The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO_(2)hydrogenation.However,the structure–activity relationship of the reaction remains poorly unders...The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO_(2)hydrogenation.However,the structure–activity relationship of the reaction remains poorly understood due to challenges in atomic-level structural characterizations and analysis of reaction intermediates.In this study,we prepared two Zn-Al spinel oxide catalysts via coprecipitation(ZnAl-C)and hydrothermal(ZnAl-H)methods,and conducted a comparative investigation in the CO_(2)hydrogenation reaction.Surprisingly,under similar conditions,ZnAl-C exhibited significantly higher selectivity towards methanol and DME compared to ZnAl-H.Comprehensive characterizations using X-ray diffraction(XRD),Raman spectroscopy and electron paramagnetic resonance(EPR)unveiled that ZnAl-C catalyst had abundant ZnO species on its surface,and the interaction between the ZnO species and its ZnAl spinel oxide matrix led to the formation of oxygen vacancies,which are crucial for CO_(2)adsorption and activation.Additionally,state-of-the-art solid-state nuclear magnetic resonance(NMR)techniques,including ex-situ and in-situ NMR analyses,confirmed that the surface ZnO facilitates the formation of unique highly reactive interfacial formate species,which was readily hydrogenated to methanol and DME.These insights elucidate the promotion effects of ZnO on the ZnAl spinel oxide in regulating active sites and reactive intermediates for CO_(2)-to-methanol hydrogenation reaction,which is further evidenced by the significant enhancement in methanol and DME selectivity observed upon loading ZnO onto the ZnAl-H catalyst.These molecular-level mechanism understandings reinforce the idea of optimizing the ZnO-ZnAl interface through tailored synthesis methods to achieve activity-selectivity balance.展开更多
Ensuring high electrocatalytic performance simultaneously with low or even no precious-metal usage is still a big challenge for the development of electrocatalysts toward oxygen evolution reaction(OER)in anion exchang...Ensuring high electrocatalytic performance simultaneously with low or even no precious-metal usage is still a big challenge for the development of electrocatalysts toward oxygen evolution reaction(OER)in anion exchange membrane water electrolysis.Here,homogeneous high entropy oxide(HEO)film is in-situ fabricated on nickel foam(NF)substrate via magnetron sputtering technology without annealing process in air,which is composed of many spinel-structured(FeCoNiCrMo)_(3)O_(4) grains with an average particle size of 2.5 nm.The resulting HEO film(abbreviated as(FeCoNiCr-Mo)_(3)O_(4))exhibits a superior OER performance with a low OER overpotential of 216 mV at 10 mA cm^(–2) and steadily operates at 100 mA cm^(–2) for 200 h with a decay of only 272μV h^(–1),which is far better than that of commercial IrO_(2) catalyst(290 mV,1090μV h^(–1)).Tetramethylammonium cation(TMA^(+))probe experiment,activation energy analysis and theoretical calculations unveil that the OER on(FeCoNiCrMo)_(3)O_(4) follows an adsorbate evolution mechanism pathway,where the energy barrier of rate-determining step for OER on(FeCoNiCrMo)_(3)O_(4) is substantially lowered.Also,methanol molecular probe experiment suggests that a weakened ^(*)OH bonding on the(FeCoNiCrMo)_(3)O_(4) surface and a rapid deprotonation of ^(*)OH,further enhancing its OER performance.This work provides a feasible solution for designing efficient high entropy oxides electrocatalysts for OER,accelerating the practical process of water electrolysis for H2 production.展开更多
The exploration of new catalytic hosts is highly important to tackle the sluggish electrochemical kinetics of sulfur redox for achieving high energy density of lithium–sulfur batteries.Herein,for the first time,we pr...The exploration of new catalytic hosts is highly important to tackle the sluggish electrochemical kinetics of sulfur redox for achieving high energy density of lithium–sulfur batteries.Herein,for the first time,we present high-entropy oxide(HEO,(Mg_(0.2)Mn_(0.2)Ni_(0.2)Co_(0.2)Zn_(0.2))Fe_(2)O_(4))nanofibers as catalytic host of sulfur.The HEO nanofibers show a synergistic effect among multiple metal cations in spinel structure that enables strong chemical confinement of soluble polysulfides and fast kinetics for polysulfide conversion.Consequently,the S/HEO composite displays the high gravimetric capacity of 1368.7 mAh g^(−1) at 0.1 C rate,excellent rate capability with the discharge capacity of 632.1 mAh g^(−1) at 5 C rate,and desirable cycle stability.Furthermore,the S/HEO composite shows desirable sulfur utilization and good cycle stability under a harsh operating condition of high sulfur loading(4.6 mg cm^(−2))or low electrolyte/sulfur ratio(5μL mg^(−1)).More impressively,the high volumetric capacity of 2627.9 mAh cm^(−3) is achieved simultaneously for the S/HEO composite due to the high tap density of 1.92 g cm^(−3),nearly 2.5 times of the conventional sulfur/carbon composite.Therefore,based on high-entropy oxide materials,this work affords a fresh concept of elevating the gravimetric/volumetric capacities of sulfur cathodes for lithium–sulfur batteries.展开更多
Spinel oxides containing Co and Ni are a promising substitute as a noble metal catalyst for methane combustion.Achieving a complete oxidation of methane under 400°C remains challenging,andhydrothermal 60 h NiClit...Spinel oxides containing Co and Ni are a promising substitute as a noble metal catalyst for methane combustion.Achieving a complete oxidation of methane under 400°C remains challenging,andhydrothermal 60 h NiClittle impact on activity,especially at high space velocities due to the long hydrothermal time with less absorbed oxygen species and crystal defects.Overall,these results help clarify methane activa-tion mechanisms and aid the development of more efficient low-cost catalysts.展开更多
Spinel oxides,with the formula AB_(2)O_(4)(A and B represent metal ions)perform superior electrocatalytic characteristic when A and B are transition metals like Co,Fe,Mn,etc.Abundant researches have been attached to t...Spinel oxides,with the formula AB_(2)O_(4)(A and B represent metal ions)perform superior electrocatalytic characteristic when A and B are transition metals like Co,Fe,Mn,etc.Abundant researches have been attached to the structure designments while methods are often energy-intensive and inefficient.Here,we devised a universal strategy to achieve rapid synthesis of nanocrystalline spinel materials with multiple components(Co_(3)O_(4),Mn_(3)O_(4),CoMn_(2)O_(4)and CoFe_(2)O_(4)are as examples),where phase formation is within 15 s.Under the Joule-heating shock,a crack-break process of microcosmic phase transformation is observed by in-situ transmission electron microscopy.The half-wave potential values of Co_(3)O_(4)-JH,Mn_(3)O_(4)-JH,CoMn_(2)O_(4)-JH and CoFe_(2)O_(4)-JH in the electrocatalytic oxygen reduction reaction were 0.77,0.78,0.79 and 0.76,respectively.This suggests that the Joule heating is a fast and efficient method for the preparation of spinel oxide electrocatalysts.展开更多
