Intrinsic pentagon defect engineering in multiple spatial-scale carbon frameworks for efficient triiodide reduction

Intrinsic topological defect engineering has been proven as a promising strategy to elevate the electrocatalytic activity of carbon materials.However,the controllable construction of high-density and specific topological defects in carbon frameworks to reveal the relationship between reactivity and defect structure remains a challenging task.Herein,the intrinsic pentagon carbon sites that can favor electron overflow and enhance their binding affinity towards the intermediates of catalytic reaction are firstly presented by the work function and the p-band center calculations.To experimentally verify this,the cage-opening reaction of fullerene is proposed and utilized for synthesizing carbon quantum dots with specific pentagon configuration(CQDs-P),subsequently utilizing CQDs-P to modulate the micro-scale defect density of three-dimensional reduced graphene oxide(rGO)viaπ-πinteractions.The multiple spatial-scale rGO-conjugated CQDs-P structure simultaneously possesses abundant pentagon and edge defects as catalytic active sites and long-range-orderedπelectron delocalization system as conductive network.The defects-rich CQDs-P/rGO-4 all-carbon-based catalyst exhibits superb catalytic activity for triiodide reduction reaction with a high photoelectric conversion efficiency of 8.40%,superior to the Pt reference(7.97%).Theoretical calculations suggest that pentagon defects in the carbon frameworks can promote charge transfer and modulate the adsorption/dissociation behavior of the reaction intermediates,thus enhancing the electrocatalytic activity of the catalyst.This work confirms the role of intrinsic pentagon defects in catalytic reactions and provides a new insight into the synthesis of defects-rich carbon catalysts.

Effect of transport agent boron triiodide on the synthesis and crystal quality of boron arsenide

Cubic boron arsenide(BAs)has attracted great attention due to its high thermal conductivity,however,its controllable,stable,and ideal preparation remains challenging.Herein,we investigated the effect of iodine-containing transport agents I_(2) and boron triiodide(BI_(3))on BAs synthesized and grown through chemical vapor transport.Results show that similar to the commonly used I_(2),BI_(3) accelerates the synthesis and improves the mass fraction of BAs from ~12% to over 90% at 820℃ and 1.5 MPa,a value beyond the promoting effect of only increasing temperature and pressure.Both agents enhance the quality of BAs crystals by reducing the full width at half maximum by up to 10%-20%.I_(2) agglomerates the grown crystals with twin defects(~50 nm wide),and BI_(3) improves the crystal anisotropy and element uniformity of BAs crystals with narrow twins(~15 nm wide)and increases the stoichiometry ratio(~0.990)to almost 1.Owing to the boron interstitials from the excessive boron supply,the spacing of layers in {111} increases to 0.286 nm in the presence of I_(2).Owing to its coordinated effect,BI_(3) only slightly influences the layer spacing at 0.275 nm,which is close to the theoretical value of 0.276 nm.In the chemical vapor transport,the anisotropic crystals with flat surfaces exhibit single-crystal characteristics under the action of BI_(3).Different from that of I_(2),the coordinated effect of BI_(3) can promote the efficient preparation of high-quality BAs crystal seeds and facilitate the advanced application of BAs.

Tetrahydrofuran Ring Opening with Acyl Chlorides or Anhydrides Catalyzed by Gallium Triiodides: A Novel and Facile Method for the Preparation of Iodo Esters

Tetrahydrofuran ring can be opened with acyl chlorides or anhydrides catalyzed by gallium triiodides to afford iodo esters under mild conditions in good yields.

Glutamic acid-assisted hydrothermal recrystallization to configure bamboo-like carbon nanotubes for improved triiodide reduction

Carbon nanotubes(CNTs)have been far and wide employed as the counter electrodes(CEs)in dyesensitized solar cells because of their individual physical and chemical properties.However,the techniques available now,such as chemical vapor deposition,arc discharge and laser ablation for synthesizing CNTs,commonly suffer from rigorous operations and complicated steps,which make the process difficult to be controlled.Herein,we present a simple and facile glutamic acid-assisted hydrothermal recrystallization strategy to construct bamboo-like CNTs(GHP-BC-x).Generally,the conventional organic dye3,4,9,10-perylene tetracarboxylic dianhydride(PTCDA)is used as a precursor and glutamic acid efficiently promotes the recrystallization of the perylene cores'planarπ-conjugated system in PTCDA under hydrothermal conditions and then self-assembles into one-dimensio nal nano rods with improved crystallization degree,finally resulting in the morphology of bamboo-like CNTs after carbonization.When applied as the counter electrodes,the GHP-BC-3 displays a remarkable power conversion efficiency of8.25%,benefiting from the superb electrical conductivity and mass transfer dynamics,superior to that of Pt CE(7.62%).

