Inner-pore reduction nucleation of palladium nanoparticles in highly conductive wurster-type covalent organic frameworks for efficient oxygen reduction electrocatalysis

Covalent organic frameworks(COFs)have emerged as a class of promising supports for electrocatalysis because of their advantages including good crystallinity,highly ordered pores,and structural diversity.However,their poor conductivity represents the main obstruction to their practical application.Here,we reported a novel synthesis strategy for synergistically endowing a triphenylamine-based COFs with improved electrical conductivity and excellent catalytic activity for oxygen reduction,via the in-situ redox deposition and confined growth of palladium nanoparticles inside the porous structure of COFs using reductive triphenylamine frameworks as reducing agent;meanwhile,the triphenylamine unit was oxidized to radical cation structure and affords radical cation COFs with conductivity as high as3.2*10^(-1) S m^(-1).Such a uniform confine palladium nanoparticle on highly conductive COFs makes it an efficient electrocatalyst for four-electron oxygen reduction reaction(4e-ORR),showing excellent activities and fast kinetics with a remarkable half-wave potential(E_(1/2))of 0.865 V and an ultralow Tafel slope of 39.7 mV dec^(-1) in alkaline media even in the absence of extra commercial conductive fillers.The generality of this strategy was proved by preparing the different metal and metal alloy nanoparticles supported on COFs(Au@COF,Pt@COF,AuPd@COF,AgPd@COF,and PtPd@COF)using reductive triphenylamine frameworks as reducing agent.This work not only provides a facile strategy for the fabrication of highly conductive COF supported ORR electrocatalysts,but also sheds new light on the practical application of Zn-air battery.

Palladium Nanoparticles Loaded on Carbon Modified TiO_2 Nanobelts for Enhanced Methanol Electrooxidation

Carbon modified TiO_2 nanobelts(TiO_2-C) were synthesized using a hydrothermal growth method,as a support material for palladium(Pd) nanoparticles(Pd/TiO_2-C) to improve the electrocatalytic performance for methanol electrooxidation by comparison to Pd nanoparticles on bare TiO_2 nanobelts(Pd/TiO_2)and activated carbon(Pd/AC). Cyclic voltammetry characterization was conducted with respect to saturated calomel electrode(SCE) in an alkaline methanol solution, and the results indicate that the specific activity of Pd/TiO_2-C is 2.2 times that of Pd/AC and 1.5 times that of Pd/TiO_2. Chronoamperometry results revealed that the TiO_2-C support was comparable in stability to activated carbon, but possesses an enhanced current density for methanol oxidation at a potential of -0.2 V vs. SCE. The current study demonstrates the potential of Pd nanoparticle loaded on hierarchical TiO_2-C nanobelts for electrocatalytic applications such as fuel cells and batteries.

Bio-synthesized palladium nanoparticles using alginate for catalytic degradation of azo-dyes

Palladium nanoparticles(PdNPs)were synthesized in a green way using sodium alginate functioning as both reductant and stabilizer.The formation of as-synthesized Pd NPs was supervised by Ultraviolet–visible(UV–Vis)spectroscopy and confirmed by the surface plasmon resonance(SPR)band.The effect of several synthesis factors such as precursor ratio,solution p H,reaction time,and temperature were investigated by the factorial design of experiments in order to optimize the experimental conditions.The optimal synthesis parameters were achieved by heating 1.0 ml of 1.0%sodium alginate(SA),3.0 ml of 10-2 mol·L-1 H2PdCl4 at 80°C for a period of 30 min in a neutral reaction medium(pH=6).High-resolution transmission electron microscope(HRTEM),energy dispersive X-ray(EDX)spectroscopy,selected area electron diffraction(SAED)pattern,X-ray powder diffraction(XRD),and dynamic light scattering(DLS)were used to confirm the uniform spherical shapes and high crystallinity of Pd NPs with average particle size of(2.12±1.42)nm.The SEM images show the distribution of Pd NPs presented among the SA.FTIR spectra indicate that SA is a good capping agent to stabilize Pd NPs for a long time.The catalytic degradation of model azo-dyes such as mono-azo(Cibacron Yellow FN–2R)and di-azo(Cibacron Deep Red S–B)were confirmed the catalytic activity of Pd NPs.The Pd NPs can accelerate the degradation rate by more than 80 and 10 times respectively as confirmed by kinetics constant(k)values.

