Crystal facet engineering coexposed CuIn(200)and In(101)in CuIn alloy nanocatalysts enabling selective and stable CO_(2)electroreduction

The electrocatalytic carbon dioxide reduction reaction(eCO_(2)RR)into high-value-added chemicals and fuels is a promising strategy to mitigate global warming.However,it remains a significant stumbling block to the rationally tuning lattice plane of the catalyst with high activity to produce the target product in the eCO_(2)RR process.To attempt to solve this problem,the Culn bimetallic alloy nanocatalyst with specifically exposed lattice planes is modulated and electrodeposited on the nitrogen-doped porous carbon cloth by a simple two-step electrodeposition method,which induces high Faraday efficiency of 80%towards HCOO-(FEHCOO-)with a partial current density of 13.84 mA cm-2at-1.05 V(vs.RHE).Systematic characterizations and theoretical modeling reveal that the specific coexposed Culn(200)and In(101)lattice facets selectively adsorbed the key intermediate of OCHO*,reducing the overpotential of HCOOH and boosting the FEHCOO-in a wide potential window(-0.65--1.25 V).Moreover,a homogeneous distribution of Culn nanoparticles with an average diameter of merely~3.19 nm affords exposure to abundant active sites,meanwhile prohibiting detachment and agglomeration of nanoparticles during eCO_(2)RR for enhanced stability attributing to the self-assembly electrode strategy.This study highlights the synergistic effect between catalytic activity and facet effect,which opens a new route in surface engineering to tune their electrocatalytic performance.

SMFs-supported Pd nanocatalysts in selective acetylene hydrogenation:Pore structure-dependent deactivation mechanism

In the present study,CNFs,ZnO and Al2O3 were deposited on the SMFs panels to investigate the deactivation mechanism of Pd-based catalysts in selective acetylene hydrogenation reaction.The examined supports were characterized by SEM,NH3-TPD and N2adsorption-desorption isotherms to indicate their intrinsic characteristics.Furthermore,in order to understand the mechanism of deactivation,the resulted green oil was characterized using FTIR and SIM DIS.FTIR results confirmed the presence of more unsaturated constituents and then,more branched hydrocarbons formed upon the reaction over alumina-supported catalyst in comparison with the ones supported on CNFs and ZnO,which in turn,could block the pores mouths.Besides the limited hydrogen transfer,N2 adsorption-desorption isotherms results supported that the lowest pore diameters of Al2O3/SMFs close to the surface led to fast deactivation,compared with the other catalysts,especially at higher temperatures.

Catalytic Performance of CeO_2/ZnO Nanocatalysts on the Oxidative Coupling of Methane with Carbon Dioxide and their Fractal Features

CeO2/ZnO nanocatalysts were prepared from the coupling route of homogeneous precipita-tion with microemulsion and the impregnation method. The catalytic performance of these two kinds of catalysts on the oxidative coupling of methane with carbon dioxide was tested and compared; the frac-tal behavior of the nanocatalysts was analyzed using fractal theory. The CeO2/ZnO nanocatalysts had much higher activity than the catalysts prepared by impregnation method. There was no regular relation-ship between the average size of CeO2/ZnO nanocatalysts and their catalytic performance; however, the conversion of methane increased with the increase of the fractal dimension of CeO2/ZnO nanocatalysts.

In situ preparation of well-dispersed CuO nanocatalysts in heavy oil for catalytic aquathermolysis

We developed an in situ synthesis strategy for preparing well-dispersed CuO nanoparticles as aquathermolysis catalyst for viscosity reduction in Shengli heavy oil(China). A Cu(OH)_2-contained microemulsion was employed as a carrier to disperse the precursor Cu(OH)_2 to the heavy oil phase. Under aquathermolysis condition(240 ℃, 2.5 MPa of N_2), the Cu(OH)_2 precursors would first be converted in situ to well-crystallized and size-homogeneous CuO nanoparticles naturally, catalyzed by which the viscosity of Shengli heavy oil could be reduced as much as 94.6%; simultaneously, 22.4% of asphaltenes were converted to light components. The agglomeration of the in situ prepared monoclinic CuO nanoparticles could be negligible throughout the catalytic reaction. Based on the characterization results of ~1 H NMR, elemental analysis and GC-MS of oil samples before and after catalytic aquathermolysis, the mechanism for viscosity reduction of heavy oil in the catalytic system was investigated.

