Optimizing high-coordination shell of Co-based single-atom catalysts for efficient ORR and zinc-air batteries

Atom-level modulation of the coordination environment for single-atom catalysts(SACs)is considered as an effective strategy for elevating the catalytic performance.For the MNxsite,breaking the symmetrical geometry and charge distribution by introducing relatively weak electronegative atoms into the first/second shell is an efficient way,but it remains challenging for elucidating the underlying mechanism of interaction.Herein,a practical strategy was reported to rationally design single cobalt atoms coordinated with both phosphorus and nitrogen atoms in a hierarchically porous carbon derived from metal-organic frameworks.X-ray absorption spectrum reveals that atomically dispersed Co sites are coordinated with four N atoms in the first shell and varying numbers of P atoms in the second shell(denoted as Co-N/P-C).The prepared catalyst exhibits excellent oxygen reduction reaction(ORR)activity as well as zinc-air battery performance.The introduction of P atoms in the Co-SACs weakens the interaction between Co and N,significantly promoting the adsorption process of ^(*)OOH,resulting in the acceleration of reaction kinetics and reduction of thermodynamic barrier,responsible for the increased intrinsic activity.Our discovery provides insights into an ultimate design of single-atom catalysts with adjustable electrocatalytic activities for efficient electrochemical energy conversion.

REFINEMENTS OF THE NORM OF TWO ORTHOGONAL PROJECTIONS

In this paper,some refinements of norm equalities and inequalities of combination of two orthogonal projections are established.We use certain norm inequalities for positive contraction operator to establish norm inequalities for combination of orthogonal projections on a Hilbert space.Furthermore,we give necessary and sufficient conditions under which the norm of the above combination of o`rthogonal projections attains its optimal value.

Hierarchical FeO_(χ)H_(y)@Ni_(3)B hybrid for efficient alkaline oxygen evolution at high current density

Electrocatalysts with high activity and long-term durability are vital toward large-scale hydrogen pro-duction from electrocatalytic water splitting.Here,the self-supported electrode(FeO_(χ)H_(y)@Ni_(3)B/NF)with hierarchical heterostructure was simply prepared by using Ni_(3)B chunks grown on nickel foam as sub-strate to in situ form vertical FeO_(χ)H_(y)nanosheets.Such hybrid shows efficient oxygen evolution reaction activity with overpotentials as low as 267 and 249 mV at 100 mA cm^(-2)in 1 M KOH solution and 30 wt%KOH solution,respectively.Meanwhile,it also exhibits excellent catalytic stability,sustaining catalysis at 500 mA cm^(-2)in 1 M KOH solution for 200 h,and even for 200 h at 1000 mA cm^(-2)in 30 wt%KOH solution.Further experimental results reveal that the FeO_(χ)H_(y)@Ni_(3)B/NF is endowed with superhydrophilic and superaerophobic surface properties,which not only provide more mass transport channels,as well as facilitated the diffusion of reaction intermediates and gas bubbles.Also,it holds faster reaction kinetics,more accessible active sites and accelerated electron transfer rates due to strong synergistic interactions attheheterogeneous interface.

Varicella-Zoster Virus Encephalitis with Hyponatremia in an Immunocompetent Elderly Patient:A Case Report

As a common cause of viral encephalitis,varicella-zoster virus(VZV)may invade the central nervous system of immunosuppressed patients during reactivation.Herein,we report a rare case of an immunocompetent patient with VZV encephalitis who developed severe hyponatremia and was considered to have a suspected primary infection.The patient was diagnosed with the support of second-generation sequencing and had persistent hyponatremia after being cured.Although rare,this case suggests that VZV encephalitis may occur in unexpected patients and present with unusual clinical manifestations,requiring advanced detection methods and clinical expertise for resolution.

Protective effect of Cordyceps sinensis extract on rat brain microvascular endothelial cells injured by oxygen-glucose deprivation

