The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their perform...The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e^(-)pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,significantly reducing the production of hydrogen peroxide(H_(2)O_(2)).Remarkably,the optimized catalyst demonstrated superior fuel cell performance,with peak power densities of 1.32 W cm^(-2) in oxygen and 0.61 W cm^(-2) in air environments,respectively.A significant decrease in H_(2)O_(2) by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.展开更多
Spinel metal oxides containing Mn,Co,or Fe(AB_(2)O_(4),A/B=Mn/Fe/Co)are one of the most promising nonPt electrocatalysts for oxygen reduction reaction(ORR)in alkaline conditions.However,the low conductivity of metal o...Spinel metal oxides containing Mn,Co,or Fe(AB_(2)O_(4),A/B=Mn/Fe/Co)are one of the most promising nonPt electrocatalysts for oxygen reduction reaction(ORR)in alkaline conditions.However,the low conductivity of metal oxides and the poor intrinsic activities of transition metal sites lead to unsatisfactory ORR performance.In this study,eutectic molten salt(EMS)treatment is employed to reconstruct the atomic arrangement of MnFe_(2)O_(4)electrocatalyst as a prototype for enhancing ORR performance.Comprehensive analyses by using XAFS,soft XAS,XPS,and electrochemical methods reveal that the EMS treatment reduces the oxygen vacancies and spinel inverse in MnFe_(2)O_(4)effectively,which improves the electric conductivity and increases the population of more catalytically active Mn^(2+)sites with tetrahedral coordination.Moreover,the enhanced Mn-O interaction after EMS treatment is conducive to the adsorption and activation of O_(2),which promotes the first electron transfer step(generally considered as the ratedetermining step)of the ORR process.As a result,the EMS treated MnFe_(2)O_(4)catalyst delivers a positive shift of 40 mV in the ORR half-wave potential and a two-fold enhanced mass/specific activity.This work provides a convenient approach to manipulate the atomic architecture and local electronic structure of spinel oxides as ORR electrocatalysts and a comprehensive understanding of the structureperformance relationship from the molecular/atomic scale.展开更多
Electrocatalytic CO_(2)reduction reaction(CO_(2)RR),driven by clean electric energy such as solar and wind,can not only alleviate environmental greenhouse effect stemming from excessive CO_(2)emissions,but also realiz...Electrocatalytic CO_(2)reduction reaction(CO_(2)RR),driven by clean electric energy such as solar and wind,can not only alleviate environmental greenhouse effect stemming from excessive CO_(2)emissions,but also realize the storage of renewable energy,for it guarantees the production of value-added chemicals and fuels.Among CO_(2)RR products,formic acid shows great advantages in low energy consumption and high added-value,and thus producing formic acid is generally considered as a profitable line for CO_(2)RR.Bismuth-based electrocatalysts exhibit high formic acid selectivity in CO_(2)RR.Herein,we review the recent progress in bismuth-based electrocatalysts for CO_(2)RR,including material synthesis,performance optimization/validation,and electrolyzers.The effects of morphologies,structure,and composition of bismuth-based electrocatalysts on CO_(2)RR performance are highlighted.Simultaneously,in situ spectroscopic characterization and DFT calculations for reaction mechanism of CO_(2)RR on Bi-based catalysts are emphasized.The applications and optimization of electrolyzers with high current density for CO_(2)RR are summarized.Finally,conclusions and future directions in this field are prospected.展开更多
With tunable local electronic environment,high mass density of MN4sites,and ease of preparation,metal-organic conjugated coordinative polymer(CCP) with inherent electronic conductivity provides a promising alternative...With tunable local electronic environment,high mass density of MN4sites,and ease of preparation,metal-organic conjugated coordinative polymer(CCP) with inherent electronic conductivity provides a promising alternative to the well-known M-N-C electrocatalysts.Herein,the coordination reaction between Cu^(2+)and 1,2,4,5-tetraaminobenzene(TAB) was conducted on the surface of metallic Cu nanowires,forming a thin layer of CuN4-based CCP(Cu-TAB) on the Cu nanowire.More importantly,interfacial transfer of electrons from Cu core to the CuN4-based CCP nanoshell was observed within the resulting CuTAB@Cu,which was found to enrich the local electronic density of the CuN4sites.As such,the CuTAB@Cu demonstrates much improved affinity to the*COOH intermediate formed from the rate determining step;the energy barrier for C-C coupling,which is critical to convert CO_(2)into C2products,is also decreased.Accordingly,it delivers a current density of-9.1 mA cm^(-2)at a potential as high as 0.558 V(vs.RHE) in H-type cell and a Faraday efficiency of 46.4% for ethanol.This work emphasizes the profound role of interfacial interaction in tuning the local electronic structure and activating the CuN4-based CCPs for efficient electroreduction of CO_(2).展开更多
As the rapid development of more powerful and safer lithiumion batteries, the mechanism study of gases evolution is attacking more and more attention in recent years. Especially under overcharge/discharge and/or high-...As the rapid development of more powerful and safer lithiumion batteries, the mechanism study of gases evolution is attacking more and more attention in recent years. Especially under overcharge/discharge and/or high-temperature working condition.展开更多
