Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphen...Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphene-modified non-compensated Cu/N-co-doped titanium dioxide(Cu-N-TiO_(2)/rGO)photocatalyst was designed for the efficient synthesis of H_(2)O_(2) via a dual-channel pathway.Precise modulation of the TiO_(2) conduction band position was achieved through the synergistic coupling of Cu 3d orbitals hybridized with Ti 3d orbitals and hybridization of N 2p orbitals with O 2p orbitals.This approach significantly improved the utilization of sunlight while satisfying the redox potential requirements.Cu doping not only promoted the formation of oxygen vacancies but also reduced the formation of Ti^(3+)ions,the photogenerated charge recombination centers.The non-compensated doping of N effectively increased the solubility of Cu^(2+)ions in the titanium dioxide lattice,enhanced the adsorption of hydroxyl radical intermediates,and created conditions for the subsequent hydroxyl radical combinations promoting the generation of H_(2)O_(2).In addition,the introduction of highly conductive graphene improved the interfacial carrier separation efficiency while realizing the spatial separation of redox sites,creating conditions for dual-channel reactions.The experimental results showed that the H_(2)O_(2) yield of Cu-N-TiO_(2)/rGO under simulated sunlight reached 1266.7μmol/L,which was 25.2 times higher than that of pristine TiO_(2).This study elucidated the synergistic mechanism of the energy band structure modulation and interfacial optimization,which provided a new idea for the design of dual-channel H_(2)O_(2) production photocatalysts.展开更多
The development of high-performance transition metal sulfide(TMS)/carbon composites to replace conventional graphite anode remains a critical challenge for advancing lithium-ion batteries(LIBs).In this study,a facile ...The development of high-performance transition metal sulfide(TMS)/carbon composites to replace conventional graphite anode remains a critical challenge for advancing lithium-ion batteries(LIBs).In this study,a facile self-sacrifice template method is developed to prepare FeS encapsulated into N,S co-doped carbon(FeS/NSC)composite using melamine-cyanuric acid(MCA)supermolecule as a multifunctional template precursor.The function of MCA supermolecule for material synthesis is explored,revealing its special function as a dispersant,dopant and pore-forming agent.Furthermore,the effect of Fe source dosage on the morphology,structure and composition of the final products is explored.The resultant FeS/NSC-0.1(where 0.1 represents the mass of added Fe source)exhibits the most optimal proportion,characterized by a good dispersion status of FeS within the NSC matrix,effective N,S co-doping and ample porosity.Benefiting from these merits,the FeS/NSC-0.1 anode demonstrates significantly improved cycling stability and rate capability when compared to the counterparts.Undoubtedly,this work offers a universal method to produce advanced transition metal sulfide/carbon composite electrodes for energy storage and conversion systems.展开更多
Harnessing the redox potential of biochar to activate airborne O_(2)for contaminant removal is challenging.In this study,ferrihydrite(Fh)modified the boron(B),nitrogen(N)co-doped biochars(BCs)composites(Fh/B(n)NC)were...Harnessing the redox potential of biochar to activate airborne O_(2)for contaminant removal is challenging.In this study,ferrihydrite(Fh)modified the boron(B),nitrogen(N)co-doped biochars(BCs)composites(Fh/B(n)NC)were developed for enhancing the degradation of a model pollutant,tetracycline(TC),merely by airborne O_(2).Fh/B(3)NC showed excellent O_(2)activation activity for efficient TC degradation with a apparent TC degradation rate of 5.54,6.88,and 22.15 times that of B(3)NC,Fh,and raw BCs,respectively,where 1O_(2)and H_(2)O_(2)were identified as the dominant ROS for TC degradation.The B incorporation into the carbon lattice of Fh/B(3)NC promoted the generation of electron donors,sp2 C and the reductive B species,hence boosting Fe(III)reduction and 1O_(2)generation.O_(2)adsorption was enhanced due to the positively charged adsorption sites(C-B+and N-C+).And 1O_(2)was generated via Fe(II)catalyzed low-efficient successive one-electron transfer(O_(2)→O_(2)·−→1O_(2),H_(2)O_(2)),as well as biochar catalyzed high-efficient two-electron transfer(O_(2)→H_(2)O_(2)→1O_(2))that does not involve.O_(2)−as the intermediate.Moreover,Fh/B,N co-doped biochar showed a wide pH range,remarkable anti-interference capabilities,and effective detoxification.These findings shed new light on the development of environmentally benign BCs materials capable of degradading organic pollutants.展开更多