Kinetic studies on extra heavy crude oil upgrading using nanocatalysts by applying CFD techniques

Regarding the growth of global energy consumption and the paucity of light crude oil, extracting and using heavy and extra heavy crude oil has received much more attention, but the application of this kind of oil is complicated due to its very high molecular weight. High viscosity and low flowability complicate the transportation of heavy and extra heavy crude oil. Accordingly, it is essential to reduce the viscosity of heavy and extra heavy crude oil through in-situ operations or immediate actions after extraction to reduce costs. Numerical simulations are influential methods, because they reduce calculation time and costs. In this study, the cracking of extra heavy crude oil using computational fluid dynamics is simulated, and a unique kinetic model is proposed based on experimental procedures to predict the behavior of extra heavy crude oil cracking reaction. Moreover, the hydrodynamics and heat transfer of the system and influence of nanocatalysts and temperature on the upgrading of crude oil are studied. The geometry of a reactor is produced using commercial software, and some experiments are performed to examine the validity and accuracy of the numerical results. The findings reveal that there is a good agreement between the numerical and experimental results. Furthermore, to investigate the main factors affecting the process, sensitivity analysis is adopted. Results show that type of catalyst and concentration of catalyst are the parameters that influence the viscosity reduction of extra heavy crude oil the most. The findings further revealed that when using a 25 nm SiO_2 nanocatalyst, a maximum viscosity reduction of 98.67% is observed at 623 K. Also, a catalyst concentration of 2.28 wt% is best for upgrading extra heavy crude oil. The results obtained through sensitivity analysis, simulation model, and experiments represent effectual information for the design and development of high performance upgrading processes for energy applications.

In situ XRD Studies on Heat-treated PtRu/C Nanocatalysts

Extremely small PtRu/C nanocatalysts were prepared via a carbonyl route. A thorough in situ reduction X-ray structural characterization of these catalysts was performed. After synthesis and storage under ambient condi- tions, the diffraction patterns of PtRu/C catalysts were seriously modified, indicating the surface oxide formation. In the reduced state, the particle size is around 2 nm. The observed relative fluctuations of lattice constants are 3%, which is far too large to be explained by a compositional fluctuation. Their origin is attributed to strong but isotropic strains and is related to the alloy formation. The annealing experiments show all the catalysts present an exceptional thermal stability when annealed in inert ambient, especially that of the Pt1Ru1/C catalyst. Besides, it is interesting to note that there is no thermal expansion evidence from the patterns.

Graphene derivatives supported nanocatalysts for oxygen reduction reaction

Very recent progress on the graphene derivatives supported variable nanocatalysts for oxygen reduction reaction （ORR） in fuel cell is reviewed. First, common electrochemical techniques to characterize graphene-based electrocatalysts are mentioned. Second, recent updates on gra- phene-derived electrocatalysts are introduced. In this part, both electrochemical activity and stabil- ity of Pt catalysts can be improved when they are supported by reduced graphene oxide （RGO）. Other noble-metal catalysts including Pd, Au, and Ag showing comparable performance have been investigated. The stability of Pd catalyst is enhanced by RGO or few-layered graphene support. Syn- thetic approaches for Au or Ag catalysts supported on graphene oxide are discussed. In addition, non-noble transition metals in N4-chelate complexes can reduce oxygen electrochemically. Fe and Co are cheap alternative catalysts for ORR. In most cases, the stability and tolerance issues are overcome well, but their overall performances don＇t seem to surpass Pt/C catalyst yet,

Surface engineering of 1D nanocatalysts for value-added selective electrooxidation of organic chemicals

Electrolytic water splitting by renewable energy is a technology with great potential for producing hydrogen(H_(2))without carbon emission,but this technical route is hindered by its huge energy(electricity)cost,which is mainly wasted by the anode oxygen evolution reaction(OER)while the value of the anode product(oxygen)is very limited.Replacing the high-energy-cost OER with a selective organic compound electrooxidation carried out at a relatively lower potential can reduce the electricity cost while producing value-added chemicals.Currently,H_(2) generation coupled with synthesis of value-added organic compounds faces the challenge of low selectivity and slow generation rate of the anodic products.One-dimensional(1D)nanocatalysts with a unique morphology,well-defined active sites,and good electron conductivity have shown excellent performance in many electrocatalytic reactions.The rational design and regulation of 1D nanocatalysts through surface engineering can optimize the adsorption energy of intermediate molecules and improve the selectivity of organic electrooxidation reactions.Herein,we summarized the recent research progress of 1D nanocatalysts applied in different organic electrooxidation reactions and introduced several different fabrication strategies for surface engineering of 1D nanocatalysts.Then,we focused on the relationship between surface engineering and the selectivity of organic electrooxidation reaction products.Finally,future challenges and development prospects of 1D nanocatalysts in the coupled system consisting of organic electrooxidation and hydrogen evolution reactions are briefly outlined.

