Rational construction of carbon-based materials with high-efficiency bifunctionality and low cost as the substitute of precious metal catalyst shows a highly practical value for rechargeable Zn-air batteries(ZABs)yet ...Rational construction of carbon-based materials with high-efficiency bifunctionality and low cost as the substitute of precious metal catalyst shows a highly practical value for rechargeable Zn-air batteries(ZABs)yet it still remains challenging.Herein,this study employs a simple mixing-calcination strategy to fabricate a high-performance bifunctional composite catalyst composed of N-doped graphitic carbon encapsulating Co nanoparticles(Co@NrC).Benefiting from the core-shell architectural and compositional advantages of favorable electronic configuration,more exposed active sites,sufficient electric conductivity,rich defects,and excellent charge transport,the optimal Co@NrC hybrid(Co@NrC-0.3)presents outstanding catalytic activity and stability toward oxygen-related electrochemical reactions(oxygen reduction and evolution reactions,i.e.,ORR and OER),with a low potential gap of 0.766 V.Besides,the rechargeable liquid ZAB assembled with this hybrid electrocatalyst delivers a high peak power density of 168 mW cm^(−2),a small initial discharge-charge potential gap of 0.45 V at 10 mA cm^(−2),and a good rate performance.Furthermore,a relatively large power density of 108 mW cm^(−2) is also obtained with the Co@NrC-0.3-based flexible solid-state ZAB,which can well power LED lights.Such work offers insights in developing excellent bifunctional electrocatalysts for both OER and ORR and highlights their potential applications in metal-air batteries and other energy-conversion/storage devices.展开更多
The poor stability of non-noble metal catalysts in oxygen reduction reaction(ORR) is a main bottleneck that limits their big-scale application in metal-air batteries. Herein, we construct a chainmail catalyst(Co-NC-AD...The poor stability of non-noble metal catalysts in oxygen reduction reaction(ORR) is a main bottleneck that limits their big-scale application in metal-air batteries. Herein, we construct a chainmail catalyst(Co-NC-AD) with outstanding stability, via the competitive complexation and post absorption strategy,consisting of highly graphitic layers wrapped uniform-size Co nanoparticles(Co-NPs). Experiments combined with density functional theory(DFT) calculations jointly confirmed that the electron transfer occurred from the inner Co-NPs to the external graphitic layers. It facilitated the adsorption process of oxygen molecules and the hybridization of the O-2 p and C-1 p orbitals, which accelerated the ORR reaction kinetics. Consequently, our prepared Co-NC-AD shows excellent ORR activity, offered with a more positive initial potential(E_(onset)= 0.95 V) and half-wave potential(E_(1/2)= 0.86 V). The remarkable stability and resistance of methanol poisoning are merited from the protection effect of stable graphitic layers. In addition, the high electrochemical performance of Co-NC-AD-based zinc-air battery demonstrates their potential for practical applications. Therefore, our work provides new ideas for the design of nanoconfined catalysts with high stability and activity.展开更多
An efficient sustainable and scalable strategy for the synthesis of porous cobalt/nitrogen co-doped carbons(Co@NCs) via pyrolysis of aniline-modified ZIFs,has been demonstrated.Aniline can coordinate and absorb on the...An efficient sustainable and scalable strategy for the synthesis of porous cobalt/nitrogen co-doped carbons(Co@NCs) via pyrolysis of aniline-modified ZIFs,has been demonstrated.Aniline can coordinate and absorb on the surface of ZIF(ZIF-CoZn3-PhA),accelerate the precipitation of ZIFs,thus resulting in smaller ZIF particle size.Meanwhile,the aniline on the surface of ZIF-CoZn3-PhA promotes the formation of the protective carbon shell and smaller Co nanoparticles,and increases nitrogen content of the catalyst.Because of these prope rties of Co@NC-PhA-3,the oxidative esterification of 5-hydroxymethylfurfural can be carried out under ambient conditions.According to our experimental and computational results,a synergistic catalytic effect between CoNx sites and Co nanoparticles has been established,in which both Co nanoparticles and CoNx can activate O2 while Co nanoparticles bind and oxidize HMF.Moreover,the formation and release of active oxygen species in CoNx sites are reinfo rced by the electronic interaction between Co nanoparticles and CoNx.展开更多
Electrocatalytic production of hydrogen peroxide(H_(2)O_(2))by two-electron oxygen reduction reaction(2e^(-)ORR)under acidic condition has been considered to have great application value.Co nanoparticles(CoNPs)coupled...Electrocatalytic production of hydrogen peroxide(H_(2)O_(2))by two-electron oxygen reduction reaction(2e^(-)ORR)under acidic condition has been considered to have great application value.Co nanoparticles(CoNPs)coupled with N-doped carbon are a class of potential electrocatalysts.The effective strategies to further enhance their performances are to improve the active sites and stability.Herein,the material containing ultrafine CoNPs confined in a nitrogen-doped carbon matrix(NC@CoNPs)was synthesized by pyrolyzing corresponding precursors,which was obtained through regulating the topological structure of ZIF-67/ZIF-8 with dopamine(DA).The DA self-polymerization process induced the formation of CoNPs with smaller sizes and formed polydopamine film decreased the detachment of CoNPs from the catalyst.High density of Co-N_(x) active sites and defective sites could be identified on NC@CoNPs,leading to high activity and H_(2)O_(2) selectivity,with an onset potential of 0.57 V(vs.RHE)and∼90%selectivity in a wide potential range.An on-site electrochemical removal of organic pollutant was achieved rapidly through an electro-Fenton process,demonstrating its great promise for on-site water treatment application.展开更多
