The persistent stability of ruthenium dioxide(RuO_(2))in acidic oxygen evolution reactions(OER)is compromised by the involvement of lattice oxygen(LO)and metal dissolution during the OER process.Heteroatom doping has ...The persistent stability of ruthenium dioxide(RuO_(2))in acidic oxygen evolution reactions(OER)is compromised by the involvement of lattice oxygen(LO)and metal dissolution during the OER process.Heteroatom doping has been recognized as a viable strategy to foster the stability of RuO_(2)for acidic OER applications.This study presented an ion that does not readily gain or lose electrons,Ba^(2+),into RuO_(2)(Ba-RuO_(2))nanosheet(NS)catalyst that increased the number of exposed active sites,achieving a current density of 10 mA/cm^(2)with an overpotential of only 229 mV and sustaining this output for over 250 h.According to density functional theory(DFT)and X-ray absorption spectroscopy,Ba doping resulted in a longer Ru-O bond length,which in turn diminished the covalency of the bond.This alteration curtailed the involvement of LO and the dissolution of ruthenium(Ru),thereby markedly improving the durability of the catalyst over extended periods.Additionally,attenuated total reflectance-surface enhanced infrared absorption spectroscopy analysis substantiated that the OER mechanism shifted from a LO-mediated pathway to an adsorbate evolution pathway due to Ba doping,thereby circumventing Ru over-oxidation and further enhancing the stability of RuO_(2).Furthermore,DFT findings uncovered that Ba doping optimizes the adsorption energy of intermediates,thus enhancing the OER activity in acidic environments.This study offers a potent strategy to guide future developments on Ru-based oxide catalysts'stability in an acidic environment.展开更多
Ruthenium dioxide(RuO_(2))is one of the most promising acidic oxygen evolution reaction(OER)catalysts to replace the expensive and prevalent iridium(Ir)-based materials.However,the lattice oxygen oxidation induced Ru ...Ruthenium dioxide(RuO_(2))is one of the most promising acidic oxygen evolution reaction(OER)catalysts to replace the expensive and prevalent iridium(Ir)-based materials.However,the lattice oxygen oxidation induced Ru dissolution during OER compromises the activity and stability.Amorphous materials have been identified as a viable strategy to promote the stability of RuO_(2)in acidic OER applications.This study reported a nanoporous amorphous-rich RuMnO_(x)(A-RuMnO_(x))aerogel for efficient and stable acidic OER.Compared with highly crystalline RuMnO_(x),the weakened Ru–O covalency of A-RuMnO_(x)by forming amorphous structure is favorable to inhibiting the oxidation of lattice oxygen.Meanwhile,this also optimizes the electronic structure of Ru sites from overoxidation and reduces the reaction energy barrier of the rate-determining step.As a result,A-RuMnO_(x)aerogel exhibits an ultra-low overpotential of 145 mV at 10 mA cm^(-2)and durability exceeding 100 h,as well as high mass activity up to 153 mA mg^(-1)_(Ru)at 1.5 V vs.reversible hydrogen electrode(RHE).This work provides valuable guidance for preparing highly active and stable Ru-based catalysts for acidic OER.展开更多
The copper-based electrocatalysts feature attractive potentials of converting CO_(2)into multi-carbon(C_(2+))products,while the instability of Cu-O often induces the reduction of Cu^(+)/Cu^(0) catalytic sites at the c...The copper-based electrocatalysts feature attractive potentials of converting CO_(2)into multi-carbon(C_(2+))products,while the instability of Cu-O often induces the reduction of Cu^(+)/Cu^(0) catalytic sites at the cathode and refrains the capability of stable electrolysis especially at high powers.In this work,we developed an Erbium(Er)oxide-modified Cu(Er-O-Cu)catalyst with enhanced covalency of Cu-O and more stable active sites.The f-p-d coupling strengthens the covalency of Cu-O,and the stability of Cu^(+)sites under electroreduction condition is critical for promoting the C-C coupling and improving the C_(2+)product selectivity.As a result,the Er-O-Cu sites exhibited a high Faradaic efficiency of C_(2+)products(FEC_(2+))of 86%at 2200 mA cm^(-2),and a peak partial current density of|j_(C2+)|of 1900 mA cm^(-2),comparable to the best reported values for the CO_(2)-to-C_(2+)electroreduction.The CO_(2)electrolysis by the Er-O-Cu sites was further scaled up to 100 cm^(2)to achieve high-power(~200 W)electrolysis with ethylene production rate of 16 mL min^(-1).展开更多
Transition metal oxides have garnered significant attention as electrocatalysts for the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER).However,their sluggish reaction kinetics and poor stability ...Transition metal oxides have garnered significant attention as electrocatalysts for the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER).However,their sluggish reaction kinetics and poor stability hinder commercial applications.Herein,we report the synthesis of a bimetallic cobalt manganese oxide,Co_(0.99)Mn_(2.01)O_(4)(CMO),synthesized via a hydrothermal technique,which serves as a highly efficient bifunctional ORR/OER electrocatalyst owing to its impressive halfwave potential of 0.767 V and low overpotential of 1.677 V at 10 mA cm^(-2).Theoretical calculations revealed that the d-band centers of Co 3d and Mn 3d in CMO,located at tetrahedral and octahedral sites,are positioned near the Fermi level,facilitating the adsorption of electrocatalytic intermediates.Furthermore,the distance between the Co 3d and O 2p band centers in CMO is smaller than that in Co_(3)O_(4),and the distance between the Mn 3d and O 2p band centers in CMO is shorter than that in Mn_(2)O_(3),indicating that the Co–O and Mn–O bonds in CMO exhibit greater covalency,significantly enhancing ORR/OER activity.Notably,CMO serves as an advanced air electrode material for rechargeable zinc-air batteries(ZABs),demonstrating improved charge–discharge performance with a low voltage gap of 0.87 V at 5 mA cm^(-2),high peak power density of 124 mW cm^(-2),and excellent cycle stability of over 540 h at 5 mA cm^(-2).This superior ORR/OER activity,combined with the simple material combination,makes CMO a promising catalyst for rechargeable ZABs.展开更多