Fe_(3)O_(4)-carbon spheres core–shell supported palladium nanoparticles:A robust and recyclable catalyst for suzuki coupling reaction

Suzuki-Miyaura(S-M)is regarded the most powerful way for synthesis biaryls,triaryls,or incorporating of substituted aryl moieties in organic preparation by the cross-coupling of aryl boronic acid with aryl halides using the Pd catalyst.This work reports the combining of the hydrothermal and microwaveassisted protocol to convert the glucose to magnetic carbon spheres(Fe_(3)O_(4)-CSPs)decorated with Pd nanoparticles(NPs)as the catalyst for Suzuki-Miyaura cross-coupling reactions.The physicochemical properties in the produced composite were examined using FESEM,HRTEM,nitrogen isotherms,Raman spectroscopy,FTIR,XPS,and XRD.The as-fabricated composite Pd/Fe_(3)O_(4)-CSPs is mostly spherical with a core–shell structure and possesses a great surface area of 253.2 m^(2).g^(-1).Its catalytic performance demonstrates that the composite has excellent stability and high tolerance Suzuki-Miyaura crosscoupling reactions in 30 min at 80℃.Both activated and deactivated aryl halides provided excellent yield.The as-fabricated catalyst was recycled for up to four catalytic cycles without a substantial decline in performance.Moreover,this research offers a facile roadmap for synthesizing Pd/Fe_(3)O_(4)-CSPs composites and promoting the practical implementation of Pd/Fe_(3)O_(4)-CSPs catalysts for organic transformation processes.

Preparation,Characterization and Catalytic Activity of Palladium Nanoparticles Embedded in the Mesoporous Silica Matrices

Novel in-situ reduction approach was applied for the synthesis of palladium nanoparticles in the pores of mesoporous silica materials with grafted siliconhydride groups. Matrices possessing different structural properties (MCM-41, SBA-15 and Silochrom) were used. Samples were studied by nitrogen adsorption-desorption method, low-angle X-ray diffraction, transmission electron microscopy (TEM) and FT-IR/PAS spectroscopy. The temperature-programmed oxidation (TPO) and reduction (TPR) methods were applied to examine reducibility of palladium species. Palladium containing catalysts were tested in methane oxidation reaction. It was demonstrated that relatively large pores in SBA-15 type silica facilitated formation of well-dispersed palladium nanoparticles confined in the pores channels. In the case of MCM-41 support, metallic palladium nanoparticles were formed on the external surface. The obtained materials showed high catalytic activity. Lower activity of the samples containing small crystallites located in the pore volume at high temperatures was related to worse accessibility of active sites to the reation mixture.

Palladium nanoparticles/wool keratin-assisted carbon composite-modified flexible and disposable electrochemical solid-state pH sensor

Several p H-dependent processes and reactions take place in the human body;hence,the p H of body fluids is the best indicator of disturbed health conditions.However,accurate and real-time diagnosis of the p H of body fluids is complicated because of limited commercially available p H sensors.Hence,we aimed to prepare a flexible,transparent,disposable,userfriendly,and economic strip-based solid-state p H sensor using palladium nanoparticles(Pd NPs)/N-doped carbon(NC)composite material.The Pd NPs/NC composite material was synthesized using wool keratin(WK)as a precursor.The insitu prepared Pd NPs played a key role in the controlled switching of protein structure to the N-doped carbon skeleton withπ–πarrangement at the mesoscale level,which mimics the A–B type polymeric structure,and hence,is highly susceptible to H+ions.The optimized carbonization condition in the presence of Pd NPs showed that the material obtained using a modified Ag/Ag Cl reference electrode had the highest p H sensitivity with excellent stability and durability.The optimized p H sensor showed high specificity and selectivity with a sensitivity of 55 m V/p H unit and a relative standard deviation of 0.79%.This study is the first to synthesize Pd NPs using WK as a stabilizing and reducing agent.The applicability of the sensor was investigated for biological samples,namely,saliva and gastric juices.The proposed protocol and material have implications in solid-state chemistry,where biological material will be the best choice for the synthesis of materials with anticipated performance.

