MOF-derived porous graphitic carbon with optimized plateau capacity and rate capability for high performance lithium-ion capacitors

The development of anode materials with high rate capability and long charge-discharge plateau is the key to improve per-formance of lithium-ion capacitors(LICs).Herein,the porous graphitic carbon(PGC-1300)derived from a new triply interpenetrated co-balt metal-organic framework(Co-MOF)was prepared through the facile and robust carbonization at 1300°C and washing by HCl solu-tion.The as-prepared PGC-1300 featured an optimized graphitization degree and porous framework,which not only contributes to high plateau capacity(105.0 mAh·g^(−1)below 0.2 V at 0.05 A·g^(−1)),but also supplies more convenient pathways for ions and increases the rate capability(128.5 mAh·g^(−1)at 3.2 A·g^(−1)).According to the kinetics analyses,it can be found that diffusion regulated surface induced capa-citive process and Li-ions intercalation process are coexisted for lithium-ion storage.Additionally,LIC PGC-1300//AC constructed with pre-lithiated PGC-1300 anode and activated carbon(AC)cathode exhibited an increased energy density of 102.8 Wh·kg^(−1),a power dens-ity of 6017.1 W·kg^(−1),together with the excellent cyclic stability(91.6%retention after 10000 cycles at 1.0 A·g^(−1)).

Highly Thermally Conductive and Structurally Ultra‑Stable Graphitic Films with Seamless Heterointerfaces for Extreme Thermal Management

Highly thermally conductive graphitic film(GF)materials have become a competitive solution for the thermal management of high-power electronic devices.However,their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety.Here,we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks(LNS),which reveals a bubbling process characterized by“permeation-diffusion-deformation”phenomenon.To overcome this long-standing structural weakness,a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film(GF@Cu)with seamless heterointerface.This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K.Moreover,GF@Cu maintains high thermal conductivity up to 1088 W m^(−1)K^(−1)with degradation of less than 5%even after 150 LNS cycles,superior to that of pure GF(50%degradation).Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.

Hybrid 2D/3D Graphitic Carbon Nitride-Based High-Temperature Position-Sensitive Detector

Ultraviolet position-sensitive detectors(PSDs)are expected to undergo harsh environments,such as high temperatures,for a wide variety of applications in military,civilian,and aerospace.However,no report on relevant PSDs operating at high temperatures can be found up to now.Herein,we design a new 2D/3D graphitic carbon nitride(g-C_(3)N_(4))/gallium nitride(GaN)hybrid heterojunction to construct the ultraviolet high-temperature-resistant PSD.The g-C_(3)N_(4)/GaN PSD exhibits a high position sensitivity of 355 mV mm^(-1),a rise/fall response time of 1.7/2.3 ms,and a nonlinearity of 0.5%at room temperature.The ultralow formation energy of-0.917 eV atom^(-1)has been obtained via the thermodynamic phase stability calculations,which endows g-C_(3)N_(4)with robust stability against heat.By merits of the strong built-in electric field of the 2D/3D hybrid heterojunction and robust thermo-stability of g-C_(3)N_(4),the g-C_(3)N_(4)/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm^(-1)and 1.4%,respectively,with high repeatability at a high temperature up to 700 K,outperforming most of the other counterparts and even commercial silicon-based devices.This work unveils the high-temperature PSD,and pioneers a new path to constructing g-C_(3)N_(4)-based harsh-environment-tolerant optoelectronic devices.

Highly N-doped carbon with low graphitic-N content as anode material for enhanced initial Coulombic efficiency of lithium-ion batteries