Lithium-sulfur(Li-S)batteries have been considered as the next generation high energy storage devices.However,its commercialization has been hindered by several issues,especially the dissolution and shuttle of the sol...Lithium-sulfur(Li-S)batteries have been considered as the next generation high energy storage devices.However,its commercialization has been hindered by several issues,especially the dissolution and shuttle of the soluble lithium polysulfides(LiPSs)as well as the slow reaction kinetics of LiPSs which may make shuttling effect even worse.Herein,we report a strategy to address this issue by in-situ transformation of Co−N_(x) coordinations in cobalt polyphthalocyanine(CoPPc)into Co nanoparticles(Co NPs)embedded in carbon matrix and mono-dispersed on graphene flakes.The Co NPs can provide rich binding and catalytic sites,while graphene flakes act as ideally LiPSs transportation and electron conducting platform.With a remarkable enhanced reaction kinetics of LiPSs via these merits,the sulfur host with a sulfur content up to 70 wt%shows a high initial capacity of 1048 mA∙h/g at 0.2C,good rate capability up to 399 mA·h/g at 2C.展开更多
Developing a highly active and durable non-noble metal catalyst for aqueous-phase levulinic acid(LA)hydrogenation to g-valerolactone(GVL)is an appealing yet challenging task.Herein,we report well-dispersed Co nanopart...Developing a highly active and durable non-noble metal catalyst for aqueous-phase levulinic acid(LA)hydrogenation to g-valerolactone(GVL)is an appealing yet challenging task.Herein,we report well-dispersed Co nanoparticles(NPs)embedded in nitrogen-doped mesoporous carbon nanofibers as an efficient catalyst for aqueous-phase LA hydrogenation to GVL.The Co zeolitic imidazolate framework(ZIF-67)nanocrystals were anchored on the sodium dodecyl sulfate modified wipe fiber(WF-S),yielding one-dimensional(1-D)structured composite(ZIF-67/WF-S).Subsequently,Co NPs were uniformly embedded in nitrogen-doped mesoporous carbon nanofibers(Co^(R)NC/SMCNF)through a pyrolysis-reduction strategy using ZIF-67/WF-S as the precursor.Benefiting from introducing modified wipe fiber WF-S to enhance the dispersion of Co NPs,and Co^(0) with Co-N_xdual active sites,the resulting Co^(R)NC/SMCNF catalyst shows brilliant catalytic activity(206 h^(-1) turnover frequency).Additionally,the strong metal-support interactions greatly inhibited the Co NPs from aggregation and leaching from the mesoporous carbon nanofibers,and thus increasing the reusability of the Co^(R)NC/SMCNF catalyst(reusable nine times without notable activity loss).展开更多
The development of simple and effective strategies to prepare electrocatalysts,which possess unique and stable structures comprised of metal/nonmetallic atoms for oxygen reduction reaction(ORR)and oxygen evolution rea...The development of simple and effective strategies to prepare electrocatalysts,which possess unique and stable structures comprised of metal/nonmetallic atoms for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),is currently an urgent issue.Herein,an efficient bifunctional electrocatalyst featured by ultralong N,S-doped carbon nano-hollow-sphere chains about 1300 nm with encapsulated Co nanoparticles(Co-CNHSCs)is developed.The multifunctional catalytic properties of Co together with the heteroatom-induced charge redistribution(i.e.,modulating the electronic structure of the active site)result in superior catalytic activities toward OER and ORR in alkaline media.The optimized catalyst Co-CNHSC-3 displays an outstanding electrocatalytic ability for ORR and OER,a high specific capacity of 1023.6 mAh gZn^(-1),and excellent reversibility after 80 h at 10mA cm^(-2)in a Zn-air battery system.This work presents a new strategy for the design and synthesis of efficient multifunctional carbon-based catalysts for energy storage and conversion devices.展开更多
The cyclopentanone and derivatives are a class of crucial fine chemicals for various industries and currently produced by conventional petrochemical synthetic routes.Here,we demonstrated a new synthetic approach to di...The cyclopentanone and derivatives are a class of crucial fine chemicals for various industries and currently produced by conventional petrochemical synthetic routes.Here,we demonstrated a new synthetic approach to directly fabricate N-doped carbon nanotube(N-CNTs)networks with confined Co nanoparticles from Co^(2+)-impregnated bulk g-C_(3)N_(4) as high performance hydrogenation rearrangement(HR)catalyst to efficiently convert a wide spectrum of biomass-derived furanic aldehydes to the corresponding cyclopentanones in water under a record-low H2 pressure of 0.5 MPa and mild temperature.We unveiled a Co-catalysed bulk g-C_(3)N_(4) decomposition/carbonisation CNTs formation mechanism.A new HR pathway was also unveiled.展开更多
Although SiO_(2)-based anode is a strong competitor to supersede graphite anode for lithium-ion batteries,it still has problems such as low electrochemical activity, enormous loss of active lithium, and serious volume...Although SiO_(2)-based anode is a strong competitor to supersede graphite anode for lithium-ion batteries,it still has problems such as low electrochemical activity, enormous loss of active lithium, and serious volume expansion. In order to solve these problems, we used a graphene network loaded with cobalt metal nanoparticles(rGO-Co) to coat SiO_(2) porous hollow spheres(SiO_(2)@rGO-Co). The construction of porous hollow structure and graphene network can shorten the lithium-ion(Li^(+)) diffusion distance and enhance the conductivity of the composite, which improves the electrochemical activity of SiO_(2) effectively. They also alleviate the volume expansion of the anode in the cycling process. Moreover,nano-scale cobalt metal particles dispersed on graphene catalyze the conversion reaction of SiO_(2) and activate the locked Li+in Li_(2)O through a reversible reaction, which improves the charge and discharge capacity of the anode. The capacity of SiO_(2)@rGO-Co reaches 370.4 m Ah/g after 100 cycles at 0.1 A/g,which is 6.19 times the capacity of pure SiO_(2)(59.8 mAh/g) under the same circumstance. What is more,its structure also exhibits excellent cycle stability, with a volume expansion rate of only 13.0% after 100 cycles at a current density of 0.1 A/g.展开更多