The optical absorption spectra of the covalent crystals ZnX(X=S,Se) doped with Co 2+ are studied using the double covalency factors,which considers the anisotropic distortion of e g and t 2g orbits for d el...The optical absorption spectra of the covalent crystals ZnX(X=S,Se) doped with Co 2+ are studied using the double covalency factors,which considers the anisotropic distortion of e g and t 2g orbits for d electron.When the paramagnetic g factor is calculated,the contributions of the spin orbit coupling from the ligand ions are taken into account besides that from the central ion,which is the double ξ model.The calculated results indicate that the theoretical values coincide with the experimental values very well.This suggests that the method presented in this paper could be more valid to some strongly covalent crystals.展开更多
High‐entropy materials are emerging electrocatalysts by integrating five or more elements into one single crystallographic phase to optimize the electronic structures and geometric environments.Here,a rocksalt‐type ...High‐entropy materials are emerging electrocatalysts by integrating five or more elements into one single crystallographic phase to optimize the electronic structures and geometric environments.Here,a rocksalt‐type high‐entropy oxide Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2)O(HEO)is developed as an electrocatalyst towards the oxygen evolution reaction(OER).The obtained HEO features abundant cation and oxygen vacancies originating from the lattice mismatch of neighboring metal ions,together with enlarged Co/Ni‒O covalency due to the introduction of less electronegative Mg and Zn.As a result,the HEO exhibits superior intrinsic OER activities,delivering a turnover frequency(TOF)15 and 84 folds that of CoO and NiO at 1.65 V,respectively.This study provides a mechanistic understanding of the enhanced OER on HEO and demonstrates the potential of high‐entropy strategy in developing efficient oxygen electrocatalysts by elaborately incorporating low‐cost elements with lower electronegativity.展开更多
The relationship between bond valence and bond covalency in RMn2O5 (R = La, Pr, Nd.Sm, Eu) has been investigated by a semiempirical method. This method is the generalization of thedielectric description theory of Phil...The relationship between bond valence and bond covalency in RMn2O5 (R = La, Pr, Nd.Sm, Eu) has been investigated by a semiempirical method. This method is the generalization of thedielectric description theory of Phillips. Van Vechten, Levine and Tanaka scheme. The resultsindicate that larger valences usually result in higher bond covalencies, in good agreement with thepoint that the excess charge in the bonding region is the origin of formation of bond covalency.Other factors, such as oxidation state of elements, only make a small contribution to bondcovalency.展开更多
Exploring efficient,cost-effective,and durable electrocatalysts for electrochemical oxygen evolution reaction(OER)is pivotal for the large-scale application of water electrolysis.Recent advance has demonstrated that t...Exploring efficient,cost-effective,and durable electrocatalysts for electrochemical oxygen evolution reaction(OER)is pivotal for the large-scale application of water electrolysis.Recent advance has demonstrated that the activity of electrocatalysts exhibits a strong dependence on the surface electronic structure.Herein,a series of ultrathin metal silicate hydroxide nanosheets(UMSHNs)M_(3)Si_(2)O_(5)(OH)_(4)(M=Fe,Co,and Ni)synthesized without surfactant are introduced as highly active OER electrocatalysts.Cobalt silicate hydroxide nanosheets show an optimal OER activity with overpotentials of 287 and 358 m V at 1 and 10 m A cm^(-2),respectively.Combining experimental and theoretical studies,it is found that the OER activity of UMSHNs is dominated by the metal-oxygen covalency(MOC).High OER activity can be achieved by having a moderate MOC as reflected by aσ^(*)-orbital(e_(g))filling near unity and moderate[3d]/[2p]ratio.Moreover,the UMSHNs exhibit favorable chemical stability under oxidation potential.This contribution provides a scientific guidance for further development of active metal silicate hydroxide catalysts.展开更多
The increasing demand for green hydrogen production requires the development of advanced ruthenium(Ru)-based oxide catalysts for the anodic oxygen evolution reaction(OER).Here,we report the development of a Ga-doped R...The increasing demand for green hydrogen production requires the development of advanced ruthenium(Ru)-based oxide catalysts for the anodic oxygen evolution reaction(OER).Here,we report the development of a Ga-doped RuO_(2)catalyst(GaRuO_(2))that demonstrates enhanced OER performance attributed to modulated Ru-O bond covalency.The fully occupied 3d orbital of Ga stabilizes its oxidation state during OER,while its atomic radius,similar to Ru,helps maintain the initial crystal lattice structure upon doping.In-situ characterization,kinetic analysis and theoretical calculations reveal that the weakened Ru-O bond covalency lowers the energy barriers for *OH and *OOH formation,thus contributing to an enhanced OER performance.The resultant Ga-RuO_(2)achieves a current density of 10 mA cm^(-2) at a low overpotential of 203 mV and demonstrates durable operation for 500 h in acid.This work provides valuable insights into the electronic structure engineering of Ru-based catalysts for practical water electrolysis applications.展开更多
Oxygen evolution reaction(OER)is crucial for hydrogen production as well as other energy storage technologies.CoFe-layered double hydroxide(CoFe-OH)has been widely considered as one of the most efficient electrocataly...Oxygen evolution reaction(OER)is crucial for hydrogen production as well as other energy storage technologies.CoFe-layered double hydroxide(CoFe-OH)has been widely considered as one of the most efficient electrocatalysts for OER in basic aqueous solution.However,it still suffers from low activity in neutral electrolyte.This paper describes partially oxidized CoFe-OH(PO-CoFe-OH)with enhanced covalency of M-O bonds and displays enhanced OER performance under mild condition.Mechanism studies reveal the suitably enhanced M-O covalency in PO-CoFe-OH shifts the OER mechanism to lattice oxygen oxidation mechanism and also promotes the rate-limiting deprotonation,providing superior OER performance.It just requires the overpotentials of 186 and 365 mV to drive the current density densities of 1 and 10 mA·cm^(-2) in 0.1 M KHCO_(3) aqueous solution(pH=8.3),respectively.It provides a new process for rational design of efficient catalysts for water oxidation in mild conditions.展开更多