N-doped carbons as one of the most prominent anode materials to replace standard graphite exhibit outstanding Li+storage performance.However,N-doped carbon anodes still suffer from low N-doping levels and low initial Coulombic efficiency(ICE).In this study,high N-doped and low graphitic-N carbons(LGNCs)with enhanced ICE were synthesized by taking advantage of a denitrification strategy for graphitic carbon nitride(g-C_(3)N_(4)).In brief,more than 14.5 at%of N from g-C_(3)N_(4)(55.1 at%N)was retained by reacting graphitic-N with lithium,which was subsequently removed.As graphitic-N is largely responsible for the irreversible capacity,the anode's performance was significantly increased.Compared to general N-doped carbons with high graphitic-N proportion(>50%)and low N content(<15 at%),LGNCs delivered a low proportion of 10.8%-17.2% within the high N-doping content of 14.5-42.7 at%,leading to an enhanced specific capacity of 1499.9mAh g^(-1) at an ICE of 93.7% for the optimal sample of LGNC(4:1).This study provides a facile strategy to control the N content and speciation,achieving both high Li+storage capacity and high ICE,and thus promoting research and application of N-doped carbon materials.

Composite polymer electrolyte reinforced by graphitic carbon nitride nanosheets for room-temperature all-solid-state lithium batteries

By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic conductivity at room temperature, narrow electrochemical stability window and uncontrolled growth of lithium dendrite. To alleviate these problems, we introduce the ultrathin graphitic carbon nitride nanosheets(GCN) as advanced nanofillers into PEO based electrolytes(GCN-CPE). Benefiting from the high surface area and abundant surface N-active sites of GCN, the GCN-CPE displays decreased crystallinity and enhanced ionic conductivity. Meanwhile, Fourier transform infrared and chronoamperometry studies indicate that GCN can facilitate Li+migration in the composite electrolyte. Additionally, the GCN-CPE displays an extended electrochemical window compared with PEO based electrolytes. As a result, Li symmetric battery assembled with GCN-CPE shows a stable Li plating/stripping cycling performance, and the all-solid-state Li/LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622) batteries using GCN-CPE exhibit satisfactory cyclability and rate capability in a voltage range of 3-4.2 V at 30 ℃.

Edge atomic Fe sites decorated porous graphitic carbon as an efficient bifunctional oxygen catalyst for Zinc-air batteries

The development of advanced bifunctional oxygen electrocatalysts for oxygen reduction and evolution reactions(ORR and OER) is critical to the practical application of zinc-air batteries(ZABs). Herein, a silica-assisted method is reported to integrate numerous accessible edge Fe-Nx sites into porous graphitic carbon(named Fe-N-G) for achieving highly active and robust oxygen electrocatalysis. Silica facilitates the formation of edge Fe-Nx sites and dense graphitic domains in carbon by inhibiting iron aggregation.The purification process creates a well-developed mass transfer channel for Fe-N-G. Consequently,Fe-N-G delivers a half-wave potential of 0.859 V in ORR and an overpotential of 344 m V at10 m A cm^(-2)in OER. During long-term operation, the graphitic layers protect edge Fe-Nx sites from demetallation in ORR and synergize with Fe OOH species endowing Fe-N-G with enhanced OER activity.Density functional theory calculations reveal that the edge Fe-Nx site is superior to the in-plane Fe-Nx site in terms of OH* dissociation in ORR and OOH* formation in OER. The constructed ZAB based on Fe-N-G cathode shows a higher peak power density of 133 m W cm^(-2)and more stable cycling performance than Pt/C + RuO2counterparts. This work provides a novel strategy to obtain high-efficiency bifunctional oxygen electrocatalysts through space mediation.

Extraordinary Ultrahigh-Capacity and Long Cycle Life Lithium-Ion Batteries Enabled by Graphitic Carbon Nitride-Perylene Polyimide Composites

