Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and sustainability.Ov...Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and sustainability.Over the past decade,well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction mechanisms.However,active sites,key intermediate species,precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental methods.In this Review,we sum-marize the extensive efforts on model catalysts since the 2000s,particularly in the past decade,to overcome the influences of material and structure limitations in metal-free carbon catalysis.Using both nanomolecule model and bulk model,the real contribution of each alien species,defect and edge configuration to a series of fundamentally important reactions,such as thermocatalytic reactions,electrocatalytic reactions,were systematically studied.Combined with in situ techniques,isotope labeling and size control,the detailed reaction mechanisms,the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular level.Furthermore,the outlook of model carbon catalysis has also been proposed in this work.展开更多
Zinc-ion batteries(ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zin...Zinc-ion batteries(ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion, and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution, and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. Therefore, this work systematically introduces the research progress of zinc metal-free anodes in “rocking chair” ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides,transition metal sulfides, MXene(two dimensional transition metal carbide) composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. This paper is expected to provide a reference for the further promotion of commercial rechargeable ZIBs.展开更多
Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination ra...Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination rate.Herein,a novel metal-free 2D/2D van der Waals heterojunction,composed of a two-dimensional(2D)COF with ketoenamine linkage(TpPa-1-COF)and 2D defective hexagonal boron nitride(h-BN),is successfully constructed through in situ solvothermal method.Benefitting from the presence of VDW heterojunction,larger contact area and intimate electronic coupling can be formed between the interface of TpPa-1-COF and defective h-BN,which make contributions to promoting charge car-riers separation.The introduced defects can also endow the h-BN with porous structure,thus providing more reactive sites.Moreover,the TpPa-1-COF will undergo a structural transformation after being integrated with defective h-BN,which can enlarge the gap between the conduction band position of the h-BN and TpPa-1-COF,and suppress electron backflow,corroborated by experimental and density functional theory calculations results.Accordingly,the resulting porous h-BN/TpPa-1-COF metal-free VDW heterojunction displays out-standing solar energy catalytic activity for water splitting without co-catalysts,and the H_(2) evolution rate can reach up to 3.15 mmol g^(−1) h^(−1),which is about 67 times greater than that of pristine TpPa-1-COF,also surpassing that of state-of-the-art metal-free-based photocatalysts reported to date.In particular,it is the first work for constructing COFs-based heterojunctions with the help of h-BN,which may provide new avenue for designing highly efficient metal-free-based photocatalysts for H_(2) evolution.展开更多
Electrochemical CO2 reduction to chemicals or fuels presents one of the most promising strategies for managing the global carbon balance, which yet poses a significant challenge due to lack of efficient and durable el...Electrochemical CO2 reduction to chemicals or fuels presents one of the most promising strategies for managing the global carbon balance, which yet poses a significant challenge due to lack of efficient and durable electrocatalyst as well as the understanding of the CO2 reduction reaction(CO2RR) mechanism.Benefiting from the large surface area, high electrical conductivity, and tunable structure, carbon-based metal-free materials(CMs) have been extensively studied as cost-effective electrocatalysts for CO2RR.The development of CMs with low cost, high activity and durability for CO2RR has been considered as one of the most active and competitive directions in electrochemistry and material science.In this review article,some up-to-date strategies in improving the CO2RR performance on CMs are summarized.Specifically, the approaches to optimize the adsorption of CO2RR intermediates, such as tuning the physical and electronic structure are introduced, which can enhance the electrocatalytic activity of CMs effectively.Finally, some design strategies are proposed to prepare CMs with high activity and selectivity for CO2RR.展开更多
To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surfa...To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surface/interface engineering is found to be effective in achieving novel physicochemical properties and synergistic effects in nanomaterials for electrocatalysis.Among various engineering strategies,heteroatom-doping has been regarded as a most promising method to improve the electrocatalytic performance via the regulation of electronic structure of catalysts,and numerous works were reported on the synthesis method and mechanism investigation of heteroatom-doping electrocatalysts,though the heteroatom-doping can only provide limited active sites.Engineering of other defects such as vacancies and edge sites and construction of heterostructure have shown to open up a potential avenue for the development of noble metal-free electrocatalysts.In addition,surface functionalization can attach various molecules onto the surface of materials to easily modify their physical or chemical properties,being as a promising complement or substitute for offering materials with catalytic properties.This paper gives the insights into the diverse strategies of surface/interface engineering of the highefficiency noble metal-free electrocatalysts for energy-related electrochemical reactions.The significant advances are summarized.The unique advantages and mechanisms for specific applications are highlighted.The current challenges and outlook of this growing field are also discussed.展开更多
