Single atom catalyst is of great importance for the oxygen reduction reaction(ORR).However,facile preparation of single atom catalyst without using well-designed precursors or labor-intensive acid leaching remains an ...Single atom catalyst is of great importance for the oxygen reduction reaction(ORR).However,facile preparation of single atom catalyst without using well-designed precursors or labor-intensive acid leaching remains an urgent challenge.Herein,a simple pyrolysis of Fe3+-loaded mesoporous phenolic resin(mPF)-melamine precursor is used to prepare the single atom iron-anchored N-doped mesoporous graphitic carbon nanospheres(Fe/N-MGN).Investigation of the synthesis reveals the appropriate Fe-assisted catalysis effect and mPF template effect,which not only spurs the highly graphitic porous framework of Fe/N-MGN with plentiful pyridinic N/graphitic N,but also assures the dispersed single atom Fe anchoring without elaborated procedures.As a result,the as-synthesized Fe/N-MGN demonstrates high catalytic activity,good durability and excellent methanol tolerance for ORR.This work promises a facile method to regulate the graphitic carbon growth and single atom Fe loading for the highly efficient electrocatalysis.展开更多
All-solid-state lithium batteries(ASSLBs)based on sulfide electrolytes promise next-generation energy storage with high energy density and safety.However,the sulfide electrolytes suffer from phase instability and slug...All-solid-state lithium batteries(ASSLBs)based on sulfide electrolytes promise next-generation energy storage with high energy density and safety.However,the sulfide electrolytes suffer from phase instability and sluggish interfacial charge transport when pairing with layered oxide cathodes at high voltages.Herein,a simple and efficient strategy is proposed using two-dimensional Ti_(3)C_(2)T_(x)MXene as starting material to in-situ construct a 15 nm Li_(2)TiO_(3) layer on a typical oxide cathode,LiCoO_(2).The in-situ transformation of Ti_(3)C_(2)T_(x)into Li_(2)TiO_(3) layer occurs at a low temperature of 500℃,avoiding the phase deterioration of LiCoO_(2).The thin Li_(2)TiO_(3) layer is Li^(+)conducting and electrochemically stable,thereby preventing the interfacial decomposition of sulfide electrolytes induced by LiCoO_(2) at high voltages and facilitating Li+transport at the interface.Moreover,Li_(2)TiO_(3) can stabilize the layer structure of LiCoO_(2) at high voltages.Consequently,the sulfide-based ASSLB using LiCoO_(2)@Li_(2)TiO_(3) cathode can operate stably at a high voltage of up to 4.5 V(vs.Li+/Li),delivering an outstanding initial specific discharge capacity of 138.8 m Ah/g with a high capacity retention of 86.2% after 100 cycles at 0.2 C.The in-situ transformation strategy may also apply to other MXenes,offering a general approach for constructing other advanced lithiated coatings for oxide cathodes.展开更多
The development of high-performance aqueous batteries calls for an in-depth knowledge of their chargedischarge redox and failure mechanism,as well as a systematic understanding of the dynamic evolution of microstructu...The development of high-performance aqueous batteries calls for an in-depth knowledge of their chargedischarge redox and failure mechanism,as well as a systematic understanding of the dynamic evolution of microstructure,phase composition,chemical composition,and local chemical environment of the materials for battery.In-situ characterization technology is expected to understand and reveal the problems faced by aqueous rechargeable batteries,such as the dissolution of electrode materials,the growth of metal negative electrode dendrites,passivation,corrosion,side reactions and a series of problems.Based on this,typical in-situ characterization techniques and their basic mechanisms are summarized,including in-situ optical visualization,in-situ microscopy techniques(in-situ scanning electron microscopy(SEM),in-situ transmission electron microscopy(TEM)),in-situ X-ray techniques(in-situ X-ray diffraction(XRD),in-situ X-ray photoelectron spectroscopy(XPS),in-situ near-edge structural X-ray absorption spectroscopy(XANES)),and in-situ spectroscopy techniques(in-situ Raman spectroscopy,in-situ Fourier transform infrared(FTIR)).Moreover,some emerging techniques concerning aqueous battery research,especially gas evolution and materials dissolution issues,such as in-situ electrochemical quartz crystal microbalance(EQCM).in-situ fiber-optic sensing,in-situ gas chromatography(GC) are introduced.At last,the applications of advanced in-situ characterizations in future research of aqueous batteries are emphasized and discussed,along with some of the remaining challenges and possible solutions.展开更多
