Inducing Fe 3d Electron Delocalization and Spin‑State Transition of FeN_(4) Species Boosts Oxygen Reduction Reaction for Wearable Zinc–Air Battery

Transition metal-nitrogen-carbon materials(M-N-Cs),particularly Fe-N-Cs,have been found to be electroactive for accelerating oxygen reduction reaction(ORR)kinetics.Although substantial efforts have been devoted to design Fe-N-Cs with increased active species content,surface area,and electronic conductivity,their performance is still far from satisfactory.Hitherto,there is limited research about regulation on the electronic spin states of Fe centers for Fe-N-Cs electrocatalysts to improve their catalytic performance.Here,we introduce Ti_(3)C_(2) MXene with sulfur terminals to regulate the electronic configuration of FeN_(4) species and dramatically enhance catalytic activity toward ORR.The MXene with sulfur terminals induce the spin-state transition of FeN_(4) species and Fe 3d electron delocalization with d band center upshift,enabling the Fe(II)ions to bind oxygen in the end-on adsorption mode favorable to initiate the reduction of oxygen and boosting oxygen-containing groups adsorption on FeN_(4) species and ORR kinetics.The resulting FeN_(4)-Ti_(3)C_(2)Sx exhibits comparable catalytic performance to those of commercial Pt-C.The developed wearable ZABs using FeN_(4)-Ti_(3)C_(2)Sx also exhibit fast kinetics and excellent stability.This study confirms that regulation of the electronic structure of active species via coupling with their support can be a major contributor to enhance their catalytic activity.

Electronic shell study of prolate Lin(n=15–17)clusters:Magnetic superatomic molecules

The non-spherical lowest-lying Lin(n=15–17)isomers were found with high symmetric compact structures,of which the stability was not rationalized in a previous report(J.Chem.Phys.1199444(2003)).Based on the newly proposed super-valence bond model,the three prolate lithium clusters can be viewed as magnetic superatomic molecules,which are composed by sharing valence electron pairs and nuclei between two superatom units,namely,Li10 or Li11,and thus their stability can be given a good understanding.Molecular orbital and chemical bonding analysis clearly reveal that the Lin(n=15–17)clusters with prolate shapes are magnetic superatomic molecules.Our work may aid in the developments of the cluster-assembled materials or superatom-bonds.

Electron delocalization enhances the thermoelectric performance of misfit layer compound(Sn_(1-x)Bi_(x)S)_(1.2)(TiS_(2))_(2)

The misfit layer compound(SnS)_(1.2)(TiS_(2))_(2)is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure.However,the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying.Here,we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons.This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range.It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons,indicating that it independently modulates phonon and charge transport properties.These effects collectively give rise to a maximum ZT of 0.3 at 720 K.In addition,we apply the single Kane band model and the Debye–Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound(SnS)_(1.2)(TiS_(2))_(2).

Optimizing the electronic spin state and delocalized electron of NiCo_(2)(OH)_(x)/MXene composite by interface engineering and plasma boosting oxygen evolution reaction

The electrocatalytic activity of transition-metal-based compounds is closely related to the electronic configuration.However,optimizing the surface electron spin state of catalysts remains a challenge.Here,we developed a spin-state and delocalized electron regulation method to optimize oxygen evolution reaction(OER)performance by in-situ growth of NiCo_(2)(OH)_(x) using Oswald ripening and coordinating etching process on MXene and plasma treatment.X-ray absorption spectroscopy,magnetic tests and electron paramagnetic resonance reveal that the coupling of NiCo_(2)(OH)_(x) and MXene can induce remarkable spin-state transition of Co^(3+)and transition metal ions electron delocalization,plasma treatment further optimizes the 3 d orbital structure and delocalized electron density.The unique Jahn-Teller phenomenon can be brought by the intermediate spin state(t2 _(g)^(5) e_(g)^(1))of Co^(3+),which benefits from the partial electron occupied egorbitals.This distinct electron configuration(t2_(g)^(5) e_(g)^(1))with unpaired electrons leads to orbital degeneracy,that the adsorption free energy of intermediate species and conductivity were further optimized.The optimized electrocatalyst exhibits excellent OER activity with an overpotential of 268 m V at 10 m A cm^(-2).DFT calculations show that plasma treatment can effectively regulate the d-band center of TMs to optimize the adsorption and improve the OER activity.This approach could guide the rational design and discovery of electrocatalysts with ideal electron configurations in the future.