Graphitic carbon nitride(g-C_(3)N_(4))is widely used in organic metal-ion batteries owing to its high porosity,facile synthesis,stability,and high-rate performance.However,pristine g-C_(3)N_(4)nanosheets exhibit poor electrical conductivity,irreversible metal-ion storage capacity,and short-term cycling owing to their high concentration of graphitic-N species.Herein,a series of 3,4:9,10-perylenetetracarboxylic diimide-coupled g-C_(3)N_(4)composite anode materials,CN-PI_(x)(x=0.2,0.5,0.75,and 1),was investigated,which exhibited an unusually high surface nitrogen content(23.19-39.92 at.%)and the highest pyridinic-N,pyrrolic-N,and graphitic-N contents reported to date.The CN-PI_(1)anode delivers an unprecedented and continuously increasing ultrahigh discharging capacity of exceeding 8400 mAh g^(-1)(1.96 mWh cm^(-2))at 100 mA g^(-1)with high specific energy density(E_(sp))of~7700 Wh kg^(-1)and the volumetric energy density(E_(v))of~14956 Wh L-1 and an excellent long-term stability(414 mAh g^(-1)or 0.579 mWh cm^(-2)at 1 A g^(-1)).Furthermore,the activation of the CN-PI_(x)electrodes contributes to their superior electrochemical performance,resulting from the fact that the Li+is not only stored in the CN-PI_(x)composites but also CN-PI_(x)activated the Li^(0)adlayer on the CN-PI_(1)-Cu heterojunction as an SEI layer to avoid the direct contact of Li^(0)phase and the electrolyte.The CN-PI_(1)full cell with LiCoO_(2)as the cathode delivers a discharge capacity of~587 mAh g^(-1)at a 1 A g^(-1)after 250 cycles with a Coulombic efficiency nearly 99%.This study provides a strategy to develop N-doped g-C_(3)N_(4)-based anode materials for realizing long-lasting energy storage devices.

Smart Interfacing between Co-Fe Layered Double Hydroxide and Graphitic Carbon Nitride for High-efficiency Electrocatalytic Nitrogen Reduction

Bimetallic compounds such as hydrotalcite-type layered double hydroxides(LDHs)are promising electrocatalysts owing to their unique electronic structures.However,their abilities toward nitrogen adsorption and reduction are undermined since the surface-mantled,electronegative-OH groups hinder the charge transfer between transition metal atoms and nitrogen molecules.Herein,a smart interfacing strategy is proposed to construct a coupled heterointerface between LDH and 2D g-C_(3)N_(4),which is proven by density functional theory(DFT)investigations to be favorable for nitrogen adsorption and ammonia desorption compared with neat LDH surface.The interfaced LDH and g-C_(3)N_(4) is further hybridized with a self-standing TiO_(2) nanofibrous membrane(NM)to maximize the interfacial effect owing to its high porosity and large surface area.Profited from the synergistic superiorities of the three components,the LDH@C_(3)N_(4)@TiO_(2) NM delivers superior ammonia yield(2.07×10^(−9) mol s^(−1) cm^(−2))and Faradaic efficiency(25.3%),making it a high-efficiency,noble-metal-free catalyst system toward electrocatalytic nitrogen reduction.

Sustainable catalytic graphitization of biomass to graphitic porous carbon by constructing permeation network with organic ligands

Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling over the graphitization degree and pore structure of biochar is the key to its structural diversification.Herein,a clean and energy-efficient method is developed to synthesize adjustable graphitic degree and structure porosity GPC from rice husk-based carbon(RHC)at a relatively low temperature of 800–1000°C with environment-benign organometallic catalyst ethylenediaminetetraacetic acid ferric sodium salt(EDTA-iron)and the recovery ratio of catalyst is as high as 97%.The formed by the organic ligands of EDTA-iron facilitates the etching of RHC surface and pore by iron,resulting in highly graphitized and developed porous GPCs.The pore structure and graphitization degree of GPCs can be adjusted by altering the catalyst loading,temperature,and holding time.The catalyst EDTA-iron with a lower concentration mainly plays the role of etching,which promotes the formation of porous carbon with larger surface area(SBET=1187.2 m^(2)·g^(-1)).The catalyst with higher concentration mainly plays the role of catalyzing graphitization and promotes the obtaining of graphitic carbon with high graphitization degree(ID/IG=0.19).The mechanism of EDTA-iron catalyzed graphitization of RHC is explored by the comprehensive analysis of BET,XRD,Raman,TEM and TGA.This research not only provides an efficient method for the preparation of high-quality biomass-based graphite carbon,but also provides a feasible method for the preparation of biomass-based porous carbon.