Oxidative desulfurization(ODS)is a promising technology to produce clean fuel with requiring superior catalysts to lower kinetic barriers.Although most ODS catalysts are based on crystalline transition-metal oxides(TM...Oxidative desulfurization(ODS)is a promising technology to produce clean fuel with requiring superior catalysts to lower kinetic barriers.Although most ODS catalysts are based on crystalline transition-metal oxides(TMOs),extraordinary activity also can be achieved with amorphous TMOs.However,the origin of the remarkable catalytic activity of the amorphous TMOs remains greatly ambiguous.Here,we found the crucial role of Mo–O covalency in ruling the intrinsic catalytic activity of amorphous molybdenum oxides(MoO_(x)).Experimental and theoretical analysis indicated that the nonequivalent connectivity in the amorphous structure strongly enhanced Mo–O covalency,thereby increasing the content of electrophilic oxygen and nucleophilic molybdenum to favor the MoO_(x)–H_(2)O_(2) interaction.With the boosted Mo–O covalency to improve the flexibility of the charge state,the amorphous MoO_(x)-based composite catalyst(PE-MoO_(x)/S-0.05)exhibited outstanding catalytic activity for ODS of fuel oil.The turnover frequency(TOF)value of the catalyst(18.63 h^(-1))was almost an order of magnitude higher than that of most reported crystalline MoO_(x)/molecular sieve composite catalysts.The in-depth understanding of the origin of the amorphous TMOs activity for ODS provides a valuable reference for developing ODS catalysts.展开更多
CO_(2)reduction technology can promote the resource utilization of carbon and help alleviate global warming and energy supply pressure.It is an effective way to achieve energy conversion and utilization.Covalent organ...CO_(2)reduction technology can promote the resource utilization of carbon and help alleviate global warming and energy supply pressure.It is an effective way to achieve energy conversion and utilization.Covalent organic frameworks(COFs)are porous crystalline materials formed by connecting organic monomers through covalent bonds.They have the characteristics of functional diversity and rich chemical properties.Their advantages,such as high porosity,a wide range of visible light absorption,and excellent charge separation efficiency,give them good potential in CO_(2)capture,separation,and conversion.Currently,Cu is a key metal in the catalytic CO_(2)reduction reaction(CO_(2)RR)for the preparation of high-value-added chemicals.The preparation of highly stable and large-pore Cu-based COFs using COFs as an ideal sacrificial template for loading Cu can be used to develop high-performance electrocatalysts and photocatalysts.In this review,we discuss the latest advancements in this field,including the development of various Cu-based COFs and their applications as catalysts for CO_(2)RR.Here,we mainly introduce the synthesis strategies,some important characterization information,and the applications of electrocatalytic and photocatalytic CO_(2)conversion using these previously reported Cu-based COFs.展开更多
It was found that the highly covalent nature of the metal-ligand interactions in the Fe-S cluster clearly played an important role in determining the reactivity of the sites. A semi-empirical model, based on the Phill...It was found that the highly covalent nature of the metal-ligand interactions in the Fe-S cluster clearly played an important role in determining the reactivity of the sites. A semi-empirical model, based on the Phillips theory of bonding was developed for quantitative explanation of covalency in Fe-S cluster, showing that Mossbauer spectroscopy and electronic absorption spectroscopy provided the direct experimental probe of covalency of Fe-S4 clusters.展开更多
Responsive colorimetric materials exhibit significant potential for application in fields such as smart food packaging and wound monitoring.The functional integration of pH-indicators with material carriers enables br...Responsive colorimetric materials exhibit significant potential for application in fields such as smart food packaging and wound monitoring.The functional integration of pH-indicators with material carriers enables breakthrough applications in nontraditional domains.In this study,we developed a novel material covalently grafted with a pH indicator that exhibited naked-eye pH-responsive color shifts.The covalent grafting of pH-responsive bromothymol blue onto carboxymethyl cellulose(CMC)was confirmed using advanced characterization techniques,including Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The pH-sensitive chromophore was covalently immobilized onto the CMC matrix through esterification,thereby establishing firm chemical conjugation.Moreover,a superior color-changing performance was achieved within several minutes in response to different pH values.The reusability and stability of this material offer distinct advantages over single-use pH test strips.pH-responsive colorimetric materials hold promise for efficient,noninvasive monitoring in intelligent packaging(food freshness),medical diagnostics(wound status,infections),biosensing,and environmental applications.展开更多
This research explores the influence of crystallinity on gas chromatographic(GC) separation using covalent organic frameworks(COFs) as stationary phases.Three COF materials(CTF-DCBs) with varying crystallinity were sy...This research explores the influence of crystallinity on gas chromatographic(GC) separation using covalent organic frameworks(COFs) as stationary phases.Three COF materials(CTF-DCBs) with varying crystallinity were synthesized and characterized.CTF-DCB-1,with superior crystallinity,demonstrated highselectivity GC separation of benzene isomers as well as styrene/phenylacetylene mixtures,while CTFDCB-2 and CTF-DCB-3 exhibited lower crystallinity and worse separation performance.Thermodynamic and kinetic tests showed that CTF-DCB-1 had the worst thermodynamic adsorption but low diffusion mass transfer resistance,which resulted in the best separation.Therefore,optimizing the crystallinity of COFs is necessary for balancing the kinetic diffusion and thermodynamic interactions towards the analytes,achieving high-performance GC stationary phases.展开更多