Copper-based nanocatalysts toward chemoselective hydrogenation reaction

Cu-based catalysts are widely used in various heterogeneous catalytic reaction systems,the precise control of their electronic structure is an intrinsic require-ment for the rational design of metal catalysts,and it is also an important basis for clarifying their structure-activity relationships.Changing the electronic structure of Cu-based catalysts is an important way to improve the catalytic hydrogenation performance of Cu-based catalysts by controlling the adsorption intensity be-tween the reaction adsorbate and the active center.In this paper,the application of selective hydrogenation of Cu-based catalysts is reviewed,with a special emphasis on the selective catalytic hydrogenation reduction of p-nitrostyrene and CO_(2).This review particularly emphasizes the application of Cu-based catalysts in the field of selective hydrogenation and discusses the influence of their different properties on selective hydrogenation performance.

Tungsten-based nanocatalysts with different structures for visible light responsive photocatalytic degradation of bisphenol A

Environmental pollution,such as water contamination,is a critical issue that must be absolutely addressed.Here,three different morphologies of tungsten-based photocatalysts(WO_(3)nanorods,WO_(3)/WS_(2)nanobricks,WO_(3)/WS_(2)nanorods)are made using a simple hydrothermal method by changing the solvents(H_(2)O,DMF,aqueous HCl solution).The as-prepared nanocatalysts have excellent thermal stability,large porosity,and high hydrophilicity.The results show all materials have good photocatalytic activity in aqueous media,with WO_(3)/WS_(2)nanorods(NRs)having the best activity in the photodegradation of bisphenol A(BPA)under visible-light irradiation.This may originate from increased migration of charge carriers and effective prevention of electron–hole recombination in WO_(3)/WS_(2)NRs,whereby this photocatalyst is able to generate more reactive·OH and·O_(2)^(–)species,leading to greater photocatalytic activity.About 99.6% of BPA is photodegraded within 60 min when using 1.5 g/L WO_(3)/WS_(2)NRs and 5.0 mg/L BPA at pH 7.0.Additionally,the optimal conditions(pH,catalyst dosage,initial BPA concentration)for WO_(3)/WS_(2)NRs are also elaborately investigated.These rod-like heterostructures are expressed as potential catalysts with excellent photostability,efficient reusability,and highly active effectivity in different types of water.In particular,the removal efficiency of BPA by WO_(3)/WS_(2)NRs reduces by only 1.5% after five recycling runs and even reaches 89.1%in contaminated lake water.This study provides promising insights for the nearly complete removal of BPA from wastewater or different water resources,which is advantageous to various applications in environmental remediation.

Development, dilemma and potential strategies for the application of nanocatalysts in wastewater catalytic ozonation: A review

With the continuous development of nanomaterials in recent years,the application of nanocatalysts in catalytic ozone oxidation has attracted more and more researchers’attention due to their excellent catalytic properties.In this review,we systematically summarized the current research status of nanocatalysts mainly involving material categories,mechanisms and catalytic efficiency.Based on summary and analysis,we found most of the reported nanocatalysts were in the stage of laboratory research,which was caused by the nanocatalysts defects such as easy aggregation,difficult separation,and easy leakage.These defects might result in severe resource waste,economic loss and potentially adverse effects imposed on the ecosystem and human health.Aiming at solving these defects,we further analyzed the reasons and the existing reports,and revealed that coupling nano-catalyst and membrane,supported nanocatalysts and magnetic nanocatalysts had promising potential in solving these problems and promoting the actual application of nanocatalysts in wastewater treatment.Furthermore,the advantages,shortages and our perspectives of these methods are summarized and discussed.

Synthesis of amorphous Pd-based nanocatalysts for efficient alcoholysis of styrene oxide and electrochemical hydrogen evolution

Amorphous nanomaterials with long-range disordered structures could possess distinct properties and promising applications,especially in catalysis,as compared with their conventional crystalline counterparts.It is imperative to achieve the controlled preparation of amorphous noble metal-based nanomaterials for the exploration of their phase-dependent applications.Here,we report a facile wet-chemical reduction strategy to synthesize various amorphous multimetallic Pd-based nanomaterials,including PdRu,PdRh,and PdRuRh.The phase-dependent catalytic performances of distinct Pd-based nanomaterials towards diverse catalytic applications have been demonstrated.Specifically,the usage of PdRu nanocatalysts with amorphous and crystalline face-centered cubic(fcc)phases can efficiently switch the ring-opening route of styrene oxide to obtain different products with high selectivity through alcoholysis reaction and hydrogenation reaction,respectively.Moreover,when used as an electrocatalyst for hydrogen evolution reaction(HER),the synthesized amorphous PdRh nanocatalyst exhibits low overpotential and high turnover frequency values,outperforming its crystalline fcc counterpart and most of the reported Pd-based HER electrocatalysts.