Transition metal carbides(MXenes)used as electromagnetic wave absorption materials face two critical challenges:impedance mismatch caused by high conductivity and the easy restacking and agglomeration of ultrathin nan...Transition metal carbides(MXenes)used as electromagnetic wave absorption materials face two critical challenges:impedance mismatch caused by high conductivity and the easy restacking and agglomeration of ultrathin nanosheets.To address these issues,this study proposes the construction of an S/N co-doped MXene nanoribbon/nanosheet composite structure.An alkali-assisted chemical scissor strategy was used to successfully prepare a nanoribbon/nanosheet hybrid,which effectively suppressed nanosheet stacking and significantly increased the number of active interfaces and defect sites.By controlling the doping temperature,the doping configurations of S and N in MXenes can be precisely regulated,including lattice substitution(LS),functional group substitution(FS),and surface absorption(SA).With increasing doping temperature,the configuration of S/N dopants evolves from a combination of FS-type N and LS-type S to a coexistence of SA-and LS-type species.The former synergistically enhances conductive loss and polarization loss,whereas the latter suppresses electron transport and consequently reduces the complex permittivity of the material.The optimized composite exhibited considerably improved comprehensive electromagnetic wave-absorption performance at a low filler loading(10 wt%)and thin thickness(1.26 mm),achieving a minimum reflection loss(RLmin)of-53.77 dB and an effective absorption bandwidth(EAB)of 4.51 GHz.This work not only clarifies the regulatory mechanism of doping configurations on high-frequency electromagnetic properties but also provides a theoretical foundation for the rational design of high-performance MXene-based electromagnetic wave absorbing materials.展开更多
A series of photocatalysts of un-doped, single-doped and co-doped nanometer titanium diox- ide （TiO2） have been successfully prepared by template method using Fe（NO3）3.9H2O, La（NO3）3.6H2O, and tetrabutyl titanat...A series of photocatalysts of un-doped, single-doped and co-doped nanometer titanium diox- ide （TiO2） have been successfully prepared by template method using Fe（NO3）3.9H2O, La（NO3）3.6H2O, and tetrabutyl titanate as precursors and glucan as template. Scanning electron microscopy, X-ray diffraction, and N2 adsorption-desorption measurement were employed to characterize the morphology, crystal structure and surface structure of the samples. The photo-absorbance of the obtained catalysts was measured by UV-Vis absorption spectroscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl orange in an aqueous solution. The characterizations indicated that the prepared photocatalysts consisted of anatase phase and possessed high surface area of ca. 163-176 m2/g. It was shown that the Fe and La co-doped nano-TiO2 could be activated by visible light and could thus be used as an effective catalyst in photo-oxidation reactions. The synergistic effect of Fe and La co-doping played an important role in improving the photocatalytic activity. In addition, the possibility of cyclic usage of co-doped nano-TiO2 was also confirmed, the photocatalytic activity of codoped nano-TiO2 remained above 89.6% of the fresh sample after being used four times.展开更多
For rechargeable aqueous zinc-ion batteries(ZIBs),the design of nanocomposites comprised of electrochemically active materials and carbon materials with novel structures has great prom-ise in addressing the issue of e...For rechargeable aqueous zinc-ion batteries(ZIBs),the design of nanocomposites comprised of electrochemically active materials and carbon materials with novel structures has great prom-ise in addressing the issue of electrical conductivity and structural stability in the electrode materials during electrochemical cycling.We report the production of a novel flexible electrode material,by anchoring MnO_(2) nanosheets on a B,N co-doped carbon nanotube ar-ray(BNCNTs)grown on carbon cloth(BNCNTs@MnO_(2)),which was fabricated by in-situ pyrolysis and hydrothermal growth.The generated BNCNTs were strongly bonded to the surface of the car-bon fibers in the carbon cloth which provides both excellent elec-tron transport and ion diffusion,and improves the stability and dur-ability of the cathode.Importantly,the BNCNTs offer more active sites for the hydrothermal growth of MnO_(2),ensuring a uniform dis-tribution.Electrochemical tests show that BNCNTs@MnO_(2) delivers a high specific capacity of 310.7 mAh g^(−1) at 0.1 A g^(−1),along with excellent rate capability and outstanding cycling stability,with a 79.7% capacity retention after 8000 cycles at 3 A g^(−1).展开更多