As a key low-carbon energy source,nuclear power plays a vital role in the global transition toward sustainable energy.Photocatalytic uranium extraction from seawater(UES)offers a promising solution to ensure long-term...As a key low-carbon energy source,nuclear power plays a vital role in the global transition toward sustainable energy.Photocatalytic uranium extraction from seawater(UES)offers a promising solution to ensure long-term uranium supply but is challenged by ultra-low uranium concentrations and ion interference.To overcome these issues,we design three diketopyrrolopyrrole-based covalent organic frameworks(COFs)via a synergisticπ-extended lock and carboxyl-functionalized anchor molecular engineering strategy.Among them,TPy-DPP-COF features a covalently lockedπ-conjugated structure that enhances planarity,optimizes energy alignment,and minimizes exciton binding energy,thereby promoting charge transfer and suppressing recombination.Concurrently,carboxyl groups enable uranyl-specific coordination and create local electric fields to facilitate charge separation.These features contribute to the outstanding performance of TPy-DPP-COF,which achieves a high uranium adsorption capacity of 16.33 mg g−1 in natural seawater under irradiation,with only 29.3%capacity loss after 10 cycles,surpassing industrial benchmarks.Density functional theory(DFT)calculations and experimental studies reveal a synergistic photocatalysis-adsorption pathway,with DPP units acting as active sites for uranium reduction.This work highlights a molecular design strategy for developing efficient COF-based photocatalysts for practical marine uranium recovery.展开更多
Interlocked covalent organic cages have aesthetic skeletons endowed with structural and topological complexity.Their self-assembly provides a unique possibility to mimic the hierarchical self-assembly of biomacromolec...Interlocked covalent organic cages have aesthetic skeletons endowed with structural and topological complexity.Their self-assembly provides a unique possibility to mimic the hierarchical self-assembly of biomacromolecules.In recent years,significant progresses in interlocked covalent organic cages have been witnessed.Different topological structures have been fabricated via various non-template induced methods,and diverse weak interactions are demonstrated to play critical roles in guiding the formation of interlocked structures.Therefore,this article systematically summarizes the recent advances in interlocked covalent organic cages,especially their design,synthesis,and self-assembly properties.Depending on different types of chemical reactions,irreversible and reversible reactions are separately introduced.In each section,proper monomer selection,critical topology design,key driving forces as well as detailed interlocked mechanisms for the formation of interlocked structures,and their self-assembly behaviors in single crystals are discussed detailedly.Finally,the challenge and future development of interlocked covalent organic cages are briefly prospected.展开更多
Supramolecular catalysis uses noncovalent interactions,such as hydrogen bonding,π-π stacking,and host-vip recognition,to control reactivity and selectivity in chemical reactions [1,2].Unlike traditional covalent c...Supramolecular catalysis uses noncovalent interactions,such as hydrogen bonding,π-π stacking,and host-vip recognition,to control reactivity and selectivity in chemical reactions [1,2].Unlike traditional covalent catalysis,supramolecular systems can create dynamic and adaptable microenvironments tailored to specific substrates,similar to how enzymes work.This strategy has shown great promise in asymmetric catalysis,cascade reactions,and green chemistry applications.Recent advances focus on leveraging less conventional noncovalent forces to expand the toolbox of supramolecular strategies in catalysis.展开更多
The recovery of gold from waste electronic and electric equipment(WEEE) has gained great attention with the increased number of WEEE,because it can largely alleviate the pressure on the environment and resources.Coval...The recovery of gold from waste electronic and electric equipment(WEEE) has gained great attention with the increased number of WEEE,because it can largely alleviate the pressure on the environment and resources.Covalent organic frameworks(COFs) are ideal adsorbents for gold recovery owing to their large surface area,good stability,easily functionalized ability,periodic structures,and definitive nanopores.Herein,a cyano-functionalized COF(COF-CN) with high crystallinity was large-scale prepared under mild conditions for the recovery of gold.The introduction of cyano groups enable COF-CN to exhibit excellent gold recovery performance,which possesses fast adsorption kinetics,high cycling stability,and adsorption capacity up to 663.67 mg/g.Excitingly,COF-CN showed extremely high selectivity for gold ions,even in the presence of various competing cations and anions.The COF-CN maintained excellent selectivity and removal efficiency in gold recovery experiments from WEEE.The facile synthesis of COF-CN and its outstanding selectivity in actual samples make it an attractive opportunity for practical gold recovery.展开更多
基金supported by Young Project of Education Department in Guizhou Province(No.2022099)the Natural Science Special of Guizhou University(No.X202220 Special Post A)the National Natural Science Foundation of China(Grant No.22208071)。
文摘The persistent stability of ruthenium dioxide(RuO_(2))in acidic oxygen evolution reactions(OER)is compromised by the involvement of lattice oxygen(LO)and metal dissolution during the OER process.Heteroatom doping has been recognized as a viable strategy to foster the stability of RuO_(2)for acidic OER applications.This study presented an ion that does not readily gain or lose electrons,Ba^(2+),into RuO_(2)(Ba-RuO_(2))nanosheet(NS)catalyst that increased the number of exposed active sites,achieving a current density of 10 mA/cm^(2)with an overpotential of only 229 mV and sustaining this output for over 250 h.According to density functional theory(DFT)and X-ray absorption spectroscopy,Ba doping resulted in a longer Ru-O bond length,which in turn diminished the covalency of the bond.This alteration curtailed the involvement of LO and the dissolution of ruthenium(Ru),thereby markedly improving the durability of the catalyst over extended periods.Additionally,attenuated total reflectance-surface enhanced infrared absorption spectroscopy analysis substantiated that the OER mechanism shifted from a LO-mediated pathway to an adsorbate evolution pathway due to Ba doping,thereby circumventing Ru over-oxidation and further enhancing the stability of RuO_(2).Furthermore,DFT findings uncovered that Ba doping optimizes the adsorption energy of intermediates,thus enhancing the OER activity in acidic environments.This study offers a potent strategy to guide future developments on Ru-based oxide catalysts'stability in an acidic environment.