The magnetic and electronic properties of spinel oxide LiV2O4 have been systematically studied by using the spin-polarized first-principles electronic structure calculations.We find that a series of magnetic states,in...The magnetic and electronic properties of spinel oxide LiV2O4 have been systematically studied by using the spin-polarized first-principles electronic structure calculations.We find that a series of magnetic states,in which the ferromagnetic(FM)V4 tetrahedra are linked together through the corner-sharing antiferromagnetic(AFM)V4 tetrahedra,possess degenerate energies lower than those of other spin configurations.The large number of these energetically degenerated states being the magnetic ground state give rise to strong magnetic frustration as well as large magnetic entropy in LiV2O4.The corresponding band structure and density of states of such a typical magnetic state in this series,i.e.,the ditetrahedron(DT)AFM state,demonstrate that LiV2O4 is in the vicinity of a metal-insulator transition.Further analysis suggests that the t2g and eg orbitals of the V atoms play different roles in the magnetic exchange interactions.Our calculations are consistent with previous experimental measurements and shed light on understanding the exotic magnetism and the heavy-fermion behavior of LiV2O4.展开更多
Coordinatively unsaturated metal sites(CUS)located at tetrahedral(T_(d))in spinel structure are highly effective for activating peroxymonosulfate(PMS)in Fenton-like catalysis.However,the conventional T_(d)-octahedral(...Coordinatively unsaturated metal sites(CUS)located at tetrahedral(T_(d))in spinel structure are highly effective for activating peroxymonosulfate(PMS)in Fenton-like catalysis.However,the conventional T_(d)-octahedral(Oh)connectivity in spinel structures restricts internal electron transfer,limiting the regeneration of low-valent metals and creating a trade-off between catalytic activity and long-term stability.Herein,we address this challenge by engineering a novel T_(d)-T_(d) connectivity in amorphous CoFeO_(x) nanosheets(a-CoFeO_(x) NSs).Soft X-ray absorption spectroscopy(sXAS)measurements reveal that in a-CoFeO_(x) nanosheets,the ligand field symmetry around Co atoms is dominated by a T_(d) coordination,in contrast to the O_(h) coordination in the crystalline state,which introduces T_(d)-T_(d) connection.Density functional theory(DFT)calculations confirm that the T_(d)-T_(d) connection in a-CoFeO_(x) structure significantly strengthens electron transfer to activate PMS,which exhibited a first-order kinetic constant(k_(obs))of 0.27 min^(-1) for sulfamethoxazole(SMX)removal with high stability.This study reveals that the phase-engineered CUS can further enhance catalytic activity and provides a simple and scalable strategy for optimizing spinel-type catalysts.展开更多
Overall seawater splitting driven by regenerable electricity is an ideal pathway formass production of green hydrogen.Nonetheless,its anodic oxygen evolution half-reaction(OER)confronts sluggish kinetics,competitive c...Overall seawater splitting driven by regenerable electricity is an ideal pathway formass production of green hydrogen.Nonetheless,its anodic oxygen evolution half-reaction(OER)confronts sluggish kinetics,competitive chlorine evolution,and chloride corrosion or poisoning problems,needing to develop high-efficient and robust electrocatalysts toward those challenges.Herein,novel defect-rich single-phase(NiCoMnCrFe)_(3)O_(4) high-entropy spinel oxide(HEO)is fabricated by low-temperature annealing of highentropy layered double hydroxide precursor.Due to the presence of abundant defects,unique“cocktail”effect,and efficient electronic structure regulation,such(NiCoMnCrFe)_(3)O_(4) can deliver 500 mA cm^(−2) current density at the overpotentials of 268/384 mV in alkaline freshwater/seawater,outperforming its counterparts,commercial IrO_(2),and most reported OER catalysts.Moreover,it manifests exceptional OER durability and anticorrosion capability.Theoretical calculations reveal that the eg occupancies of surface Mn atoms are closer to 1.0,which may be the activity origin of such HEO.Importantly,the constructed(NiCoMnCrFe)_(3)O_(4)||Pt/C electrolyzer only requires 1.57 V cell voltage for driving overall seawater splitting to reach 500 mA cm^(−2) current under real industrial conditions.This work may spur the development of advanced OER electrocatalysts by combining entropy and defect engineering and accelerate their applications in seawater splitting,metal–air batteries,or marine biomass electrocatalytic conversion fields.展开更多
A robust oxygen‐related electrocatalyst,composed of spinel iron‐cobalt oxide and nitrogen‐dopedordered mesoporous carbon(NOMC),was developed for rechargeable metal‐air batteries.Electrochemicaltests revealed that ...A robust oxygen‐related electrocatalyst,composed of spinel iron‐cobalt oxide and nitrogen‐dopedordered mesoporous carbon(NOMC),was developed for rechargeable metal‐air batteries.Electrochemicaltests revealed that the optimal catalyst Fe_(0.5)Co/NOMC exhibits superior activity with ahalf‐wave potential of 0.89 V(vs.reversible hydrogen electrode)for the oxygen reduction reactionand an overpotential of 0.31 V at 10 mA cm^(−2)for the oxygen evolution reaction.For demonstration,the catalyst was used in the assembly of a rechargeable zinc‐air battery,which exhibited an exceptionallyhigh energy density of 820 Wh kg−1 at 100 mA cm^(−2),a high power density of 153 mW cm^(−2)at1.0 V,and superior cycling stability up to 432 cycles(144 h)under ambient air.展开更多
Electrocatalytic reduction reactions play a crucial role in electrochemical energy conversion and storage technology,which are emerging technologies to ameliorate environmental problems.Spinel oxides are widely explor...Electrocatalytic reduction reactions play a crucial role in electrochemical energy conversion and storage technology,which are emerging technologies to ameliorate environmental problems.Spinel oxides are widely explored in electrocatalytic oxidation reactions but have a poor intrinsic ability to reduction reactions,making their electrocatalytic ability less effective.To improve this,defect engineering is a valuable method for regulating the electronic structure and coordination environment.Herein,this manuscript discusses the use of defect spinel oxides in electrocatalytic reduction reactions,including the different types of defects,construction methods,and characterization techniques.It also outlines the various applications of defect spinel oxides in different electrocatalytic reduction reactions.Finally,it goes over the challenges and future outlooks for defect spinels.This review aims to thoroughly explain how defect spinels work in electrocatalytic reduction reactions and serve as a helpful guide for creating effective electrocatalysts.展开更多
Developing stable and efficient nonprecious-metal-based oxygen evolution catalysts in the neutral electrolyte is a challenging but essential goal for various electrochemical systems.Particularly,cobalt-based spinels h...Developing stable and efficient nonprecious-metal-based oxygen evolution catalysts in the neutral electrolyte is a challenging but essential goal for various electrochemical systems.Particularly,cobalt-based spinels have drawn a considerable amount of attention but most of them operate in alkali solutions.However,the frequently studied Co-Fe spinel system never exhibits appreciable stability in nonbasic conditions,not to mention attract further investigation on its key structural motif and transition states for activity loss.Herein,we report exceptional stable Co-Fe spinel oxygen evolution catalysts(~30%Fe is optimal)in a neutral electrolyte,owing to its unique metal ion arrangements in the crystal lattice.The introduced iron content enters both the octahedral and tetrahedral sites of the spinel as Fe^(2+)and Fe^(3+)(with Co ions having mixed distribution as well).Combining density functional theory calculations,we find that the introduction of Fe to Co_(3)O_(4)lowers the covalency of metal-oxygen bonds and can help suppress the oxidation of Co^(2+/3+)and 0^(2-).It implies that the Co-Fe spinel will have minor surface reconstruction and less lattice oxygen loss during the oxygen evolution reaction process in comparison with Co_(3)O_(4)and hence show much better stability.These findings suggest that there is still much chance for the spinel structures,especially using reasonable sublattices engineering via multimetal doping to develop advanced oxygen evolution catalysts.展开更多