The metal-free synthesis of graphene on singlecrystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth ...The metal-free synthesis of graphene on singlecrystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed,single-crystal silicon substrate using metal-free, ambientpressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates.展开更多
Although scientists have conducted long-term and extensive studies on oxygen reduction reaction(ORR)catalyzed by metal-free carbon materials,they mainly have focused on the preparation and properties of various doped ...Although scientists have conducted long-term and extensive studies on oxygen reduction reaction(ORR)catalyzed by metal-free carbon materials,they mainly have focused on the preparation and properties of various doped carbon materials.There is still a lack of systematic scientific guidance on the relationship between the surface structure regulation and activity of carbon-based catalysts.In this review,some of electrochemical and computational fundamental concepts about ORR are concisely summarized.The effects of edge defect and nonmetallic doping of carbon materials on ORR behavior and mechanism have been reviewed,and activity origin identification and intermediate conversion mechanism have been discussed.The outlooks for future researches on metal-free ORR electrocatalysis are suggested.展开更多
Oxidative desulfurization(ODS)has been proved to be an efficient strategy for the production of clean fuel oil.Numerous metal-based materials have been employed as excellent ODS catalysts,but being hindered by their h...Oxidative desulfurization(ODS)has been proved to be an efficient strategy for the production of clean fuel oil.Numerous metal-based materials have been employed as excellent ODS catalysts,but being hindered by their high-cost and potential secondary pollution.In this work,we employed graphene analogous hexagonal boron nitride(h-BN)as a metal-free catalyst for ODS with hydrogen peroxide(H2O2)as the oxidant.The h-BN catalyst was characterized and proved to be a few-layered structure with relatively high specific surface areas.The h-BN catalyst showed a 99.4%of sulfur removal in fuel oil under the optimized reaction conditions.Besides,the h-BN can be recycled for 8 times without significant decrease in the catalytic performance.Detailed mechanism analysis found that it is the boron radicals in h-BN activated H2O2 to generate·OH species,which can readily oxidize sulfides to corresponding sulfones for separation.This work would provide another choice in choosing metal-free catalysts for ODS.展开更多
Since the discovery of the first carbon-based metal-free electrocatalysts(C-MFECs,i.e.,N-doped carbon nanotubes)for the oxygen reduction reaction in 2009,the field of C-MFECs has grown enormously over the last 10 year...Since the discovery of the first carbon-based metal-free electrocatalysts(C-MFECs,i.e.,N-doped carbon nanotubes)for the oxygen reduction reaction in 2009,the field of C-MFECs has grown enormously over the last 10 years.C-MFECs,as alternatives to nonprecious transition metals and/or precious noble metal-based electrocatalysts,have been consistently demonstrated as efficient catalysts for oxygen reduction,oxygen evolution,hydrogen evolution,carbon dioxide reduction,nitrogen reduction,and many other(electro-)chemical reactions.Recent research and development of C-MFECs have indicated their potential applications in fuel cells,metal-air batteries,and hydrogen generation through water oxidation as well as electrochemical production of various commodity chemicals,such as ammonia,alcohols,hydrogen peroxide,and other useful hydrocarbons.Further research and development of C-MFECs would surely revolutionize traditional energy conversion and storage technologies with minimal environmental impact.In this short review article,we summarize the journey of C-MFECs over the past 10 years with an emphasis on materials development and their structure-property characterization for applications in fuel cells and metal-air batteries.Current challenges and future prospects of this emerging field are also discussed.展开更多
Oxygen and nitrogen-functionalized carbon nanotubes (OCNTs and NCNTs) were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Tempe...Oxygen and nitrogen-functionalized carbon nanotubes (OCNTs and NCNTs) were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.展开更多
The oxygen reduction/evolution reactions(ORR/OER) are a key electrode process in the development of electrochemical energy conversion and storage devices,such as metal-air batteries and reversible fuel cells.The searc...The oxygen reduction/evolution reactions(ORR/OER) are a key electrode process in the development of electrochemical energy conversion and storage devices,such as metal-air batteries and reversible fuel cells.The search for low-cost high-performance nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER alternatives to the widely-used noble metal-based catalysts is a research focus.This review aims to outline the opportunities and available options for these nanocarbon-based bifunctional electrocatalysts.Through discussion of some current scientific issues,we summarize the development and breakthroughs of these electrocatalysts.Then we provide our perspectives on these issues and suggestions for some areas in the further work.We hope that this review can improve the interest in nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER.展开更多