A new catalyst of Co/La_(4)Ga_(2)O_(9) for CO_(2) hydrogenation to produce ethanol was prepared by reducing LaCo^(0).5 Ga0.5 O3,which showed excellent selectivity to ethanol(%35 C-mol%)at mild reaction conditions(270&...A new catalyst of Co/La_(4)Ga_(2)O_(9) for CO_(2) hydrogenation to produce ethanol was prepared by reducing LaCo^(0).5 Ga0.5 O3,which showed excellent selectivity to ethanol(%35 C-mol%)at mild reaction conditions(270°C,3.5 MPa,3000 m L g-1 h-1).The catalysts were characterized by N_(2) adsorption/desorption,XRD,XAFS,CO and CO_(2)-TPD,H2 chemisorption,XPS and TEM techniques.The interaction between Co nanoparticles(NPs)and La2+4 Ga_(2)O_(9) oxide resulted in Co^(0)-Coon the surface of Co NPs.It was proposed that La_(4)Ga_(2)O_(9) could catalyze reverse water gas shift reaction(r-WGS),which converted CO_(2) to CO.Then,the CO migrated to Co^(0)-Co^(2+)on Co NPs,where it was hydrogenated to form ethanol like higher alcohols synthesis from syngas.The results suggest that by controlling the oxidation state of cobalt,and combined with a kind of active site for activating CO_(2) to form CO,a catalyst with excellent selectivity to ethanol could be obtained for CO_(2) hydrogenation,which means that the complex reaction may be proceed with high selectivity using only one active metal component.展开更多
Rechargeable room temperature sodium–sulfur(RT Na–S)batteries are seriously limited by low sulfur utilization and sluggish electrochemical reaction activity of polysulfide intermediates.Herein,a 3D“branch-leaf”bio...Rechargeable room temperature sodium–sulfur(RT Na–S)batteries are seriously limited by low sulfur utilization and sluggish electrochemical reaction activity of polysulfide intermediates.Herein,a 3D“branch-leaf”biomimetic design proposed for high performance Na–S batteries,where the leaves constructed from Co nanoparticles on carbon nanofibers(CNF)are fully to expose the active sites of Co.The CNF network acts as conductive“branches”to ensure adequate electron and electrolyte supply for the Co leaves.As an effective electrocatalytic battery system,the 3D“branch-leaf”conductive network with abundant active sites and voids can effectively trap polysulfides and provide plentiful electron/ions pathways for electrochemical reaction.DFT calculation reveals that the Co nanoparticles can induce the formation of a unique Co–S–Na molecular layer on the Co surface,which can enable a fast reduction reaction of the polysulfides.Therefore,the prepared“branch-leaf”CNF-L@Co/S electrode exhibits a high initial specific capacity of 1201 mAh g^−1 at 0.1 C and superior rate performance.展开更多
Developing high-performance and low-cost electrocatalysts is key to achieve the clean-energy target.Herein,a dual regulation method is proposed to prepare a 3D honeycomb-like carbon-based catalyst with stable Fe/Co co...Developing high-performance and low-cost electrocatalysts is key to achieve the clean-energy target.Herein,a dual regulation method is proposed to prepare a 3D honeycomb-like carbon-based catalyst with stable Fe/Co co-dopants.Fe atoms are highly dispersed and fixed to the polymer microsphere,followed by a high-temperature decomposition,for the generation of carbon-based catalyst with a honeycomb-like structure.The as-prepared catalyst contains a large number of Fe/Co nanoparticles(Fe/Co NPs),providing the excellent catalytic activity and durability in oxygen reduction reaction,oxygen evolution reaction and hydrogen evolution reaction.The Zn-air battery assembled by the as-prepared catalyst as air cathode shows a good charge and discharge capacity,and it exhibits an ultra-long service life by maintaining a stable charge and discharge platform for a 311-h cycle.Further X-ray absorption fine structure characterization and density functional theory calculation confirms that the Fe doping optimizes the intermediate adsorption process and electron transfer of Co.展开更多
The design of efficient cathode with great cycle performance,high flexibility,and low cost is essential for the commercialization of zinc–air battery(ZAB).Herein,we report the exploration of freestanding bifunctional...The design of efficient cathode with great cycle performance,high flexibility,and low cost is essential for the commercialization of zinc–air battery(ZAB).Herein,we report the exploration of freestanding bifunctional cathode with rationally designed structures,namely,tiny Co nanoparticles embedded in Ndoped carbon nanofiber aerogels,which have desired features including uniform Co dispersity,balanced distribution of N-C species,hierarchically porous structure with increased fraction of meso-to micropores,and moderate amounts of defects.Accordingly,the as-fabricated cathodes exhibit positive half-wave potential of 0.82 V for oxygen reduction and small overpotential of 350 mV at 10 mA cm^(−2) for oxygen evolution,respectively,which deliver smaller reversible oxygen electrode index(0.76 V)than the commercial Pt/C+RuO_(2)(0.80 V)and most Co-based electrocatalysts ever reported.Impressively,the as-constructed liquid rechargeable ZAB behaves high peak power density(160 mW cm^(−2)),large specific capacity(759.7 mAh g^(−1) at 10 mA cm^(−2),tested after 120 h of OCV tests),and robust stability over 277 h.Moreover,the as-assembled quasi-solid-state ZAB using such freestanding cathode represents excellent mechanical flexibility and outstanding cycle performance,regardless of being serviced under extremely bending conditions from 0°to 180°,underscoring their promising applications as durable bifunctional cathode for portable metalair batteries.展开更多
Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to ...Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to prepare Co composites via metallurgical pyrolysis under controllable conditions.The obtained nitrogen-doped porous carbon-Co nanocomposite possesses core–shell structure(Co@C–N).Co@C–N exhibits the best Li storage performances as anode active matter.After the 200th cycles at current density of 0.2 A g^(-1),a reversible capacity of 870 mAh g^(-1)is retained.A reversible capacity of 275 mAh g^(-1)still maintains with 5 A g^(-1).Co@C–N presents a high reversible capacity with excellent cycle stability.Considering the corresponding experimental and theoretical results,the Co0-based N-doped porous carbon composite is proposed to work as LIBs anode matter.These results provide a new design idea for electrode matters of metallic ion battery,and demonstrate that MOFs pyrolysis is an effective method for the construction of elemental state anode materials.展开更多