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 hi...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.展开更多
[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略...[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略制备了Fe-N-C单原子催化剂,并将其应用于亚硝酸盐制氨反应.[结果]多种结构表征结果显示,Fe-N-C催化剂表面的Fe物种呈现高度分散特征并以单原子形式存在.此外,Fe物种的化学环境主要是+2和+3价混合态,且通过与4个吡啶氮配位而稳定存在,即Fe-N-C催化剂的金属中心微观配位环境为Fe-N4结构.与纯氮碳(N-C)载体相比,本研究制备的Fe-N-C催化剂具有优异的亚硝酸盐还原性能,不仅表现出更高的起始还原电位(0 V vs可逆氢电极),具有接近100%的产氨法拉第效率和高的氨产率[8.4 mg/(h·cm^(2))],并且在连续20次催化循环测试中显示出优异的催化稳定性.[结论]本研究制备的Fe-N-C单原子催化剂对亚硝酸盐还原制氨具有优异的电催化活性,其高活性可能来源于对NO_(2)^(-)的显著吸附,并进一步促进活性氢参与脱氧加氢过程.该Fe-N-C单原子催化亚硝酸盐还原体系可为后续合成氨的活性中心设计提供指导方向.展开更多
Doping engineering is an effective strategy for graphitic carbon nitride(g-C_(3)N_(4))to improve its photocat-alytic hydrogen evolution reaction(HER)performance.In this work,a novel nitrogen and sulfur co-doped g-C_(3...Doping engineering is an effective strategy for graphitic carbon nitride(g-C_(3)N_(4))to improve its photocat-alytic hydrogen evolution reaction(HER)performance.In this work,a novel nitrogen and sulfur co-doped g-C_(3)N_(4)(N,S-g-C_(3)N_(4))is elaborately designed on the basis of theoretical predictions of first-principle density functional theory(DFT).The calculated Gibbs free energy of adsorbed hydrogen(ΔGH∗)for N,S-g-C_(3)N_(4) at the N-doping active sites is extremely close to zero(0.01 eV).Inspired by the theoretical predictions,the N,S-g-C_(3)N_(4) is successfully fabricated through ammonia-rich pyrolysis synthesis strategy,in which ammonia is in-situ obtained by pyrolyzing melamine.Subsequent characterizations indicate that the N,S-g-C_(3)N_(4) possesses high specific surface area,outstanding light utilization,good hydrophilicity,and efficient carrier transfer efficiency.Consequently,the N,S-g-C_(3)N_(4) displays an extremely high H2 evolution rate of 8269.9μmol g−1 h−1,achieves an apparent quantum efficiency(AQE)of 3.24%,and also possesses outsatnding durability.Theoretical calculations further demonstrate that N and S dopants can not only introduce doping energy level to reduce the band gap,but also induce charge redistribution to facilitate hydrogen adsorption,thus promoting the photocatalytic HER process.Moreover,femtosecond transient absorption(fs-TA)spectroscopy further corroborates the efficient photogenerated carrier transport of N,S-g-C_(3)N_(4).This research highlights a promising and reliable strategy to achieve superior photocatalytic activity,and exhibits significant guidance for precise designing high-efficiency photocatalysts.展开更多
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 ...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.展开更多
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 pros...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.展开更多
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 en...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.展开更多
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 ...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.展开更多
文摘Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphene-modified non-compensated Cu/N-co-doped titanium dioxide(Cu-N-TiO_(2)/rGO)photocatalyst was designed for the efficient synthesis of H_(2)O_(2) via a dual-channel pathway.Precise modulation of the TiO_(2) conduction band position was achieved through the synergistic coupling of Cu 3d orbitals hybridized with Ti 3d orbitals and hybridization of N 2p orbitals with O 2p orbitals.This approach significantly improved the utilization of sunlight while satisfying the redox potential requirements.Cu doping not only promoted the formation of oxygen vacancies but also reduced the formation of Ti^(3+)ions,the photogenerated charge recombination centers.The non-compensated doping of N effectively increased the solubility of Cu^(2+)ions in the titanium dioxide lattice,enhanced the adsorption of hydroxyl radical intermediates,and created conditions for the subsequent hydroxyl radical combinations promoting the generation of H_(2)O_(2).In addition,the introduction of highly conductive graphene improved the interfacial carrier separation efficiency while realizing the spatial separation of redox sites,creating conditions for dual-channel reactions.The experimental results showed that the H_(2)O_(2) yield of Cu-N-TiO_(2)/rGO under simulated sunlight reached 1266.7μmol/L,which was 25.2 times higher than that of pristine TiO_(2).This study elucidated the synergistic mechanism of the energy band structure modulation and interfacial optimization,which provided a new idea for the design of dual-channel H_(2)O_(2) production photocatalysts.