Objective:To investigate the protective effect of Cordyceps sinensis extract (CSE)on injury of primary cultured rat brain microvascular endothelial cells (rBMECs) induced by oxygen-glucose deprivation (OGD).Methods:We isolated and cultured primary rBMECs in order to establish an in vitro OGD model.Cellular activity was detected using a cell counting kit to determine the appropriate dosage.The rBMECs were divided into control,model,low-,mid-,and high-dose (5,10,20 μg.mL-1) CSE groups under OGD for 6 hours.CSE was dissolved in cell culture medium to the appropriate concentration,passed through a 0.22 μm sterile filter,and administered for 12 hours before and during OGD.Cellular morphology was observed under a microscope.Lactate dehydrogenase level in cultural supernatant,superoxide dismutase activity,and the content of nitric oxide and malondialdehyde in cells were tested by colorimetric methods.Levels of tumor necrosis factor-α and interleukin-1 beta in cells were determined by enzyme-linked immunosorbent assay.Results:After 12-hour administration of CSE at the concentration of 5,10,20 iμg.mL-1 before and during OGD,compared with the model group,the CSE groups obviously alleviated the damage of rBMECs induced by OGD,inhibited the apoptosis and the necrosis of the cells,and improved cellular morphology of rBMECs.Additionally,compared with the model group,CSE also restrained lactate dehydrogenase leakage in hypoxic cells (P <.01),significantly increased superoxide dismutase activity (P <.05),and reduced the levels of nitric oxide,malondialdehyde,tumor necrosis factor-α,and interleukin-1 beta (P <.05).Conclusion:C.sinensis extract plays a significant role in protecting injured primary cultured rBMECs induced by OGD.The mechanism may be related with the increase of cellular antioxidative capacity and anti-inflammatory effect.

PARAMETER ESTIMATION OF PATH-DEPENDENT MCKEAN-VLASOV STOCHASTIC DIFFERENTIAL EQUATIONS

This work concerns a class of path-dependent McKean-Vlasov stochastic differential equations with unknown parameters.First,we prove the existence and uniqueness of these equations under non-Lipschitz conditions.Second,we construct maximum likelihood estimators of these parameters and then discuss their strong consistency.Third,a numerical simulation method for the class of path-dependent McKean-Vlasov stochastic differential equations is offered.Finally,we estimate the errors between solutions of these equations and that of their numerical equations.

面向碱性析氢反应的原子级优化Fe-Pt金属间化合物催化剂表面终结态探索

Controlling the atomic arrangement of elemental atoms in intermetallic catalysts to govern their surface and subsurface properties is a crucial but challenging endeavor in electrocatalytic reactions.In hydrogen evolution reaction(HER),adjusting the d-band center of the conventional noble-metallic Pt by introducing Fe enables the optimization of catalytic performance.However,a notable gap exists in research on the effective transition from disordered Fe/Pt alloys to highly ordered intermetallic compounds(IMCs)such as FePt_(3)in the alkaline HER,hampering their broader application.In this study,a series of catalysts FePt_(3-x)H(x=5,6,7,8 and 9)supported on carbon nanotubes(CNTs)were synthesized via a simple impregnation method,along with a range of heat treatment processes,including annealing in a reductive atmosphere,to regulate the order degree of the arrangement of Fe/Pt atoms within the FePt_(3)catalyst.By using advanced microscopy and spectroscopy techniques,we systematically explored the impact of the order degree of FePt_(3)in the HER.The as-prepared FePt_(3)-8H exhibited notable HER catalytic activity with low overpotentials(η=37 mV in 1.0 mol L^(-1)KOH)at j=10 mA cm^(-2).The surface of the L1_(2)FePt_(3)-8H catalyst was demonstrated to be Pt-rich.The Pt on the surface was not easily oxidized due to the unique Fe/Pt coordination,resulting in significant enhancement of HER performance.

Highly-efficient CoRuO_(x)nanocatalysts for acidic oxygen evolution:The merit of optimum ordering degree of carbon nanotube support

Hydrogen production from proton exchange membrane water electrolysis is constrained by the sluggish kinetics of the anodic oxygen evolution reaction.RuO_(2)has attracted considerable attention due to its low reaction overpotential,but its inferior stability remains a major challenge.Herein,a strategy is proposed to enhance the catalytic activity and stability of CoRuOx nanoparticles by doping Co and regulating the ordering degree of carbon nanotubes(CNTs)by air annealing.It was found that the CoRuOx@CNTs-300 catalyst exhibited the best catalytic activity and stability when the annealing temperature was 300°C.At the current density of 10 mA cm−2,the overpotential of this catalyst was only 201 mV,which was nearly 100 mV lower than that of commercial RuO_(2)(300 mV).Surprisingly,there was no significant increase in the overpotential when tested at a current density of 10 mA cm−2 for 50 h.The density functional theory calculations indicate that the high activity of the catalyst is due to the electronic coupling of CoRuOx nanoparticles and CNTs,and that the introduction of Co and CNTs improves the electronic structure and solvation energies of the Ru in the active site,dramatically increasing the structural stability.