The carbon-based metal-free materials as catalysts(named as carbocatalysts) have been attracting tremendous attentions in electric-,solar-and thermal-driven reactions nowadays.Compared to electrocatalysis and photocat...The carbon-based metal-free materials as catalysts(named as carbocatalysts) have been attracting tremendous attentions in electric-,solar-and thermal-driven reactions nowadays.Compared to electrocatalysis and photocatalysis,the thermal-driven catalysis(thermocatalysis) including liquid phase and gas phase reactions involves wider scope and is relatively easy to realize practical large-scale applications.Over the past several years,some striking achievements on the design of new carbon-based metal-free materials with well-defined structures and heteroatom groups as well as the revelation of new reaction mechanisms and active sites in thermocatalysis have been obtained.However,comparative discussions regarding these recent achievements have been rarely highlighted.In this review,we systematically summarize and discuss six kinds of carbocatalysts and their applications in thermocatalysis.These materials include typical oxygen-attached carbon,surface modified carbon(graft with certain organic compounds),mono-doped carbon,co-doped carbon,carbon nitride and materials with carbon as dopant.Some new reaction processes as well as the related reaction mechanisms,active sites and intermediates are reviewed critically.Moreover,an outlook on the in-depth investigation of the metalfree carbocatalysis in the future is provided.展开更多
Herein,we report on the effect of a high gravity field on metal-free catalytic reduction,taking the nitrobenzene(NB)reduction and methylene blue(MB)degradation as model reactions in a highgravity rotating tube reactor...Herein,we report on the effect of a high gravity field on metal-free catalytic reduction,taking the nitrobenzene(NB)reduction and methylene blue(MB)degradation as model reactions in a highgravity rotating tube reactor packed with three-dimensional(3D)nitrogen-doped graphene foam(NGF)as a metal-free catalyst.The apparent rate constant(kapp)of the metal-free catalytic reduction of NB in the rotating tube reactor under a high gravity level of 6484g(g=9.81 m s-2)was six times greater than that in a conventional stirred reactor(STR)under gravity.Computational fluid dynamics(CFD)simulations indicated that the improvement of the catalytic efficiency was attributed to the much higher turbulent kinetic energy and faster surface renewal rate in the high-gravity tube reactor in comparison w让h those in a conventional STR.The structure of the 3D metal-free catalysts was stable during the reaction process under a high gravity field,as confirmed by X-ray photoelectron spectroscopy(XPS)and Raman spectra.In the other model reaction,the rate of MB degradation also increased as the high gravity level in creased gradually,which aligns with the result for the NB catalytic reduction system.These results demonstrate the potential to use a high-gravity rotating packed tube reactor for the process intensification of metal-free catalytic reduction reactions.展开更多
Graphene-modified asphalt(GMA)for road application was prepared via using metal-free phthalocyanine-dispersed to modify an SK-70#base asphalt with graphene.The preparation parameters are as follows:the content of grap...Graphene-modified asphalt(GMA)for road application was prepared via using metal-free phthalocyanine-dispersed to modify an SK-70#base asphalt with graphene.The preparation parameters are as follows:the content of graphene is 0.26%based on the mass percentage of absolute ethanol,the content of nonmetal phthalocyanine is 190%based on the mass percentage of graphene,and then the GMA is prepared via unique high-speed shearing with continuing to ventilate nitrogen,which can prevent the aging of modified asphalt in the high-speed shearing process,and effectively evaluate the modifier.The penetration,softening point,force ductility,and fracture energy of GMA were significantly improved based on the base asphalt.Thus,the incorporation of graphene could enhance the base asphalt’s high-and low-temperature stability.The modification mechanism was researched via metallographic microscopy,computed tomography(CT),Fourier transform infrared spectroscopy(FTIR),and atomic force microscopy(AFM).Adsorption and physical dispersion of the asphaltenes and resins in the phthalocyanine-graphene system were confirmed.展开更多
Rational design and facile preparation of low-cost and efficient catalysts for the selective converting of biomass-derived monosaccharides into high value-added chemicals is highly demanded,yet challenging.Herein,we f...Rational design and facile preparation of low-cost and efficient catalysts for the selective converting of biomass-derived monosaccharides into high value-added chemicals is highly demanded,yet challenging.Herein,we first demonstrate a N doped defect-rich carbon(NC-800-5)as metal-free catalyst for the selective oxidation of D-xylose into D-xylonic acid in alkaline aqueous solution at 100℃ for 30 min,with 57.4%yield.The doped graphitic N is found to be the active site and hydroxyl ion participating in the oxidation of D-xylose.Hydroxyl ion and D-xylose first adsorb on NC-800-5 surface,and the aldehyde group of D-xylose is catalyzed to form germinal diols ion.Then,C–H bond break to yield carboxylic group.Furthermore,NC-800-5 catalyst shows high stability in recycled test.展开更多