Unsatisfactory conductivity and volume effects have hindered the commercial application of siliconbased materials as advanced anode materials for high-performance lithium-ion batteries. Herein, nitrogen doped carbon s...Unsatisfactory conductivity and volume effects have hindered the commercial application of siliconbased materials as advanced anode materials for high-performance lithium-ion batteries. Herein, nitrogen doped carbon silicon matrix composite with atomically dispersed Co sites(Si/Co-N-C) is obtained via the design of the frame structure loaded with nano-components and the multi-element hybrid strategy. Co atoms are uniformly fixed to the N-C frame and tightly packed with nanoscale silicon particles as an activation and protection building block. The mechanism of the N-C framework of loaded metal Co in the Si alloying process is revealed by electrochemical kinetic analysis and ex situ characterization tests.Impressively, the nitrogen-doped Co site activates the intercalation of the outer carbon matrix to supplement the additional capacity. The Co nanoparticles with high conductivity and support enhance the conductivity and structural stability of the composite, accelerating the Li^(+)/Na^(+) diffusion kinetics. Density functional theory(DFT) calculation confirms that the hetero-structure Si/Co-N-C adjusts the electronic structure to obtain good lithium-ion adsorption energy, reduces the Li^(+)/Na^(+) migration energy barrier.This work provides meaningful guidance for the development of high-performance metal/non-metal modified anode materials.展开更多
Searching low cost and non-precious metal catalysts for high-performance oxygen reduction reaction is highly desired. Herein, Co nanoparticles embedded in nitrogen-doped carbon(Co/N—C) nanotubes with internal void sp...Searching low cost and non-precious metal catalysts for high-performance oxygen reduction reaction is highly desired. Herein, Co nanoparticles embedded in nitrogen-doped carbon(Co/N—C) nanotubes with internal void space are successfully synthesized by space-confined pyrolysis, which effectively improve the cobalt loading content and restrict the encapsulated particles down to nanometer. Different from the typical conformal carbon encapsulation, the resulting Co/N—C nanotubes possess more cobalt nanoparticles embedded in the nanotubes, which can provide more coupling sites and active sites in the oxygen reduction reaction(ORR). Moreover, the one-dimensional and porous structure provides a high surface area and a fast electron transfer pathway for the ORR. And the Co/N—C electrode presents excellent electrocatalytic ORR activity in terms of low onset potential(30 mV lower than that of Pt/C), small Tafel slop(45.5 mV dec^(-1)) and good durability(88.5% retention after 10,000 s).展开更多
An efficient photocatalytic CO_(2) reduction has been reported in ZIF-67-derived-Co nanoparticles(NPs)encapsulated in nitrogen-doped carbon layers(N-C/Co).This work demonstrates that the pyrolysis temperature is cruci...An efficient photocatalytic CO_(2) reduction has been reported in ZIF-67-derived-Co nanoparticles(NPs)encapsulated in nitrogen-doped carbon layers(N-C/Co).This work demonstrates that the pyrolysis temperature is crucial in tuning the grain size and components of metallic Co^(0) of N-C/Co composite catalysts,which optimizes their photocatalytic activities.Syntheses were conducted at 600,700,and 800℃ giving the N-C/Co-600,N-C/Co-700,and N-C/Co-800 samples,respectively.N-C layers can well wrap the Co NPs obtained at a low pyrolysis temperature(600℃)owing to their smaller grains than those of other samples.A high metallic Co^(0) content in the N-C/Co-600 sample can be attributed to the effective inhibition of surface oxidation.By contrast,the surface CoOx oxides in the N-C/Co-700 and N-C/Co-800 samples cover inside Co cores,inhibiting charge separation and transfer.As a result,the N-C/Co-600 sample yields the best photocatalytic activity.The carbon monoxide and hydrogen generation rates are as high as 1.62×10^(4) and 2.01×10^(4)μmol g^(−1)h^(−1),respectively.Additionally,the Co NPs make composite catalysts magnetic,enabling rapid and facile recovery of catalysts with the assistance of an external magnetic field.This work is expected to provide an instructive guideline for designing metal-organic framework-derived carbon/metal composite catalysts.展开更多
In this study,we synthesize a catalyst comprising cobalt nanoparticles supported on MXene by pyrolyzing a composite in a N2 environment.Specifically,the composite comprises a bimetallic Zn/Co zeolitic imidazole framew...In this study,we synthesize a catalyst comprising cobalt nanoparticles supported on MXene by pyrolyzing a composite in a N2 environment.Specifically,the composite comprises a bimetallic Zn/Co zeolitic imidazole framework grown in situ on the outer surface of MXene.The catalytic efficiency of the catalyst is tested for the self-coupling of 4-methoxybenzylamine to produce value-added imine,where atmospheric oxygen(1 atm)is used as the oxidant.Based on the results,the catalyst displayed impressive catalytic activity,achieving 95.4%yield of the desired imine at 383 K for 8 h.Furthermore,the catalyst showed recyclability and tolerance toward benzylamine substrates with various functional groups.The outstanding performance of the catalyst is primarily attributed to the synergetic catalytic effect between the cobalt nanoparticles and MXene support,while also benefiting from the three-dimensional porous structure.Additionally,a preliminary investigation of potential reaction mechanisms is conducted.展开更多
Owing to the complexity of electron transfer pathways,the sluggish oxygen evolution reaction process is defined as the bottleneck for the practical application of Zn-air batteries.In this effort,metal nanoparticles(Co...Owing to the complexity of electron transfer pathways,the sluggish oxygen evolution reaction process is defined as the bottleneck for the practical application of Zn-air batteries.In this effort,metal nanoparticles(Co,Ni,Fe,etc.)encapsulated within nitrogen-doped carbon materials with abundant edge sites were synthesized by one-step pyrolysis treatment using cigarette butts as raw materials,which can drastically accelerate the overall rate of oxygen evolution reaction by facilitating the adsorption of oxygenated intermediates by the edge-induced topological defects.The prepared catalyst of nitrogen-doped carbon porous nanosheets loaded with Co nanoparticles(Co@NC-500)exhibits enhanced catalytic activity toward oxygen evolution reaction,with a low overpotential of 350 mV at the current density of 10 mA·cm^(-2).Furthermore,the Zn-air battery assembled with Co@NC-500 catalyst demonstrates a desirable performance affording an open-circuit potential of 1.336 V and power density of 33.6 mW·cm^(-2),indicating considerable practical application potential.展开更多
基金the Theme-based Scheme(project number:T23-601/17-R)from Research Grant Council,University Grants Committee,Hong Kong SAR,China.