基金financial support from the National Natural Science Foundation of China(22478278,22308246)the Central Government Guides the Local Science and Technology Development Special Fund(YDZJSX20231A015)the Fundamental Research Program of Shanxi Province(202203021212266)。
文摘Ruthenium dioxide(RuO_(2))is one of the most promising acidic oxygen evolution reaction(OER)catalysts to replace the expensive and prevalent iridium(Ir)-based materials.However,the lattice oxygen oxidation induced Ru dissolution during OER compromises the activity and stability.Amorphous materials have been identified as a viable strategy to promote the stability of RuO_(2)in acidic OER applications.This study reported a nanoporous amorphous-rich RuMnO_(x)(A-RuMnO_(x))aerogel for efficient and stable acidic OER.Compared with highly crystalline RuMnO_(x),the weakened Ru–O covalency of A-RuMnO_(x)by forming amorphous structure is favorable to inhibiting the oxidation of lattice oxygen.Meanwhile,this also optimizes the electronic structure of Ru sites from overoxidation and reduces the reaction energy barrier of the rate-determining step.As a result,A-RuMnO_(x)aerogel exhibits an ultra-low overpotential of 145 mV at 10 mA cm^(-2)and durability exceeding 100 h,as well as high mass activity up to 153 mA mg^(-1)_(Ru)at 1.5 V vs.reversible hydrogen electrode(RHE).This work provides valuable guidance for preparing highly active and stable Ru-based catalysts for acidic OER.
基金the National Key Research and Development Program of China(2024YFB4106400,2024YFB4106401)the National Natural Science Foundation of China(22025502,U23A20552)。
文摘The copper-based electrocatalysts feature attractive potentials of converting CO_(2)into multi-carbon(C_(2+))products,while the instability of Cu-O often induces the reduction of Cu^(+)/Cu^(0) catalytic sites at the cathode and refrains the capability of stable electrolysis especially at high powers.In this work,we developed an Erbium(Er)oxide-modified Cu(Er-O-Cu)catalyst with enhanced covalency of Cu-O and more stable active sites.The f-p-d coupling strengthens the covalency of Cu-O,and the stability of Cu^(+)sites under electroreduction condition is critical for promoting the C-C coupling and improving the C_(2+)product selectivity.As a result,the Er-O-Cu sites exhibited a high Faradaic efficiency of C_(2+)products(FEC_(2+))of 86%at 2200 mA cm^(-2),and a peak partial current density of|j_(C2+)|of 1900 mA cm^(-2),comparable to the best reported values for the CO_(2)-to-C_(2+)electroreduction.The CO_(2)electrolysis by the Er-O-Cu sites was further scaled up to 100 cm^(2)to achieve high-power(~200 W)electrolysis with ethylene production rate of 16 mL min^(-1).
基金financially supported by the Nature Science Foundation of Hubei Province of China(No.2024AFB754)the start-up research funds from Wuhan Institute of Technology(No.K202201)
文摘Transition metal oxides have garnered significant attention as electrocatalysts for the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER).However,their sluggish reaction kinetics and poor stability hinder commercial applications.Herein,we report the synthesis of a bimetallic cobalt manganese oxide,Co_(0.99)Mn_(2.01)O_(4)(CMO),synthesized via a hydrothermal technique,which serves as a highly efficient bifunctional ORR/OER electrocatalyst owing to its impressive halfwave potential of 0.767 V and low overpotential of 1.677 V at 10 mA cm^(-2).Theoretical calculations revealed that the d-band centers of Co 3d and Mn 3d in CMO,located at tetrahedral and octahedral sites,are positioned near the Fermi level,facilitating the adsorption of electrocatalytic intermediates.Furthermore,the distance between the Co 3d and O 2p band centers in CMO is smaller than that in Co_(3)O_(4),and the distance between the Mn 3d and O 2p band centers in CMO is shorter than that in Mn_(2)O_(3),indicating that the Co–O and Mn–O bonds in CMO exhibit greater covalency,significantly enhancing ORR/OER activity.Notably,CMO serves as an advanced air electrode material for rechargeable zinc-air batteries(ZABs),demonstrating improved charge–discharge performance with a low voltage gap of 0.87 V at 5 mA cm^(-2),high peak power density of 124 mW cm^(-2),and excellent cycle stability of over 540 h at 5 mA cm^(-2).This superior ORR/OER activity,combined with the simple material combination,makes CMO a promising catalyst for rechargeable ZABs.