Owing to the complexity of multicomponent gases,developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging.The spinel MMn_(2)O_(4)(M=Co,Ni,or Cu)catalysts were successfully...Owing to the complexity of multicomponent gases,developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging.The spinel MMn_(2)O_(4)(M=Co,Ni,or Cu)catalysts were successfully synthesized via the sol–gel method and tested for their catalytic performance for simultaneous degradation of benzene and toluene.The CuMn_(2)O_(4)sample exhibited the best catalytic performance,the conversion of benzene reached 100%at 350℃,and toluene conversion reached 100%at 250℃.XRD,N_(2)adsorption-desorption,HRTEM-EDS,ED-XRF,Raman spectroscopy,H_(2)-TPR,NH_(3)-TPD,O_(2)-TPD and XPS were used to characterize the physical and chemical properties of MMn_(2)O_(4)catalysts.The excellent redox properties,high concentration of surface Mn4+,and adsorption of oxygen species over the CuMn_(2)O_(4)sample facilitated the simultaneous and efficient removal of benzene and toluene.Additionally,in situ DRIFTS illustrated the intermediate species and reaction mechanism for the synergetic catalytic oxidation of benzene and toluene.Notably,as an effective catalytic material,spinel oxide exhibited excellent synergistic degradation performance for benzene and toluene,providing some insight for the development of efficient multicomponent VOC catalysts.展开更多
The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto...The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto the nickel-based superalloy substrate by high velocity oxygen fuel（HVOF）.It suggests that the TGO usually consists of a great number of chromium oxides,cobalt oxides and spinel oxides besides alumina during the initial period of the high temperature oxidation if the specimens are not subjected to the appropriate vacuum pre-oxidation process.Furthermore,the amount of alumina is strongly dependent on the partial pressure of oxygen;while the CoCr2O4 spinel oxides are usually formed under the conditions of higher partial pressure of oxygen during the initial period and the lower partial pressure of oxygen during the subsequent period of the isothermal oxidation.After the appropriate vacuum pre-oxidation process,the TGO is mainly composed of alumina that contains lower Y element,while alumina that contains higher Y element sporadically distributes,and the spinel oxides cannot be found.After a longer period of the isothermal oxidation,a small amount of porous CoCr2O4 and the chrome oxide sporadically distribute near the continuous alumina.Additionally,after the appropriate vacuum pre-oxidation process,the TGO growth rate is relatively slow.展开更多
Spinel cobalt oxide(Co_(3)O_(4)),consisting of tetrahedral Co^(2+)(CoTd)and octahedral Co^(3+)(CoOh),is considered as promising earth-abundant electrocatalyst for chlorine evolution reaction(CER).Identifying the catal...Spinel cobalt oxide(Co_(3)O_(4)),consisting of tetrahedral Co^(2+)(CoTd)and octahedral Co^(3+)(CoOh),is considered as promising earth-abundant electrocatalyst for chlorine evolution reaction(CER).Identifying the catalytic contribution of geometric Co site in the electrocatalytic CER plays a pivotal role to precisely modulate electronic configuration of active Co sites to boost CER.Herein,combining density functional theory calculations and experiment results assisted with operando analysis,we found that the Co_(Oh) site acts as the main active site for CER in spinel Co_(3)O_(4),which shows better Cl^(-)adsorption and more moderate intermediate adsorption toward CER than CoTd site,and does not undergo redox transition under CER condition at applied potentials.Guided by above findings,the oxygen vacancies were further introduced into the Co_(3)O_(4) to precisely manipulate the electronic configuration of Co_(Oh) to boost Cl^(-)adsorption and optimize the reaction path of CER and thus to enhance the intrinsic CER activity significantly.Our work figures out the importance of geometric configuration dependent CER activity,shedding light on the rational design of advanced electrocatalysts from geometric configuration optimization at the atomic level.展开更多
A series of Co/Mg-Al oxide samples, CoMgAl-x （x = （Mg ＋ Co）]AI molar ratio of 1-5）, were prepared by the self-combustion method followed by H2 reduction. The catalytic performance and stability of the samples wer...A series of Co/Mg-Al oxide samples, CoMgAl-x （x = （Mg ＋ Co）]AI molar ratio of 1-5）, were prepared by the self-combustion method followed by H2 reduction. The catalytic performance and stability of the samples were studied in dry reforming ofCH4. XRD and H2-TPR characterization results showed that the reduced CoMgAl-x samples mainly consisted of solid solution and spinel phases with cobalt particles. The spinel phases contained COB04 and ConMgl-nAl204 （0 〈 n 〈 1 ） varying with the （Mg ＋ Co）/AI ratio, The effect of （Mg ＋ Co）/A1 molar ratio on the catalytic behavior was investigated in detail and CoMgAI-3 exhibited the highest catalytic activity and stability among the catalysts studied.展开更多
The oxygen evolution reaction(OER)serves as a fundamental half–reaction in the electrolysis of water for hydrogen production,which is restricted by the sluggish OER reaction kinetics and unable to be practically appl...The oxygen evolution reaction(OER)serves as a fundamental half–reaction in the electrolysis of water for hydrogen production,which is restricted by the sluggish OER reaction kinetics and unable to be practically applied.The traditional lattice oxygen oxidation mechanism(LOM)offers an advantageous route by circumventing the formation of M-OOH^(*)in the adsorption evolution mechanism(AEM),thus enhancing the reaction kinetics of the OER but resulting in possible structural destabilization due to the decreased M–O bond order.Fortunately,the asymmetry of tetrahedral and octahedral sites in transition metal spinel oxides permits the existence of non-bonding oxygen,which could be activated by rational band structure design for direct O-O coupling,where the M–O bond maintains its initial bond order.Here,non-bonding oxygen was introduced into NiFe_(2)O_(4)via annealing in an oxygen-deficient atmosphere.Then,in-situ grown sulfate species on octahedral nickel sites significantly improved the reactivity of the non-bonding oxygen electrons,thereby facilitating the transformation of the redox center from metal to oxygen.LOM based on non-bonding oxygen(LOMNB)was successfully activated within NiFe_(2)O_(4),exhibiting a low overpotential of 206 mV to achieve a current density of 10 mA cm^(-2)and excellent durability of stable operation for over 150 h.Additionally,catalysts featuring varying band structures were synthesized for comparative analysis,and it was found that the reversible redox processes of non-bonding oxygen and the accumulation of non-bonding oxygen species containing 2p holes are critical prerequisites for triggering and sustaining the LOMNB pathway in transition metal spinel oxides.These findings may provide valuable insights for the future development of spinel-oxide-based LOM catalysts.展开更多