Herein,we for the first time demonstrate the synthesis of exfoliated C4N nanosheets via a top-down approach and exploit their use as a new class of organic polymeric catalyst for the oxygen reduction reaction(ORR).The...Herein,we for the first time demonstrate the synthesis of exfoliated C4N nanosheets via a top-down approach and exploit their use as a new class of organic polymeric catalyst for the oxygen reduction reaction(ORR).The obtained C4N nanosheets are semi-conductive with a small band gap of 1.41 eV and contain abundant pyrazine-nitrogen moieties uniformly distributed throughout C4N.Density function theory calculations reveal that the intramolecular charge transfer induced by pyrazine-nitrogen in C4N enables effective charge redistribution to activate the conjugated structure and facilitate the oxygen adsorption,while the exfoliated sheet-like C4N formation renders improved electrochemical active surface area and results in high exposure of active sites.As a result,despite the bulk C4N is not active,the sheet-like C4N yield markedly improved ORR performance,even on a par with the commercial Pt/C catalyst.Our recent findings not only enrich the family members of two-dimensional conjugated polymer nanosheets but also open up new opportunity to explore new metal-free organic polymeric materials for efficient oxygen reduction catalysis and beyond.展开更多
A metal-free catalytic system combining oxidized carbon nanotubes (oCNTs) and ionic liquids (ILs) is presented for the oxidation of aromatic thiophene compounds with H2O2 as an oxidant. The oCNTs exhibit impressively ...A metal-free catalytic system combining oxidized carbon nanotubes (oCNTs) and ionic liquids (ILs) is presented for the oxidation of aromatic thiophene compounds with H2O2 as an oxidant. The oCNTs exhibit impressively high activity and stability in the system, which show an even better performance than those of some reported metal catalysts. The ILs are proved to have indispensable influence on the enhanced catalytic performance of the oCNTs. Detailed characterization by TG-MS and XPS demonstrates that the carbonyl groups are the active sites for the oxidation process, which is further supported by the deactivation and the model catalysts experiments. The quantitative analysis of different oxygen groups in oCNTs could be achieved by an isothermal temperature programmed TG-MS method. The concentration of carbonyl groups is 1.46 mmol per 1 g oCNTs and the tuiriover frequency of oCNTs could also be obtained (10.7 h^-1 in the presence of OmimPF6). H2O2 decomposition experiments combined with the EPR results reveal that the presence of OmimPF6 can avoid the intermediate HO· to form O2 and then improve the catalytic performance of oCNTs for the oxidation of dibenzothiophene.展开更多
Photocatalytic water splitting has gained increasing attention, since it utilizes renewable resources, such as water and solar energy, to produce hydrogen. Using the first-principles density functional theory, we inve...Photocatalytic water splitting has gained increasing attention, since it utilizes renewable resources, such as water and solar energy, to produce hydrogen. Using the first-principles density functional theory, we investigate the properties of the single layer C_2N which was successfully synthesized. We reveal that monolayer C_2N has a substantial direct band gap of 2.45 eV. To regulate its band gap, four different nonmetal elements(B, O, P, and S) on the cation and anion sites are considered. Among them, B-doped N site is the most effective one, with the lowest formation energy and a band gap of 2.01 eV. P-doped N site is the next, with a band gap of 2.08 eV, though its formation energy is higher. The band alignments with respect to the water redox levels show that, for these two dopings, the thermodynamic criterion for the overall water splitting is satisfied. We therefore predict that B-or P-doped C_2N, with an appropriate band gap and an optimal band-edge position, would be a promising photocatalyst for visible-light water splitting.展开更多
The metal-free combination of catalytic amounts of PPh3,B(C6F5)3,and PhSiH_3 can efficiently hydrosilylate aldehydes, ketones,aldimines and ketimines to afford the corresponding reduction products in good yields.
Tirazine based microporous polymeric (TMP) network was found to be an efficient metal-free catalyst for the epoxidation of styrene. The reactions were performed in water as an environmentally benign medium using H2O2 ...Tirazine based microporous polymeric (TMP) network was found to be an efficient metal-free catalyst for the epoxidation of styrene. The reactions were performed in water as an environmentally benign medium using H2O2 as a green oxidant at ambient temperature. The reaction afforded higher yield with 90% conversion of styrene and 98% selectivity to styrene oxide in 6 h. The triazine based microporous polymeric network can be readily recovered and reused up to 4 cycles without significant loss in catalytic activity and selectivity.展开更多
基金We are grateful for financial support from the“Hundred Talents Program”of the Chinese Academy of Sciences and the“Young Talents Training Program”of the Shanghai Branch of the Chinese Academy of Sciences.We acknowledge the financial support from the National Science Youth Foundation of China(22202205)Xiamen City Natural Science Foundation of China(3502Z20227256)Fujian Provincial Natural Science Foundation of China(2022J01502).
文摘Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and sustainability.Over the past decade,well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction mechanisms.However,active sites,key intermediate species,precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental methods.In this Review,we sum-marize the extensive efforts on model catalysts since the 2000s,particularly in the past decade,to overcome the influences of material and structure limitations in metal-free carbon catalysis.Using both nanomolecule model and bulk model,the real contribution of each alien species,defect and edge configuration to a series of fundamentally important reactions,such as thermocatalytic reactions,electrocatalytic reactions,were systematically studied.Combined with in situ techniques,isotope labeling and size control,the detailed reaction mechanisms,the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular level.Furthermore,the outlook of model carbon catalysis has also been proposed in this work.