Electrochemically assisted production of biogenic palladium nanoparticles for the catalytic removal of micropollutants in wastewater treatment plants effluent

Biogenic palladium nanoparticles(bio-Pd NPs)are used for the reductive transformation and/or dehalogenation of persistent micropollutants.In this work,H2(electron donor)was produced in situ by an electrochemical cell,permitting steered production of differently sized bio-Pd NPs.The catalytic activity was first assessed by the degradation of methyl orange.The NPs showing the highest catalytic activity were selected for the removal of micropollutants from secondary treated municipal wastewater.The synthesis at different H2 flow rates(0.310 L/hr or 0.646 L/hr)influenced the bio-Pd NPs size.The NPs produced over 6 hr at a lowH2 flow rate had a larger size(D50=39.0 nm)than those produced in 3 hr at a high H2 flow rate(D50=23.2 nm).Removal of 92.1%and 44.3%of methyl orange was obtained after 30 min for the NPs with sizes of 39.0 nm and 23.2 nm,respectively.Bio-Pd NPs of 39.0 nm were used to treat micropollutants present in secondary treated municipal wastewater at concentrations ranging fromμg/L to ng/L.Effective removal of 8 compounds was observed:ibuprofen(69.5%)<sulfamethoxazole(80.6%)<naproxen(81.4%)<furosemide(89.7%)<citalopram(91.7%)<diclofenac(91.9%)<atorvastatin(>94.3%)<lorazepam(97.2%).Re-moval of fluorinated antibiotics occurred at>90%efficiency.Overall,these data indicate that the size,and thus the catalytic activity of the NPs can be steered and that the removal of challengingmicropollutants at environmentally relevant concentrations can be achieved through the use of bio-Pd NPs.

Topochemical polymerization of hydrogen-bonded organic framework for supporting ultrafine palladium nanoparticles

Topochemical polymerization of molecular crystals into porous materials is of significance due to their promising applications in the field of adsorption and catalysis,yet rarely reported due to the synthesis difficulty.Herein,a hydrogen-bonded organic framework(HOF-45)has been fabricated by the crystallization of a cage-like building block containing three alkynyl groups.It exhibits almost mesoporous structure demonstrated by single crystal X-ray diffraction study.Light-driven topochemical polymerization of HOF-45 with ethanedithiol covalently links alkynyl groups in HOF-45,generating a hydrogen-bond and covalentbond cross-linked material(HOF-45C).In contrast to HOF-45,cross-linked HOF-45C retains the crystalline nature and displays improved solution resistence according to the powder X-ray diffraction data.In particular,HOF-45C is able to support the growth of ultrafine palladium nanoparticles with the average size of ca.1.9 nm for rapidly promoting the degradation of nitrophenol,methyl orange,and congo red with the help of NaBH_(4)as well as Suzuki-Miyaura coupling reaction.This work inputs a new idea on the HOFs application in preparing covalent-linked porous organic materials.

Room-Temperature Suzuki-Miyaura Reaction Catalyzed by Palladium Nanoparticles in Lactate-Anion Ionic Liquid

A palladium nanoparticle catalyst(PdNPs@[Bmim]Lac)has been prepared by a simple,mild and efficient chemical approach using 1-butyl-3-methylimidazolium lactate([Bmim]Lac)ionic liquid)as a stabilizer.This catalyst exhibits excellent activity,stability,recyclability and simple manipulation in Suzuki-Miyaura reactions at room temperature in air.

Palladium Nanoparticles/Graphdiyne Oxide Nanocomposite with Excellent Peroxidase-like Activity and Its Application for Glutathione Detection

In this study, palladium nanoparticles loaded graphdiyne oxide (Pd/GDYO) nanocomposite were fabricated by in-situ reduction of palladium chloride in the dispersion of GDYO, and characte-rized by Raman spectra, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The synthesized Pd/GDYO was first found to have catalytic activities similar to those of the peroxidase enzyme, which can catalyze the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine(TMB) in the presence of hydrogen peroxide(H2O2). Steady-state kinetic studies showed that the catalytic reaction of Pd/GDYO follows a ping-pong mechanism, and Pd/GDYO has a stronger activity to TMB with a Michaelis constant(Km) value of 5.32×10-4 mmol/L. Based on the shielding effect of glutathione(GSH) on the Pd/GDYO-H2O2-TMB reaction system, a colorimetric detection method for GSH was deve-loped with a wide linear range from 0.1 μmol/L to 40 μmol/L and a limit of detection of 0.1 μmol/L. The method was successfully applied for fast and accurate detection of GSH in injection powder drugs. It was expected that this peroxidase-like Pd/GDYO nano- composite would have wide applications in the fields of biomedicine and environmental chemistry.