Enhanced visible-light photocatalytic activity of Z-scheme graphitic carbon nitride/oxygen vacancy-rich zinc oxide hybrid photocatalysts

With the objectives of enhancing the stability,optical properties and visible-light photocatalytic activity of photocatalysts,we modified oxygen vacancy-rich zinc oxide（Vo-ZnO） with graphitic carbon nitride（g-C3N4）. The resulting g-C3N4/Vo-ZnO hybrid photocatalysts showed higher visible-light photocatalytic activity than pure Vo-ZnO and g-C3N4. The hybrid photocatalyst with a g-C3N4 content of 1 wt% exhibited the highest photocatalytic degradation activity under visible-light irradiation（λ≥ 400 nm）. In addition,the g-C3N4/Vo-ZnO photocatalyst was not deactivated after five cycles of methyl orange degradation,indicating that it is stable under light irradiation. Finally,a Z-scheme mechanism for the enhanced photocatalytic activity and stability of the g-C3N4/Vo-ZnO hybrid photocatalyst was proposed. The fast charge separation and transport within the g-C3N4/Vo-ZnO hybrid photocatalyst were attributed as the origins of its enhanced photocatalytic performance.

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

Enhanced visible-light photo-oxidation of nitric oxide using bismuth-coupled graphitic carbon nitride composite heterostructures

Pure bismuth（Bi） metal-modified graphitic carbon nitride（g-C3N4） composites（Bi-CN） with a pomegranate-like structure were prepared by an in situ method.The Bi-CN composites were used as photocatalysts for the oxidation of nitric oxide（NO） under visible-light irradiation.The inclusion of pure Bi metal in the g-C3N4 layers markedly improved the light absorption of the Bi-CN composites from the ultraviolet to the near-infrared region because of the typical surface plasmon resonance of Bi metal.The separation and transfer of photogenerated charge carriers were greatly accelerated by the presence of built-in Mott-Schottky effects at the interface between Bi metal and g-C3N4.As a result,the Bi-CN composite photocatalysts exhibited considerably enhanced efficiency in the photocatalytic removal of NO compared with that of Bi metal or g-C3N4 alone.The pomegranate-like structure of the Bi-CN composites and an explanation for their improved photocatalytic activity were proposed.This work not only provides a design for highly efficient g-C3N4-based photocatalysts through modification with Bi metal,but also offers new insights into the mechanistic understanding of g-C3N4-based photo catalysis.

Interfacial engineering of graphitic carbon nitride(g-C_3N_4)-based metal sulfide heterojunction photocatalysts for energy conversion: A review

As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemical, graphitic carbon nitride (g-C3N4) has become research hotspots in the community. However, g-C3N4 photocatalyst still suffers from many problems, resulting in unsatisfactory photocatalytic activity such as low specific surface area, high charge recombination and insufficient visible light utilization. Since 2009, g-C3N4-based heterostructures have attracted the attention of scientists worldwide for their greatly enhanced photocatalytic performance. Overall, this review summarizes the recent advances of g-C3N4-based nanocomposites modified with transition metal sulfide (TMS), including (1) preparation of pristine g-C3N4,(2) modification strategies of g-C3N4,(3) design principles of TMS-modified g-C3N4 heterostructured photocatalysts, and (4) applications in energy conversion. What is more, the characteristics and transfer mechanisms of each classification of the metal sulfide heterojunction system will be critically reviewed, spanning from the following categories:(1) Type I heterojunction,(2) Type II heterojunction,(3) p-n heterojunction,(4) Schottky junction and (5) Z-scheme heterojunction. Apart from that, the application of g-C3N4-based heterostructured photocatalysts in H2 evolution, CO2 reduction, N2 fixation and pollutant degradation will also be systematically presented. Last but not least, this review will conclude with invigorating perspectives, limitations and prospects for further advancing g-C3N4-based heterostructured photocatalysts toward practical benefits for a sustainable future.