基金financially supported by the National Natural Science Foundation of China (Nos.51872090 and51772097)the Hebei Natural Science Fund for Distinguished Young Scholar,China (No.E2019209433)+2 种基金the Youth Talent Program of Hebei Provincial Education Department,China (No.BJ2018020)the Natural Science Foundation of Hebei Province,China (No.E2020209151)the Science and Technology Project of Hebei Education Department,China (No.SLRC2019028)。
文摘Zinc-ion batteries(ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion, and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution, and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. Therefore, this work systematically introduces the research progress of zinc metal-free anodes in “rocking chair” ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides,transition metal sulfides, MXene(two dimensional transition metal carbide) composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. This paper is expected to provide a reference for the further promotion of commercial rechargeable ZIBs.
基金supported by the National Natural Science Foundation of China(Nos.22101105,52071171,52202248)the Research Fund for the Doctoral Program of Liaoning Province(2021-BS-086)+6 种基金Liaoning BaiQianWan Talents Program(LNBQW2018B0048)Shenyang Science and Technology Project(21-108-9-04)Australian Research Council(ARC)through Future Fellowship(FT210100298,FT210100806)Discovery Project(DP220100603)Linkage Project(LP210100467,LP210200504,LP210200345,LP220100088)Industrial Transformation Training Centre(IC180100005)schemesthe Australian Government through the Cooperative Research Centres Projects(CRCPXIII000077).
文摘Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination rate.Herein,a novel metal-free 2D/2D van der Waals heterojunction,composed of a two-dimensional(2D)COF with ketoenamine linkage(TpPa-1-COF)and 2D defective hexagonal boron nitride(h-BN),is successfully constructed through in situ solvothermal method.Benefitting from the presence of VDW heterojunction,larger contact area and intimate electronic coupling can be formed between the interface of TpPa-1-COF and defective h-BN,which make contributions to promoting charge car-riers separation.The introduced defects can also endow the h-BN with porous structure,thus providing more reactive sites.Moreover,the TpPa-1-COF will undergo a structural transformation after being integrated with defective h-BN,which can enlarge the gap between the conduction band position of the h-BN and TpPa-1-COF,and suppress electron backflow,corroborated by experimental and density functional theory calculations results.Accordingly,the resulting porous h-BN/TpPa-1-COF metal-free VDW heterojunction displays out-standing solar energy catalytic activity for water splitting without co-catalysts,and the H_(2) evolution rate can reach up to 3.15 mmol g^(−1) h^(−1),which is about 67 times greater than that of pristine TpPa-1-COF,also surpassing that of state-of-the-art metal-free-based photocatalysts reported to date.In particular,it is the first work for constructing COFs-based heterojunctions with the help of h-BN,which may provide new avenue for designing highly efficient metal-free-based photocatalysts for H_(2) evolution.
基金supported by the National Key R&D Program of China (2016YFB0600902)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB17000000)+2 种基金Dalian National Laboratory for Clean Energy (DNL180401)the Youth Innovation Promotion Association CASthe Singapore Ministry of Education Academic Research Fund (AcRF) Tier 1: RG9/17, RG115/17, RG115/18 and Tier 2: MOE2016-T2-2-004
文摘Electrochemical CO2 reduction to chemicals or fuels presents one of the most promising strategies for managing the global carbon balance, which yet poses a significant challenge due to lack of efficient and durable electrocatalyst as well as the understanding of the CO2 reduction reaction(CO2RR) mechanism.Benefiting from the large surface area, high electrical conductivity, and tunable structure, carbon-based metal-free materials(CMs) have been extensively studied as cost-effective electrocatalysts for CO2RR.The development of CMs with low cost, high activity and durability for CO2RR has been considered as one of the most active and competitive directions in electrochemistry and material science.In this review article,some up-to-date strategies in improving the CO2RR performance on CMs are summarized.Specifically, the approaches to optimize the adsorption of CO2RR intermediates, such as tuning the physical and electronic structure are introduced, which can enhance the electrocatalytic activity of CMs effectively.Finally, some design strategies are proposed to prepare CMs with high activity and selectivity for CO2RR.
基金supported by the Natural Science Foundation of Shandong Province(ZR2019PB013)the Natural Science Foundation of Tianjin(19JCZDJC37700)the National Natural Science Foundation of China(21421001 and 21875118)。
文摘To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surface/interface engineering is found to be effective in achieving novel physicochemical properties and synergistic effects in nanomaterials for electrocatalysis.Among various engineering strategies,heteroatom-doping has been regarded as a most promising method to improve the electrocatalytic performance via the regulation of electronic structure of catalysts,and numerous works were reported on the synthesis method and mechanism investigation of heteroatom-doping electrocatalysts,though the heteroatom-doping can only provide limited active sites.Engineering of other defects such as vacancies and edge sites and construction of heterostructure have shown to open up a potential avenue for the development of noble metal-free electrocatalysts.In addition,surface functionalization can attach various molecules onto the surface of materials to easily modify their physical or chemical properties,being as a promising complement or substitute for offering materials with catalytic properties.This paper gives the insights into the diverse strategies of surface/interface engineering of the highefficiency noble metal-free electrocatalysts for energy-related electrochemical reactions.The significant advances are summarized.The unique advantages and mechanisms for specific applications are highlighted.The current challenges and outlook of this growing field are also discussed.