Metal-air batteries,like Zn-air batteries(ZABs)are usually suffered from low energy conversion efficiency and poor cyclability caused by the sluggish OER and ORR at the air cathode.Herein,a novel bimetallic Co/CoFe na...Metal-air batteries,like Zn-air batteries(ZABs)are usually suffered from low energy conversion efficiency and poor cyclability caused by the sluggish OER and ORR at the air cathode.Herein,a novel bimetallic Co/CoFe nanomaterial supported on nanoflower-like N-doped graphitic carbon(NC)was prepared through a strategy of coordination construction-cation exchange-pyrolysis and used as a highly efficient bifunctional oxygen electrocatalyst.Experimental characterizations and density functional theory calculations reveal the formation of Co/CoFe heterostructure and synergistic effect between metal layer and NC support,leading to improved electric conductivity,accelerated reaction kinetics,and optimized adsorption energy for intermediates of ORR and OER.The Co/CoFe@NC exhibits high bifunctional activities with a remarkably small potential gap of 0.70 V between the half-wave potential(E_(1/2))of ORR and the potential at 10 mA cm^(-2)(E_(j=10))of OER.The aqueous ZAB constructed using this air electrode exhibits a slight voltage loss of only 60 mV after 550-cycle test(360 h,15 days).A sodium polyacrylate(PANa)-based hydrogel electrolyte was synthesized with strong water-retention capability and high ionic conductivity.The quasi-solid-state ZAB by integrating the Co/CoFe@NC air electrode and PANa hydrogel electrolyte demonstrates excellent mechanical stability and cyclability under different bending states.展开更多
Alloying Pt with transition metals can significantly improve the catalytic properties for the oxygen reduction reaction(ORR).However,the application of Pt-transition metal alloys in fuel cells is largely limited by po...Alloying Pt with transition metals can significantly improve the catalytic properties for the oxygen reduction reaction(ORR).However,the application of Pt-transition metal alloys in fuel cells is largely limited by poor long-term durability because transition metals can easily leach.In this study,we developed a nonmetallic doping approach and prepared a P-doped Pt catalyst with excellent durability for the ORR.Carbon-supported core-shell nanoparticles with a P-doped Pt core and Pt shell(denoted as PtPx@Pt/C)were synthesized via heat-treatment phosphorization of commercial Pt/C,followed by acid etching.Compositional analysis using electron energy loss spectroscopy and X-ray photoelectron spectroscopy clearly demonstrated that Pt was enriched in the near-surface region(approximately 1 nm)of the carbon-supported core-shell nanoparticles.Owning to P doping,the ORR specific activity and mass activity of the PtP_(1.4)@Pt/C catalyst were as high as 0.62 mA cm^(–2)and 0.31 mAμgPt–^(1),respectively,at 0.90 V,and they were enhanced by 2.8 and 2.1 times,respectively,in comparison with the Pt/C catalyst.More importantly,PtP_(1.4)@Pt/C exhibited superior stability with negligible mass activity loss(6%after 30000 potential cycles and 25%after 90000 potential cycles),while Pt/C lost 46%mass activity after 30000 potential cycles.The high ORR activity and durability were mainly attributed to the core-shell nanostructure,the electronic structure effect,and the resistance of Pt nanoparticles against aggregation,which originated from the enhanced ability of the PtP_(1.4)@Pt to anchor to the carbon support.This study provides a new approach for constructing nonmetal-doped Pt-based catalysts with excellent activity and durability for the ORR.展开更多
Si-based materials have been extensively studied because of their high theoretical capacity,low working potential,and abundant reserves,but serious initial irreversible capacity loss and poor cyclic performance result...Si-based materials have been extensively studied because of their high theoretical capacity,low working potential,and abundant reserves,but serious initial irreversible capacity loss and poor cyclic performance resulting from large volume change of Si during lithiation and delithiation processes restrict their widespread application.Herein,we report the preparation of multi-shell coated Si(DS-Si)nanocomposites by in-situ electroless deposition method using Si granules as the active materials and copper sulfate as Cu sources.The ratio of Si and Cu was readily tuned by varying the concentration of copper sulfate.The multi-shell(Cu@CuxSi/SiO2)coating on Si surface promotes the formation of robust and dense SEI films and the transportation of electron.Thus,the obtained DS-Si composites exhibit an initial coulombic efficiency of 86.2%,a capacity of 1636 mAh g^-1 after 100 discharge-charge cycles at 840 mA g^-1,and an average charge capacity of 1493 mAh g^-1 at 4200 mA g^-1.This study provides a low-cost and large-scale approach to the preparation of nanostructured Si-metal composites anodes with good electrochemical performance for lithium ion batteries.展开更多
Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electroch...Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.展开更多