Electron delocalization-enhanced sulfur reduction kinetics on an MXene-derived heterostructured electrocatalyst

Lithium-sulfur(Li-S)batteries mainly rely on the reversible electrochemical reaction of between lithium ions(Li^(+))and sulfur species to achieve energy storage and conversion,therefore,increasing the number of free Li^(+)and improving the Li^(+)diffusion kinetics will effectively enhance the cell performance.Here,Mo-based MXene heterostructure(MoS_(2)@Mo_(2)C)was developed by partial vulcanization of Mo_(2)C MXene,in which the introduction of similar valence S into Mo-based MXene(Mo_(2)C)can create an electron delocalization effect.Through theoretical simulations and electrochemical characterisation,it is demonstrated that the MoS_(2)@Mo_(2)C heterojunction can effectively promote ion desolvation,increase the amount of free Li^(+),and accelerate Li^(+)transport for more efficient polysulfide conversion.In addition,the MoS_(2)@Mo_(2)C material is also capable of accelerating the oxidation and reduction of polysulfides through its sufficient defects and vacancies to further enhance the catalytic efficiency.Consequently,the Li-S battery with the designed MoS_(2)@Mo_(2)C electrocatalyst performed for 500 cycles at 1 C and still maintained the ideal capacity(664.7 mAh·g^(−1)),and excellent rate performance(567.6 mAh·g^(−1)at 5 C).Under the extreme conditions of high loading,the cell maintained an excellent capacity of 775.6 mAh·g^(−1)after 100 cycles.It also retained 838.4 mAh·g^(−1)for 70 cycles at a low temperature of 0℃,and demonstrated a low decay rate(0.063%).These results indicate that the delocalized electrons effectively accelerate the catalytic conversion of lithium polysulfide,which is more practical for enhancing the behaviour of Li-S batteries.

Quasi-aromaticity in Cluster Chemistry Ⅲ. Localized Molecular Orbital Study on Electron-rich Cobalt-sulfur Cluster Compounds[Co_6(μ_3-X)_8L_6]￣(n+)(X=S,Se;L=PPh_3,PEt_3,CO;n=0,1)

The localized molecular orbitals and energy levels for [Co_6 (μ_3-S)_8 (PH_3)_6]￣(n+)(n=0, 1) as model molecules of the electron-rich [Co_6 (μ_3-S)_8 (PPh_3)_6]￣(n+) (n=0,1) cluster compounds have been calculated by using Edmiston-Ruedenberg energy localization scheme under the spin-unrestricted CNDO/2 approximation. It is shown that the cluster skeletons of these two isostructural molecules consist of the edge-localized two-centered two-electron (Co-S) bonds plus a pair of the skeleton electrons delocalized on the whole cluster core,leading an extra stability of the cluster core.The one-electron oxidation for the neutral molecule gives rise to a one-electron σ (Co-Co) bond.which further resonates among the three diagonal lines of the {Co_6} octahedron. The comparison between [Co_6 (μ_3-S)_8(PPh_3)_6] and [Co_6(μ_3-CO)_8(CO)_6]￣(4-) indicates that the latter possesses face-localized bridging-bonds which are further delocalized on the whole surface of the cluster octahedron by the back-donation bonds from the lone electron pairs on the Co atoms to the capping carbonyl CO ligands. The structural features of the series of the [Co6(μ_3-X)_8L_6]￣(n+)(X =S, Se; L=PPh_3,PEt_3, CO;n=0, 1) cluster compounds are briefly rationalized on the basis of the localization description as well.

Preparation and ^（183）W NMR Investigation of Iridium－containing Dawson Derivative

Ｐｒｅｐａｒａｔｉｏｎａｎｄ;ＷＮＭＲＩｎｖｅｓｔｉｇａｔｉｏｎｏｆＩｒｉｄｉｕｍ－ｃｏｎｔａｉｎｉｎｇＤａｗｓｏｎＤｅｒｉｖａｔｉｖｅＬＩＵＨｕｉ－ｚｈａｎｇ；ＹＵＥＢｉｎ；ＬＩＭｉｎｇ－ｘｉｎｇ；ＣＨＥＮＺｈｉ－ｊｉａｎｇ；ＪＩＮＳｏｎ?..