Efficient and affordable electrocatalysts for reversible oxygen reduction and oxygen evolution reactions(ORR and OER,respectively)are highly sought-after for use in rechargeable metal-air batteries.However,the constru...Efficient and affordable electrocatalysts for reversible oxygen reduction and oxygen evolution reactions(ORR and OER,respectively)are highly sought-after for use in rechargeable metal-air batteries.However,the construction of high-performance electrocatalysts that possess both largely accessible active sites and superior ORR/OER intrinsic activities is challenging.Herein,we report the design and successful preparation of a 3D hierarchically porous graphene framework with interconnected interlayer macropores and in-plane mesopores,enriched with pyridinic-nitrogen-cobalt(pyri-N-Co)active sites,namely,CoFe/3D-NLG.The pyri-N-Co bonding significantly accelerates sluggish oxygen electrocatalysis kinetics,in turn substantially improving the intrinsic ORR/OER activities per active site,while copious interlayer macropores and in-plane mesopores enable ultra-efficient mass transfer throughout the graphene architecture,thus ensuring sufficient exposure of accessible pyri-N-Co active sites to the reagents.Such a robust catalyst structure endows CoFe/3D-NLG with a remarkably enhanced reversible oxygen electrocatalysis performance,with the ORR half-wave potential identical to that of the benchmark Pt/C catalyst,and OER activity far surpassing that of the noble-metal-based RuO2 catalyst.Moreover,when employed as an air electrode for a rechargeable Zn-air battery,CoFe/3D-NLG manifests an exceedingly high open-circuit voltage(1.56 V),high peak power density(213 mW cm^(–2)),ultra-low charge/discharge voltage(0.63 V),and excellent charge/discharge cycling stability,outperforming state-of-the-art noble-metal electrocatalysts.展开更多
Oxygen evolution reaction is one of the key processes in the promising renewable energy technique of electrocatalytic water splitting.Developing high ecient oxygen evolution reaction(OER)catalysts requires determinati...Oxygen evolution reaction is one of the key processes in the promising renewable energy technique of electrocatalytic water splitting.Developing high ecient oxygen evolution reaction(OER)catalysts requires determination of the optimal values of the descriptor parameters.Using spinel CoFe2O4 as the model catalyst,this work demonstrates that irradiation with pulsed UV laser can control the quantity of surface oxygen vacancy and thus modify the OER activity,in a volcano-shape evolution trend.This strategy sheds light on quantita-tively investigation of the relationship between surface cation valence,anion vacancy,and physicochemical properties of transition-metal-based compounds.展开更多
The sluggish reaction kinetics of oxygen evolution reaction(OER)and the high price of noble metal catalysts hinder the wide application of water electrolysis for hydrogen generation.High-entropy oxides(HEOs)with multi...The sluggish reaction kinetics of oxygen evolution reaction(OER)and the high price of noble metal catalysts hinder the wide application of water electrolysis for hydrogen generation.High-entropy oxides(HEOs)with multi-components and high entropy stabilized structures have attracted great research interests due to their efficient and durable performance in electrolytic water splitting reactions.However,the development of efficient HEO electrocatalysts are often hindered by the limited surface exposed active sites because high temperature is usually required to form a high entropy stabilized structure.Herein,a flaky high-entropy oxide with a spinel structure,(FeCoNiCrMn)_(3)O_(4),was synthesized by using the sacrificial layered carbon template in situ prepared by the volatile reaction between ammonium sulfate and molten glucose.High-resolution TEM results show the as-prepared(FeCoNiCrMn)_(3)O_(4) flakes are composed of nanosized HEO particles.The nanosized(FeCoNiCrMn)_(3)O_(4) HEO electrocatalysts exhibit excellent OER activity,with an overpotential of 239 mV at 10 mA/cm^(2) and a Tafel slope of 52.4 mV/dec.The electrocatalyst has excellent stability.Even at a high current density of 100 mA/cm^(2),the activity remains unchanged during the stability test for 24 h.The results here shed a new light in the design and fabrication of highly efficient HEO electrocatalysts.展开更多
The magnetic, conductivity, and dielectric properties have been investigated in single-phase polycrystalline Y0.1Co1.9MnO4. The temperature-dependent magnetisation reveals the ferromagnetic transition in sample at a l...The magnetic, conductivity, and dielectric properties have been investigated in single-phase polycrystalline Y0.1Co1.9MnO4. The temperature-dependent magnetisation reveals the ferromagnetic transition in sample at a low temperature （～186 K）. Magnetisation as a function of field H （M H loop） indicated the weak ferromagnetism of the sample at room temperature. The constant e and dielectric loss tg5 measurements represent a ferroelectric phase transition at a higher temperature （~650 K）, while the conductivity shows an insulator-metallic transition. The ferro- electric hysterisis loops and capacitance voltage measurements confirm the ferroelectric nature of the sample at room temperature. The observed ferromagnetism and ferroelectric nature in this material suggests a potential multiferroic application.展开更多
基金financially National Key R&D Program of China(No.2022YFA1504800)National Natural Science Foundation of China(Grant No.22325405,22372160,22321002)+1 种基金Liaoning Revitalization Talents Program(XLYC1807207)DICP I202104。
文摘The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO_(2)hydrogenation.However,the structure–activity relationship of the reaction remains poorly understood due to challenges in atomic-level structural characterizations and analysis of reaction intermediates.In this study,we prepared two Zn-Al spinel oxide catalysts via coprecipitation(ZnAl-C)and hydrothermal(ZnAl-H)methods,and conducted a comparative investigation in the CO_(2)hydrogenation reaction.Surprisingly,under similar conditions,ZnAl-C exhibited significantly higher selectivity towards methanol and DME compared to ZnAl-H.Comprehensive characterizations using X-ray diffraction(XRD),Raman spectroscopy and electron paramagnetic resonance(EPR)unveiled that ZnAl-C catalyst had abundant ZnO species on its surface,and the interaction between the ZnO species and its ZnAl spinel oxide matrix led to the formation of oxygen vacancies,which are crucial for CO_(2)adsorption and activation.Additionally,state-of-the-art solid-state nuclear magnetic resonance(NMR)techniques,including ex-situ and in-situ NMR analyses,confirmed that the surface ZnO facilitates the formation of unique highly reactive interfacial formate species,which was readily hydrogenated to methanol and DME.These insights elucidate the promotion effects of ZnO on the ZnAl spinel oxide in regulating active sites and reactive intermediates for CO_(2)-to-methanol hydrogenation reaction,which is further evidenced by the significant enhancement in methanol and DME selectivity observed upon loading ZnO onto the ZnAl-H catalyst.These molecular-level mechanism understandings reinforce the idea of optimizing the ZnO-ZnAl interface through tailored synthesis methods to achieve activity-selectivity balance.