Water promoted structural evolution of Ag nanocatalysts supported on alumina

Water is often involved in many catalytic processes,which can strongly affect structural evolution of catalysts during pretreatments and catalytic reactions.In this work,we demonstrate a promotional effect of H_(2)O on both oxidative dispersion and spontaneous aggregation of Ag nanocatalysts supported on alumina.Ag nanoparticles supported onγ-Al_(2)O_(3) and Ag nanowires on Al_(2)O_(3)(0001)can be dispersed into nanoclusters via annealing in O_(2)above 300℃,which is accelerated by introduction of H_(2)O into the oxidative atmosphere.Furthermore,the formed highly dispersed Ag nanoclusters are subject to spontaneous aggregation in humid atmosphere at room temperature.Ex situ and in situ characterizations in both powder and model catalysts suggest that formation of abundant surface hydroxyls and/or water adlayer on the Al_(2)O_(3) surface in the H_(2)O-containing atmosphere facilitates the surface migration of Ag species,thus promoting both dispersion and aggregation processes.The aggregation of the supported Ag nanostructures induced by the humid oxidative atmosphere enhances CO oxidation but inhibits selective catalytic reduction of NO with C_(3)H_(6).This work illustrates the critical role of H_(2)O in structure and catalytic performance of metal nanocatalysts,which can be widely present in heterogeneous catalysis.

Pd-based nanocatalysts for oxygen reduction reaction:Preparation,performance,and in-situ characterization

Electrochemical energy devices such as fuel cells have received extensive concern in recent decades.However,the commercial applications of fuel cells have been restricted by the slow kinetics of oxygen reduction reaction(ORR).Pd-based fuel cell catalysts are strong candidates for enhanced ORR activities,especially under alkaline conditions.Therefore,extensive exploration has been made to improve the performance of Pd-based nano-catalysts for oxygen reduction reaction.This paper reviews the research progress of preparation,electrocatalytic performance,and in-situ characterization of various Pd-based oxygen reduction catalysts,from zero-dimensional nanoparticles,to one-dimensional nanowires,to two-dimensional nanosheets,and to Pd single-atom catalysts.It may provide some help for improving the activity of Pd-based catalysts and understanding the reaction mecha-nisms and structure-activity relationships.

Nanocrystals:Solution-Based Synthesis and Applications as Nanocatalysts

Nanocrystals are emerging as key materials due to their novel shape-and size-dependent chemical and physical properties that differ drastically from their bulk counterparts.The main challenges in this field remain rationally controlled synthesis and large scale production.This article reviews recent progress in our laboratory related to solution-based synthesis of various nanostructures,including zero-dimensional(0-D)nanocrystals,1-D nanowires and nanorods,hollow structures,and superlattice materials.On the other hand,the essential goal for nanoresearchers is to achieve industrial applications of nanostructured materials.In the past decades,these fascinating materials have been widely used in many promising fields such as nanofabrication,nanodevices,nanobiology,and nanocatalysis.Herein,we focus on their applications as nanocatalysts and try to illustrate the main problems and future directions in this area based on our recent endeavors in catalytic applications of nanocrystals.

Engineering carbon nanocatalysts towards efficient degradation of emerging organic contaminants via persulfate activation:A review

The engineering of carbon nanocatalysts for the persulfate activated elimination of emerging organic contaminants(EOCs)demonstrates promising potential compared with metal-based counterparts due to their unique advantage of high stability and low toxicity.The early reviews introduced the theoretical background of persulfate activation together with a detailed summary of different mechanisms responsible for degradation of EOCs.To further unify the state of knowledge,identify the research gaps,and prompt new research in this area,we present a thorough review on current trends in research on metal-free carbon nanocatalysts(e.g.,0D nanodiamond,1D carbon nanotubes and carbon nanofibers,2D graphene and graphitic carbon nitride,and 3D carbon nanocatalysts),with emphasis on their applications in persulfate activation and EOCs decontamination.We also discuss the current challenges and future perspectives in practically relevant applications.Last,we highlight that the development of sustainable carbon nanocatalysts/persulfate systems lies at the interface of multiple disciplines,which calls for future in-depth interdisciplinary collaborations.