Developing efficient and low-cost electrocatalysts is essential for the electroreduction of N_(2) to NH_(3).Here,highly monodispersed MoO_(3) clusters loaded on a coral-like CeO_(x)compound with abundant oxygen vacanc...Developing efficient and low-cost electrocatalysts is essential for the electroreduction of N_(2) to NH_(3).Here,highly monodispersed MoO_(3) clusters loaded on a coral-like CeO_(x)compound with abundant oxygen vacancies are successfully prepared by an impregnation-reduction method.The MoO_(3) clusters with small sizes of 2.6±0.5 nm are induced and anchored by the oxygen vacancies of CeO_(x),resulting in excellent nitrogen reduction reaction(NRR)performance.Additionally,the synergistic effects between MoO_(3) and CeO_(x)lead to a further improvement of the electrochemical performance.The as-prepared MoO_(3)-CeO_(x)catalyst shows an NH_(3) yield rate of 32.2 μg h^(-1) mg^(-1) cat and a faradaic efficiency of 7.04%at-0.75 V(vs.reversible hydrogen electrode)in 0.01 M Dulbecco’s Phosphate Buffered Saline.Moreover,it displays decent electrochemical stability over 30,000 s.Besides,the electrochemical NRR mechanism for MoO_(3)-CeO_(x)is investigated by in-situ Fourier transform infrared spectroscopy.N-H stretching,H-N-H bending,and N-N stretching are detected during the reaction,suggesting that an associative pathway is followed.This work provides an approach to designing and synthesizing potential electrocatalysts for NRR.展开更多
Metal-organic frameworks(MOFs)h ave attracted widespread attention due to their large surface area and porous structure.Rationally designing the nanostructures of MOFs to promote their application in ethanol electroox...Metal-organic frameworks(MOFs)h ave attracted widespread attention due to their large surface area and porous structure.Rationally designing the nanostructures of MOFs to promote their application in ethanol electrooxidation is still a challenge.Here,a novel Cu-NCNs(Cu-nitrogen-doped carbon nanotubes)support was synthesized by pyrolysis of melamine(MEL)and Cu-ZIF-8 together,and then,Pd-Au nanoalloys were loaded by sodium borohydride reduction method to prepare PdAu@Cu-NCNs catalysts.The generating mesoporous carbon with high specific surface area and favorable electron and mass transport can be used as a potential excellent carrier for PdAu nanoparticles.In addition,the balance of catalyst composition and surface structure was tuned by controlling the content of Pd and Au.Thus,the best-performed Pd_(2)Au_(2)@Cu-NCN-1000-2(where 1000 means the carrier calcination temperature,and 2 means the calcination constant temperature time)catalyst exhibits better long-term stability and electrochemical activity for ethanol oxidation in alkaline media(4.80 A·mg^(-1)),which is 5.05 times higher than that of commercial Pd/C(0.95 A·mg^(-1)).Therefore,this work is beneficial to further promoting the application of MOFs in direct ethanol fuel cells(DEFCs)and can be used as inspiration for the design of more efficient catalyst support structures.展开更多
The catalytic performance of Pt-based catalysts depends sensitively on their d-band centers.Nevertheless,there are still huge challenges to evaluate their d-band centers from experimental technologies,and modulate the...The catalytic performance of Pt-based catalysts depends sensitively on their d-band centers.Nevertheless,there are still huge challenges to evaluate their d-band centers from experimental technologies,and modulate them to analyze their selectivity in ethanol oxidation reaction(EOR).Here,Pt1Au1alloy supported on the commercial carbon material(Pt_(1)Au_(1)/C)is employed as a typical example to investigate its d-band center shift of surface Pt,and as electrocatalysts to study its selectivity towards EOR.Significantly,a highly reliable in situ Fourier-transform infrared spectroscopy CO-probe strategy is developed to characterize the d-band center shift of surface Pt.The modified electronic effect and site effect of Pt_(1)Au_(1)/C dictated the adsorption configuration of intermediate species and the OH species coverage,thereby influencing its selectivity.More importantly,we developed a universal cyclic voltammetry peak differentiation fitting method as an electrochemical analysis technique to investigate CO_(2)selectivity,which is potentially extendable to other Pt-based electrocatalysts.展开更多
Lithium-sulfur batteries are a promising candidate for next-generation energy storage due to their high theoretical energy density.However,S insulation and the lithium polysulfide intermediate’s shuttle effect greatl...Lithium-sulfur batteries are a promising candidate for next-generation energy storage due to their high theoretical energy density.However,S insulation and the lithium polysulfide intermediate’s shuttle effect greatly hinder its practical application.In this paper,a three-dimensional porous graphene oxide(GO)/MXene(Ti_(3)C_(2)T_(x))(GM)aerogel is designed and applied to a lithium-sulfur battery to settle the problem mentioned.In this strategy,two-dimensional(2D)GO sheets and highly conductive MXene nanosheets are integrated to form a 3D porous aerogel structure,creating a 3D conductive network and large polar surfaces,which can simultaneously achieve fast Li-ion/electron transport,strong chemical anchoring sulfur,and promot redox reactions between poly sulfides.Therefore,the cathode shows excellent sulfur utilization and cycle stability.The prepared GM electrode battery has been tested for nearly nine months at 0.1C,providing the high initial capacity of 1255.62 mAh·g^(-1)and maintaining615.7 mAh·g^(-1)after 450 cycles.展开更多
Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction(ORR) in fuel cells.However,poor stability of Fe/N/C catalyst,mainly attributed to the oxidation...Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction(ORR) in fuel cells.However,poor stability of Fe/N/C catalyst,mainly attributed to the oxidation corrosion by aggressive ·OH radical,severely hampers its applications.However,the exact mechanism for generation of ·OH is unclear yet.Herein,we developed a fluorescent method to effectively detect ·OH generated from ORR on Fe/N/C catalyst by using coumarin as a fluorescent probe.A great difference in potential dependence between ·OH and H2O2 generated from the ORR was observed,which suggests that ·OH is not generated from the decomposition of H2O2 as traditional viewpoint.展开更多