基金supported by the Science Technology Talents Lifting Project of Hunan Province(No.2022TJ-N16)the Natural Science Foundation of Hunan Province(Nos.2024JJ4022,2023JJ30277,2025JJ60382)+3 种基金the China Postdoctoral Fellowship Program(GZC20233205)the Scientifc Research Fund of Hunan Provincial Education Department,China(No.24B0270)the National Natural Science Foundation of China(No.32201646)the Key Project of Jiangxi Provincial Research and Development Program(No.20243BBI91001).
文摘The development of high-performance transition metal sulfide(TMS)/carbon composites to replace conventional graphite anode remains a critical challenge for advancing lithium-ion batteries(LIBs).In this study,a facile self-sacrifice template method is developed to prepare FeS encapsulated into N,S co-doped carbon(FeS/NSC)composite using melamine-cyanuric acid(MCA)supermolecule as a multifunctional template precursor.The function of MCA supermolecule for material synthesis is explored,revealing its special function as a dispersant,dopant and pore-forming agent.Furthermore,the effect of Fe source dosage on the morphology,structure and composition of the final products is explored.The resultant FeS/NSC-0.1(where 0.1 represents the mass of added Fe source)exhibits the most optimal proportion,characterized by a good dispersion status of FeS within the NSC matrix,effective N,S co-doping and ample porosity.Benefiting from these merits,the FeS/NSC-0.1 anode demonstrates significantly improved cycling stability and rate capability when compared to the counterparts.Undoubtedly,this work offers a universal method to produce advanced transition metal sulfide/carbon composite electrodes for energy storage and conversion systems.
基金supported by the National Natural Science Foundation of China(No.U21A20293).
文摘Harnessing the redox potential of biochar to activate airborne O_(2)for contaminant removal is challenging.In this study,ferrihydrite(Fh)modified the boron(B),nitrogen(N)co-doped biochars(BCs)composites(Fh/B(n)NC)were developed for enhancing the degradation of a model pollutant,tetracycline(TC),merely by airborne O_(2).Fh/B(3)NC showed excellent O_(2)activation activity for efficient TC degradation with a apparent TC degradation rate of 5.54,6.88,and 22.15 times that of B(3)NC,Fh,and raw BCs,respectively,where 1O_(2)and H_(2)O_(2)were identified as the dominant ROS for TC degradation.The B incorporation into the carbon lattice of Fh/B(3)NC promoted the generation of electron donors,sp2 C and the reductive B species,hence boosting Fe(III)reduction and 1O_(2)generation.O_(2)adsorption was enhanced due to the positively charged adsorption sites(C-B+and N-C+).And 1O_(2)was generated via Fe(II)catalyzed low-efficient successive one-electron transfer(O_(2)→O_(2)·−→1O_(2),H_(2)O_(2)),as well as biochar catalyzed high-efficient two-electron transfer(O_(2)→H_(2)O_(2)→1O_(2))that does not involve.O_(2)−as the intermediate.Moreover,Fh/B,N co-doped biochar showed a wide pH range,remarkable anti-interference capabilities,and effective detoxification.These findings shed new light on the development of environmentally benign BCs materials capable of degradading organic pollutants.
基金financially supported by the National Natural Science Foundation of China(Nos.52222106,52371171,51971008,and 52121001)the National Key R&D Program of China(No.2021YBF3501304)the Fundamental Research Funds for the Central Universities.The authors acknowledge the facilities and the scientific and technical assistance of the Analysis&Testing Center,Beihang University.