Enhancing the photocatalytic activity and photostability of zinc oxide nanorod arrays via graphitic carbon mediation

Low optical absorption and photocorrosion are two crucial issues limiting the practical applications of zinc oxide(ZnO)-based photocatalysts.In this paper,we report the fabrication of graphitic-carbon-mediated ZnO nanorod arrays(NRAs)with enhanced photocatalytic activity and photostability for CO2 reduction under visible light irradiation.ZnO NRA/C-x(x=005,01,02,and 03)nanohybrids are prepared by calcining pre-synthesized ZnO NRAs with different amounts of glucose(0.05,0.1,0.2,and 0.3 g)as a carbon source via a hydrothermal method.X-ray photoelectron spectroscopy reveals that the obtained ZnO NRA/C-x nanohybrids are imparted with the effects of both carbon doping and carbon coating,as evidenced by the detected C-O-Zn bond and the C-C,C-O and C=O bonds,respectively.While the basic structure of ZnO remains unchanged,the UV-Vis absorption spectra show increased absorbance owing to the carbon doping effect in the ZnO NRA/C-x nanohybrids.The photoluminescence(PL)intensities of ZnO NRA/C-x nanohybrids are lower than that of bare ZnO NRA,indicating that the graphitic carbon layer coated on the surface of the ZnO NRA significantly enhances the charge carrier separation and transport,which in turn enhances the photoelectrochemical property and photocatalytic activity of the ZnO NRA/C-x nanohybrids for CO2 reduction.More importantly,a long-term reaction of photocatalytic CO2 reduction demonstrates that the photostability of ZnO NRA/C-x nanohybrids is significantly increased in comparison with the bare ZnO NRA.

Recent Advances of Graphitic Carbon Nitride-Based Structures and Applications in Catalyst, Sensing, Imaging, and LEDs

The graphitic carbon nitride(g-C_3N_4) which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible-light-responsive photocatalyst in the area of environmental remediation. The g-C_3N_4-based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high physicochemical stabilities and are ‘‘earth-abundant.'' This review summarizes the latest progress related to the design and construction of g-C_3N_4-based materials and their applications including catalysis, sensing,imaging, and white-light-emitting diodes. An outlook on possible further developments in g-C_3N_4-based research for emerging properties and applications is also included.

Promotion of activation ability of N vacancies to N2 molecules on sulfur-doped graphitic carbon nitride with outstanding photocatalytic nitrogen fixation ability

Nitrogen vacancies and sulfur co-doped g-C3N4 with outstanding N2 photofixation ability was synthesized via dielectric barrier discharge plasma treatment. X-ray diffraction, ultraviolet–visible spectroscopy, N2 adsorption, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and temperature-programmed desorption were used to characterize the as-prepared catalyst. The results showed that plasma treatment cannot change the morphology of the as-prepared catalyst but introduces nitrogen vacancies and sulfur into g-C3N4 lattice simultaneously. The as-prepared co-doped g-C3N4 displays an ammonium ion production rate as high as 6.2 mg·L^-1·h^-1·gcat^-1, which is 2.3 and 25.8 times higher than that of individual N-vacancy-doped g-C3N4 and neat g-C3N4, respectively, as well as showing good catalytic stability. Experimental and density functional theory calculation results indicate that, compared with individual N vacancy doping, the introduction of sulfur can promote the activation ability of N vacancies to N2 molecules, leading to promoted N2 photofixation performance.

Monolayer Graphitic Carbon Nitride as Metal-Free Catalyst with Enhanced Performance in Photo- and Electro-Catalysis