Surface engineering has been found to be an efficient strategy to boost the catalytic performance of noble-metal-based nanocatalysts.In this work,a small amount of P was doped to the surface of PtNi concave cube(P-PtN...Surface engineering has been found to be an efficient strategy to boost the catalytic performance of noble-metal-based nanocatalysts.In this work,a small amount of P was doped to the surface of PtNi concave cube(P-PtNi CNC).Interestingly,the P-PtNi CNC nanocatalyst shows an enhanced methanol oxidation reaction(MOR)performance with achieving 8.19 times of specific activity than that of comercial Pt/C.The electrochemical in situ Fourier transform infrared spectroscopy(FTIR)results reveal that the surface P doping promotes the adsorption energy of OH,enhancing the resistance against CO poisoning.Therefore,the intermediate adsorbed CO(COads)reacted with adsorbed OH(OHads)through the Langmuir–Hinshelwood(LH)mechanism to generate CO_(2)and release surface active sites for further adsorption.This work provides a promising strategy via the incorporation of non-metallic elements into the PtNi alloys bounded with high-index facets(HIFs)as efficient fuel cell catalysts.展开更多
Air cathode performance is essential for rechargeable zinc–air batteries(ZABs).In this study,we develop a self-templated synthesis technique for fabricating bimetallic alloys(FeNi_(3)),bimetallic nitrides(FeNi_(3)N)a...Air cathode performance is essential for rechargeable zinc–air batteries(ZABs).In this study,we develop a self-templated synthesis technique for fabricating bimetallic alloys(FeNi_(3)),bimetallic nitrides(FeNi_(3)N)and heterostructured FeNi_(3)/FeNi_(3)N hollow nanotubes.Owing to its structural and compositional advantages,FeNi_(3)/FeNi_(3)N exhibits remarkable bifunctional oxygen electrocatalytic performance with an extremely small potential gap of 0.68V between the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Theoretical calculations reveal reduced Gibbs free energy for the rate-limiting O–O bond formation during OER due to the self-adaptive surface reconfiguration,which induces a synergistic effect between Fe(Ni)OOH developed in situ on the surface and the inner FeNi_(3)/FeNi_(3)N.ZAB fabricated using the FeNi_(3)/FeNi_(3)N catalyst shows high power density,small charge/discharge voltage gap and excellent cycling stability.In addition to its excellent battery performance,the corresponding quasi-solid-state ZAB shows robust flexibility and integrability.The synthesis method is extended to prepare a CoFe/CoFeN oxygen electrocatalyst,demonstrating its applicability to other iron-group elements.展开更多
Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically...Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically driven Pt3Ni alloy core by the monomer attachment,(2) a nickel(Ni) shell formation due to the depletion of the Pt salt precursor, and(3) the oxidation and of the Ni shell into Ni(OH)2 flakes. We also further observed the nucleation and growth of the Ni(OH)2 flakes on an existing layer either at the middle part or at the step edge. More interestingly, the dynamic transformation among a Pt3Ni alloy, Ni clusters and Ni(OH)2 flakes was also imaged even at a high electron dose rate.展开更多
Two dimensional(2D)nanocrystal functional superlattices with a well controlled structure are of significant importance in photonic,plasmonic and optoelectronic applications and have been well studied,but it remains ch...Two dimensional(2D)nanocrystal functional superlattices with a well controlled structure are of significant importance in photonic,plasmonic and optoelectronic applications and have been well studied,but it remains challenging to understand the formation mechanism and development pathway of the superlattice.In this study,we employed in-situ liquid cell transmission electron microscopy to study the formation of 2D superlattice and its local phase transition from hexagonal-to-square nanocrystal ordering.When colloidal nanocrystals flowed in the solution,long-range ordered hexagonal superlattice could be formed either through shrinking and rearrangement of nanocrystal aggregates or via nanocrystal attachment.As the nanocrystals’shape transformed from truncated octahedral to cube,the local superlattice rearranged to square geometry.Moreover,our observations and quantitative analyses reveal that the phase transition from hexagonal to square mainly originates from the strong van der Waals interactions between the vertical(100)facets.The tracking of 2D cube superlattice formation in real-time could provide unique insights on the governing force of superlattice assembling and stabilization.展开更多
基金financially National Natural Science Foundation of China (22288102, 22172134, U1932201, U2032202)Science and Technology Planning Project of Fujian Province (2022H0002)support from the EPSRC (EP/W03784X/1)。
文摘The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e^(-)pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,significantly reducing the production of hydrogen peroxide(H_(2)O_(2)).Remarkably,the optimized catalyst demonstrated superior fuel cell performance,with peak power densities of 1.32 W cm^(-2) in oxygen and 0.61 W cm^(-2) in air environments,respectively.A significant decrease in H_(2)O_(2) by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.