文摘Rational construction of carbon-based materials with high-efficiency bifunctionality and low cost as the substitute of precious metal catalyst shows a highly practical value for rechargeable Zn-air batteries(ZABs)yet it still remains challenging.Herein,this study employs a simple mixing-calcination strategy to fabricate a high-performance bifunctional composite catalyst composed of N-doped graphitic carbon encapsulating Co nanoparticles(Co@NrC).Benefiting from the core-shell architectural and compositional advantages of favorable electronic configuration,more exposed active sites,sufficient electric conductivity,rich defects,and excellent charge transport,the optimal Co@NrC hybrid(Co@NrC-0.3)presents outstanding catalytic activity and stability toward oxygen-related electrochemical reactions(oxygen reduction and evolution reactions,i.e.,ORR and OER),with a low potential gap of 0.766 V.Besides,the rechargeable liquid ZAB assembled with this hybrid electrocatalyst delivers a high peak power density of 168 mW cm^(−2),a small initial discharge-charge potential gap of 0.45 V at 10 mA cm^(−2),and a good rate performance.Furthermore,a relatively large power density of 108 mW cm^(−2) is also obtained with the Co@NrC-0.3-based flexible solid-state ZAB,which can well power LED lights.Such work offers insights in developing excellent bifunctional electrocatalysts for both OER and ORR and highlights their potential applications in metal-air batteries and other energy-conversion/storage devices.
基金supported by the National Natural Science Foundation of China(51872115,51932003)the 2020 International Cooperation Project of the Department of Science and Technology of Jilin Province(20200801001GH)+1 种基金the Project supported by State Key Laboratory of Luminescence and Applications(KLA-2020-05)the Project for Self-innovation Capability Construction of Jilin Province Development and Reform Commission(2021C026)。
文摘The poor stability of non-noble metal catalysts in oxygen reduction reaction(ORR) is a main bottleneck that limits their big-scale application in metal-air batteries. Herein, we construct a chainmail catalyst(Co-NC-AD) with outstanding stability, via the competitive complexation and post absorption strategy,consisting of highly graphitic layers wrapped uniform-size Co nanoparticles(Co-NPs). Experiments combined with density functional theory(DFT) calculations jointly confirmed that the electron transfer occurred from the inner Co-NPs to the external graphitic layers. It facilitated the adsorption process of oxygen molecules and the hybridization of the O-2 p and C-1 p orbitals, which accelerated the ORR reaction kinetics. Consequently, our prepared Co-NC-AD shows excellent ORR activity, offered with a more positive initial potential(E_(onset)= 0.95 V) and half-wave potential(E_(1/2)= 0.86 V). The remarkable stability and resistance of methanol poisoning are merited from the protection effect of stable graphitic layers. In addition, the high electrochemical performance of Co-NC-AD-based zinc-air battery demonstrates their potential for practical applications. Therefore, our work provides new ideas for the design of nanoconfined catalysts with high stability and activity.
基金the Fundamental Research Funds for the Central Universities (No.30920021120)Key Laboratory of Biomass Energy and Material,Jiangsu Province (No. JSBEM201912) for financial supporta project funded by the Priority Academic Program development of Jiangsu Higher Education Institution。
文摘An efficient sustainable and scalable strategy for the synthesis of porous cobalt/nitrogen co-doped carbons(Co@NCs) via pyrolysis of aniline-modified ZIFs,has been demonstrated.Aniline can coordinate and absorb on the surface of ZIF(ZIF-CoZn3-PhA),accelerate the precipitation of ZIFs,thus resulting in smaller ZIF particle size.Meanwhile,the aniline on the surface of ZIF-CoZn3-PhA promotes the formation of the protective carbon shell and smaller Co nanoparticles,and increases nitrogen content of the catalyst.Because of these prope rties of Co@NC-PhA-3,the oxidative esterification of 5-hydroxymethylfurfural can be carried out under ambient conditions.According to our experimental and computational results,a synergistic catalytic effect between CoNx sites and Co nanoparticles has been established,in which both Co nanoparticles and CoNx can activate O2 while Co nanoparticles bind and oxidize HMF.Moreover,the formation and release of active oxygen species in CoNx sites are reinfo rced by the electronic interaction between Co nanoparticles and CoNx.
基金financial support from the Natural Science Foundation of China(Nos.21805052 and 2278092)Science and Technology Research Project of Guangzhou(Nos.202102020787 and 202201000002)+1 种基金Department of Science&Technology of Guangdong Province(ID:2022A156),Key Discipline of Materials Science and Engineering,Bureau of Education of Guangzhou(No.20225546)the Innovation&Entrepreneurship for the College Students of Guangzhou University(No.XJ202111078175).
文摘Electrocatalytic production of hydrogen peroxide(H_(2)O_(2))by two-electron oxygen reduction reaction(2e^(-)ORR)under acidic condition has been considered to have great application value.Co nanoparticles(CoNPs)coupled with N-doped carbon are a class of potential electrocatalysts.The effective strategies to further enhance their performances are to improve the active sites and stability.Herein,the material containing ultrafine CoNPs confined in a nitrogen-doped carbon matrix(NC@CoNPs)was synthesized by pyrolyzing corresponding precursors,which was obtained through regulating the topological structure of ZIF-67/ZIF-8 with dopamine(DA).The DA self-polymerization process induced the formation of CoNPs with smaller sizes and formed polydopamine film decreased the detachment of CoNPs from the catalyst.High density of Co-N_(x) active sites and defective sites could be identified on NC@CoNPs,leading to high activity and H_(2)O_(2) selectivity,with an onset potential of 0.57 V(vs.RHE)and∼90%selectivity in a wide potential range.An on-site electrochemical removal of organic pollutant was achieved rapidly through an electro-Fenton process,demonstrating its great promise for on-site water treatment application.
基金Project(21905220) supported by the National Natural Science Foundation of ChinaProject(BK20201190) supported by the Jiangsu Provincial Department of Science and Technology,China+2 种基金Projects(2018ZDXM-GY-135,2021JLM-36) supported by the Key Research and Development Plan of Shaanxi Province,ChinaProject(HG6J003) supported by the Fundamental Research Funds for “Young Talent Support Plan” of Xi’ an Jiaotong University,ChinaProject supported by the “1000-Plan program” of Shaanxi Province,China。
文摘Lithium-sulfur(Li-S)batteries have been considered as the next generation high energy storage devices.However,its commercialization has been hindered by several issues,especially the dissolution and shuttle of the soluble lithium polysulfides(LiPSs)as well as the slow reaction kinetics of LiPSs which may make shuttling effect even worse.Herein,we report a strategy to address this issue by in-situ transformation of Co−N_(x) coordinations in cobalt polyphthalocyanine(CoPPc)into Co nanoparticles(Co NPs)embedded in carbon matrix and mono-dispersed on graphene flakes.The Co NPs can provide rich binding and catalytic sites,while graphene flakes act as ideally LiPSs transportation and electron conducting platform.With a remarkable enhanced reaction kinetics of LiPSs via these merits,the sulfur host with a sulfur content up to 70 wt%shows a high initial capacity of 1048 mA∙h/g at 0.2C,good rate capability up to 399 mA·h/g at 2C.