文摘Ensuring high electrocatalytic performance simultaneously with low or even no precious-metal usage is still a big challenge for the development of electrocatalysts toward oxygen evolution reaction(OER)in anion exchange membrane water electrolysis.Here,homogeneous high entropy oxide(HEO)film is in-situ fabricated on nickel foam(NF)substrate via magnetron sputtering technology without annealing process in air,which is composed of many spinel-structured(FeCoNiCrMo)_(3)O_(4) grains with an average particle size of 2.5 nm.The resulting HEO film(abbreviated as(FeCoNiCr-Mo)_(3)O_(4))exhibits a superior OER performance with a low OER overpotential of 216 mV at 10 mA cm^(–2) and steadily operates at 100 mA cm^(–2) for 200 h with a decay of only 272μV h^(–1),which is far better than that of commercial IrO_(2) catalyst(290 mV,1090μV h^(–1)).Tetramethylammonium cation(TMA^(+))probe experiment,activation energy analysis and theoretical calculations unveil that the OER on(FeCoNiCrMo)_(3)O_(4) follows an adsorbate evolution mechanism pathway,where the energy barrier of rate-determining step for OER on(FeCoNiCrMo)_(3)O_(4) is substantially lowered.Also,methanol molecular probe experiment suggests that a weakened ^(*)OH bonding on the(FeCoNiCrMo)_(3)O_(4) surface and a rapid deprotonation of ^(*)OH,further enhancing its OER performance.This work provides a feasible solution for designing efficient high entropy oxides electrocatalysts for OER,accelerating the practical process of water electrolysis for H2 production.
基金Financial supports from the National Natural Science Foundation of China(21935006 and 22008102)are gratefully acknowledged.
文摘The exploration of new catalytic hosts is highly important to tackle the sluggish electrochemical kinetics of sulfur redox for achieving high energy density of lithium–sulfur batteries.Herein,for the first time,we present high-entropy oxide(HEO,(Mg_(0.2)Mn_(0.2)Ni_(0.2)Co_(0.2)Zn_(0.2))Fe_(2)O_(4))nanofibers as catalytic host of sulfur.The HEO nanofibers show a synergistic effect among multiple metal cations in spinel structure that enables strong chemical confinement of soluble polysulfides and fast kinetics for polysulfide conversion.Consequently,the S/HEO composite displays the high gravimetric capacity of 1368.7 mAh g^(−1) at 0.1 C rate,excellent rate capability with the discharge capacity of 632.1 mAh g^(−1) at 5 C rate,and desirable cycle stability.Furthermore,the S/HEO composite shows desirable sulfur utilization and good cycle stability under a harsh operating condition of high sulfur loading(4.6 mg cm^(−2))or low electrolyte/sulfur ratio(5μL mg^(−1)).More impressively,the high volumetric capacity of 2627.9 mAh cm^(−3) is achieved simultaneously for the S/HEO composite due to the high tap density of 1.92 g cm^(−3),nearly 2.5 times of the conventional sulfur/carbon composite.Therefore,based on high-entropy oxide materials,this work affords a fresh concept of elevating the gravimetric/volumetric capacities of sulfur cathodes for lithium–sulfur batteries.
基金supported by the National Key Research and Development Program of China (2016YFC0204301)~~
文摘Spinel oxides containing Co and Ni are a promising substitute as a noble metal catalyst for methane combustion.Achieving a complete oxidation of methane under 400°C remains challenging,andhydrothermal 60 h NiClittle impact on activity,especially at high space velocities due to the long hydrothermal time with less absorbed oxygen species and crystal defects.Overall,these results help clarify methane activa-tion mechanisms and aid the development of more efficient low-cost catalysts.
基金supported by the National Programs for NanoKey Project(No.2022YFA1504002)the National Natural Science Foundation of China(Nos.22121005,22020102002,and 21835004)the Fundamental Research Funds for the Central Universities,and Collaborative Innovation Center of Chemical Science and Engineering(Tianjin)。
文摘Spinel oxides,with the formula AB_(2)O_(4)(A and B represent metal ions)perform superior electrocatalytic characteristic when A and B are transition metals like Co,Fe,Mn,etc.Abundant researches have been attached to the structure designments while methods are often energy-intensive and inefficient.Here,we devised a universal strategy to achieve rapid synthesis of nanocrystalline spinel materials with multiple components(Co_(3)O_(4),Mn_(3)O_(4),CoMn_(2)O_(4)and CoFe_(2)O_(4)are as examples),where phase formation is within 15 s.Under the Joule-heating shock,a crack-break process of microcosmic phase transformation is observed by in-situ transmission electron microscopy.The half-wave potential values of Co_(3)O_(4)-JH,Mn_(3)O_(4)-JH,CoMn_(2)O_(4)-JH and CoFe_(2)O_(4)-JH in the electrocatalytic oxygen reduction reaction were 0.77,0.78,0.79 and 0.76,respectively.This suggests that the Joule heating is a fast and efficient method for the preparation of spinel oxide electrocatalysts.
基金Project supported by the National Key R&D Program of China(Grant Nos.2017YFA0302903 and 2019YFA0308603)the National Natural Science Foundation of China(Grant Nos.11774422,11774424,and 11674374)+1 种基金the CAS Interdisciplinary Innovation Team,the Fundamental Research Funds for the Central Universities,Chinathe Research Funds of Renmin University of China(Grant No.19XNLG13).
