Surface-to-bulk engineering with high-valence W^(6+) enabling stabilized single-crystal LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2) cathode

Single-crystal Nickel-rich layered oxides has been recognized as one of the promising cathodes for nextgeneration lithium batteries on account of their high capacity,while its practical application was hindered by structural instability and slow Li^(+) transfer kinetics.Herein,a surface-to-bulk engineered single-crystal LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(Ni90) cathode,which features W-doped bulk and Li_(2)WO_(4) surface layer,was successfully achieved by a one-step high-valence W^(6+) modification.The as-obtained W-modified Ni90 delivers excellent cycling stability(89.8% capacity retention after 300 cycles at 0.5 C)and rate capability.The enhanced electrochemical performance was ascribed to the doped-W induced stabilized lattice oxygen,reduced Li^(+)/Ni^(2+) mixing and inhibited H2-H3 phase transition in the bulk,and Li_(2)WO_(4) layer generated stabilized cathode/electrolyte interface.In addition,the thinner LiF-rich cathode electrolyte interphase(CEI) on surface and smaller grain size for W-modified Ni90 benefit to its Li^(+) diffusion dynamics.The effect of high-valence W^(6+)on single-crystal Ni-rich cathode was firstly revealed in detail,which deepens the understanding of electrochemical behavior of Ni-rich cathode with high-valence cations modification,and provides clues for design of high-performance layered cathodes.

Topotactically constructed nickel-iron(oxy)hydroxide with abundant in-situ produced high-valent iron species for efficient water oxidation

The low efficiency of oxygen evolution reaction(OER) is regarded as one of the major roadblocks for metal-air batteries and water electrolysis.Herein,a high-performance OER catalyst of NiFe_(0.2)(oxy)hydroxide(NiFe_(0.2)-O_(x)H_(y)) was developed through topotactic transformation of a Prussian blue analogue in an alkaline solution,which exhibits a low overpotential of only 263 mV to reach a current density of 10 mA cm^(-2) and a small Tafel slope of 35 mV dec-1.Ex-situ/operando Raman spectroscopy results indicated that the phase structure of NiFe_(0.2)-O_(x)H_(y) was irreversibly transformed from the type of α-Ni(OH)_(2) to γ-NiOOH with applying an anodic potential,while ex-situ/operando 57Fe Mossbauer spectroscopic studies evidenced the in-situ production of abundant high-valent iron species under OER conditions,which effectively promoted the OER catalysis.Our work elucidates that the amount of high-valent iron species in-situ produced in the NiFe(oxy)hydroxide has a positive correlation with its water oxidation reaction performance,which further deepens the understanding of the mechanism of NiFe-based electrocatalysts.

Enhancing water-dissociation kinetics and optimizing intermediates adsorption free energy of cobalt phosphide via high-valence Zr incorporating for alkaline water electrolysis

Developing high-efficiency electrocatalysts for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) is required to enhance the sluggish kinetics of water dissociation and optimize the adsorption free energy of reaction intermediates.Herein,we tackle this challenge by incorporating high-valence Zr into CoP(ZrxCo_(1-x)P),which significantly accelerates the elementary steps of water electrolysis.Theoretical calculations indicate that the appropriate Zr incorporation effectively expedites the sluggish H2O dissociation kinetics and optimizes the adsorption energy of reaction intermediates for boosting the alkaline water electrolysis.These are confirmed by the experimental results of Zr_(0.06)Co_(0.94)P catalyst that delivers exceptional electrochemical activity.The overpotentials at the current density of 10 mA cm^(-2)(j10) are only 62(HER) and 240 mV(OER) in alkaline media.Furthermore,the Zr_(0.06)Co_(0.94)P/CC‖Zr_(0.06)Co_(0.94)P/CC system exhibits superior overall water splitting activity(1.53 V/j10),surpassing most of the reported bifunctional catalysts.This high-valence Zr incorporation and material design methods explore new avenues for realizing high-performance non-noble metal electrocatalysts.