Metallo-aerogels derived from chitosan with encapsulated metal nanoparticles as robust,efficient and selective nanocatalysts towards reduction of nitroarenes

A series of robust metallo-aerogels are readily fabricated by pyrolysis of xerogels derived from chitosan-metal(M=Fe,Co,Ni)hydrogels.Owing to the strong coordination between metal ions and the functional groups(NH2 and OH)of chitosan,metallo-aerogels consisting of encapsulated metal-nanoparticles(MNPs)by graphite shells were obtained,as supported by various characterizations including high-resolution transmission electron microscope(HR-TEM),X-ray diffraction(XRD),and Raman.The resulting metalloaerogels could be functioned as highly stable,efficient and selective nanocatalysts towards the hydrogenation of nitroarenes to amines at low catalyst loading(1.2 mol.%-2.4 mol.%).Remarkably,the metallo-aerogels could be reused for more than 30 runs without obvious loss of activity and selectivity.These distinguished performances were attributed to the graphitic shells formed during the pyrolysis,which hampered the possible aggregation of MNPs,prevented metal leaching and increased their stability.

Monolayer MoS_2 decorated Cu_7S_4-Au nanocatalysts for sensitive and selective detection of mercury(Ⅱ)

Sensitive and selective detection of Hg（II） contamination is of great importance with concern of public health. Herein, we successfully fabricated monolayer MoS2 （S-MoS2） decorated Cu7S4-Au （Cu7S4-Au@S-MoS2） nanocomposite modified electrode for the sensitive and selective detection of Hg（II） via anodic stripping voltammetric technique. Due to the excellent electrocatalytic reduction performance arisen from the abundant active edge sites of small monolayer MoS2 and good affinity of Au toward Hg, the current method displayed high sensitivity （LOD = 190 nmol L-l） and enhanced selectivity. As control, nanostructures including Cu7S4-Au, Cu7S4@S-MoS2 and Cu7S4-Au@M-MoS2 （M： multilayer） were also investigated, but showed low re- sponse to Hg（Ⅱ）, suggesting that both Au domains and active edge sites of monolayer MoS2 have crucial synergistic effects on the high-performance for recognition of Hg（Ⅱ）. Moreover, the developed method displays satisfied performance for the detection of Hg（Ⅱ） in real samples, which indicates its potentials in practical applications.

Phase engineering of metal nanocatalysts for electrochemical CO_(2) reduction

The electrochemical CO_(2) reduction reaction(CO_(2)RR)offers a green and sustainable process to convert CO_(2) into valuable chemical stocks and fuels.Metal is one of the most promising types of catalysts to drive an efficient and selective CO_(2)RR.The catalytic performance of metal nanocatalysts is strongly dependent on their structural features.Recently,phase engineering of nanomaterials(PEN)has emerged as a prominent tactic to regulate the catalytic performance of metal nanocatalysts for the CO_(2)RR.A broad range of metal nanocatalysts with conventional and unconventional crystal phases has been developed,and remarkable achievements have been made.This review summarizes the most recent developments in phase engineering of metal nanocatalysts for the electrochemical CO_(2)RR.We first introduce the different crystal phases of metal nanocatalysts used in the CO_(2)RR and then discuss various synthetic strategies for unconventional phases of metal nanocatalysts.After that,detailed discussions of metal nanocatalysts with conventional and unconventional phases,including amorphous phases,are presented.Finally,the challenges and perspectives in this emerging area are discussed.

One-Pot Green Synthesis of 1, 4-Dihydropyridine Derivatives Using Polyindole TiO2 Nanocatalyst by Solvent Free Method

This study used a Polyindole in combination with TiO2 nanocatalyst as an efficient heterogeneous catalyst to carry out a multi-component Hantzsch reaction involving different aromatic aldehydes with methyl acetoacetate, and aqueous ammonium to create 1,4-dihydropyridine derivatives under solvent free condition at ambient temperature. A broad range of aldehydes and methyl acetoacetates, ranging from heteroaromatic to polyaromatic one, with high level of functional group tolerance can be used to provide the desired products possessing relevant medicinal moiety in high yields. This technology has prospective advantages over current protocols, including the utilization of a cheap, stable, recyclable, and safe catalyst, quicker reaction times with higher yields and simple product isolation.