Formation of α,α'-Bis(substituted benzylidene)cycloalkanones from Masked Aldehydes Promoted by Samarium(III) Triiodide

Diacetates 1 and N-[(1-benzotriazol-l-yl)alkyl]amides 2, both masked forms of aldehydes, could undergo deprotection and condensation with cycloalkanones in a one-pot procedure promoted by samarium(III) iodide (SmI3) to afford α,α'-bis(substituted benzylidene) cycloalkanones in good yields.

A chain-type diamine strategy towards strongly anisotropic triiodide of DMEDA·I6

Linearly bonded triiodide chains with fairly small distance between the adjacent iodine ions feature a facile electron transfer and highly anisotropic properties.Here,we demonstrate a novel strategy towards a new one-dimensional linear triiodide DMEDA·I6,using chain-type N,N'-dimethylethanediamine(DMEDA)cation to coordinate triiodine ions.This triiodide has the shortest distance between adjacent I3^- and good linearity.An estimated electronic band gap of1.36 e V indicates its semiconducting properties.100 fold differences both in polarization-sensitive absorption and effective mass were achieved by simulation,with directions parallel and perpendicular to the a-axis of DMEDA·I6.The DMEDA·I6 single crystal-based photodetectors show a good switching characteristic and a distinct polarization-sensitive photoresponse with linear dichroic photodetection ratio of about 1.9.Strongly anisotropic features and semiconducting properties of DMEDA·I6 make this triiodide system an interesting candidate for polarization related applications.

Surface active-site engineering in hierarchical PtNi nanocatalysts for efficient triiodide reduction reaction

Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis,but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature.We herein report a surface active-site engineering strategy for constructing the hierarchical PtNi nanocatalysts with an atomic Pt-skin layer(PtNi@Pt-SL)towards efficient triiodide reduction reaction(TRR)via an acid-dealloying approach.The facile acid-dealloying process promotes the formation of surface Pt active sites on the hierarchical Pt-alloys,and thus results in good catalytic performance towards TRR.Theoretical calculation reveals that the enhanced catalytic property stems from the moderate energy barriers for iodide atoms on the surface Pt active-sites.The surface active-site engineering strategy paves a new way for the design of active and durable electrocatalysts.

Air-stable synaptic devices based on bismuth triiodide and carbon nanotubes

Artificial synaptic devices with the functions of emulating important biological synaptic behaviors are playing an increasingly important role in the development of neuromorphic computing systems.Single-walled carbon nanotubes(SWCNTs)with excellent electrical properties and high stability have been studied as active materials for synaptic devices.However,the performance of optical synaptic devices(OSDs)based on pure SWCNTs is limited by the weak light absorption property.Herein,bismuth triiodide(BiI_(3)),an environmentally stable and friendly optoelectronic material,is firstly combined with SWCNTs to fabricate OSDs with decent properties of perceiving and memorizing optical information.The OSDs can exhibit typical synaptic behaviors including excitatory postsynaptic current,paired-pulse facilitation,and short/long-term memory.Distinctively,the photoresponse of the OSD is independent of pulse light wavelength in the range of 365 to 650 nm,different from most of the previously reported OSDs,which usually have wavelength-dependent photo-response.Temperature-dependent photo-response behaviors of the devices are investigated.Importantly,the OSD without encapsulation holds good excitatory post-synaptic current(EPSC)behavior after being stored in the ambient environment for 170 days,indicating reliable environmental stability.Furthermore,an OSD array with nine synaptic devices is employed to mimic the human visual perception and memory functions.These results suggest the feasibility of BiI3/SWCNTs-based OSDs for the simulation of human visual memory.

High-Performance Cobalt Selenide and Nickel Selenide Nanocomposite Counter Electrode for Both Iodide/Triiodide and Cobalt(II/III)Redox Couples in Dye-Sensitized Solar Cells

The nanocomposites of cobalt selenide and nickel selenide(Co_(0.85)Se/Ni_(0.85)Se)were successfully fabricated on FTO glass by a facile co-electrodeposition method at ambient temperature.Nanocomposite films were used as elec-trocatalysts in dye-sensitized solar cell counter electrodes for regeneration of both iodide/triiodide and cobalt(II/III)redox couples.Co_(0.85)Se/Ni_(0.85)Se were mainly composed of nanoflakes and nanoparticles.It is noted that such nanostructure generated by nanoparticles embedded with 2D nanoflakes led to high active sites and was accessible to cobalt(II/III)electrolyte,delivering better catalytic activity for the reduction of larger volume cobalt(II/III).As a result,for cobalt(II/III)electrolyte,the Co_(0.85)Se/Ni_(0.85)Se based dye-sensitized solar cell performed significantly im-proved efficiency than that of Pt and Co_(0.85)Se.Meanwhile,the Co_(0.85)Se/Ni_(0.85)Se based dye-sensitized solar cell held comparable energy conversion efficiency to that of Pt and Co_(0.85)Se for iodide/triiodide electrolyte.