文摘Transition metal carbides(MXenes)used as electromagnetic wave absorption materials face two critical challenges:impedance mismatch caused by high conductivity and the easy restacking and agglomeration of ultrathin nanosheets.To address these issues,this study proposes the construction of an S/N co-doped MXene nanoribbon/nanosheet composite structure.An alkali-assisted chemical scissor strategy was used to successfully prepare a nanoribbon/nanosheet hybrid,which effectively suppressed nanosheet stacking and significantly increased the number of active interfaces and defect sites.By controlling the doping temperature,the doping configurations of S and N in MXenes can be precisely regulated,including lattice substitution(LS),functional group substitution(FS),and surface absorption(SA).With increasing doping temperature,the configuration of S/N dopants evolves from a combination of FS-type N and LS-type S to a coexistence of SA-and LS-type species.The former synergistically enhances conductive loss and polarization loss,whereas the latter suppresses electron transport and consequently reduces the complex permittivity of the material.The optimized composite exhibited considerably improved comprehensive electromagnetic wave-absorption performance at a low filler loading(10 wt%)and thin thickness(1.26 mm),achieving a minimum reflection loss(RLmin)of-53.77 dB and an effective absorption bandwidth(EAB)of 4.51 GHz.This work not only clarifies the regulatory mechanism of doping configurations on high-frequency electromagnetic properties but also provides a theoretical foundation for the rational design of high-performance MXene-based electromagnetic wave absorbing materials.
文摘A series of photocatalysts of un-doped, single-doped and co-doped nanometer titanium diox- ide （TiO2） have been successfully prepared by template method using Fe（NO3）3.9H2O, La（NO3）3.6H2O, and tetrabutyl titanate as precursors and glucan as template. Scanning electron microscopy, X-ray diffraction, and N2 adsorption-desorption measurement were employed to characterize the morphology, crystal structure and surface structure of the samples. The photo-absorbance of the obtained catalysts was measured by UV-Vis absorption spectroscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl orange in an aqueous solution. The characterizations indicated that the prepared photocatalysts consisted of anatase phase and possessed high surface area of ca. 163-176 m2/g. It was shown that the Fe and La co-doped nano-TiO2 could be activated by visible light and could thus be used as an effective catalyst in photo-oxidation reactions. The synergistic effect of Fe and La co-doping played an important role in improving the photocatalytic activity. In addition, the possibility of cyclic usage of co-doped nano-TiO2 was also confirmed, the photocatalytic activity of codoped nano-TiO2 remained above 89.6% of the fresh sample after being used four times.
基金financial support from projects funded by the National Natural Science Foundation of China(52172038,22179017)the National Key Research and Development Program of China(2022YFB4101600,2022YFB4101601)。
文摘For rechargeable aqueous zinc-ion batteries(ZIBs),the design of nanocomposites comprised of electrochemically active materials and carbon materials with novel structures has great prom-ise in addressing the issue of electrical conductivity and structural stability in the electrode materials during electrochemical cycling.We report the production of a novel flexible electrode material,by anchoring MnO_(2) nanosheets on a B,N co-doped carbon nanotube ar-ray(BNCNTs)grown on carbon cloth(BNCNTs@MnO_(2)),which was fabricated by in-situ pyrolysis and hydrothermal growth.The generated BNCNTs were strongly bonded to the surface of the car-bon fibers in the carbon cloth which provides both excellent elec-tron transport and ion diffusion,and improves the stability and dur-ability of the cathode.Importantly,the BNCNTs offer more active sites for the hydrothermal growth of MnO_(2),ensuring a uniform dis-tribution.Electrochemical tests show that BNCNTs@MnO_(2) delivers a high specific capacity of 310.7 mAh g^(−1) at 0.1 A g^(−1),along with excellent rate capability and outstanding cycling stability,with a 79.7% capacity retention after 8000 cycles at 3 A g^(−1).
基金the financial supports from the National Natural Science Foundation of China(Grant Nos.51872005,U1508201,52072002)。
文摘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.