Freeze-induced acceleration of iodide oxidation and consequent iodination of dissolved organic matter to form organoiodine compounds

Freeze-induced acceleration of I–oxidation and the consequent iodination of dissolved organic matter(DOM)contribute to the formation of organoiodine compounds(OICs)in cold regions.The formed OICs may be a potentially important source of risk and are very closely with the environment and human health.Herein,we investigated the acceleration effects of the freeze process on I–oxidation and the formation of OICs.In comparison to reactive iodine species(RIS)formed in aqueous solutions,I–oxidation and RIS formation were greatly enhanced in frozen solution and were affected by pH,and the content of I–and O_(2).Freeze-thaw process further promoted I–oxidation and the concentration of RIS reached 45.7μmol/L after 6 freeze-thaw cycles.The consequent products of DOM iodination were greatly promoted in terms of both concentration and number.The total content of OICs ranged from 0.02 to 2.83μmol/L under various conditions.About 183–1197 OICs were detected by Fourier transform ion cyclotron resonance mass spectrometry,and more than 96.2%contained one or two iodine atoms.Most OICs had aromatic structures and were formed via substitution and addition reactions.Our findings reveal an important formation pathway for OICs and shed light on the biogeochemical cycling of iodine in the natural aquatic environment.

Nanopore-rich NiFe LDH targets the formation of the high-valent nickel for enhanced oxygen evolution reaction

Nickel-iron layered double hydroxides(NiFe LDHs)represent a promising candidate for oxygen evolution reaction(OER),however,are still confronted with insufficient activity,due to the slow kinetics of electrooxidation of Ni^(2+)cations for the high-valent active sites.Herein,nanopore-rich NiFe LDH(PR-NiFe LDH)nanosheets were proposed for enhancing the OER activity together with stability.In the designed catalyst,the confined nanopores create abundant unsaturated Ni sites at edges,and decrease the migration distance of protons down to the scale of their mean free path,thus promoting the formation of high-valent Ni^(3+)/^(4+)active sites.The unique configuration further improves the OER stability by releasing the lattice stress and accelerating the neutralization of the local acidity during the phase transformation.Thus,the optimized PR-NiFe LDH catalysts exhibit an ultralow overpotential of 278 mV at 10 mA∙cm^(−2)and a small Tafel slope of 75 mV∙dec^(−1),which are competitive among the advanced LDHs based catalysts.Moreover,the RP-NiFe LDH catalyst was implemented in anion exchange membrane(AEM)water electrolyzer devices and operated steadily at a high catalytic current of 2 A over 80 h.These results demonstrated that PR-NiFe LDH could be a viable candidate for the practical electrolyzer.This concept also provides valuable insights into the design of other catalysts for OER and beyond.

Kinetically and thermodynamically expediting elementary steps via high-valence Cr-incorporated of nickel selenide for water electrolysis

Designing high-performance electrocatalysts toward hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is essential to reduce the activation barrier and optimize free adsorption energy of reactive intermediates.Herein,we report that incorporating high-valence Cr into NiSe_(2)(Cr_(x)Ni_(1-x)Se_(2))kinetically and thermodynamically expedites elementary steps of both HER and OER.The as-prepared Cr_(0.05)Ni_(0.95)Se_(2) catalyst displays excellent HER and OER activities,with low overpotentials of 89 and 272 mV at the current density of 10 mA·cm^(-2)(j10),respectively,and remains stable during operation for 30 h.A low cell voltage of only 1.59 V is required to drive j10 in alkaline media.In situ Raman spectroscopy reveals that Cr incorporation facilitates the formation of NiOOH active species during the OER process.Meanwhile,theoretical explorations demonstrate that high-valence Cr incorporation efficiently accelerates water dissociation kinetics and improves H*adsorption during HER process,lowering the activation barrier of OER and optimizing the adsorption energy of oxygen-based intermediate,thus kinetically and thermodynamically enhancing the intrinsic performance of NiSe_(2) for over water splitting.This strategy provides a new horizon to design transition metal based electrocatalysts in the clean energy field.