基金supported by the National Natural Science Foundation of China (12241502,52002367)the Fundamental Research Funds for the Central Universities (20720220010)the National Key Research and Development Program of China (2019YFA0405602)。
文摘Spinel metal oxides containing Mn,Co,or Fe(AB_(2)O_(4),A/B=Mn/Fe/Co)are one of the most promising nonPt electrocatalysts for oxygen reduction reaction(ORR)in alkaline conditions.However,the low conductivity of metal oxides and the poor intrinsic activities of transition metal sites lead to unsatisfactory ORR performance.In this study,eutectic molten salt(EMS)treatment is employed to reconstruct the atomic arrangement of MnFe_(2)O_(4)electrocatalyst as a prototype for enhancing ORR performance.Comprehensive analyses by using XAFS,soft XAS,XPS,and electrochemical methods reveal that the EMS treatment reduces the oxygen vacancies and spinel inverse in MnFe_(2)O_(4)effectively,which improves the electric conductivity and increases the population of more catalytically active Mn^(2+)sites with tetrahedral coordination.Moreover,the enhanced Mn-O interaction after EMS treatment is conducive to the adsorption and activation of O_(2),which promotes the first electron transfer step(generally considered as the ratedetermining step)of the ORR process.As a result,the EMS treated MnFe_(2)O_(4)catalyst delivers a positive shift of 40 mV in the ORR half-wave potential and a two-fold enhanced mass/specific activity.This work provides a convenient approach to manipulate the atomic architecture and local electronic structure of spinel oxides as ORR electrocatalysts and a comprehensive understanding of the structureperformance relationship from the molecular/atomic scale.
基金This work was financially supported by grants from the National Key Research and Development Program of China(2021YFA1501504)Natural Science Foundation of China(22172135,22288102,92045302,and 22021001).
文摘Electrocatalytic CO_(2)reduction reaction(CO_(2)RR),driven by clean electric energy such as solar and wind,can not only alleviate environmental greenhouse effect stemming from excessive CO_(2)emissions,but also realize the storage of renewable energy,for it guarantees the production of value-added chemicals and fuels.Among CO_(2)RR products,formic acid shows great advantages in low energy consumption and high added-value,and thus producing formic acid is generally considered as a profitable line for CO_(2)RR.Bismuth-based electrocatalysts exhibit high formic acid selectivity in CO_(2)RR.Herein,we review the recent progress in bismuth-based electrocatalysts for CO_(2)RR,including material synthesis,performance optimization/validation,and electrolyzers.The effects of morphologies,structure,and composition of bismuth-based electrocatalysts on CO_(2)RR performance are highlighted.Simultaneously,in situ spectroscopic characterization and DFT calculations for reaction mechanism of CO_(2)RR on Bi-based catalysts are emphasized.The applications and optimization of electrolyzers with high current density for CO_(2)RR are summarized.Finally,conclusions and future directions in this field are prospected.
基金The National Key Research and Development Program of China(2021YFA1502000 and 2022YFA1505300)the National Natural Science Foundation of China (22288102, 22072124)+1 种基金support from Beijing Synchrotron Radiation Facility (1W1B, BSRF)China Scholarship Council for the financial support。
文摘With tunable local electronic environment,high mass density of MN4sites,and ease of preparation,metal-organic conjugated coordinative polymer(CCP) with inherent electronic conductivity provides a promising alternative to the well-known M-N-C electrocatalysts.Herein,the coordination reaction between Cu^(2+)and 1,2,4,5-tetraaminobenzene(TAB) was conducted on the surface of metallic Cu nanowires,forming a thin layer of CuN4-based CCP(Cu-TAB) on the Cu nanowire.More importantly,interfacial transfer of electrons from Cu core to the CuN4-based CCP nanoshell was observed within the resulting CuTAB@Cu,which was found to enrich the local electronic density of the CuN4sites.As such,the CuTAB@Cu demonstrates much improved affinity to the*COOH intermediate formed from the rate determining step;the energy barrier for C-C coupling,which is critical to convert CO_(2)into C2products,is also decreased.Accordingly,it delivers a current density of-9.1 mA cm^(-2)at a potential as high as 0.558 V(vs.RHE) in H-type cell and a Faraday efficiency of 46.4% for ethanol.This work emphasizes the profound role of interfacial interaction in tuning the local electronic structure and activating the CuN4-based CCPs for efficient electroreduction of CO_(2).
基金partially supported by the National Natural Science Foundation of China (grant no. 22021001, 22179111)the Ministry of Science and Technology of China (grant no. 2021YFA1201900)+3 种基金the Basic Research Program of Tan Kah Kee Innovation Laboratory (grant no. RD2021070401)the Principal Fund from Xiamen University (grant no. 20720210015)the Fundamental Research Funds for the Central Universities (grant no. 20720220010)the National Natural Science Foundation of China (grant no. 22202082)。
文摘As the rapid development of more powerful and safer lithiumion batteries, the mechanism study of gases evolution is attacking more and more attention in recent years. Especially under overcharge/discharge and/or high-temperature working condition.
基金This work was supported by the National Natural Science Foundation of China(21872105,22072107)the Science&Technology Commission of Shanghai Municipality(19DZ2271500).