Nonlinear Optical Susceptibility and Refractive Index of Two Polyaniline Families

By use of the Keldysh non-equilibrium Green’s-function methods, the third harmonic susceptibilities of two polyaniline families, PANI-HCl and PANI-H 3PO 4, are calculated [ x (3) ( ω )≈10 -12 esu]. It was found that the third harmonic susceptibility of polyaniline strongly depends on the delocalization of the electrons. The refractive indices n ( λ =589 nm) of PANI-HCl and PANI-H 3PO 4 are calculated by use of three common methods (the Lorentz-Lorentz theoretical model, the Gladstone-Dale group contribution and the Vogel group correlation) based on group contributions to molar refraction. The calculated n values are varied from 1.31 to 1.42 for PANI-HCl and 1.36 to 1.45 for PANI-H 3PO 4.

In situ embedded bismuth nanoparticles among highly porous carbon fibers for efficient carbon dioxide reduction

Electrocatalysis provides an optimal approach for the conversion of carbon dioxide(CO_(2))into high-value chemicals,thereby presenting a promising avenue toward achieve carbon neutrality.However,addressing the selectivity and stability challenges of metal catalysts in electrolytic reduction remains a daunting task.In this study,the electrospinning method is employed to fabricate porous carbon nanofibers loaded with bismuth nanoparticles with the help of in situ pyrolysis.The porous carbon nanofibers as conductive support would facilitate the dispersion of bismuth active sites while inhibiting their aggregation and promoting the mass transfer,thus enhancing their electrocatalytic activity and stability.Additionally,nitrogen doping induces electron delocalization in bismuth atoms through metal-support interactions,thus enabling efficient adsorption of intermediates for improving selectivity based on the theoretical calculation.Consequently,Bi@PCNF-500 exhibits the exceptional selectivity and stability across a wide range of potential windows.Notably,its faradaic efficiency(FE)of formate reaches 92.7%in H-cell and94.9%in flow cell,respectively,with good electrocatalytic stability.The in situ characterization and theoretical calculations elucidate the plausible reaction mechanism to obtain basic rules for designing efficient electrocatalyst.

Fast interfacial electrocatalytic desolvation enabling lowtemperature and long-cycle-life aqueous Zn batteries

Low-temperature zinc batteries(LT-ZIBs)based on aqueous electrolytes show great promise for practical applications owing to their natural resource abundance and low cost.However,they suffer from sluggish kinetics with elevated energy barriers due to the dissociation of bulky Zn(H2O)62+solvation structure and free Zn2+diffusion,resulting in unsatisfactory lifespan and performance.Herein,dissimilar to solvation shell tuning or layer spacing enlargement engineering,delocalized electrons in cathode through constructing intrinsic defect engineering is proposed to achieve a rapid electrocatalytic desolvation to obtain free Zn2+for insertion/extraction.As revealed by density functional theory calculations and interfacial spectroscopic characterizations,the intrinsic delocalized electron distribution propels the Zn(H2O)62+dissociation,forming a reversible interphase and facilitating Zn2+diffusion across the electrolyte/cathode interface.The as-fabricated oxygen defect-rich V2O5 on hierarchical porous carbon(ODVO@HPC)electrode exhibits high capacity robustness from 25 to20℃.Operating at-20℃,the ODVO@HPC delivers 191 mAh g-1 at 50 A g-1 and lasts for 50000 cycles at 10 A g-1,significantly enhancing the power density and lifespan under low-temperature environments in comparison to previous reports.Even with areal mass loading of-13 mg cm2,both coin cells and pouch batteries maintain excellent stability and areal capacities,realizing practical high-performance LT-ZIBs.

Outer delocalized electron aggregation of bromide bridged core–shell CuBr@C for hydrogen evolution reaction

Modulation of the surface electron distribution is a challenging problem that determines the adsorption ability of catalytic process.Here,we address this challenge by bridging the inner and outer layers of the core–shell structure through the bridge Br atom.Carbon shell wrapped copper bromide nanorods(CuBr@C)are constructed for the first time by chemical vapour deposition with hexabromobenzene(HBB).HBB pyrolysis provides both bridge Br atom and C shells.The C shell protects the stability of the internal halide structure,while the bridge Br atom triggers the rearrangement of the surface electrons and exhibits excellent electrocatalytic activity.Impressively,the hydrogen evolution reaction(HER)activity of CuBr@C is significantly better than that of commercial N-doped carbon nanotubes,surpassing commercial Pt/C at over 200 mA·cm^(−2).Density functional theory(DFT)calculations reveal that bridge Br atoms inspire aggregation of delocalized electrons on C-shell surfaces,leading to optimization of hydrogen adsorption energy.