基金financially supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 11405253, 11225527, 11575283, 11205235, U1632129, U1332205)Shanghai Science Foundation (14YF1407500)the Youth Innovation Promotion Association CAS (2016237)
文摘The metal-free synthesis of graphene on singlecrystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed,single-crystal silicon substrate using metal-free, ambientpressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates.
基金support from the National Natural Science Foundation of China(nos.21872041,21373091)the Science and Technology Project of Guangzhou city(no.201704030040)。
文摘Although scientists have conducted long-term and extensive studies on oxygen reduction reaction(ORR)catalyzed by metal-free carbon materials,they mainly have focused on the preparation and properties of various doped carbon materials.There is still a lack of systematic scientific guidance on the relationship between the surface structure regulation and activity of carbon-based catalysts.In this review,some of electrochemical and computational fundamental concepts about ORR are concisely summarized.The effects of edge defect and nonmetallic doping of carbon materials on ORR behavior and mechanism have been reviewed,and activity origin identification and intermediate conversion mechanism have been discussed.The outlooks for future researches on metal-free ORR electrocatalysis are suggested.
基金All authors appreciate the financial support from the National Key R&D Program of China(2017YFB0306504)the National Natural Science Foundation of China(No.21722604,21878133 and 21908082)+2 种基金China Postdoctoral Science Foundation(No.2019M651743)Natural Science Foundation of Jiangsu Province(BK20190852,BK20190854)Natural Science Foundation for Jiangsu Colleges and Universities(19KJB530005).
文摘Oxidative desulfurization(ODS)has been proved to be an efficient strategy for the production of clean fuel oil.Numerous metal-based materials have been employed as excellent ODS catalysts,but being hindered by their high-cost and potential secondary pollution.In this work,we employed graphene analogous hexagonal boron nitride(h-BN)as a metal-free catalyst for ODS with hydrogen peroxide(H2O2)as the oxidant.The h-BN catalyst was characterized and proved to be a few-layered structure with relatively high specific surface areas.The h-BN catalyst showed a 99.4%of sulfur removal in fuel oil under the optimized reaction conditions.Besides,the h-BN can be recycled for 8 times without significant decrease in the catalytic performance.Detailed mechanism analysis found that it is the boron radicals in h-BN activated H2O2 to generate·OH species,which can readily oxidize sulfides to corresponding sulfones for separation.This work would provide another choice in choosing metal-free catalysts for ODS.
基金The authors thank our colleagues for their contributions to the work cited.This study was partially supported by the ARC DP190103881,US Air Force Research Laboratory(AFRL),UNSW,and CWRU.
文摘Since the discovery of the first carbon-based metal-free electrocatalysts(C-MFECs,i.e.,N-doped carbon nanotubes)for the oxygen reduction reaction in 2009,the field of C-MFECs has grown enormously over the last 10 years.C-MFECs,as alternatives to nonprecious transition metals and/or precious noble metal-based electrocatalysts,have been consistently demonstrated as efficient catalysts for oxygen reduction,oxygen evolution,hydrogen evolution,carbon dioxide reduction,nitrogen reduction,and many other(electro-)chemical reactions.Recent research and development of C-MFECs have indicated their potential applications in fuel cells,metal-air batteries,and hydrogen generation through water oxidation as well as electrochemical production of various commodity chemicals,such as ammonia,alcohols,hydrogen peroxide,and other useful hydrocarbons.Further research and development of C-MFECs would surely revolutionize traditional energy conversion and storage technologies with minimal environmental impact.In this short review article,we summarize the journey of C-MFECs over the past 10 years with an emphasis on materials development and their structure-property characterization for applications in fuel cells and metal-air batteries.Current challenges and future prospects of this emerging field are also discussed.
基金supported by the German Federal Ministry of Education and Research (BMBF) for the CarboKat Project (03X0204D) within the scope of the Inno.CNT Alliance
文摘Oxygen and nitrogen-functionalized carbon nanotubes (OCNTs and NCNTs) were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.
基金the financial support provided by the National Natural Science Foundation of China(Grant Nos.51932005 and 21773269)the Joint Research Fund LiaoningShenyang National Laboratory for Materials Science(Grant No.20180510047)Liao Ning Revitalization Talents Program(XLYC1807175)。
文摘The oxygen reduction/evolution reactions(ORR/OER) are a key electrode process in the development of electrochemical energy conversion and storage devices,such as metal-air batteries and reversible fuel cells.The search for low-cost high-performance nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER alternatives to the widely-used noble metal-based catalysts is a research focus.This review aims to outline the opportunities and available options for these nanocarbon-based bifunctional electrocatalysts.Through discussion of some current scientific issues,we summarize the development and breakthroughs of these electrocatalysts.Then we provide our perspectives on these issues and suggestions for some areas in the further work.We hope that this review can improve the interest in nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER.
