatalyst for practical use.To alleviate its high recombination rate of photo-excited charge carriers and maximize the photocatalytic performances,it is paramount to design highly effective transfer channels for photo-excited charge carriers.Ferroelectric materials can have the charge carriers transport in opposite directions owing to the internal spontaneous polarization,which may be suitable for constructing the heterostructure with g-C3N4 for efficient charge separation.Inspired by this concept,herein ferroelec tric PbTiO3,which can be the visible-light absorber,is coupled with g-C3N4 to construct PbTiO3/g-C3N4 heterostructure with close contact via Pb-N bond by the facile post thermal treatment.The optimized PbTiO3/g-C3N4 heterostructure exhibited excellent photocatalytic and photoelectrochemical activities under visible light irradiation.Moreover,the simultaneous application of ultrasound-induced mechanical waves can further improve its photocatalytic activities through reinforcing the built-in piezoelectric field.This work proposes a widely applicable strategy for the fabrication of high-performance ferroelectric based photocatalysts and also provides some new ideas for developing the understanding of ferroelectric photocatalysis.     

Protonation of g-C3N4 and its temperature-sensing properties

Journal of Materials Science: Materials in Electronics - Graphitic carbon nitride (g-C3N4) was obtained through heat treatment of melamine and the g-C3N4 flakers were then protonated with sulfuric...