文摘Metal-air batteries,like Zn-air batteries(ZABs)are usually suffered from low energy conversion efficiency and poor cyclability caused by the sluggish OER and ORR at the air cathode.Herein,a novel bimetallic Co/CoFe nanomaterial supported on nanoflower-like N-doped graphitic carbon(NC)was prepared through a strategy of coordination construction-cation exchange-pyrolysis and used as a highly efficient bifunctional oxygen electrocatalyst.Experimental characterizations and density functional theory calculations reveal the formation of Co/CoFe heterostructure and synergistic effect between metal layer and NC support,leading to improved electric conductivity,accelerated reaction kinetics,and optimized adsorption energy for intermediates of ORR and OER.The Co/CoFe@NC exhibits high bifunctional activities with a remarkably small potential gap of 0.70 V between the half-wave potential(E_(1/2))of ORR and the potential at 10 mA cm^(-2)(E_(j=10))of OER.The aqueous ZAB constructed using this air electrode exhibits a slight voltage loss of only 60 mV after 550-cycle test(360 h,15 days).A sodium polyacrylate(PANa)-based hydrogel electrolyte was synthesized with strong water-retention capability and high ionic conductivity.The quasi-solid-state ZAB by integrating the Co/CoFe@NC air electrode and PANa hydrogel electrolyte demonstrates excellent mechanical stability and cyclability under different bending states.
文摘Alloying Pt with transition metals can significantly improve the catalytic properties for the oxygen reduction reaction(ORR).However,the application of Pt-transition metal alloys in fuel cells is largely limited by poor long-term durability because transition metals can easily leach.In this study,we developed a nonmetallic doping approach and prepared a P-doped Pt catalyst with excellent durability for the ORR.Carbon-supported core-shell nanoparticles with a P-doped Pt core and Pt shell(denoted as PtPx@Pt/C)were synthesized via heat-treatment phosphorization of commercial Pt/C,followed by acid etching.Compositional analysis using electron energy loss spectroscopy and X-ray photoelectron spectroscopy clearly demonstrated that Pt was enriched in the near-surface region(approximately 1 nm)of the carbon-supported core-shell nanoparticles.Owning to P doping,the ORR specific activity and mass activity of the PtP_(1.4)@Pt/C catalyst were as high as 0.62 mA cm^(–2)and 0.31 mAμgPt–^(1),respectively,at 0.90 V,and they were enhanced by 2.8 and 2.1 times,respectively,in comparison with the Pt/C catalyst.More importantly,PtP_(1.4)@Pt/C exhibited superior stability with negligible mass activity loss(6%after 30000 potential cycles and 25%after 90000 potential cycles),while Pt/C lost 46%mass activity after 30000 potential cycles.The high ORR activity and durability were mainly attributed to the core-shell nanostructure,the electronic structure effect,and the resistance of Pt nanoparticles against aggregation,which originated from the enhanced ability of the PtP_(1.4)@Pt to anchor to the carbon support.This study provides a new approach for constructing nonmetal-doped Pt-based catalysts with excellent activity and durability for the ORR.
基金supported by the China Postdoctoral Science Foundation(2018M632575)the National Natural Science Foundation of China(21875197 and 21621091)the National Key Research and Development of China(2016YFB0100202)。
文摘Si-based materials have been extensively studied because of their high theoretical capacity,low working potential,and abundant reserves,but serious initial irreversible capacity loss and poor cyclic performance resulting from large volume change of Si during lithiation and delithiation processes restrict their widespread application.Herein,we report the preparation of multi-shell coated Si(DS-Si)nanocomposites by in-situ electroless deposition method using Si granules as the active materials and copper sulfate as Cu sources.The ratio of Si and Cu was readily tuned by varying the concentration of copper sulfate.The multi-shell(Cu@CuxSi/SiO2)coating on Si surface promotes the formation of robust and dense SEI films and the transportation of electron.Thus,the obtained DS-Si composites exhibit an initial coulombic efficiency of 86.2%,a capacity of 1636 mAh g^-1 after 100 discharge-charge cycles at 840 mA g^-1,and an average charge capacity of 1493 mAh g^-1 at 4200 mA g^-1.This study provides a low-cost and large-scale approach to the preparation of nanostructured Si-metal composites anodes with good electrochemical performance for lithium ion batteries.
基金financially supported by NSFC (Grant Nos.21621091,21373008)the National Key Research and Development Program of China (2016YFB0100202)
文摘Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.
基金financially supported by the National Key Research and Development Program of China(2017YFA0206500)NSFC(Grant Nos.21673198,91934303,21621091)。
文摘Developing efficient and low-cost electrocatalysts is essential for the electroreduction of N_(2) to NH_(3).Here,highly monodispersed MoO_(3) clusters loaded on a coral-like CeO_(x)compound with abundant oxygen vacancies are successfully prepared by an impregnation-reduction method.The MoO_(3) clusters with small sizes of 2.6±0.5 nm are induced and anchored by the oxygen vacancies of CeO_(x),resulting in excellent nitrogen reduction reaction(NRR)performance.Additionally,the synergistic effects between MoO_(3) and CeO_(x)lead to a further improvement of the electrochemical performance.The as-prepared MoO_(3)-CeO_(x)catalyst shows an NH_(3) yield rate of 32.2 μg h^(-1) mg^(-1) cat and a faradaic efficiency of 7.04%at-0.75 V(vs.reversible hydrogen electrode)in 0.01 M Dulbecco’s Phosphate Buffered Saline.Moreover,it displays decent electrochemical stability over 30,000 s.Besides,the electrochemical NRR mechanism for MoO_(3)-CeO_(x)is investigated by in-situ Fourier transform infrared spectroscopy.N-H stretching,H-N-H bending,and N-N stretching are detected during the reaction,suggesting that an associative pathway is followed.This work provides an approach to designing and synthesizing potential electrocatalysts for NRR.