文摘The optical absorption spectra of the covalent crystals ZnX(X=S,Se) doped with Co 2+ are studied using the double covalency factors,which considers the anisotropic distortion of e g and t 2g orbits for d electron.When the paramagnetic g factor is calculated,the contributions of the spin orbit coupling from the ligand ions are taken into account besides that from the central ion,which is the double ξ model.The calculated results indicate that the theoretical values coincide with the experimental values very well.This suggests that the method presented in this paper could be more valid to some strongly covalent crystals.
文摘High‐entropy materials are emerging electrocatalysts by integrating five or more elements into one single crystallographic phase to optimize the electronic structures and geometric environments.Here,a rocksalt‐type high‐entropy oxide Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2)O(HEO)is developed as an electrocatalyst towards the oxygen evolution reaction(OER).The obtained HEO features abundant cation and oxygen vacancies originating from the lattice mismatch of neighboring metal ions,together with enlarged Co/Ni‒O covalency due to the introduction of less electronegative Mg and Zn.As a result,the HEO exhibits superior intrinsic OER activities,delivering a turnover frequency(TOF)15 and 84 folds that of CoO and NiO at 1.65 V,respectively.This study provides a mechanistic understanding of the enhanced OER on HEO and demonstrates the potential of high‐entropy strategy in developing efficient oxygen electrocatalysts by elaborately incorporating low‐cost elements with lower electronegativity.
文摘The relationship between bond valence and bond covalency in RMn2O5 (R = La, Pr, Nd.Sm, Eu) has been investigated by a semiempirical method. This method is the generalization of thedielectric description theory of Phillips. Van Vechten, Levine and Tanaka scheme. The resultsindicate that larger valences usually result in higher bond covalencies, in good agreement with thepoint that the excess charge in the bonding region is the origin of formation of bond covalency.Other factors, such as oxidation state of elements, only make a small contribution to bondcovalency.
基金supported by the NationallNaturallScience Foundation of China(51832004,51521001,51872218)the NationallKey Research and Development Program of China(2016YFA0202603)+3 种基金the Programme of Introducing Talents of Discipline to Universities(B17034)the Yellow Crane Talent(Science&Technology)Program of Wuhan CityFoshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-003)the FundamentallResearch Funds for the CentrallUniversities(195101005)。
文摘Exploring efficient,cost-effective,and durable electrocatalysts for electrochemical oxygen evolution reaction(OER)is pivotal for the large-scale application of water electrolysis.Recent advance has demonstrated that the activity of electrocatalysts exhibits a strong dependence on the surface electronic structure.Herein,a series of ultrathin metal silicate hydroxide nanosheets(UMSHNs)M_(3)Si_(2)O_(5)(OH)_(4)(M=Fe,Co,and Ni)synthesized without surfactant are introduced as highly active OER electrocatalysts.Cobalt silicate hydroxide nanosheets show an optimal OER activity with overpotentials of 287 and 358 m V at 1 and 10 m A cm^(-2),respectively.Combining experimental and theoretical studies,it is found that the OER activity of UMSHNs is dominated by the metal-oxygen covalency(MOC).High OER activity can be achieved by having a moderate MOC as reflected by aσ^(*)-orbital(e_(g))filling near unity and moderate[3d]/[2p]ratio.Moreover,the UMSHNs exhibit favorable chemical stability under oxidation potential.This contribution provides a scientific guidance for further development of active metal silicate hydroxide catalysts.
基金supported by the National Natural Science Foundation of China(U22B20143,U24A20546,22478121)the Shanghai Municipal Science and Technology Major Project+4 种基金the Science and Technology Commission of Shanghai Municipality(22dz1205900)the Fundamental Research Funds for the Central Universities(JKD01241702)the Japan Society for the Promotion of Science(JSPS)KAKENHI(JP23K13703,JP24K23069)the Ensemble Grants for Early Career Researchers 2024Strategic Priority Research Program of the Chinese Academy of Sciences(XDA 0400000)。
文摘The increasing demand for green hydrogen production requires the development of advanced ruthenium(Ru)-based oxide catalysts for the anodic oxygen evolution reaction(OER).Here,we report the development of a Ga-doped RuO_(2)catalyst(GaRuO_(2))that demonstrates enhanced OER performance attributed to modulated Ru-O bond covalency.The fully occupied 3d orbital of Ga stabilizes its oxidation state during OER,while its atomic radius,similar to Ru,helps maintain the initial crystal lattice structure upon doping.In-situ characterization,kinetic analysis and theoretical calculations reveal that the weakened Ru-O bond covalency lowers the energy barriers for *OH and *OOH formation,thus contributing to an enhanced OER performance.The resultant Ga-RuO_(2)achieves a current density of 10 mA cm^(-2) at a low overpotential of 203 mV and demonstrates durable operation for 500 h in acid.This work provides valuable insights into the electronic structure engineering of Ru-based catalysts for practical water electrolysis applications.
基金support from the National Natural Science Foundation of China(Nos.21878202,21975175,and U1932119)the research project supported by Shanxi Scholarship Council of China(No.2017-041)+1 种基金the Natural Science Foundation of Shanxi Province(No.201801D121052)the National Key Basic Research Program of China(No.2017YFA0403402).