A Novel Glucose Biosensor Based on Palladium Nanoparticles and Its Application in Detection of Glucose Level in Urine

A novel glucose biosensor was constructed by electrodeposition of highly dispersed palladium (Pd) nanoparticles on a glassy carbon electrode (GCE). Atomic force microscopy (AFM) was applied to characterize its surface morphology. Electrodeposited Pd nanoparticles exhibited efficiently electrocatalytic oxidation for hydrogen peroxide (H_2O_2) with relatively high sensitivity and stability,which was studied by CV technique and Raman spectroscopy,respectively. The GC/Pd/GOD/Nafion system allowed a low working potential of +0.3 V (vs. SCE). Its signal current was linearly related to the glucose concentration in the range of 1.0×10 -6 —1.2×10 -4 mol·L -1 with a detection limit of 5.0×10 -7 mol·L -1 . The sensor required no special pretreatment to suppress interference from urate and L-ascorbate. It was successfully used in detection of glucose level in human urine with high stability,sensitivity and anti-poisoning ability .

Palladium nanoparticles supported on amine-functionalized glass fiber mat for fixed-bed reactors on the effective removal of hexavalent chromium by catalytic reduction

Palladium nanoparticles were deposited on the amine-grafted glass fiber mat （GFM-NH2） catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room temperature to create the designed Pd/GFM-NH2 catalyst. By the use of large size glass fiber mat without nano/mesopores as the catalyst support, the internal mass transfer limitations due to the existence of nano/mesopores on the catalyst support were eliminated and the Pd/GFM-NH2 catalyst could be easily separated from treated water due to the large size of the catalyst support. Batch experiments demonstrate its good catalytic reduction performance of Cr（VI） with formic acid as the reducing agent. It also demonstrated an efficient Cr（VI） removal and stability in a lab-prepared, packed fixed-bed tube reactor for the continuous treatment of Cr（VI）-containing water. Thus, it has a good potential for the catalytic reduction of Cr（VI） in the water treatment practice.

Synthesis of Catalytic Systems Based on Nanocomposites Containing Palladium and Hydroxycarbonates of Rare-Earth Elements

The purpose of this work is to synthesize the catalytic systems containing palladium nanoparticles and using hydroxycarbonates of yttrium and cerium as supports,and to test the catalytic activity of the obtained catalysts in the Suzuki cross-couping reaction.Nanocomposites Pd/Y(OH)CO 3 and Pd/Ce(OH)CO 3 were synthesized according to two methods:the first one-simultaneous production of nanoscale substrate and immobilization of palladium nanoparticles on its surface(nanocomposites 1),the second one-the prior synthesis of polyvinylpyrrolidone stabilized palladium nanoparticles followed by their immobilization on the nano sized substrate surface(nanocomposites 2).The reaction between phenylboronic acid and iodobenzene is chosen as a model one.The dependence of the catalytic activity of catalysts on the method of their synthesis was established.It was established that nanocomposites 2 exhibit higher catalytic activity in the selected reaction compared to the nanocomposites 1.The TOF values for the nanocomposites 1 are 6663～14617 h 1 when using the substrate Ce(OH)CO 3 and 13774～27084 h 1 when using the substrate Y(OH)CO 3,while the nanocomposites 2 reveal TOF = 87287 h 1 for the substrate Ce(OH)CO 3 and TOF = 97746 h 1 for the substrate Y(OH)CO 3 under other equal conditions.In addition,nanocomposites 2 "work" at room temperature giving a high yield of the desired product.It is noted that the support nanoparticles Y(OH)CO 3 and Ce(OH)CO 3 also exhibit catalytic activity.The yield of the final product of the reaction using them as catalysts is 55%(TOF = 11 and 8 h 1,respectively).Thus,the use of yttrium and cerium hydroxycarbonates as supports allows to decrease the palladium content in the nanocomposites to 0.01%～1% and,consequently,reduce the cost of the catalyst while maintaining its high catalytic activity.