基金financially supported by the Program for Professor of Special Appointment(Eastern Scholar)at SIHLProject of Shanghai Municipal Science and Technology Commission(No.22DZ2291100)+6 种基金Open Fund of Anhui International Joint Research Center for Nano Carbon-based Materials and Environmental Health(No.NCMEH2022Y02)Gaoyuan Discipline of Shanghai-Materials Science and Engineering,and Shanghai Polytechnic University-Drexel University Joint Research Center for Optoelectronics and Sensingsupported by the Science Fund for Distinguished Young Scholars of Fujian Province(No.2019J06027)the Open Project of Jiangsu Key Laboratory for Carbon-Based Functional Materials&Devices(Soochow University)(No.KS2022)Collaborative Innovation Center of Suzhou Nano Science&Technologythe 111 ProjectJoint International Research Laboratory of Carbon-Based Functional Materials and Devices。
文摘Metal-organic frameworks(MOFs)h ave attracted widespread attention due to their large surface area and porous structure.Rationally designing the nanostructures of MOFs to promote their application in ethanol electrooxidation is still a challenge.Here,a novel Cu-NCNs(Cu-nitrogen-doped carbon nanotubes)support was synthesized by pyrolysis of melamine(MEL)and Cu-ZIF-8 together,and then,Pd-Au nanoalloys were loaded by sodium borohydride reduction method to prepare PdAu@Cu-NCNs catalysts.The generating mesoporous carbon with high specific surface area and favorable electron and mass transport can be used as a potential excellent carrier for PdAu nanoparticles.In addition,the balance of catalyst composition and surface structure was tuned by controlling the content of Pd and Au.Thus,the best-performed Pd_(2)Au_(2)@Cu-NCN-1000-2(where 1000 means the carrier calcination temperature,and 2 means the calcination constant temperature time)catalyst exhibits better long-term stability and electrochemical activity for ethanol oxidation in alkaline media(4.80 A·mg^(-1)),which is 5.05 times higher than that of commercial Pd/C(0.95 A·mg^(-1)).Therefore,this work is beneficial to further promoting the application of MOFs in direct ethanol fuel cells(DEFCs)and can be used as inspiration for the design of more efficient catalyst support structures.
基金granted by the National Natural Science Foundation of China(22172134,22288102,22279011)Fundamental Research Funds for the Central Universities(2022CDJXY-003)。
文摘The catalytic performance of Pt-based catalysts depends sensitively on their d-band centers.Nevertheless,there are still huge challenges to evaluate their d-band centers from experimental technologies,and modulate them to analyze their selectivity in ethanol oxidation reaction(EOR).Here,Pt1Au1alloy supported on the commercial carbon material(Pt_(1)Au_(1)/C)is employed as a typical example to investigate its d-band center shift of surface Pt,and as electrocatalysts to study its selectivity towards EOR.Significantly,a highly reliable in situ Fourier-transform infrared spectroscopy CO-probe strategy is developed to characterize the d-band center shift of surface Pt.The modified electronic effect and site effect of Pt_(1)Au_(1)/C dictated the adsorption configuration of intermediate species and the OH species coverage,thereby influencing its selectivity.More importantly,we developed a universal cyclic voltammetry peak differentiation fitting method as an electrochemical analysis technique to investigate CO_(2)selectivity,which is potentially extendable to other Pt-based electrocatalysts.
基金financially supported by the National Natural Science Foundation of Yunnan Province(Nos.202101AW070006 and 202001AU070079)。
文摘Lithium-sulfur batteries are a promising candidate for next-generation energy storage due to their high theoretical energy density.However,S insulation and the lithium polysulfide intermediate’s shuttle effect greatly hinder its practical application.In this paper,a three-dimensional porous graphene oxide(GO)/MXene(Ti_(3)C_(2)T_(x))(GM)aerogel is designed and applied to a lithium-sulfur battery to settle the problem mentioned.In this strategy,two-dimensional(2D)GO sheets and highly conductive MXene nanosheets are integrated to form a 3D porous aerogel structure,creating a 3D conductive network and large polar surfaces,which can simultaneously achieve fast Li-ion/electron transport,strong chemical anchoring sulfur,and promot redox reactions between poly sulfides.Therefore,the cathode shows excellent sulfur utilization and cycle stability.The prepared GM electrode battery has been tested for nearly nine months at 0.1C,providing the high initial capacity of 1255.62 mAh·g^(-1)and maintaining615.7 mAh·g^(-1)after 450 cycles.