文摘[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略制备了Fe-N-C单原子催化剂,并将其应用于亚硝酸盐制氨反应.[结果]多种结构表征结果显示,Fe-N-C催化剂表面的Fe物种呈现高度分散特征并以单原子形式存在.此外,Fe物种的化学环境主要是+2和+3价混合态,且通过与4个吡啶氮配位而稳定存在,即Fe-N-C催化剂的金属中心微观配位环境为Fe-N4结构.与纯氮碳(N-C)载体相比,本研究制备的Fe-N-C催化剂具有优异的亚硝酸盐还原性能,不仅表现出更高的起始还原电位(0 V vs可逆氢电极),具有接近100%的产氨法拉第效率和高的氨产率[8.4 mg/(h·cm^(2))],并且在连续20次催化循环测试中显示出优异的催化稳定性.[结论]本研究制备的Fe-N-C单原子催化剂对亚硝酸盐还原制氨具有优异的电催化活性,其高活性可能来源于对NO_(2)^(-)的显著吸附,并进一步促进活性氢参与脱氧加氢过程.该Fe-N-C单原子催化亚硝酸盐还原体系可为后续合成氨的活性中心设计提供指导方向.
基金supported by the National Natural Science Foun-dation of China(No.62004143)the Key R&D Program of Hubei Province(No.2022BAA084)the Natural Science Foundation of Hubei Province(No.2021CFB133).
文摘Doping engineering is an effective strategy for graphitic carbon nitride(g-C_(3)N_(4))to improve its photocat-alytic hydrogen evolution reaction(HER)performance.In this work,a novel nitrogen and sulfur co-doped g-C_(3)N_(4)(N,S-g-C_(3)N_(4))is elaborately designed on the basis of theoretical predictions of first-principle density functional theory(DFT).The calculated Gibbs free energy of adsorbed hydrogen(ΔGH∗)for N,S-g-C_(3)N_(4) at the N-doping active sites is extremely close to zero(0.01 eV).Inspired by the theoretical predictions,the N,S-g-C_(3)N_(4) is successfully fabricated through ammonia-rich pyrolysis synthesis strategy,in which ammonia is in-situ obtained by pyrolyzing melamine.Subsequent characterizations indicate that the N,S-g-C_(3)N_(4) possesses high specific surface area,outstanding light utilization,good hydrophilicity,and efficient carrier transfer efficiency.Consequently,the N,S-g-C_(3)N_(4) displays an extremely high H2 evolution rate of 8269.9μmol g−1 h−1,achieves an apparent quantum efficiency(AQE)of 3.24%,and also possesses outsatnding durability.Theoretical calculations further demonstrate that N and S dopants can not only introduce doping energy level to reduce the band gap,but also induce charge redistribution to facilitate hydrogen adsorption,thus promoting the photocatalytic HER process.Moreover,femtosecond transient absorption(fs-TA)spectroscopy further corroborates the efficient photogenerated carrier transport of N,S-g-C_(3)N_(4).This research highlights a promising and reliable strategy to achieve superior photocatalytic activity,and exhibits significant guidance for precise designing high-efficiency photocatalysts.
基金supported by the National Natural Science Foundation of China (Nos. U1804255 and 51872076)the Program for Innovative Research Team of Henan Scientific Committee (No. CXTD2014033)+1 种基金the Project of Central Plains Science and Technology Innovation Leading Talents,Henan Province(No. 194200510001)the Scientific and Technological Research Project,Henan province (No. 212102210651)。
文摘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.
基金This work was supported by the Major special projects of Science and Technology Department of Sichuan Province(No.2020ZDZX0020).
文摘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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10325415 and 50504017)the Natural Science Foundation of Hunan Province,China(Grant No.07JJ3102)+1 种基金the Scientific Research Fund of Hunan Provincial Education Department,China(Grant No.10C1171)the Science Development Foundation of Central South University,China(Grant Nos.08SDF02 and 09SDF09)
文摘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.
基金We gratefully acknowledge financial supports from the National Natural Science Foundation of China(No.52202371,51905125,52102364)the Natural Science Foundation of Shandong Province(No.ZR2020QE066)+2 种基金Opening Project of State Key Laboratory of Advanced Technology for Float Glass(No.2020KF08)SDUT&Zibo City Integration Development Project(No.2021SNPT0045)the fellowship of China Postdoctoral Science Foundation(No.2020M672081).
文摘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.