In Situ Electrochemical Mn(Ⅲ)/Mn(Ⅳ) Generation of Mn(Ⅱ)O Electrocatalysts for High-Performance Oxygen Reduction

Among various earth-abundant and noble metal-free catalysts for oxygen reduction reaction(ORR),manganese-based oxides are promising candidates owing to the rich variety of manganese valence.Herein,an extremely facile method for the synthesis of cubic and orthorhombic phase coexisting Mn(Ⅱ)O electrocatalyst as an efficient ORR catalyst was explored.The obtained MnO electrocatalyst with oxygen vacancies shows a significantly elevated ORR catalytic activity with a half-wave potential(E1/2) of as high as 0.895 V,in comparison with that of commercial Pt/C(E1/2=0.877 V).More impressively,the MnO electrocatalyst exhibits a marked activity enhancement after test under a constant applied potential for 1000 s thanks to the in situ generation and stable presence of high-valence manganese species(Mn^3+ and Mn^4+) during the electrochemical process,initiating a synergetic catalytic effect with oxygen vacancies,which is proved to largely accelerate the adsorption and reduction of O_2 molecules favoring the ORR activity elevation.Such an excellent ORR catalytic performance of this MnO electrocatalyst is applied in Zn-air battery,which shows an extra-high peak power density of 63.2 mW cm^-2 in comparison with that(47.4 m W cm^-2) of commercial Pt/C under identical test conditions.

Structural transformation of metal–organic framework with constructed tetravalent nickel sites for efficient water oxidation

A mixture of Ni and Fe oxides is among the most commonly active catalysts for the oxygen evolution reaction(OER)during the water oxidation process.In particular,Ni oxide incorporated with even a small amount of Fe leads to substantively enhanced OER activity.However,the critical role of Fe species during the electrocatalytic process is still under evaluation.Herein,we report nickel(oxy)hydroxide incorporated with Fe through the surface reconstruction of a bimetallic metal-organic framework(NiFe-MOF)during the water oxidation process.The spectroscopic investigations with theoretical calculations reveal the critical role of Fe in promoting the formation of highly oxidized Ni^(4+),which directly correlates with an enhanced OER activity.Both the geometric and electronic structu res of the as-reconstructed Ni_(1-x)Fe_(x)OOH electrocatalysts can be delicately tuned by the Ni-Fe ratio of the bimetallic NiFe-MOF,further affecting the catalytic activity.As a result,the Ni_(1-x)Fe_(x)OOH derived from Ni_(0.9)Fe_(0.1)-MOF delivers low overpotentials of 260 mV at 10 mA cm^(-2)and 400 mV at 300 mA cm^(-2).

有机高价碘化合物在合成中的应用

本文综述了有机高价碘化合物在合成中应用的进展,介绍了有机高价碘化合物的制备,阐述了有机高价碘化合物作为芳基,烷基,烯基,炔基,转移剂及芳基碘盐应用于复杂化合物的合成。

Degradation of carbamazepine by MWCNTs-promoted generation of high-valent iron-oxo species in a mild system with O-bridged iron perfluorophthalocyanine dimers

Metal phthalocyanine has been extensively studied as a catalyst for degradation of carbamazepine(CBZ).However,metal phthalocyanine tends to undergo their own dimerization or polymerization,thereby reducing their activity points and affecting their catalytic properties.In this study,a catalytic system consisting of O-bridged iron perfluorophthalocyanine dimers(FePcF16-O-FePcF16),multi-walled carbon nanotubes(MWCNTs)and H2O_(2) was proposed.The results showed MWCNTs loaded with FePcF16-O-FePcF16 can achieve excellent degradation of CBZ with smaller dosages of FePcF16-O-FePcF16 and H2O_(2),and milder reaction temperatures.In addition,the results of experiments revealed the reaction mechanism of non-hydroxyl radicals.The highly oxidized high-valent iron-oxo(Fe(IV)=O)species was the main reactive species in the FePcF16-O-FePcF16/MWCNTs/H2O_(2) system.It is noteworthy that MWCNTs can improve the dispersion of FePcF16-O-FePcF16,contributing to the production of highly oxidized Fe(IV)=O.Then,the pathway of CBZ oxidative degradation was speculated,and the study results also provide new ideas for metal phthalocyanine-loaded carbon materials to degrade emerging pollutants.