文摘The magnetic and electronic properties of spinel oxide LiV2O4 have been systematically studied by using the spin-polarized first-principles electronic structure calculations.We find that a series of magnetic states,in which the ferromagnetic(FM)V4 tetrahedra are linked together through the corner-sharing antiferromagnetic(AFM)V4 tetrahedra,possess degenerate energies lower than those of other spin configurations.The large number of these energetically degenerated states being the magnetic ground state give rise to strong magnetic frustration as well as large magnetic entropy in LiV2O4.The corresponding band structure and density of states of such a typical magnetic state in this series,i.e.,the ditetrahedron(DT)AFM state,demonstrate that LiV2O4 is in the vicinity of a metal-insulator transition.Further analysis suggests that the t2g and eg orbitals of the V atoms play different roles in the magnetic exchange interactions.Our calculations are consistent with previous experimental measurements and shed light on understanding the exotic magnetism and the heavy-fermion behavior of LiV2O4.
基金supported by the National Natural Science Foundation of China(Nos.22371268,52025101,U23A20676,and 52400103)Fundamental Research Funds for the Central Universities(No.WK2060000016 and WK2060000069)+6 种基金Anhui Province for Outstanding Youth(No.2208085J09)Collaborative Innovation Program of Hefei Science Center,CAS(No.2022HSC-CIP020)Anhui Development and Reform Commission(No.AHZDCYCX-2SDT2023-07)Youth Innovation Promotion Association of the Chinese Academy of Science(No.2018494)USTC Tang Scholar,Suzhou Carbon Peaking and Carbon Neutrality Science and Technology Support Key Special Funding(No.ST202217)the China Postdoctoral Science Foundation(Nos.2023M743380 and 2024T170886)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation project(No.GZC20232544).
文摘Coordinatively unsaturated metal sites(CUS)located at tetrahedral(T_(d))in spinel structure are highly effective for activating peroxymonosulfate(PMS)in Fenton-like catalysis.However,the conventional T_(d)-octahedral(Oh)connectivity in spinel structures restricts internal electron transfer,limiting the regeneration of low-valent metals and creating a trade-off between catalytic activity and long-term stability.Herein,we address this challenge by engineering a novel T_(d)-T_(d) connectivity in amorphous CoFeO_(x) nanosheets(a-CoFeO_(x) NSs).Soft X-ray absorption spectroscopy(sXAS)measurements reveal that in a-CoFeO_(x) nanosheets,the ligand field symmetry around Co atoms is dominated by a T_(d) coordination,in contrast to the O_(h) coordination in the crystalline state,which introduces T_(d)-T_(d) connection.Density functional theory(DFT)calculations confirm that the T_(d)-T_(d) connection in a-CoFeO_(x) structure significantly strengthens electron transfer to activate PMS,which exhibited a first-order kinetic constant(k_(obs))of 0.27 min^(-1) for sulfamethoxazole(SMX)removal with high stability.This study reveals that the phase-engineered CUS can further enhance catalytic activity and provides a simple and scalable strategy for optimizing spinel-type catalysts.
基金supported by the National Natural Science Foundation of China(21671106,22102073,and 62288102)the Priority Academic Program Development of Jiangsu Higher Education Institutions,the funding from Minjiang Scholars Award Program(2023)+1 种基金the Start-Up Fund for High-Leveled Talents from Fujian Normal University(Y0720316K13)the opening research foundations of the State Key Laboratory of Coordination Chemistry,Nanjing National Laboratory of Solid State Microstructures,Nanjing University.We thank the BL14W1 beamlines for XAFS tests at the Shanghai Synchrotron Radiation Facility(SSRF)(Shanghai,China).
文摘Overall seawater splitting driven by regenerable electricity is an ideal pathway formass production of green hydrogen.Nonetheless,its anodic oxygen evolution half-reaction(OER)confronts sluggish kinetics,competitive chlorine evolution,and chloride corrosion or poisoning problems,needing to develop high-efficient and robust electrocatalysts toward those challenges.Herein,novel defect-rich single-phase(NiCoMnCrFe)_(3)O_(4) high-entropy spinel oxide(HEO)is fabricated by low-temperature annealing of highentropy layered double hydroxide precursor.Due to the presence of abundant defects,unique“cocktail”effect,and efficient electronic structure regulation,such(NiCoMnCrFe)_(3)O_(4) can deliver 500 mA cm^(−2) current density at the overpotentials of 268/384 mV in alkaline freshwater/seawater,outperforming its counterparts,commercial IrO_(2),and most reported OER catalysts.Moreover,it manifests exceptional OER durability and anticorrosion capability.Theoretical calculations reveal that the eg occupancies of surface Mn atoms are closer to 1.0,which may be the activity origin of such HEO.Importantly,the constructed(NiCoMnCrFe)_(3)O_(4)||Pt/C electrolyzer only requires 1.57 V cell voltage for driving overall seawater splitting to reach 500 mA cm^(−2) current under real industrial conditions.This work may spur the development of advanced OER electrocatalysts by combining entropy and defect engineering and accelerate their applications in seawater splitting,metal–air batteries,or marine biomass electrocatalytic conversion fields.
文摘A robust oxygen‐related electrocatalyst,composed of spinel iron‐cobalt oxide and nitrogen‐dopedordered mesoporous carbon(NOMC),was developed for rechargeable metal‐air batteries.Electrochemicaltests revealed that the optimal catalyst Fe_(0.5)Co/NOMC exhibits superior activity with ahalf‐wave potential of 0.89 V(vs.reversible hydrogen electrode)for the oxygen reduction reactionand an overpotential of 0.31 V at 10 mA cm^(−2)for the oxygen evolution reaction.For demonstration,the catalyst was used in the assembly of a rechargeable zinc‐air battery,which exhibited an exceptionallyhigh energy density of 820 Wh kg−1 at 100 mA cm^(−2),a high power density of 153 mW cm^(−2)at1.0 V,and superior cycling stability up to 432 cycles(144 h)under ambient air.
基金supported by National Natural Science Foundation of China(Nos.22272047,21905088,22102155)the China Postdoctoral Science Foundation(Nos.2021M692909,2022T150587)the Provincial Natural Science Foundation of Hunan(No.2022JJ10006).
文摘Electrocatalytic reduction reactions play a crucial role in electrochemical energy conversion and storage technology,which are emerging technologies to ameliorate environmental problems.Spinel oxides are widely explored in electrocatalytic oxidation reactions but have a poor intrinsic ability to reduction reactions,making their electrocatalytic ability less effective.To improve this,defect engineering is a valuable method for regulating the electronic structure and coordination environment.Herein,this manuscript discusses the use of defect spinel oxides in electrocatalytic reduction reactions,including the different types of defects,construction methods,and characterization techniques.It also outlines the various applications of defect spinel oxides in different electrocatalytic reduction reactions.Finally,it goes over the challenges and future outlooks for defect spinels.This review aims to thoroughly explain how defect spinels work in electrocatalytic reduction reactions and serve as a helpful guide for creating effective electrocatalysts.