基金supported by the Award Program for Fujian Minjiang Scholar Professorship,the National Natural Science Foundation of China(21571035)Chemical Engineering&Technology of Zhejiang Province First-Class Discipline(Taizhou University),Zhejiang Provincial Natural Science Foundation of China(LQ20B060001)Taizhou science and technology planning project(1902gy20)。
文摘The carbon-based metal-free materials as catalysts(named as carbocatalysts) have been attracting tremendous attentions in electric-,solar-and thermal-driven reactions nowadays.Compared to electrocatalysis and photocatalysis,the thermal-driven catalysis(thermocatalysis) including liquid phase and gas phase reactions involves wider scope and is relatively easy to realize practical large-scale applications.Over the past several years,some striking achievements on the design of new carbon-based metal-free materials with well-defined structures and heteroatom groups as well as the revelation of new reaction mechanisms and active sites in thermocatalysis have been obtained.However,comparative discussions regarding these recent achievements have been rarely highlighted.In this review,we systematically summarize and discuss six kinds of carbocatalysts and their applications in thermocatalysis.These materials include typical oxygen-attached carbon,surface modified carbon(graft with certain organic compounds),mono-doped carbon,co-doped carbon,carbon nitride and materials with carbon as dopant.Some new reaction processes as well as the related reaction mechanisms,active sites and intermediates are reviewed critically.Moreover,an outlook on the in-depth investigation of the metalfree carbocatalysis in the future is provided.
基金We are grateful for financial support from National Natural Science Foundation of China(21620102007)the Fundamental Research Funds for the Central Universities of China(JD2002).
文摘Herein,we report on the effect of a high gravity field on metal-free catalytic reduction,taking the nitrobenzene(NB)reduction and methylene blue(MB)degradation as model reactions in a highgravity rotating tube reactor packed with three-dimensional(3D)nitrogen-doped graphene foam(NGF)as a metal-free catalyst.The apparent rate constant(kapp)of the metal-free catalytic reduction of NB in the rotating tube reactor under a high gravity level of 6484g(g=9.81 m s-2)was six times greater than that in a conventional stirred reactor(STR)under gravity.Computational fluid dynamics(CFD)simulations indicated that the improvement of the catalytic efficiency was attributed to the much higher turbulent kinetic energy and faster surface renewal rate in the high-gravity tube reactor in comparison w让h those in a conventional STR.The structure of the 3D metal-free catalysts was stable during the reaction process under a high gravity field,as confirmed by X-ray photoelectron spectroscopy(XPS)and Raman spectra.In the other model reaction,the rate of MB degradation also increased as the high gravity level in creased gradually,which aligns with the result for the NB catalytic reduction system.These results demonstrate the potential to use a high-gravity rotating packed tube reactor for the process intensification of metal-free catalytic reduction reactions.
基金Funded by National Natural Science Foundation of China(No.51778096)Natural Scienceof CQ CSTC(No.cstc2016jcyjA0119)
文摘Graphene-modified asphalt(GMA)for road application was prepared via using metal-free phthalocyanine-dispersed to modify an SK-70#base asphalt with graphene.The preparation parameters are as follows:the content of graphene is 0.26%based on the mass percentage of absolute ethanol,the content of nonmetal phthalocyanine is 190%based on the mass percentage of graphene,and then the GMA is prepared via unique high-speed shearing with continuing to ventilate nitrogen,which can prevent the aging of modified asphalt in the high-speed shearing process,and effectively evaluate the modifier.The penetration,softening point,force ductility,and fracture energy of GMA were significantly improved based on the base asphalt.Thus,the incorporation of graphene could enhance the base asphalt’s high-and low-temperature stability.The modification mechanism was researched via metallographic microscopy,computed tomography(CT),Fourier transform infrared spectroscopy(FTIR),and atomic force microscopy(AFM).Adsorption and physical dispersion of the asphaltenes and resins in the phthalocyanine-graphene system were confirmed.
基金Supported by Fundamental Research Funds for the Central Universities(2019PY13)National Program for Support of Top-notch Young Professionals,Science and Technology Basic Resources Investigation Program of China(2019FY100903)+5 种基金National Natural Science Foundation of China(31971614)Guangdong Natural Science Funds for Distinguished Young Scholar(2016A030306027)Guangdong Natural Science Funds(2017A030313130)Guangzhou science and technology funds(201904010078)State Key Lab of Pulp and Paper Engineering(2020C03)China Postdoctoral Science Foundation Grant(2019T120725,2019M652882).
文摘Rational design and facile preparation of low-cost and efficient catalysts for the selective converting of biomass-derived monosaccharides into high value-added chemicals is highly demanded,yet challenging.Herein,we first demonstrate a N doped defect-rich carbon(NC-800-5)as metal-free catalyst for the selective oxidation of D-xylose into D-xylonic acid in alkaline aqueous solution at 100℃ for 30 min,with 57.4%yield.The doped graphitic N is found to be the active site and hydroxyl ion participating in the oxidation of D-xylose.Hydroxyl ion and D-xylose first adsorb on NC-800-5 surface,and the aldehyde group of D-xylose is catalyzed to form germinal diols ion.Then,C–H bond break to yield carboxylic group.Furthermore,NC-800-5 catalyst shows high stability in recycled test.