基金financially supported by the National Key Research and Development Program of China(2018YFB1105100)the National Natural Science Foundation of China(51974339 and 51674270)the funding from Science Foundation of China University of Petroleum,Beijing(24620188JC005)。
文摘Developing a highly active and durable non-noble metal catalyst for aqueous-phase levulinic acid(LA)hydrogenation to g-valerolactone(GVL)is an appealing yet challenging task.Herein,we report well-dispersed Co nanoparticles(NPs)embedded in nitrogen-doped mesoporous carbon nanofibers as an efficient catalyst for aqueous-phase LA hydrogenation to GVL.The Co zeolitic imidazolate framework(ZIF-67)nanocrystals were anchored on the sodium dodecyl sulfate modified wipe fiber(WF-S),yielding one-dimensional(1-D)structured composite(ZIF-67/WF-S).Subsequently,Co NPs were uniformly embedded in nitrogen-doped mesoporous carbon nanofibers(Co^(R)NC/SMCNF)through a pyrolysis-reduction strategy using ZIF-67/WF-S as the precursor.Benefiting from introducing modified wipe fiber WF-S to enhance the dispersion of Co NPs,and Co^(0) with Co-N_xdual active sites,the resulting Co^(R)NC/SMCNF catalyst shows brilliant catalytic activity(206 h^(-1) turnover frequency).Additionally,the strong metal-support interactions greatly inhibited the Co NPs from aggregation and leaching from the mesoporous carbon nanofibers,and thus increasing the reusability of the Co^(R)NC/SMCNF catalyst(reusable nine times without notable activity loss).
基金Collaborative Innovation Center of Suzhou Nano Science and TechnologyNational Natural Science Foundation of China,Grant/Award Numbers:21773163,22271203+3 种基金EPSRC for an Overseas Travel Grant,Grant/Award Number:EP/R023816/1State Key Laboratory of Organometallic Chemistry of Shanghai Institute of Organic Chemistry,Grant/Award Number:KF2021005Priority Academic Program Development of Jiangsu Higher Education InstitutionsProject of Scientific and Technologic Infrastructure of Suzhou,Grant/Award Number:SZS201905。
文摘The development of simple and effective strategies to prepare electrocatalysts,which possess unique and stable structures comprised of metal/nonmetallic atoms for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),is currently an urgent issue.Herein,an efficient bifunctional electrocatalyst featured by ultralong N,S-doped carbon nano-hollow-sphere chains about 1300 nm with encapsulated Co nanoparticles(Co-CNHSCs)is developed.The multifunctional catalytic properties of Co together with the heteroatom-induced charge redistribution(i.e.,modulating the electronic structure of the active site)result in superior catalytic activities toward OER and ORR in alkaline media.The optimized catalyst Co-CNHSC-3 displays an outstanding electrocatalytic ability for ORR and OER,a high specific capacity of 1023.6 mAh gZn^(-1),and excellent reversibility after 80 h at 10mA cm^(-2)in a Zn-air battery system.This work presents a new strategy for the design and synthesis of efficient multifunctional carbon-based catalysts for energy storage and conversion devices.
基金supported by the National Natural Science Foundation of China(Nos.51871209 and 51902311)the Postdoctoral Science Foundation of China(No.2019M652223).
文摘The cyclopentanone and derivatives are a class of crucial fine chemicals for various industries and currently produced by conventional petrochemical synthetic routes.Here,we demonstrated a new synthetic approach to directly fabricate N-doped carbon nanotube(N-CNTs)networks with confined Co nanoparticles from Co^(2+)-impregnated bulk g-C_(3)N_(4) as high performance hydrogenation rearrangement(HR)catalyst to efficiently convert a wide spectrum of biomass-derived furanic aldehydes to the corresponding cyclopentanones in water under a record-low H2 pressure of 0.5 MPa and mild temperature.We unveiled a Co-catalysed bulk g-C_(3)N_(4) decomposition/carbonisation CNTs formation mechanism.A new HR pathway was also unveiled.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.52073212,51772205,51772208)the General Program of Municipal Natural Science Foundation of Tianjin(Nos.17JCYBJC17000,17JCYBJC22700)。
文摘Although SiO_(2)-based anode is a strong competitor to supersede graphite anode for lithium-ion batteries,it still has problems such as low electrochemical activity, enormous loss of active lithium, and serious volume expansion. In order to solve these problems, we used a graphene network loaded with cobalt metal nanoparticles(rGO-Co) to coat SiO_(2) porous hollow spheres(SiO_(2)@rGO-Co). The construction of porous hollow structure and graphene network can shorten the lithium-ion(Li^(+)) diffusion distance and enhance the conductivity of the composite, which improves the electrochemical activity of SiO_(2) effectively. They also alleviate the volume expansion of the anode in the cycling process. Moreover,nano-scale cobalt metal particles dispersed on graphene catalyze the conversion reaction of SiO_(2) and activate the locked Li+in Li_(2)O through a reversible reaction, which improves the charge and discharge capacity of the anode. The capacity of SiO_(2)@rGO-Co reaches 370.4 m Ah/g after 100 cycles at 0.1 A/g,which is 6.19 times the capacity of pure SiO_(2)(59.8 mAh/g) under the same circumstance. What is more,its structure also exhibits excellent cycle stability, with a volume expansion rate of only 13.0% after 100 cycles at a current density of 0.1 A/g.