基金the financial support by the National Natural Science Foundation of China(NSFC,grant nos.21905288 and 51904288)Zhejiang Provincial Natural Science Foundation(LZ21B030001)+3 种基金K.C.Wong Education Foundation(GJTD-2019-13)Ningbo major special projects of the Plan“Science and Technology Innovation 2025”(grant nos.2018B10056 and 2019B10046)Ningbo 3315 ProgramYongjiang Talent Introduction Program(no.2021A-115-G)
文摘Developing stable and efficient nonprecious-metal-based oxygen evolution catalysts in the neutral electrolyte is a challenging but essential goal for various electrochemical systems.Particularly,cobalt-based spinels have drawn a considerable amount of attention but most of them operate in alkali solutions.However,the frequently studied Co-Fe spinel system never exhibits appreciable stability in nonbasic conditions,not to mention attract further investigation on its key structural motif and transition states for activity loss.Herein,we report exceptional stable Co-Fe spinel oxygen evolution catalysts(~30%Fe is optimal)in a neutral electrolyte,owing to its unique metal ion arrangements in the crystal lattice.The introduced iron content enters both the octahedral and tetrahedral sites of the spinel as Fe^(2+)and Fe^(3+)(with Co ions having mixed distribution as well).Combining density functional theory calculations,we find that the introduction of Fe to Co_(3)O_(4)lowers the covalency of metal-oxygen bonds and can help suppress the oxidation of Co^(2+/3+)and 0^(2-).It implies that the Co-Fe spinel will have minor surface reconstruction and less lattice oxygen loss during the oxygen evolution reaction process in comparison with Co_(3)O_(4)and hence show much better stability.These findings suggest that there is still much chance for the spinel structures,especially using reasonable sublattices engineering via multimetal doping to develop advanced oxygen evolution catalysts.
基金supported by the National Natural Science Foundation of China(Nos.22206146,22006079,and U21A20524)the Fundamental Research Funds for the Central Universities,the Youth Innovation Promotion Association of Chinese Academy of Sciences,the Fundamental Research Program of Shanxi Province(No.202103021223280)+1 种基金the Special Fund for Science and Technology Innovation Teams of Shanxi Province(No.202204051002026)the Natural Science Foundation of Shandong Province(No.ZR2021QB133).
文摘Owing to the complexity of multicomponent gases,developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging.The spinel MMn_(2)O_(4)(M=Co,Ni,or Cu)catalysts were successfully synthesized via the sol–gel method and tested for their catalytic performance for simultaneous degradation of benzene and toluene.The CuMn_(2)O_(4)sample exhibited the best catalytic performance,the conversion of benzene reached 100%at 350℃,and toluene conversion reached 100%at 250℃.XRD,N_(2)adsorption-desorption,HRTEM-EDS,ED-XRF,Raman spectroscopy,H_(2)-TPR,NH_(3)-TPD,O_(2)-TPD and XPS were used to characterize the physical and chemical properties of MMn_(2)O_(4)catalysts.The excellent redox properties,high concentration of surface Mn4+,and adsorption of oxygen species over the CuMn_(2)O_(4)sample facilitated the simultaneous and efficient removal of benzene and toluene.Additionally,in situ DRIFTS illustrated the intermediate species and reaction mechanism for the synergetic catalytic oxidation of benzene and toluene.Notably,as an effective catalytic material,spinel oxide exhibited excellent synergistic degradation performance for benzene and toluene,providing some insight for the development of efficient multicomponent VOC catalysts.
基金Project supported the by State Key Laboratory of Internal Combustion Engines of Tianjin University,ChinaProject(51507077)supported by the National Natural Science Foundation of China+1 种基金Project(15KJB470005)supported by the Natural Science Research of Higher Education Institutions of Jiangsu Province,ChinaProjects(YKJ201308,QKJB201401)supported by Nanjing Institute of Technology,China
文摘The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto the nickel-based superalloy substrate by high velocity oxygen fuel（HVOF）.It suggests that the TGO usually consists of a great number of chromium oxides,cobalt oxides and spinel oxides besides alumina during the initial period of the high temperature oxidation if the specimens are not subjected to the appropriate vacuum pre-oxidation process.Furthermore,the amount of alumina is strongly dependent on the partial pressure of oxygen;while the CoCr2O4 spinel oxides are usually formed under the conditions of higher partial pressure of oxygen during the initial period and the lower partial pressure of oxygen during the subsequent period of the isothermal oxidation.After the appropriate vacuum pre-oxidation process,the TGO is mainly composed of alumina that contains lower Y element,while alumina that contains higher Y element sporadically distributes,and the spinel oxides cannot be found.After a longer period of the isothermal oxidation,a small amount of porous CoCr2O4 and the chrome oxide sporadically distribute near the continuous alumina.Additionally,after the appropriate vacuum pre-oxidation process,the TGO growth rate is relatively slow.
基金the National Natural Science Foundation of China(U21A20286,22206054 and 21805069)Natural Science Foundation of Hubei(2021CFB094)the Fundamental Research Funds for the Central China Normal University(CCNU)for financial support。
文摘Spinel cobalt oxide(Co_(3)O_(4)),consisting of tetrahedral Co^(2+)(CoTd)and octahedral Co^(3+)(CoOh),is considered as promising earth-abundant electrocatalyst for chlorine evolution reaction(CER).Identifying the catalytic contribution of geometric Co site in the electrocatalytic CER plays a pivotal role to precisely modulate electronic configuration of active Co sites to boost CER.Herein,combining density functional theory calculations and experiment results assisted with operando analysis,we found that the Co_(Oh) site acts as the main active site for CER in spinel Co_(3)O_(4),which shows better Cl^(-)adsorption and more moderate intermediate adsorption toward CER than CoTd site,and does not undergo redox transition under CER condition at applied potentials.Guided by above findings,the oxygen vacancies were further introduced into the Co_(3)O_(4) to precisely manipulate the electronic configuration of Co_(Oh) to boost Cl^(-)adsorption and optimize the reaction path of CER and thus to enhance the intrinsic CER activity significantly.Our work figures out the importance of geometric configuration dependent CER activity,shedding light on the rational design of advanced electrocatalysts from geometric configuration optimization at the atomic level.