High-valance molybdenum doped Co_(3)O_(4) nanowires:Origin of the superior activity for 5-hydroxymethyl-furfural oxidation

Co_(3)O_(4) has been widely explored in electrocatalytic 5-hydroxymethyl-furfural(HMF) oxidation. However,the poor intrinsic ability has seriously limited its electrochemical ability. Heteroatom-doping is an efficient method to enhance the electrocatalytic ability of catalyst by regulating electronic structure. Herein,we have modulated the electronic structure of Co_(3)O_(4) by high valance Mo^(6+)-doping. With the introduction of Mo^(6+), the content of Co^(2+) was increased and metal-oxygen bond was strength. Electrochemical results suggested that the electrocatalytic ability of Co_(3)O_(4) towards HMF oxidation has been dramatically improved and reaction kinetics has been fasten. Theoretical calculations demonstrated that the surrounding cobalt sites after Mo^(6+)-doping with assembled electron has a strong adsorption ability towards HMF molecule leading to more favourable oxidation of HMF. Post characterizations demonstrated pristine Co_(3)O_(4) structure was kept after electrolysis cycles and CoOOH active species were formed. This work provides a valuable reference for developing efficient heteroatom-doped electrocatalysts for HMF oxidation.

N-碘代丁二酰亚胺(NIS)参与的碘化反应最新研究进展

有机碘化合物是一类非常重要的功能性分子,其合成研究具有重要意义.鉴于N-碘代丁二酰亚胺(NIS)具有反应活性高、廉价易得和环境友好等优点,一直以来都是碘化反应的优选碘试剂.近年来利用NIS参与的碘化反应制备有机碘化合物有了重要新进展,引起了极大地关注.综述了这一领域的最新研究进展,主要包括NIS与芳烃/末端炔烃的C—H碘化反应、NIS与不饱和化合物和亲核试剂的碘化双官能团化反应,以及NIS与不饱和化合物的串联碘环化反应.

The degradation pathways of contaminants by reactive oxygen species generated in the Fenton/Fenton-like systems

Reactive oxygen species(ROSs)in Fenton process are of great importance in treating contaminants in wastewater.It is crucial to understand their chemical properties,formation,and reaction mechanisms with contaminants.This review summarizes the reactive oxygen species in Fenton process,including hydroxyl radical(·OH),superoxide radical(O_(2)·-),singlet oxygen(1O_(2)),hydroperoxyl radical(HO_(2)·),and high-valent iron.·OH shows a trend to react with chemistry groups with abundant electrons through H-atom abstraction,radical adduct formation and single electron transfer.Electron transfer is discovered to be an important pathway when1O_(2)degrades organic pollutants.Ring-opening andβ-scission are proposed to be the possible ways of1O_(2)to certain contaminants.Proton abstraction,nucleophilic substitution,and single electron transfer are proposed to explain how O_(2)·-degrade pollutants.As the conjugated acid of O_(2)·-,radical adduct formation and H-atom abstraction are reported for the reaction mechanisms of hydroperoxyl radical.High-valent iron in Fenton,namely Fe(IV),reacts with certain pollutants via single-or two-electron transfer.This review is important for researchers to understand the ROSs produced in Fenton and how they react with pollutants.

Pd-catalyzed asymmetric carbonyl alkynylation:Synthesis of axial chiral ynones

Ynones are important skeletons in bioactive molecules and valuable building blocks for organic synthesis,thus great efforts have been devoted to their preparation.While,introducing prochiral substrates to construct ynones bearing a chiral framework is unrealized to date.Herein,we reported the first example of Pd/SOP-catalyzed asymmetric carbonylative alkynylation via a non-classical carbonylative Sonogashiratype approach(acyl-Pd(Ⅱ)species generated from nucleophiles).By using cyclic diaryliodonium salts as prochiral substrates,various axial chiral ynones with good functional group tolerance(39 examples),satisfied yields(71%-96%)and excellent enantioselectivities(generally 94%-99%ee)were produced.Synthesis of bioactive compounds,scale-up experiment and useful transformations were also conducted to demonstrate the utility of this process.