基金supported by the National Key Research and Development Program of China(2017YFA0206500)the National Natural Science Foundation of China(21603103,21875194,21902125,91645121)
文摘Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction(ORR) in fuel cells.However,poor stability of Fe/N/C catalyst,mainly attributed to the oxidation corrosion by aggressive ·OH radical,severely hampers its applications.However,the exact mechanism for generation of ·OH is unclear yet.Herein,we developed a fluorescent method to effectively detect ·OH generated from ORR on Fe/N/C catalyst by using coumarin as a fluorescent probe.A great difference in potential dependence between ·OH and H2O2 generated from the ORR was observed,which suggests that ·OH is not generated from the decomposition of H2O2 as traditional viewpoint.
基金the National Natural Science Foundation of China(No.21573286)the Natural Science Foundation of Hebei Province of China(No.E2020408004)the Funded by Science and Technology Project of Hebei Education Department(No.QN2021124).
文摘Surface engineering has been found to be an efficient strategy to boost the catalytic performance of noble-metal-based nanocatalysts.In this work,a small amount of P was doped to the surface of PtNi concave cube(P-PtNi CNC).Interestingly,the P-PtNi CNC nanocatalyst shows an enhanced methanol oxidation reaction(MOR)performance with achieving 8.19 times of specific activity than that of comercial Pt/C.The electrochemical in situ Fourier transform infrared spectroscopy(FTIR)results reveal that the surface P doping promotes the adsorption energy of OH,enhancing the resistance against CO poisoning.Therefore,the intermediate adsorbed CO(COads)reacted with adsorbed OH(OHads)through the Langmuir–Hinshelwood(LH)mechanism to generate CO_(2)and release surface active sites for further adsorption.This work provides a promising strategy via the incorporation of non-metallic elements into the PtNi alloys bounded with high-index facets(HIFs)as efficient fuel cell catalysts.
基金supported by the National Natural Science Foundation of China(22072107,21872105)the Science&Technology Commission of Shanghai Municipality(19DZ2271500)the Fundamental Research Funds for the Central Universities.
文摘Air cathode performance is essential for rechargeable zinc–air batteries(ZABs).In this study,we develop a self-templated synthesis technique for fabricating bimetallic alloys(FeNi_(3)),bimetallic nitrides(FeNi_(3)N)and heterostructured FeNi_(3)/FeNi_(3)N hollow nanotubes.Owing to its structural and compositional advantages,FeNi_(3)/FeNi_(3)N exhibits remarkable bifunctional oxygen electrocatalytic performance with an extremely small potential gap of 0.68V between the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Theoretical calculations reveal reduced Gibbs free energy for the rate-limiting O–O bond formation during OER due to the self-adaptive surface reconfiguration,which induces a synergistic effect between Fe(Ni)OOH developed in situ on the surface and the inner FeNi_(3)/FeNi_(3)N.ZAB fabricated using the FeNi_(3)/FeNi_(3)N catalyst shows high power density,small charge/discharge voltage gap and excellent cycling stability.In addition to its excellent battery performance,the corresponding quasi-solid-state ZAB shows robust flexibility and integrability.The synthesis method is extended to prepare a CoFe/CoFeN oxygen electrocatalyst,demonstrating its applicability to other iron-group elements.
基金the National Key Research and Development Program of China(2017YFA0206500)the National Natural Science Foundation of China(21673198,21373008,21621091)。
文摘Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically driven Pt3Ni alloy core by the monomer attachment,(2) a nickel(Ni) shell formation due to the depletion of the Pt salt precursor, and(3) the oxidation and of the Ni shell into Ni(OH)2 flakes. We also further observed the nucleation and growth of the Ni(OH)2 flakes on an existing layer either at the middle part or at the step edge. More interestingly, the dynamic transformation among a Pt3Ni alloy, Ni clusters and Ni(OH)2 flakes was also imaged even at a high electron dose rate.
基金financially supported by the National Key Research and Development Program of China (2017YFA0206500)the National Natural Science Foundation of China (21673198, 21373008 and 21621091)
文摘Two dimensional(2D)nanocrystal functional superlattices with a well controlled structure are of significant importance in photonic,plasmonic and optoelectronic applications and have been well studied,but it remains challenging to understand the formation mechanism and development pathway of the superlattice.In this study,we employed in-situ liquid cell transmission electron microscopy to study the formation of 2D superlattice and its local phase transition from hexagonal-to-square nanocrystal ordering.When colloidal nanocrystals flowed in the solution,long-range ordered hexagonal superlattice could be formed either through shrinking and rearrangement of nanocrystal aggregates or via nanocrystal attachment.As the nanocrystals’shape transformed from truncated octahedral to cube,the local superlattice rearranged to square geometry.Moreover,our observations and quantitative analyses reveal that the phase transition from hexagonal to square mainly originates from the strong van der Waals interactions between the vertical(100)facets.The tracking of 2D cube superlattice formation in real-time could provide unique insights on the governing force of superlattice assembling and stabilization.
基金grants from Major State Basic Research Development Program of China (No.201SCB932303)Top-Notch Young Talents Program of China,and National Natural Science Foundation of China (Nos.21373175,2151101071,and 21321062).