Localized molecular orbital studies on B_4C1_4,1,5-C_2B_3H_5 and B_nH_n^(2-)(n = 6-10, 12)

The wave functions, level energies and Mulliken population analysis of localized molecular orbitals (LMO's) for B4Cl4, 1,5-C2B3H5 and the closo-BnHn2- (n = 6-10, 12) are calculated by using the Edmiston-Reudenberg energy localization scheme under the CNDO/2 approximation in order to reveal the nature of quasi-aromaticity of the closo-BnHn2- (n > 5). It has been found that all the B-H or B-Cl LMO's are highly localized between the B and H (or Cl) atoms, corresponding to B-H or B-Cl o-bond, while the Bn framework bonding is formed mainly by the three-centered two-electron B-B-B bonds on the polyhedral faces. In the cases of B4Cl4 and 1,5-C2B3H5, these three-centered B-B-B bonds just fill their polyhedral faces; however, for the framework bonding of the closo-BnHn2- (n > 5), the valence electron deficiency leads to the delocalization of their three-centered B-B-B bonds, and as delocalizability of this three-centered B-B-B bond increases, some three-centered B-B-B bonds are further delocalized to become a four-centered B-B-B-B bond. It is important that for the cioao-BnHn2- (n > 5), the sequence of this delocalizability of the three-centered B-B-B bond is consistent with the degree of quasi-aromaticity of the closo-boranes.

Stabilizing photo-induced vacancy defects in MOF matrix for highperformance SERS detection

Photo-induced vacancy defects are employed strategically to imbue semiconductors with enhanced performance characteristics for many important applications such as surface-enhanced Raman scattering(SERS)sensing,photocatalysis,and photovoltaic applications.However,the long-term maintenance and use of photo-induced vacancy defects remain elusive,because of their rapid self-healing upon air exposure.In this study,we demonstrate that photo-induced oxygen vacancy(PIVO)defects can be stabilized by the photoexcitation of metal–organic framework(MOF)materials,which is crucial for SERS analysis.The PIVO defects in MOF materials are stable for at least two weeks in the ambient atmosphere,owing to the combination of steric hindrance and electron delocalization around vacancy defects,which significantly contrasts the short lifetime(within minutes)of PIVO defects in metal-oxide semiconductors.With the formation of stable PIVO defects,a prominent SERS enhancement surpassing that of pristine MOFs is achieved,accompanied with a reduced limit of detection by three orders of magnitude.Moreover,the additional SERS enhancement rendered by PIVO defects can be stably retained and is effective for monitoring various small molecules,such as dopamine and bisphenol A.

Pronounced interfacial interaction in icosahedral Au@C_(60) core-shell nanostructure for boosting direct plasmonic photocatalysis under alkaline condition

The unique hot carrier-driven direct plasmonic photocatalysis of coinage metal nanomaterials(NMs)via energetic localized surface plasmon resonance(LSPR)in visible-light region has been explored in recent years.However,the low photoinduced electron transfer efficiency and insufficient separation of electronhole pairs would severely preclude their widespread practical applications.Herein,we demonstrate an interesting plasmonic photocatalyst based on the construction of icosahedral(Ih)Au@C_(60) core-shell NMs,taking advantage of specific delocalizedπelectrons structure of a tight C_(60) shell and enhanced LSPR property of Ih Au core.Then,the pronounced interfacial interaction at junction region endows the obtained Au@C_(60) NMs with an outstanding photoinduced hot carrier-transmission during photocatalytic reaction,facilitating a remarkably higher(1.89 times)photocatalytic activity toward visible-light driven degradation of crystal violet(CV)dyes,as compared to bare Au NMs.Impressively,the photocatalytic activity of Ih Au@C_(60) NMs can be effectively optimized by changing the p H value of reaction solution,with the kinetic rate constant reaching the maximum value of 0.179 min^(-1) in pH011.4 solution,while 0.005 min^(-1) at pH03.0.Moreover,due to the protection of a tight C_(60) shell,the Ih Au@C_(60) NMs also possess excellent photocatalytic stability/reusability in recycling runs,holding great potential for the design of robust and high-performance plasmonic photocatalysts in repeated practical applications.