Amine-functionalized hierarchically porous carbon supported Pd nanocatalysts for highly efficient H2 generation from formic acid with fast-diffusion channels

Formic acid(FA)has come to be considered a potential candidate for hydrogen storage,and the development of efficient catalysts for H2releasing is crucial for realizing the sustainable process from FA.Herein,we have developed the ultrafine Pd nanoparticle(NPs)with amine-functionalized carbon as a support,which was found to show an excellent catalytic activity in H_(2)generation from FA dehydrogenation.The synergetic mechanism between amine-group and Pd active site was demonstrated to facilitate H2generation byβ-hydride elimination.Moreover,the texture of support for Pd NPs also plays an important role in determining the reactivity of FA,since the diffusion of gaseous products makes the kinetics of diffusion as a challenge in this high performance Pd catalysts.As a result,the as-prepared Pd/NH_(2)-TPC catalyst with the small sized Pd nanoparticles and the hierarchically porous structures shows a turnover of frequency(TOF)value of 4312 h^(-1)for the additive-free FA dehydrogenation at room temperature,which is comparable to the most promising heterogeneous catalysts.Our results demonstrated that the intrinsic catalytic activities of active site as well as the porous structure of support are both important factors in determining catalytic performances in H2generation from FA dehydrogenation,which is also helpful to develop high-activity catalysts for other advanced gas-liquid-solid reactions systems.

Direct observation of the plasmon-enhanced palladium catalysis with single-molecule fluorescence microscopy

Plasmonic nanostructures have been proved effective not only in catalyzing chemical reactions,but also in improving the activity of non-plasmonic photocatalysts.It is essential to reveal the synergy between the plasmonic structure and the non-plasmonic metal photocatalyst for expounding the underlying mechanism of plasmon-enhanced catalysis.Herein,the enhancement of resazurin reduction at the heterostructure of silver nanowire(AgNW)and palladium nanoparticles(PdNPs)is observed in situ by single-molecule fluorescence microscopy.The catalysis mapping results around single AgNW suggest that the catalytic activity of PdNPs is enhanced for~20 times due to the excitation of localized surface plasmon resonance(LSPR)in the vicinity of the AgNW.This catalysis enhancement is also highly related to the wavelength and polarization of the excitation light.In addition,the palladium catalysis is further enhanced by~10 times in the vicinity of a roughened AgNW or a AgNW-AgNW nanogap because of the improvement of catalytic hotspots.These findings clarify the contribution of plasmon excitation in palladium catalysis at microscopic scale,which will help to deepen the understanding of the plasmon-enhanced photocatalysis and provide a guideline for developing highly efficient plasmon-based photocatalysts.

Enhanced catalytic activity of monodispersed AgPd alloy nanoparticles assembled on mesoporous graphitic carbon nitride for the hydrolytic dehydrogenation of ammonia borane under sunlight

We address the composition-controlled synthesis of monodispersed AgPd alloy nanoparticles （NPs）, their assembly for the first time on mesoporous graphitic carbon nitride （mpg-C3N4）, and the unprecedented catalysis of mpg-CgN4@AgPd in the hydrolytic dehydrogenation of ammonia borane （AB） at room temperature. Monodispersed AgPd alloy NPs were synthesized using a high-temperature organic-phase surfactant-assisted protocol comprising the co-reduction of silver（I） acetate and palladium（II） acetylacetonate in the presence of oleylamine, oleic acid, and 1-0ctadecene. This protocol allowed the synthesis of four different compositions of AgPd alloy NPs. The AgPd alloy NPs were then assembled on mpg-C3N4, reduced graphene oxide, and Ketjenblack using a liquid-phase self-assembly method. Among the three supports tested, the mpg-CBN4@AgPd catalysts provided the best activity because of the Mott-Schottky effect, which was driven by the favorable work function difference between mpg-CBN4 and the metal NPs. Moreover, the activity of the mpg-CBN4@AgPd catalyst was further enhanced by an acetic acid treatment （AAt）, and a record initial turnover frequency of 94.1 mOl（hydrogen）＇mOl（catalyst）-l-min-1 was obtained. Furthermore, the mpg-CBN4@Ag42Pdss-AAt catalyst also showed moderate durability for the hydrolysis of AB. This study also includes a wealth of kinetic data for the mpg-CBN4@AgPd-catalyzed hydrolysis of AB.