The exfoliation of bulk graphitic carbon nitride(g-C_(3)N_(4))into monolayer has been intensively studied to induce maximum sur-face area for fundamental studies,but ended in failure to realize chemi-cally and physically well-defined monolayer of g-C_(3)N_(4)mostly due to the difficulty in reducing the layer thickness down to an atomic level.It has,therefore,remained as a challenging issue in two-dimensional(2D)chemistry and physics communities.In this study,an“atomic monolayer of g-C_(3)N_(4)with perfect two-dimensional limit”was successfully prepared by the chemically well-defined two-step routes.The atomically resolved monolayer of g-C_(3)N_(4)was also confirmed by spectroscopic and micro-scopic analyses.In addition,the experimental Cs-HRTEM image was collected,for the first time,which was in excellent agreement with the theoretically simulated;the evidence of monolayer of g-C_(3)N_(4)in the perfect 2D limit becomes now clear from the HRTEM image of orderly hexagonal symmetry with a cavity formed by encirclement of three adjacent heptazine units.Compared to bulk g-C_(3)N_(4),the present g-C_(3)N_(4)monolayer showed significantly higher photocatalytic gen-eration of H2O2 and H2,and electrocatalytic oxygen reduction reaction.In addition,its photocatalytic efficiency for H2O2 production was found to be the best for any known g-C_(3)N_(4)nanomaterials,underscoring the remarkable advantage of monolayer formation in optimizing the catalyst performance of g-C_(3)N_(4).

Band Engineering and Morphology Control of Oxygen‑Incorporated Graphitic Carbon Nitride Porous Nanosheets for Highly Efficient Photocatalytic Hydrogen Evolution

Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation efficiency,remain as the bottleneck to achieve highly efficient hydrogen evolution.Here,a hollow oxygen-incorporated g-C3N4 nanosheet(OCN)with an improved surface area of 148.5 m2 g^−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere,wherein the C–O bonds are formed through two ways of physical adsorption and doping.The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects,leading to the formation of hollow morphology,while the O-doping results in reduced band gap of g-C3N4.The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6μmol g^−1 h^−1 for~20 h,which is over four times higher than that of g-C3N4(850.1μmol g^−1 h^−1)and outperforms most of the reported g-C3N4 catalysts.

Facile synthesis of Fe-containing graphitic carbon nitride materials and their catalytic application in direct hydroxylation of benzene to phenol

Fe-containing graphitic carbon nitride（Fe-g-C3N4） materials were synthesized via one-step pyroly-sis of FeCl3 and dicyandiamide. The physicochemical properties of the synthesized Fe-g-C3N4 sam-ples were characterized by N2 adsorption-desorption, X-ray diffraction, thermal gravimetric, Fourier transform infrared, UV-vis diffuse reflectance, X-ray photoelectron spectroscopy, and transmission electron microscopy. The Fe cations were anchored by nitrogen-rich g-C3N4, whereas the graphitic structures of g-C3N4 were retained after the introduction of Fe. As heterogeneous catalysts, Fe-g-C3 N4 exhibited good catalytic activity in the direct hydroxylation of benzene to phenol with H2O2, affording a maximum yield of phenol of up to 17.5%. Compared with other Fe- and V-containing g-C3N4 materials, Fe-g-C3N4 features a more convenient preparation procedure and higher catalytic productivity of phenol.

Nitrogen-doped Carbon Nanospheres-Modified Graphitic Carbon Nitride with Outstanding Photocatalytic Activity

Metals and metal oxides are widely used as photo/electro-catalysts for environmental remediation.However,there are many issues related to these metal-based catalysts for practical applications,such as high cost and detrimental environmental impact due to metal leaching.Carbon-based catalysts have the potential to overcome these limitations.In this study,monodisperse nitrogen-doped carbon nanospheres(NCs)were synthesized and loaded onto graphitic carbon nitride(g-C3N4,GCN)via a facile hydrothermal method for photocatalytic removal of sulfachloropyridazine(SCP).The prepared metal-free GCN-NC exhibited remarkably enhanced efficiency in SCP degradation.The nitrogen content in NC critically influences the physicochemical properties and performances of the resultant hybrids.The optimum nitrogen doping concentration was identified at 6.0 wt%.The SCP removal rates can be improved by a factor of 4.7 and 3.2,under UV and visible lights,by the GCN-NC composite due to the enhanced charge mobility and visible light harvesting.The mechanism of the improved photocatalytic performance and band structure alternation were further investigated by density functional theory(DFT)calculations.The DFT results confirm the high capability of the GCN-NC hybrids to activate the electron–hole pairs by reducing the band gap energy and efficiently separating electron/hole pairs.Superoxide and hydroxyl radicals are subsequently produced,leading to the efficient SCP removal.