Molecule-assisted modulation of the high-valence Co^(3+)in 3D honeycomb-like Co_(x)S_(y)networks for high-performance solid-state asymmetric supercapacitors

Modulating the oxidation states of transition metal species has been regarded as a promising strategy to tune the redox activity and achieve more active sites in electrode materials.In this work,a unique three-dimensional(3D)honeycomb-like cobalt sulfide(Co_(x)S_(y))network organized by cross-linked nanosheets(Co_(x)S_(y)-T NSs)was prepared via a simple triethanolamine(TEOA)-assisted self-templating strategy.Interestingly,it has been found for the first time that the introduction of TEOA in the reaction effectively increases the ratio of high-valence Co^(3+)in the final product.Benefiting from the synergetic effect of the tailored high-valence Co^(3+)with the 3D network structure,the Co_(x)S_(y)-T NS electrode exhibits a maximum specific capacity of 351 mA h g^(-1)(2635 F g^(-1))at 5 A g^(-1)as well as excellent cycling stability.Furthermore,with the solid-state asymmetric supercapacitor(ASC)constructed based on the Co_(x)S_(y)-T NSs and activated carbon(AC)electrodes,a high energy density up to 81.62 W h kg^(-1)has been achieved at the power density of 0.81 kW kg^(-1)and 96.2%capacitance is preserved after 7000 cycles,indicating robust cycling stability.This result highlights the simple approach of simultaneously tailoring highvalence metal species and constructing 3D network structure toward high-performance electrode materials for energy storage and conversion.

Installation of high-valence tungsten in MIL-125(Ti) for boosted photocatalytic hydrogen evolution

Metal-organic frameworks(MOFs) possess the features of highly porosity-tunable and electronic-tunable structures,. Taking advantages of these merits, we successfully installed high-valence W6+ions onto the Ti-oxo clusters of MIL-125(Ti)(W-MIL-125). The installed W^(6+) ions which form a W–O–Ti structure trigger the metal-to-cluster charge transfer(MCCT), together with an enhanced light absorption.Structural and spectroscopic characterizations reveal that the MCCT process optimizes the charge transfer process and efficiently separates the photogenerated electron-hole spatially.The as-obtained sample of 3.45 W-MIL-125 with optimized electronic structure demonstrates an enhanced photocatalytic hydrogen evolution performance of 1110.7 ± 63.7 μmol g^(-1)h^(-1) under light irradiation, which is 4.0 times that of the pristine MIL-125(Ti). This work will open up a new avenue for local structural modification of MOFs to boost photocatalytic performance.

A study on singlet oxygen generation for tetracycline degradation via modulating the size ofα-Fe_(2)O_(3)nanoparticle anchored on g-C_(3)N_(4) nanotube photocatalyst

Photocatalysis is considered as an effective technique for mitigating ecological risks posed by residual tetracycline(TC).To improve the efficiency of this technique,it is necessary to enable photocatalysts to produce highly reactive species,such as singlet oxygen(1O2).However,due to the high activation energy of 1O2,photocatalysts can hardly produce 1O2 without assistance from external oxidants.Herein,we find that the size-reducedα-Fe_(2)O_(3)nanoparticles(~4 nm)that anchored on g-C_(3)N_(4)nanotube(α-Fe_(2)O_(3)@CNNT)can spontaneously generate ^(1)O_(2) for degradation of TC.In comparison,only hydroxyl radical(·OH)can be produced by g-C_(3)N_(4)nanotube loaded with~14 nmα-Fe_(2)O_(3)nanoparticles(α-Fe_(2)O_(3)/CNNT).Owing to the high reactivity of the ^(1)O_(2) species,the photocatalytic degradation rate(Kapp)of TC withα-Fe_(2)O_(3)@CNNT(0.056 min^(−1))was 1.8 times higher than that ofα-Fe_(2)O_(3)/CNNT.The experimental results and theoretical calculations suggested that reducing the size ofα-Fe_(2)O_(3)nanoparticles anchored on g-C_(3)N_(4)nanotube decreased the surface electron density ofα-Fe_(2)O_(3),which induces the generation of high-valent Fe(IV)active sites overα-Fe_(2)O_(3)@CNNT and turns the degradation pathway into a unique ^(1)O_(2) dominated process.This study provides a new insight on the generation of ^(1)O_(2) for effective degradation of environmental pollutant.