基金the National Natural Science Foundation of China(Nos.21872101,21962014)Tianjin science and technology commission(No.18JCZDJC31300)Beijing Synchrotron Radiation Facility(BSRF)。
文摘A new catalyst of Co/La_(4)Ga_(2)O_(9) for CO_(2) hydrogenation to produce ethanol was prepared by reducing LaCo^(0).5 Ga0.5 O3,which showed excellent selectivity to ethanol(%35 C-mol%)at mild reaction conditions(270°C,3.5 MPa,3000 m L g-1 h-1).The catalysts were characterized by N_(2) adsorption/desorption,XRD,XAFS,CO and CO_(2)-TPD,H2 chemisorption,XPS and TEM techniques.The interaction between Co nanoparticles(NPs)and La2+4 Ga_(2)O_(9) oxide resulted in Co^(0)-Coon the surface of Co NPs.It was proposed that La_(4)Ga_(2)O_(9) could catalyze reverse water gas shift reaction(r-WGS),which converted CO_(2) to CO.Then,the CO migrated to Co^(0)-Co^(2+)on Co NPs,where it was hydrogenated to form ethanol like higher alcohols synthesis from syngas.The results suggest that by controlling the oxidation state of cobalt,and combined with a kind of active site for activating CO_(2) to form CO,a catalyst with excellent selectivity to ethanol could be obtained for CO_(2) hydrogenation,which means that the complex reaction may be proceed with high selectivity using only one active metal component.
基金This work is financially supported by Grants from the National Natural Science Foundation of China(No.21773188,21972111,U1530401)Natural Science Foundation of Chongqing(cstc2018jcyjAX0714).
文摘Rechargeable room temperature sodium–sulfur(RT Na–S)batteries are seriously limited by low sulfur utilization and sluggish electrochemical reaction activity of polysulfide intermediates.Herein,a 3D“branch-leaf”biomimetic design proposed for high performance Na–S batteries,where the leaves constructed from Co nanoparticles on carbon nanofibers(CNF)are fully to expose the active sites of Co.The CNF network acts as conductive“branches”to ensure adequate electron and electrolyte supply for the Co leaves.As an effective electrocatalytic battery system,the 3D“branch-leaf”conductive network with abundant active sites and voids can effectively trap polysulfides and provide plentiful electron/ions pathways for electrochemical reaction.DFT calculation reveals that the Co nanoparticles can induce the formation of a unique Co–S–Na molecular layer on the Co surface,which can enable a fast reduction reaction of the polysulfides.Therefore,the prepared“branch-leaf”CNF-L@Co/S electrode exhibits a high initial specific capacity of 1201 mAh g^−1 at 0.1 C and superior rate performance.
基金supported by the National Natural Science Foundation of China(No.51973009)supported by open foundation of Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured Materials,Guangxi University(No.2022GXYSOF21).
文摘Developing high-performance and low-cost electrocatalysts is key to achieve the clean-energy target.Herein,a dual regulation method is proposed to prepare a 3D honeycomb-like carbon-based catalyst with stable Fe/Co co-dopants.Fe atoms are highly dispersed and fixed to the polymer microsphere,followed by a high-temperature decomposition,for the generation of carbon-based catalyst with a honeycomb-like structure.The as-prepared catalyst contains a large number of Fe/Co nanoparticles(Fe/Co NPs),providing the excellent catalytic activity and durability in oxygen reduction reaction,oxygen evolution reaction and hydrogen evolution reaction.The Zn-air battery assembled by the as-prepared catalyst as air cathode shows a good charge and discharge capacity,and it exhibits an ultra-long service life by maintaining a stable charge and discharge platform for a 311-h cycle.Further X-ray absorption fine structure characterization and density functional theory calculation confirms that the Fe doping optimizes the intermediate adsorption process and electron transfer of Co.
基金supported by National Natural Science Foundation of China(Grant No.51972178)Zhejiang Provincial Nature Science Foundation(Grant No.LY20E020009).
文摘The design of efficient cathode with great cycle performance,high flexibility,and low cost is essential for the commercialization of zinc–air battery(ZAB).Herein,we report the exploration of freestanding bifunctional cathode with rationally designed structures,namely,tiny Co nanoparticles embedded in Ndoped carbon nanofiber aerogels,which have desired features including uniform Co dispersity,balanced distribution of N-C species,hierarchically porous structure with increased fraction of meso-to micropores,and moderate amounts of defects.Accordingly,the as-fabricated cathodes exhibit positive half-wave potential of 0.82 V for oxygen reduction and small overpotential of 350 mV at 10 mA cm^(−2) for oxygen evolution,respectively,which deliver smaller reversible oxygen electrode index(0.76 V)than the commercial Pt/C+RuO_(2)(0.80 V)and most Co-based electrocatalysts ever reported.Impressively,the as-constructed liquid rechargeable ZAB behaves high peak power density(160 mW cm^(−2)),large specific capacity(759.7 mAh g^(−1) at 10 mA cm^(−2),tested after 120 h of OCV tests),and robust stability over 277 h.Moreover,the as-assembled quasi-solid-state ZAB using such freestanding cathode represents excellent mechanical flexibility and outstanding cycle performance,regardless of being serviced under extremely bending conditions from 0°to 180°,underscoring their promising applications as durable bifunctional cathode for portable metalair batteries.
基金the National Natural Science Foundation of China(Nos.31530010 and 21401168)the Special Project of Guangdong Province to Introduce Innovation and Entrepreneurship Team(No.2016ZT06N467)is acknowledged.
文摘Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to prepare Co composites via metallurgical pyrolysis under controllable conditions.The obtained nitrogen-doped porous carbon-Co nanocomposite possesses core–shell structure(Co@C–N).Co@C–N exhibits the best Li storage performances as anode active matter.After the 200th cycles at current density of 0.2 A g^(-1),a reversible capacity of 870 mAh g^(-1)is retained.A reversible capacity of 275 mAh g^(-1)still maintains with 5 A g^(-1).Co@C–N presents a high reversible capacity with excellent cycle stability.Considering the corresponding experimental and theoretical results,the Co0-based N-doped porous carbon composite is proposed to work as LIBs anode matter.These results provide a new design idea for electrode matters of metallic ion battery,and demonstrate that MOFs pyrolysis is an effective method for the construction of elemental state anode materials.