Tunable fabrication of single-crystalline CsPbI_(3) nanobelts and their application as photodetectors

Lead halide perovskites have received increasing attention recently as a candidate material in various optoelectronic areas because of their high performance as light absorbers.Herein,we report the growth of CsPbI_(3) nanobelts via a solution process.A single-crystalline CsPbI_(3) nanobelt with uniform morphology can be achieved by controlling the amount of PbI_(2).A single-crystalline CsPbI_(3) nanobelt possesses a mean width,length,and thickness of 100 nm,5μm,and 20 nm,respectively.In this work,photodetectors(PDs)based on individual CsPbI_(3) nanobelts are constructed and found to perform well with an external quantum efficiency and responsivity of 2.39×10^(5)% and 770 A/W,respectively.The PDs also show a high detectivity of up to 3.12×10^(12) Jones,which is at par with that of Si PDs.The PDs developed in this work exhibit great promise in various optoelectronic nanodevices.

Modulating MAPbI3 perovskite solar cells by amide molecules:Crystallographic regulation and surface passivation

A controllable crystallization is of practical importance to produce high-quality perovskite thin films with reduced structural defects.Lewis bases as electron-pair donor chemicals can strongly coordinate to lead ions and have been extensively employed to manipulate the growth of perovskite crystals.In this work,we demonstrate a series of Lewis-base amides,for morphological regulation of methylammonium lead triiodide(MAPbI3)thin films.The screened acetamide was demonstrated to decently improve the grain size,along with a spatial distribution at grain boundaries(GBs).The mesostructured solar cells of acetamide-modified absorbers yielded an optimized power conversion efficiency(PCE)of 20.04%with a mitigated open-circuit voltage(V_(OC))deficit of 0.39 V.This work provides a facile and cost-effective strategy toward controllable fabrication of high-performance MAPbI3 solar cells.

Remarkable rate acceleration of SmI3-mediated iodination of acetates of Baylis-Hillman adducts in ionic liquid: facile synthesis of (Z)-allyl iodides

Stereoselective transformation of Baylis-Hillman acetates I into corresponding （Z）-allyl iodides 2 has been achieved by treatment of I with samarium triiodide in THF. Remarkable rate acceleration of samarium triiodide-mediated iodination of 1 was found when ionic liquid 1-n-butyl-3-methyl-imidazolium tetrafluroborate （[bmim]BF4） was used as reaction media in stead of THF. This novel approach proceeds readily at 50 ℃ within a few minutes to afford （Z）-allyl iodides 2 in excellent yields. A mechanism involving stereoselective iodination of the acetates of Baylis-Hillman adducts by samarium triiodide is described, in which a six-membered ring transition state played a key role in the stereoselective formation of 2.

One-Pot Reaction of Aldehydes,α-Haloketones and (Phenylsulfonyl)acetonitrile Promoted by SmI3

One-pot reaction of aldehydes, ?haloketones and (phenylsulfonyl)acetonitrile promoted by SmI3 proceeded smoothly to give 1-cyano-1-phenylsulfonyl-2-aryl-3-aroyl-propane derivatives in moderate to good yields.

轨道杂化诱导吸附-催化效应在四电子水系锌碘电池的应用

The successive I^(–)/I^(0)/I^(+)redox couples in the four-electron zinc-iodine aqueous battery(4eZIB)is plagued by the instability of the electrophilic I~+species,which could either be hydrolyzed or be neutralized by the I_(3)~–redox intermediates.We present an adsorption-catalysis approach that effectively suppresses the hydrolysis of ICl species and also provides an enhanced reaction kinetics to surpass the formation of triiodide ions.We elucidate that the improved stability is attributed to the pronounced orbital hybridization between the d orbitals of Fe-N_4 moieties(atomic Fe supported on nitrogen doped carbon)and the p orbitals of iodine species(I_(2)and ICl).Such d-p orbital hybridization leads to enhanced adsorption for iodine species,increased energy barrier for proton detachment from the ICl.HOH intermediate during hydrolysis,and efficient catalysis of the iodine redox reactions with high conversion efficiency.The proposed 4eZIB demonstrates practical areal capacity(>3 mAh cm^(-2))with a near-unity coulombic efficiency,high energy density of 420 Wh kg^(-1)(based on cathode mass),and long-term stability(over 10,000 cycles).Even at–20℃,the battery exhibits stable performance for over 1000 cycles with high iodine utilization ratio.