文摘Oxygen evolution reaction(OER)is crucial for hydrogen production as well as other energy storage technologies.CoFe-layered double hydroxide(CoFe-OH)has been widely considered as one of the most efficient electrocatalysts for OER in basic aqueous solution.However,it still suffers from low activity in neutral electrolyte.This paper describes partially oxidized CoFe-OH(PO-CoFe-OH)with enhanced covalency of M-O bonds and displays enhanced OER performance under mild condition.Mechanism studies reveal the suitably enhanced M-O covalency in PO-CoFe-OH shifts the OER mechanism to lattice oxygen oxidation mechanism and also promotes the rate-limiting deprotonation,providing superior OER performance.It just requires the overpotentials of 186 and 365 mV to drive the current density densities of 1 and 10 mA·cm^(-2) in 0.1 M KHCO_(3) aqueous solution(pH=8.3),respectively.It provides a new process for rational design of efficient catalysts for water oxidation in mild conditions.
基金supported by the National Natural Science Foundation of China(51978178,52270064,and 51521006)the Department of Science and Technology of Guangdong Province of China(2022A1515010226)+3 种基金the Program for Innovative Research Teams of Guangdong Higher Education Institutes of China(2021KCXTD043)Key Laboratory of Petrochemical Pollution Control of Guangdong Higher Education Institutes(KLGHEI 2017KSYS004)the Science and Technology Innovation Program of Hunan Province of China(2021RC2058)the Startup Fund of Guangdong University of Petrochemical Technology(2018rc63)。
文摘Oxidative desulfurization(ODS)is a promising technology to produce clean fuel with requiring superior catalysts to lower kinetic barriers.Although most ODS catalysts are based on crystalline transition-metal oxides(TMOs),extraordinary activity also can be achieved with amorphous TMOs.However,the origin of the remarkable catalytic activity of the amorphous TMOs remains greatly ambiguous.Here,we found the crucial role of Mo–O covalency in ruling the intrinsic catalytic activity of amorphous molybdenum oxides(MoO_(x)).Experimental and theoretical analysis indicated that the nonequivalent connectivity in the amorphous structure strongly enhanced Mo–O covalency,thereby increasing the content of electrophilic oxygen and nucleophilic molybdenum to favor the MoO_(x)–H_(2)O_(2) interaction.With the boosted Mo–O covalency to improve the flexibility of the charge state,the amorphous MoO_(x)-based composite catalyst(PE-MoO_(x)/S-0.05)exhibited outstanding catalytic activity for ODS of fuel oil.The turnover frequency(TOF)value of the catalyst(18.63 h^(-1))was almost an order of magnitude higher than that of most reported crystalline MoO_(x)/molecular sieve composite catalysts.The in-depth understanding of the origin of the amorphous TMOs activity for ODS provides a valuable reference for developing ODS catalysts.
文摘CO_(2)reduction technology can promote the resource utilization of carbon and help alleviate global warming and energy supply pressure.It is an effective way to achieve energy conversion and utilization.Covalent organic frameworks(COFs)are porous crystalline materials formed by connecting organic monomers through covalent bonds.They have the characteristics of functional diversity and rich chemical properties.Their advantages,such as high porosity,a wide range of visible light absorption,and excellent charge separation efficiency,give them good potential in CO_(2)capture,separation,and conversion.Currently,Cu is a key metal in the catalytic CO_(2)reduction reaction(CO_(2)RR)for the preparation of high-value-added chemicals.The preparation of highly stable and large-pore Cu-based COFs using COFs as an ideal sacrificial template for loading Cu can be used to develop high-performance electrocatalysts and photocatalysts.In this review,we discuss the latest advancements in this field,including the development of various Cu-based COFs and their applications as catalysts for CO_(2)RR.Here,we mainly introduce the synthesis strategies,some important characterization information,and the applications of electrocatalytic and photocatalytic CO_(2)conversion using these previously reported Cu-based COFs.
基金Project supported by the National Natural Science Foundation of China （No. 50472050） and the Program for New Century Excellent Talents in University and the Foundation for the Author of National Excellent Doctoral Dissertation of China （No. 200434）.
文摘It was found that the highly covalent nature of the metal-ligand interactions in the Fe-S cluster clearly played an important role in determining the reactivity of the sites. A semi-empirical model, based on the Phillips theory of bonding was developed for quantitative explanation of covalency in Fe-S cluster, showing that Mossbauer spectroscopy and electronic absorption spectroscopy provided the direct experimental probe of covalency of Fe-S4 clusters.
基金financially supported by the National Natural Science Foundation of China(No.52303209)the“Lingyan”Program of Zhejiang Province(No.2024C03076)+1 种基金Zhejiang University K.P.Chao’s High Technology Development Foundationthe generous support provided by the joint research fund from the Shaoxing Institute of Zhejiang University and Shaoxing Maternity and Child Health Care Hospital。
文摘Responsive colorimetric materials exhibit significant potential for application in fields such as smart food packaging and wound monitoring.The functional integration of pH-indicators with material carriers enables breakthrough applications in nontraditional domains.In this study,we developed a novel material covalently grafted with a pH indicator that exhibited naked-eye pH-responsive color shifts.The covalent grafting of pH-responsive bromothymol blue onto carboxymethyl cellulose(CMC)was confirmed using advanced characterization techniques,including Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The pH-sensitive chromophore was covalently immobilized onto the CMC matrix through esterification,thereby establishing firm chemical conjugation.Moreover,a superior color-changing performance was achieved within several minutes in response to different pH values.The reusability and stability of this material offer distinct advantages over single-use pH test strips.pH-responsive colorimetric materials hold promise for efficient,noninvasive monitoring in intelligent packaging(food freshness),medical diagnostics(wound status,infections),biosensing,and environmental applications.