Bi-based metal-organic frameworks(Bi-MOFs)as efficient catalysts for the CO_(2)electroreduction reaction(CRR)have been extensively investigated.It has been established that Bi-MOFs usually undergo in-situ transformati...Bi-based metal-organic frameworks(Bi-MOFs)as efficient catalysts for the CO_(2)electroreduction reaction(CRR)have been extensively investigated.It has been established that Bi-MOFs usually undergo in-situ transformation during the CRR,ultimately converting into Bi nanostructures.However,the effect of the MOF precursors on the structure of the derived Bi catalysts and consequently on their electrocatalytic properties has not been clearly elucidated.In this work,we prepared four variants of a novel Bi-MOF with different morphologies and dimensions,and explored the effects of the precursors on the resulting Bi catalysts and their CRR performance.A precursor-dependent in-situ transformation and its profound impact on tuning the CO_(2)-formate FE towards~100%have been revealed.Among the four examined variants,Bi-MOF with nanocube-like morphology(BiMOF-NC)is transformed into thin and flat Bi nanosheets capable of successfully enveloping the fibers of carbon paper(working electrode),while the other three variants with increased size and dodecahedral/octahedral geometry have been transformed into Bi nanoflowers,exposing a fair portion of the carbon fibers in the working electrode.Furthermore,the transformation rate was found to be dependent on the precursors and BiMOF-NC exhibited the highest rate of reconstruction compared with other samples.Consequently,the Bi catalyst derived from BiMOF-NC delivered a selectivity for the formate product of nearly 100%at-1.2 V(vs.reversible hydrogen electrode(RHE))and of over 95%in a wide potential range due to efficient suppression of the competing hydrogen evolution reaction(HER)over carbon fibers.The in-situ transformed BiMOFNC also demonstrated equivalently high formate selectivity at large current densities(≥100 mA cm^(-2))in flow cell reactors as that in H-type reactors,underscoring its potential for industrial applications.This work highlights the necessity of finely tuning the structural features of MOF precursors to achieve optimized electrocatalytic performance.展开更多
基金This study was supported by the National Natural Science Foundation of China(Nos.21675032 and 81861138040)the Fundamental Research Funds for the Central Universities and DHU Distinguished Young Professor Program.We appreciate the kind help from Dr.Li Wang in Center of Analysis and Measurement,Fudan University for preparation of complicated samples and elemental analysis.
文摘Single atom catalyst is of great importance for the oxygen reduction reaction(ORR).However,facile preparation of single atom catalyst without using well-designed precursors or labor-intensive acid leaching remains an urgent challenge.Herein,a simple pyrolysis of Fe3+-loaded mesoporous phenolic resin(mPF)-melamine precursor is used to prepare the single atom iron-anchored N-doped mesoporous graphitic carbon nanospheres(Fe/N-MGN).Investigation of the synthesis reveals the appropriate Fe-assisted catalysis effect and mPF template effect,which not only spurs the highly graphitic porous framework of Fe/N-MGN with plentiful pyridinic N/graphitic N,but also assures the dispersed single atom Fe anchoring without elaborated procedures.As a result,the as-synthesized Fe/N-MGN demonstrates high catalytic activity,good durability and excellent methanol tolerance for ORR.This work promises a facile method to regulate the graphitic carbon growth and single atom Fe loading for the highly efficient electrocatalysis.
基金the financial support from the National Natural Science Foundation of China(Nos.52201242,52250010)Natural Science Foundation of Jiangsu Province(Nos.BK20200386,BK20200186)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)the Fundamental Research Funds for the Central Universities(No.2242022R40018)。
文摘All-solid-state lithium batteries(ASSLBs)based on sulfide electrolytes promise next-generation energy storage with high energy density and safety.However,the sulfide electrolytes suffer from phase instability and sluggish interfacial charge transport when pairing with layered oxide cathodes at high voltages.Herein,a simple and efficient strategy is proposed using two-dimensional Ti_(3)C_(2)T_(x)MXene as starting material to in-situ construct a 15 nm Li_(2)TiO_(3) layer on a typical oxide cathode,LiCoO_(2).The in-situ transformation of Ti_(3)C_(2)T_(x)into Li_(2)TiO_(3) layer occurs at a low temperature of 500℃,avoiding the phase deterioration of LiCoO_(2).The thin Li_(2)TiO_(3) layer is Li^(+)conducting and electrochemically stable,thereby preventing the interfacial decomposition of sulfide electrolytes induced by LiCoO_(2) at high voltages and facilitating Li+transport at the interface.Moreover,Li_(2)TiO_(3) can stabilize the layer structure of LiCoO_(2) at high voltages.Consequently,the sulfide-based ASSLB using LiCoO_(2)@Li_(2)TiO_(3) cathode can operate stably at a high voltage of up to 4.5 V(vs.Li+/Li),delivering an outstanding initial specific discharge capacity of 138.8 m Ah/g with a high capacity retention of 86.2% after 100 cycles at 0.2 C.The in-situ transformation strategy may also apply to other MXenes,offering a general approach for constructing other advanced lithiated coatings for oxide cathodes.