Time-resolved photoluminescence:a precision tool for shallow trap density determination in perovskite films

Determining the trap density in the absorbing layer thin film of perovskite solar cells is a critically important task,as it directly influences the efficiency of the devices.Here,we proposed time-resolved photoluminescence(TRPL)as a nondestructive method to assess trap density.A model was constructed to investigate carrier recombination and transition in perovskite materials.The model was utilized for numerical calculations and successfully fitted TRPL signals of perovskite materials.Furthermore,a genetic algorithm was employed to optimize the parameters.Finally,statistical methods were applied to obtain the parameters associated with the trap states of the material.This approach facilitates the successful determination of trap densities for different samples with clear differentiation.

An MFC capable of regenerating the cathodic electron acceptor under sunlight

A renewable MFC (microbial fuel cell) cathode was used in this study because the iodide ion could react with oxygen to generate triiodide under natural sunlight.The feasibility of the regeneration of triiodide ion under natural sunlight and the effect of the regenerated triiodide ion concentration on the MFC performance were studied.The results showed that the power density of the MFC using triiodide ion as cathodic electron acceptor was significantly higher than that of using ferricyanate,and that the iodide ion can be oxidized to triiodide ion by oxygen in air at the expense of natural sunlight.In addition,it was obvious from the experimental results that the MFC performance was improved with the increase of the triiodide concentration,indicating that the concentration of triiodide ion had a critical effect on the MFC performance.The linear sweep voltammetry (LSV) curves for the electro-reduction of triiodide ion on the carbon paper were obtained and the results suggested that the diffusion process of triiodide ions to cathode was the control factor for the MFC performance.

GaI_3 Catalyzed Tetrahydropyranylation of Alcohols and Phenols

In dichloromethane, the nucleophilic addition of alcohols or phenols to 3,4-dihydro-2H-pyran (DHP) was cata-lyzed effectively by gallium triiodide which was generated in situ by the reaction of gallium metal and iodine to give the corresponding tetrahydropyranyl acetals in good to excellent yields.

Nanostructure Pt Electrode Obtained via Self-assembly of Nanoparticles on Conductive Oxide-coated Glass Substrate

Self-assembly of platinum nanoparticles were applied to fabrication of counter electrode for dye-sensitized solar cells on conductive oxide-coated glass substrate. The present Pt electrode exhibits high exchange current density of 220 mA/cm2, which is comparable to those prepared by electrodeposition, magnetron sputtering or thermal decomposition of platinum chloride. After analysis by transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), it was found that the catalyst was structurally characterized as nanosized platinum metal clusters and was continuously arranged on electrode surface. The present nanostructure electrode had high electrocatalytic activity for the reduction of iodine in organic solution.

A Simple Access to Chalcones via Modified Mukaiyama Aldol Condensation Promoted by SmI_3/TMSCl

Promoted by SmI3, acetophenones and benzaldehydes can undergo the Mukaiyama type aldol condensation in the presence of TMSCl to form chalcones in good yields.

Water-induced reversible dissolution/reorganization transformations of Cu(Ⅱ)-K(I) heterometallic coordination polymers

Three new heterometallic coordination compounds, namely, [KCu（I3）（L）2（H2O）2]n （1）, [KCu（I3）（L）2（H20）]n （2） and [CIIK4（I3）z（L＇）4]n （3）, were prepared and characterized （HL=5-methylpyrazine-2-carboxylic acid, HL＇=p-tolylacetic acid）. Structural studies revealed that 1 and 2 exhibit 3D frameworks with rectangular channels occupied by triiodide ions. Both compounds can be symbolized as a 5-connected net with pcu topology. In compound 3, a one-dimensional polyhedral chain is connected by hexanuclear mask like clusters [Cu2K408]. These chains are further linked each other via rare （1,1,3,3）-triiodide ion-bridging units to generate a 3D （4,5,6）-connected net with the point symbol of { 12}2{4·12^2}4{4^6}{4^8·62}4{49.66}4. It is noteworthy that water-induced reversible dissolution/reorganization processes occur between 1/2 and [Cu（L）2（HzO）],＇3nH20. The thermal and photoluminescence properties of compounds 1, 2, and 3 were investigated as well.