基金supported by the Ministry of Science and Technology(No.2009CB623506)the National Natural Science Foundation of China(No.21173050)Shanghai Leading Academic Discipline Project(No.B108)
文摘A series of Co/Mg-Al oxide samples, CoMgAl-x （x = （Mg ＋ Co）]AI molar ratio of 1-5）, were prepared by the self-combustion method followed by H2 reduction. The catalytic performance and stability of the samples were studied in dry reforming ofCH4. XRD and H2-TPR characterization results showed that the reduced CoMgAl-x samples mainly consisted of solid solution and spinel phases with cobalt particles. The spinel phases contained COB04 and ConMgl-nAl204 （0 〈 n 〈 1 ） varying with the （Mg ＋ Co）/AI ratio, The effect of （Mg ＋ Co）/A1 molar ratio on the catalytic behavior was investigated in detail and CoMgAI-3 exhibited the highest catalytic activity and stability among the catalysts studied.
文摘The oxygen evolution reaction(OER)serves as a fundamental half–reaction in the electrolysis of water for hydrogen production,which is restricted by the sluggish OER reaction kinetics and unable to be practically applied.The traditional lattice oxygen oxidation mechanism(LOM)offers an advantageous route by circumventing the formation of M-OOH^(*)in the adsorption evolution mechanism(AEM),thus enhancing the reaction kinetics of the OER but resulting in possible structural destabilization due to the decreased M–O bond order.Fortunately,the asymmetry of tetrahedral and octahedral sites in transition metal spinel oxides permits the existence of non-bonding oxygen,which could be activated by rational band structure design for direct O-O coupling,where the M–O bond maintains its initial bond order.Here,non-bonding oxygen was introduced into NiFe_(2)O_(4)via annealing in an oxygen-deficient atmosphere.Then,in-situ grown sulfate species on octahedral nickel sites significantly improved the reactivity of the non-bonding oxygen electrons,thereby facilitating the transformation of the redox center from metal to oxygen.LOM based on non-bonding oxygen(LOMNB)was successfully activated within NiFe_(2)O_(4),exhibiting a low overpotential of 206 mV to achieve a current density of 10 mA cm^(-2)and excellent durability of stable operation for over 150 h.Additionally,catalysts featuring varying band structures were synthesized for comparative analysis,and it was found that the reversible redox processes of non-bonding oxygen and the accumulation of non-bonding oxygen species containing 2p holes are critical prerequisites for triggering and sustaining the LOMNB pathway in transition metal spinel oxides.These findings may provide valuable insights for the future development of spinel-oxide-based LOM catalysts.
文摘Efficient and affordable electrocatalysts for reversible oxygen reduction and oxygen evolution reactions(ORR and OER,respectively)are highly sought-after for use in rechargeable metal-air batteries.However,the construction of high-performance electrocatalysts that possess both largely accessible active sites and superior ORR/OER intrinsic activities is challenging.Herein,we report the design and successful preparation of a 3D hierarchically porous graphene framework with interconnected interlayer macropores and in-plane mesopores,enriched with pyridinic-nitrogen-cobalt(pyri-N-Co)active sites,namely,CoFe/3D-NLG.The pyri-N-Co bonding significantly accelerates sluggish oxygen electrocatalysis kinetics,in turn substantially improving the intrinsic ORR/OER activities per active site,while copious interlayer macropores and in-plane mesopores enable ultra-efficient mass transfer throughout the graphene architecture,thus ensuring sufficient exposure of accessible pyri-N-Co active sites to the reagents.Such a robust catalyst structure endows CoFe/3D-NLG with a remarkably enhanced reversible oxygen electrocatalysis performance,with the ORR half-wave potential identical to that of the benchmark Pt/C catalyst,and OER activity far surpassing that of the noble-metal-based RuO2 catalyst.Moreover,when employed as an air electrode for a rechargeable Zn-air battery,CoFe/3D-NLG manifests an exceedingly high open-circuit voltage(1.56 V),high peak power density(213 mW cm^(–2)),ultra-low charge/discharge voltage(0.63 V),and excellent charge/discharge cycling stability,outperforming state-of-the-art noble-metal electrocatalysts.
基金supported by the National Key Basic Research Program of China (2016YFA0300102)the National Natural Science Foundation of China (No.11675179,No.U1532142,and No.11434009)the Fundamental Research Funds for the Central Universities
文摘Oxygen evolution reaction is one of the key processes in the promising renewable energy technique of electrocatalytic water splitting.Developing high ecient oxygen evolution reaction(OER)catalysts requires determination of the optimal values of the descriptor parameters.Using spinel CoFe2O4 as the model catalyst,this work demonstrates that irradiation with pulsed UV laser can control the quantity of surface oxygen vacancy and thus modify the OER activity,in a volcano-shape evolution trend.This strategy sheds light on quantita-tively investigation of the relationship between surface cation valence,anion vacancy,and physicochemical properties of transition-metal-based compounds.
基金The authors acknowledge support from the National Natural Science Foundation of China(NSFC)(Grant No.22109147 and 52371144)Institute of Materials,China Academy of Engineering Physics(No.TP01201701).
文摘The sluggish reaction kinetics of oxygen evolution reaction(OER)and the high price of noble metal catalysts hinder the wide application of water electrolysis for hydrogen generation.High-entropy oxides(HEOs)with multi-components and high entropy stabilized structures have attracted great research interests due to their efficient and durable performance in electrolytic water splitting reactions.However,the development of efficient HEO electrocatalysts are often hindered by the limited surface exposed active sites because high temperature is usually required to form a high entropy stabilized structure.Herein,a flaky high-entropy oxide with a spinel structure,(FeCoNiCrMn)_(3)O_(4),was synthesized by using the sacrificial layered carbon template in situ prepared by the volatile reaction between ammonium sulfate and molten glucose.High-resolution TEM results show the as-prepared(FeCoNiCrMn)_(3)O_(4) flakes are composed of nanosized HEO particles.The nanosized(FeCoNiCrMn)_(3)O_(4) HEO electrocatalysts exhibit excellent OER activity,with an overpotential of 239 mV at 10 mA/cm^(2) and a Tafel slope of 52.4 mV/dec.The electrocatalyst has excellent stability.Even at a high current density of 100 mA/cm^(2),the activity remains unchanged during the stability test for 24 h.The results here shed a new light in the design and fabrication of highly efficient HEO electrocatalysts.
基金supported by the Doctorial Start-up Fund of Guizhou University of China (Grant No. 2006/Z065020)
文摘The magnetic, conductivity, and dielectric properties have been investigated in single-phase polycrystalline Y0.1Co1.9MnO4. The temperature-dependent magnetisation reveals the ferromagnetic transition in sample at a low temperature （～186 K）. Magnetisation as a function of field H （M H loop） indicated the weak ferromagnetism of the sample at room temperature. The constant e and dielectric loss tg5 measurements represent a ferroelectric phase transition at a higher temperature （~650 K）, while the conductivity shows an insulator-metallic transition. The ferro- electric hysterisis loops and capacitance voltage measurements confirm the ferroelectric nature of the sample at room temperature. The observed ferromagnetism and ferroelectric nature in this material suggests a potential multiferroic application.