基金Research and Development Plan Project in Key Fields of Guangdong Province (2020B0101030005)Basic and Applied Basic Research Fund of Guangdong Province (2019B1515120027)+1 种基金Scientific Research Innovation Project of Graduate School of South China Normal University (2024KYLX050)Special Funds for the Cultivation of Guangdong College Students’ Scientific and Technological Innovation (“Climbing Program” Special Funds, pdjh2024a109)。
文摘Unsatisfactory conductivity and volume effects have hindered the commercial application of siliconbased materials as advanced anode materials for high-performance lithium-ion batteries. Herein, nitrogen doped carbon silicon matrix composite with atomically dispersed Co sites(Si/Co-N-C) is obtained via the design of the frame structure loaded with nano-components and the multi-element hybrid strategy. Co atoms are uniformly fixed to the N-C frame and tightly packed with nanoscale silicon particles as an activation and protection building block. The mechanism of the N-C framework of loaded metal Co in the Si alloying process is revealed by electrochemical kinetic analysis and ex situ characterization tests.Impressively, the nitrogen-doped Co site activates the intercalation of the outer carbon matrix to supplement the additional capacity. The Co nanoparticles with high conductivity and support enhance the conductivity and structural stability of the composite, accelerating the Li^(+)/Na^(+) diffusion kinetics. Density functional theory(DFT) calculation confirms that the hetero-structure Si/Co-N-C adjusts the electronic structure to obtain good lithium-ion adsorption energy, reduces the Li^(+)/Na^(+) migration energy barrier.This work provides meaningful guidance for the development of high-performance metal/non-metal modified anode materials.
基金the financial support from NNSF of China(21275076,61525402,21303047)the Program for One Hundred Person Project of Guangdong University of Technology+1 种基金Key University Science Research Project of Jiangsu Province(15KJA430006)QingLan Project
文摘Searching low cost and non-precious metal catalysts for high-performance oxygen reduction reaction is highly desired. Herein, Co nanoparticles embedded in nitrogen-doped carbon(Co/N—C) nanotubes with internal void space are successfully synthesized by space-confined pyrolysis, which effectively improve the cobalt loading content and restrict the encapsulated particles down to nanometer. Different from the typical conformal carbon encapsulation, the resulting Co/N—C nanotubes possess more cobalt nanoparticles embedded in the nanotubes, which can provide more coupling sites and active sites in the oxygen reduction reaction(ORR). Moreover, the one-dimensional and porous structure provides a high surface area and a fast electron transfer pathway for the ORR. And the Co/N—C electrode presents excellent electrocatalytic ORR activity in terms of low onset potential(30 mV lower than that of Pt/C), small Tafel slop(45.5 mV dec^(-1)) and good durability(88.5% retention after 10,000 s).
基金financially supported by the National Key Research and Development Program of China(2020YFA0710303)the National Natural Science Foundation of China(51972061,U1905215 and 52072076)。
文摘An efficient photocatalytic CO_(2) reduction has been reported in ZIF-67-derived-Co nanoparticles(NPs)encapsulated in nitrogen-doped carbon layers(N-C/Co).This work demonstrates that the pyrolysis temperature is crucial in tuning the grain size and components of metallic Co^(0) of N-C/Co composite catalysts,which optimizes their photocatalytic activities.Syntheses were conducted at 600,700,and 800℃ giving the N-C/Co-600,N-C/Co-700,and N-C/Co-800 samples,respectively.N-C layers can well wrap the Co NPs obtained at a low pyrolysis temperature(600℃)owing to their smaller grains than those of other samples.A high metallic Co^(0) content in the N-C/Co-600 sample can be attributed to the effective inhibition of surface oxidation.By contrast,the surface CoOx oxides in the N-C/Co-700 and N-C/Co-800 samples cover inside Co cores,inhibiting charge separation and transfer.As a result,the N-C/Co-600 sample yields the best photocatalytic activity.The carbon monoxide and hydrogen generation rates are as high as 1.62×10^(4) and 2.01×10^(4)μmol g^(−1)h^(−1),respectively.Additionally,the Co NPs make composite catalysts magnetic,enabling rapid and facile recovery of catalysts with the assistance of an external magnetic field.This work is expected to provide an instructive guideline for designing metal-organic framework-derived carbon/metal composite catalysts.
基金the financial support from the National Natural Science Foundation of China(Grant No.21576243).
文摘In this study,we synthesize a catalyst comprising cobalt nanoparticles supported on MXene by pyrolyzing a composite in a N2 environment.Specifically,the composite comprises a bimetallic Zn/Co zeolitic imidazole framework grown in situ on the outer surface of MXene.The catalytic efficiency of the catalyst is tested for the self-coupling of 4-methoxybenzylamine to produce value-added imine,where atmospheric oxygen(1 atm)is used as the oxidant.Based on the results,the catalyst displayed impressive catalytic activity,achieving 95.4%yield of the desired imine at 383 K for 8 h.Furthermore,the catalyst showed recyclability and tolerance toward benzylamine substrates with various functional groups.The outstanding performance of the catalyst is primarily attributed to the synergetic catalytic effect between the cobalt nanoparticles and MXene support,while also benefiting from the three-dimensional porous structure.Additionally,a preliminary investigation of potential reaction mechanisms is conducted.
基金the National Natural Science Foundation of China(Grant Nos.22179065,22111530112)the S&T project from Shanghai Tobacco Group Co.Ltd.
文摘Owing to the complexity of electron transfer pathways,the sluggish oxygen evolution reaction process is defined as the bottleneck for the practical application of Zn-air batteries.In this effort,metal nanoparticles(Co,Ni,Fe,etc.)encapsulated within nitrogen-doped carbon materials with abundant edge sites were synthesized by one-step pyrolysis treatment using cigarette butts as raw materials,which can drastically accelerate the overall rate of oxygen evolution reaction by facilitating the adsorption of oxygenated intermediates by the edge-induced topological defects.The prepared catalyst of nitrogen-doped carbon porous nanosheets loaded with Co nanoparticles(Co@NC-500)exhibits enhanced catalytic activity toward oxygen evolution reaction,with a low overpotential of 350 mV at the current density of 10 mA·cm^(-2).Furthermore,the Zn-air battery assembled with Co@NC-500 catalyst demonstrates a desirable performance affording an open-circuit potential of 1.336 V and power density of 33.6 mW·cm^(-2),indicating considerable practical application potential.