基金supported by the National Natural Science Foundation of China (Nos.22174067,22204078,and 22374077)the Natural Science Foundation of Jiangsu Province of China (No.BK20220370)+3 种基金Jiangsu Provincial Department of Education (No.22KJB150009)State Key Laboratory of Analytical Chemistry for Life Science (No.SKLACLS2218)the Priority Academic Program Development of Jiangsu Higher Education Institutions,Jiangsu Association for Science and Technology (No.TJ-2023-076)Shanghai Synchrotron Radiation Facility Beamline BL17B1 (No.2021-NFPSPT-006657)。
文摘This research explores the influence of crystallinity on gas chromatographic(GC) separation using covalent organic frameworks(COFs) as stationary phases.Three COF materials(CTF-DCBs) with varying crystallinity were synthesized and characterized.CTF-DCB-1,with superior crystallinity,demonstrated highselectivity GC separation of benzene isomers as well as styrene/phenylacetylene mixtures,while CTFDCB-2 and CTF-DCB-3 exhibited lower crystallinity and worse separation performance.Thermodynamic and kinetic tests showed that CTF-DCB-1 had the worst thermodynamic adsorption but low diffusion mass transfer resistance,which resulted in the best separation.Therefore,optimizing the crystallinity of COFs is necessary for balancing the kinetic diffusion and thermodynamic interactions towards the analytes,achieving high-performance GC stationary phases.
基金the Young Elite Scientists Sponsorship Program by JXAST(2024QT11)the National Natural Science Foundation of China(22465001,22309003)the Jiangxi Provincial Natural Science Foundation(20232BAB203042,20242BAB22002).The authors also acknowledge the Scientific Compass(http://www.shiyanjia.com)for the measurements.
文摘As a key low-carbon energy source,nuclear power plays a vital role in the global transition toward sustainable energy.Photocatalytic uranium extraction from seawater(UES)offers a promising solution to ensure long-term uranium supply but is challenged by ultra-low uranium concentrations and ion interference.To overcome these issues,we design three diketopyrrolopyrrole-based covalent organic frameworks(COFs)via a synergisticπ-extended lock and carboxyl-functionalized anchor molecular engineering strategy.Among them,TPy-DPP-COF features a covalently lockedπ-conjugated structure that enhances planarity,optimizes energy alignment,and minimizes exciton binding energy,thereby promoting charge transfer and suppressing recombination.Concurrently,carboxyl groups enable uranyl-specific coordination and create local electric fields to facilitate charge separation.These features contribute to the outstanding performance of TPy-DPP-COF,which achieves a high uranium adsorption capacity of 16.33 mg g−1 in natural seawater under irradiation,with only 29.3%capacity loss after 10 cycles,surpassing industrial benchmarks.Density functional theory(DFT)calculations and experimental studies reveal a synergistic photocatalysis-adsorption pathway,with DPP units acting as active sites for uranium reduction.This work highlights a molecular design strategy for developing efficient COF-based photocatalysts for practical marine uranium recovery.
基金supported by the Science and Technology Research Program of Chongqing Municipal Education Commission (No.KJQN202400807)Natural Science Foundation of Shanghai (No.23ZR1419600)。
文摘Interlocked covalent organic cages have aesthetic skeletons endowed with structural and topological complexity.Their self-assembly provides a unique possibility to mimic the hierarchical self-assembly of biomacromolecules.In recent years,significant progresses in interlocked covalent organic cages have been witnessed.Different topological structures have been fabricated via various non-template induced methods,and diverse weak interactions are demonstrated to play critical roles in guiding the formation of interlocked structures.Therefore,this article systematically summarizes the recent advances in interlocked covalent organic cages,especially their design,synthesis,and self-assembly properties.Depending on different types of chemical reactions,irreversible and reversible reactions are separately introduced.In each section,proper monomer selection,critical topology design,key driving forces as well as detailed interlocked mechanisms for the formation of interlocked structures,and their self-assembly behaviors in single crystals are discussed detailedly.Finally,the challenge and future development of interlocked covalent organic cages are briefly prospected.
文摘Supramolecular catalysis uses noncovalent interactions,such as hydrogen bonding,π-π stacking,and host-vip recognition,to control reactivity and selectivity in chemical reactions [1,2].Unlike traditional covalent catalysis,supramolecular systems can create dynamic and adaptable microenvironments tailored to specific substrates,similar to how enzymes work.This strategy has shown great promise in asymmetric catalysis,cascade reactions,and green chemistry applications.Recent advances focus on leveraging less conventional noncovalent forces to expand the toolbox of supramolecular strategies in catalysis.
基金financially supported by the National Natural Science Foundation of China (No.51972302)。
文摘The recovery of gold from waste electronic and electric equipment(WEEE) has gained great attention with the increased number of WEEE,because it can largely alleviate the pressure on the environment and resources.Covalent organic frameworks(COFs) are ideal adsorbents for gold recovery owing to their large surface area,good stability,easily functionalized ability,periodic structures,and definitive nanopores.Herein,a cyano-functionalized COF(COF-CN) with high crystallinity was large-scale prepared under mild conditions for the recovery of gold.The introduction of cyano groups enable COF-CN to exhibit excellent gold recovery performance,which possesses fast adsorption kinetics,high cycling stability,and adsorption capacity up to 663.67 mg/g.Excitingly,COF-CN showed extremely high selectivity for gold ions,even in the presence of various competing cations and anions.The COF-CN maintained excellent selectivity and removal efficiency in gold recovery experiments from WEEE.The facile synthesis of COF-CN and its outstanding selectivity in actual samples make it an attractive opportunity for practical gold recovery.