基金financially supported by the National Key Research and Development Program of China (No.2022YFB2404300)the Key R&D Program of Hubei Province(No.2022BAA028)。
文摘The development of high-performance aqueous batteries calls for an in-depth knowledge of their chargedischarge redox and failure mechanism,as well as a systematic understanding of the dynamic evolution of microstructure,phase composition,chemical composition,and local chemical environment of the materials for battery.In-situ characterization technology is expected to understand and reveal the problems faced by aqueous rechargeable batteries,such as the dissolution of electrode materials,the growth of metal negative electrode dendrites,passivation,corrosion,side reactions and a series of problems.Based on this,typical in-situ characterization techniques and their basic mechanisms are summarized,including in-situ optical visualization,in-situ microscopy techniques(in-situ scanning electron microscopy(SEM),in-situ transmission electron microscopy(TEM)),in-situ X-ray techniques(in-situ X-ray diffraction(XRD),in-situ X-ray photoelectron spectroscopy(XPS),in-situ near-edge structural X-ray absorption spectroscopy(XANES)),and in-situ spectroscopy techniques(in-situ Raman spectroscopy,in-situ Fourier transform infrared(FTIR)).Moreover,some emerging techniques concerning aqueous battery research,especially gas evolution and materials dissolution issues,such as in-situ electrochemical quartz crystal microbalance(EQCM).in-situ fiber-optic sensing,in-situ gas chromatography(GC) are introduced.At last,the applications of advanced in-situ characterizations in future research of aqueous batteries are emphasized and discussed,along with some of the remaining challenges and possible solutions.
基金financially supported by the National Key R&D Program of China(2021YFA1600800)the National Natural Science Foundation of China(22022508)。
文摘Bi-based metal-organic frameworks(Bi-MOFs)as efficient catalysts for the CO_(2)electroreduction reaction(CRR)have been extensively investigated.It has been established that Bi-MOFs usually undergo in-situ transformation during the CRR,ultimately converting into Bi nanostructures.However,the effect of the MOF precursors on the structure of the derived Bi catalysts and consequently on their electrocatalytic properties has not been clearly elucidated.In this work,we prepared four variants of a novel Bi-MOF with different morphologies and dimensions,and explored the effects of the precursors on the resulting Bi catalysts and their CRR performance.A precursor-dependent in-situ transformation and its profound impact on tuning the CO_(2)-formate FE towards~100%have been revealed.Among the four examined variants,Bi-MOF with nanocube-like morphology(BiMOF-NC)is transformed into thin and flat Bi nanosheets capable of successfully enveloping the fibers of carbon paper(working electrode),while the other three variants with increased size and dodecahedral/octahedral geometry have been transformed into Bi nanoflowers,exposing a fair portion of the carbon fibers in the working electrode.Furthermore,the transformation rate was found to be dependent on the precursors and BiMOF-NC exhibited the highest rate of reconstruction compared with other samples.Consequently,the Bi catalyst derived from BiMOF-NC delivered a selectivity for the formate product of nearly 100%at-1.2 V(vs.reversible hydrogen electrode(RHE))and of over 95%in a wide potential range due to efficient suppression of the competing hydrogen evolution reaction(HER)over carbon fibers.The in-situ transformed BiMOFNC also demonstrated equivalently high formate selectivity at large current densities(≥100 mA cm^(-2))in flow cell reactors as that in H-type reactors,underscoring its potential for industrial applications.This work highlights the necessity of finely tuning the structural features of MOF precursors to achieve optimized electrocatalytic performance.