基金financial support from the National Natural Science Foundation of China(No.51973240)the Fundamental Research Funds for the Central Universities(Grant No.19lgzd19 and 19lgpy117)+1 种基金China Postdoctoral Science Foundation(No.2019M653176)the Guangdong Yang Fan Innovative&Entepreneurial Research Team Program(Grant No.2016YT03C077)。
文摘Herein,we for the first time demonstrate the synthesis of exfoliated C4N nanosheets via a top-down approach and exploit their use as a new class of organic polymeric catalyst for the oxygen reduction reaction(ORR).The obtained C4N nanosheets are semi-conductive with a small band gap of 1.41 eV and contain abundant pyrazine-nitrogen moieties uniformly distributed throughout C4N.Density function theory calculations reveal that the intramolecular charge transfer induced by pyrazine-nitrogen in C4N enables effective charge redistribution to activate the conjugated structure and facilitate the oxygen adsorption,while the exfoliated sheet-like C4N formation renders improved electrochemical active surface area and results in high exposure of active sites.As a result,despite the bulk C4N is not active,the sheet-like C4N yield markedly improved ORR performance,even on a par with the commercial Pt/C catalyst.Our recent findings not only enrich the family members of two-dimensional conjugated polymer nanosheets but also open up new opportunity to explore new metal-free organic polymeric materials for efficient oxygen reduction catalysis and beyond.
基金provided by the National Natural Science Foundation of China(No.21503241,21133010,21261160487,51221264,21411130120,21473223,91545119,91545110)the“Strategic Priority Research Program” of the Chinese Academy of Sciences(CAS)(No.XDA09030103)+1 种基金CAS/State Administration for Foreign Experts Affairs(SAFEA)International Partnership Program for Creative Research Teams and the Doctoral Starting up Foundation of Liaoning Province,China(No.20121068)the financial support from Max Planck Society and China Scholarship Council
文摘A metal-free catalytic system combining oxidized carbon nanotubes (oCNTs) and ionic liquids (ILs) is presented for the oxidation of aromatic thiophene compounds with H2O2 as an oxidant. The oCNTs exhibit impressively high activity and stability in the system, which show an even better performance than those of some reported metal catalysts. The ILs are proved to have indispensable influence on the enhanced catalytic performance of the oCNTs. Detailed characterization by TG-MS and XPS demonstrates that the carbonyl groups are the active sites for the oxidation process, which is further supported by the deactivation and the model catalysts experiments. The quantitative analysis of different oxygen groups in oCNTs could be achieved by an isothermal temperature programmed TG-MS method. The concentration of carbonyl groups is 1.46 mmol per 1 g oCNTs and the tuiriover frequency of oCNTs could also be obtained (10.7 h^-1 in the presence of OmimPF6). H2O2 decomposition experiments combined with the EPR results reveal that the presence of OmimPF6 can avoid the intermediate HO· to form O2 and then improve the catalytic performance of oCNTs for the oxidation of dibenzothiophene.
基金supported by the National Natural Science Foundation of China(Grant No.11574167)
文摘Photocatalytic water splitting has gained increasing attention, since it utilizes renewable resources, such as water and solar energy, to produce hydrogen. Using the first-principles density functional theory, we investigate the properties of the single layer C_2N which was successfully synthesized. We reveal that monolayer C_2N has a substantial direct band gap of 2.45 eV. To regulate its band gap, four different nonmetal elements(B, O, P, and S) on the cation and anion sites are considered. Among them, B-doped N site is the most effective one, with the lowest formation energy and a band gap of 2.01 eV. P-doped N site is the next, with a band gap of 2.08 eV, though its formation energy is higher. The band alignments with respect to the water redox levels show that, for these two dopings, the thermodynamic criterion for the overall water splitting is satisfied. We therefore predict that B-or P-doped C_2N, with an appropriate band gap and an optimal band-edge position, would be a promising photocatalyst for visible-light water splitting.
文摘The metal-free combination of catalytic amounts of PPh3,B(C6F5)3,and PhSiH_3 can efficiently hydrosilylate aldehydes, ketones,aldimines and ketimines to afford the corresponding reduction products in good yields.
文摘Tirazine based microporous polymeric (TMP) network was found to be an efficient metal-free catalyst for the epoxidation of styrene. The reactions were performed in water as an environmentally benign medium using H2O2 as a green oxidant at ambient temperature. The reaction afforded higher yield with 90% conversion of styrene and 98% selectivity to styrene oxide in 6 h. The triazine based microporous polymeric network can be readily recovered and reused up to 4 cycles without significant loss in catalytic activity and selectivity.