通过锚定钯纳米颗粒在CsPbBr_(3)钙钛矿纳米晶体上从而增强光催化CO_(2)还原

最近,全无机铯铅溴(CsPbX_(3)(X=Cl,Br,I))钙钛矿纳米晶体被广泛应用于光催化CO_(2)还原(CO_(2)RR)领域.但是,由于纯CsPbX_(3)纳米晶体内部载流子辐射复合严重,所以精心设计基于CsPbX_(3)纳米晶体的异质结构对于分离载流子和实现高效的CO_(2)RR是非常重要的.本文中,我们介绍了利用光辅助的方法将Pd纳米颗粒锚定在CsPbX_(3)纳米晶体上.利用此方法所制备的CsPbBr_(3)@Pd纳米晶体通过在CsPbBr_(3)/Pd界面处构建肖特基结从而促进了载流子的分离并抑制了辐射复合.第一性原理计算表明:在CO_(2)RR过程中,CsPbBr_(3)@Pd纳米晶体比纯CsPbX_(3)纳米晶体具有更低的能量势垒.当CsPbBr_(3)@Pd纳米晶体被用作CO_(2)RR催化剂时,电子消耗速率高达46.2μmol g^(-1)h^(-1),是纯CsPbX_(3)纳米晶体作为光催化剂时电子消耗速率的4.8倍.这项工作不仅介绍了一种利用光辅助将钯纳米颗粒锚定在CsPbX_(3)纳米晶体上的方法,而且还证明了CsPbBr_(3)@Pd纳米晶体在光催化CO_(2)还原领域的巨大潜能.

Enhancement of visible-light-driven oxidative amine coupling under aerobic and anaerobic conditions by photocatalyst with spatial separation of photoinduced charge carriers

Spatial separation of oxidation/reduction cocatalyst is an effective means to improve the efficiency of charge separation in photocatalytic reaction systems.Herein,a yolk-shell Pd@NH_(2)-UiO-66@Cu_(2)O heterojunction was designed and synthesized by integration of electron collector Pd and hole collector Cu_(2)O inside and outside of a photoactive metal-organic framework(MOF)NH_(2)-UiO-66,respectively.The obtained Pd@NH_(2)-UiO-66@Cu_(2)O heterojunction effectively inhibits the electron and hole recombination through the photo-induced electrons and holes flow inward and outward of the composite,and promotes the reduction and oxidation abilities for the oxidative coupling of benzylamine to imines.Compared with Pd/NH_(2)-UiO-66@Cu_(2)O,Pd@NH_(2)-UiO-66,and Pd/NH_(2)-UiO-66,Pd@NH_(2)-UiO-66@Cu_(2)O exhibits the highest photocatalytic activity.More importantly,Pd@NH_(2)-UiO-66@Cu_(2)O shows a conversion rate of benzylamine up to 99%either by oxidation under aerobic conditions or by strong adsorption of H atom(Hads)under anaerobic conditions.In addition,the catalyst shows good stability and can be recycled at least ten times.This work provides useful guidance on construction of MOFs-based composites with spatially separated photoinduced charge carriers to realize efficient oxidation coupling of benzylamine in both aerobic and anaerobic conditions.

Single entity electrochemistry and the electron transfer kinetics of hydrazine oxidation

The mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.

Highly efficient catalytic performances of nitro compounds via hierarchical PdNPs-loaded MXene/polymer nanocomposites synthesized through electrospinning strategy for wastewater treatment

The problem of water pollution has become increasingly serious,and it has already threatened the survival of mankind and has become an obstacle to the healthy development of human health.Here,we prepared a novel polyvinyl alcohol(PVA)/polyacrylic acid(PAA)/MXene fiber membrane by electrospinning.After heat treatment of film and subsequent modification with Pd nanoparticles,PVA/PAA/MXene@PdNPs composite nanofiber membrane with high specific surface area and excellent catalytic performance was finally prepared.The uniform distribution of MXene sheets in the composite fiber membrane not only solves the problem that the MXene sheet is not easy to be monolayerized,but also can grow the self-reduced Pd nanoparticles on the MXene sheets.In addition,the composite nanofiber membrane exhibits excellent catalytic ability and cycle stability for 4-nitrophenol(4-NP)and 2-nitrophenol(2-NA),providing new strategy for the study of catalytic composite materials related to degradation of wastewater.