2-碘酰基苯甲酸在有机合成中的研究与应用

高价有机碘化合物的反应性质与过渡金属相似,其参与的反应具有反应条件较温和、选择性好、产率高及环境友好等优点,因而近年来关于高价有机碘试剂的研究受到广泛关注,在有机合成领域中获得了较多应用.综述了近年来高价有机碘试剂2-碘酰基苯基酸(IBX)在有机合成中的研究及应用,包括IBX在氧化羟基、含氮化合物和含硫化合物,在制备αβ-不饱和羰基化合物和α,β-不饱和酯,以及在不对称合成等方面的应用.最后介绍了近期对IBX的改进.

Prussian blue with intrinsic heme-like structure as peroxidase mimic

Despite the intrinsic peroxidase-like activity of Prussian blue nanopartides （PBNPs）, their enzyme-mimic mechanism has been scarcely investigated to date. Herein, we probed the catalytic site of PBNPs for the first time, by comparing their peroxidase-like activity with that of a series of Prussian blue analogs （PBAs） in which Fe atoms were replaced by Co, Ni, and Cu. The PBNPs exhibited the highest maximal reaction velocity （1.941 μM·s^-1）, which was at least 13 times higher than that of the PBAs, demonstrating that the peroxidase-like properties of PBNPs could be ascribed to the FeNx （x=4-6） instead of the FeC6 units. Notably, the PBNPs/H2O2 couple also showed much higher oxidizability than .OH radicals produced from the Fenton reaction, implying that a high active Fe（W）=O intermediate might be formed in the FeNx units. This study can thus pave the way for the wider application of PBNPs in biomimetic reactions.

Product identification and toxicity change during oxidation of methotrexate by ferrate and permanganate in water

Accompanying an annual increase in cancer incidence,the global use of anticancer drugs has remarkably increased with their worldwide environmental prevalence and ecological risks.In this study,the oxidation of methotrexate(MTX),a typical anticancer drug with ubiquitous occurrence and multi-endpoint toxicity,by ferrate(VI)(Fe(VI))and permanganate(Mn(VII)))was investigated in water.Fe(VI)exhibited a higher reactivity with MTX(93.34 M^(−1) s^(−1))than Mn(VII)(3.01 M^(−1) s^(−1)) at pH 8.0.The introduction of Cu(II)and Fe(III)at 1.0 mM improved the removal efficiency of 5.0μM MTX by 100.0μM Fe(VI)from 80%to 95%and 100%after 4 min,respectively.Seven oxidized products(OPs)were identified during oxidative treatments,while OP-191 and OP-205 were characterized as specific products for Fe(VI)oxidation.Initial ketonization of the L-glutamic acid moiety and cleavage of the peptide bond of MTX were proposed.Additionally,a multi-endpoint toxicity evaluation indicated no genotoxicity,neurotoxicity,or endocrine-disrupting effects of MTX and its OPs.Particularly,serious developmental toxicity in zebrafish larvae was observed in the treated MTX solutions.Based on the acute and chronic aquatic toxicity prediction,OP-190,OP-192,OP-206,and OP-208 were deemed toxic or very toxic compared to harmful MTX.Furthermore,the reduced biodegradability index from 0.15(MTX)to−0.5 to−0.2(OP-192,OP-206,and OP-468)indicated the formation of lower biodegradable OPs.Overall,this study suggests that Fe(VI)and Mn(VII)oxidation are promising treatments for remediating anticancer drug-contaminated water.However,the environmental risks associated with these treatments should be considered in the evaluation of water safety.