Strong synergy between physical and chemical properties:Insight into optimization of atomically dispersed oxygen reduction catalysts

Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.

Atomically Dispersed Ruthenium Catalysts with Open Hollow Structure for Lithium-Oxygen Batteries

Lithium–oxygen battery with ultrahigh theoretical energy density is considered a highly competitive next-generation energy storage device,but its practical application is severely hindered by issues such as difficult decomposition of discharge products at present.Here,we have developed N-doped carbon anchored atomically dispersed Ru sites cathode catalyst with open hollow structure(h-RuNC)for Lithium–oxygen battery.On one hand,the abundance of atomically dispersed Ru sites can effectively catalyze the formation and decomposition of discharge products,thereby greatly enhancing the redox kinetics.On the other hand,the open hollow structure not only enhances the mass activity of atomically dispersed Ru sites but also improves the diffusion efficiency of catalytic molecules.Therefore,the excellent activity from atomically dispersed Ru sites and the enhanced diffusion from open hollow structure respectively improve the redox kinetics and cycling stability,ultimately achieving a high-performance lithium–oxygen battery.

Atomic Dispersed Hetero‑Pairs for Enhanced Electrocatalytic CO_(2)Reduction

Electrochemical carbon dioxide reduction reaction(CO_(2)RR)involves a variety of intermediates with highly correlated reaction and ad-desorption energies,hindering optimization of the catalytic activity.For example,increasing the binding of the*COOH to the active site will generally increase the*CO desorption energy.Breaking this relationship may be expected to dramatically improve the intrinsic activity of CO_(2)RR,but remains an unsolved challenge.Herein,we addressed this conundrum by constructing a unique atomic dispersed hetero-pair consisting of Mo-Fe di-atoms anchored on N-doped carbon carrier.This system shows an unprecedented CO_(2)RR intrinsic activity with TOF of 3336 h−1,high selectivity toward CO production,Faradaic efficiency of 95.96%at−0.60 V and excellent stability.Theoretical calculations show that the Mo-Fe diatomic sites increased the*COOH intermediate adsorption energy by bridging adsorption of*COOH intermediates.At the same time,d-d orbital coupling in the Mo-Fe di-atom results in electron delocalization and facilitates desorption of*CO intermediates.Thus,the undesirable correlation between these steps is broken.This work provides a promising approach,specifically the use of di-atoms,for breaking unfavorable relationships based on understanding of the catalytic mechanisms at the atomic scale.

Distributed Resource Allocation in Dispersed Computing Environment Based on UAV Track Inspection in Urban Rail Transit

With the rapid development of urban rail transit,the existing track detection has some problems such as low efficiency and insufficient detection coverage,so an intelligent and automatic track detectionmethod based onUAV is urgently needed to avoid major safety accidents.At the same time,the geographical distribution of IoT devices results in the inefficient use of the significant computing potential held by a large number of devices.As a result,the Dispersed Computing(DCOMP)architecture enables collaborative computing between devices in the Internet of Everything(IoE),promotes low-latency and efficient cross-wide applications,and meets users’growing needs for computing performance and service quality.This paper focuses on examining the resource allocation challenge within a dispersed computing environment that utilizes UAV inspection tracks.Furthermore,the system takes into account both resource constraints and computational constraints and transforms the optimization problem into an energy minimization problem with computational constraints.The Markov Decision Process(MDP)model is employed to capture the connection between the dispersed computing resource allocation strategy and the system environment.Subsequently,a method based on Double Deep Q-Network(DDQN)is introduced to derive the optimal policy.Simultaneously,an experience replay mechanism is implemented to tackle the issue of increasing dimensionality.The experimental simulations validate the efficacy of the method across various scenarios.

Atomically Dispersed Dual‑Metal Sites Showing Unique Reactivity and Dynamism for Electrocatalysis

The real structure and in situ evolution of catalysts under working conditions are of paramount importance,especially for bifunctional electrocatalysis.Here,we report asymmetric structural evolution and dynamic hydrogen-bonding promotion mechanism of an atomically dispersed electrocatalyst.Pyrolysis of Co/Ni-doped MAF-4/ZIF-8 yielded nitrogen-doped porous carbons functionalized by atomically dispersed Co–Ni dual-metal sites with an unprecedented N8V4 structure,which can serve as an efficient bifunctional electrocatalyst for overall water splitting.More importantly,the electrocatalyst showed remarkable activation behavior due to the in situ oxidation of the carbon substrate to form C–OH groups.Density functional theory calculations suggested that the flexible C–OH groups can form reversible hydrogen bonds with the oxygen evolution reaction intermediates,giving a bridge between elementary reactions to break the conventional scaling relationship.

New insight into the design of highly dispersed Pt supported CeO_(2)-TiO_(2) catalysts with superior activity for VOCs low-temperature removal

A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless deposition method and evaluated for the deep oxidation of n-hexane as a model VOCs. The results show that the CeO_(2)and TiOxnanoparticles can highly disperse into each other and form Ce_(2)Ti_(2)O_(7)solid solution with appropriate Ce/Ti molar ratio, which significantly improves their redox ability by enhancing the interaction between CeO_(2)and TiO_(x). The dispersibility of Pt species can also be adjusted by altering the Ce/Ti molar ratio, and Pt/CeTi-2/1 catalyst with Ce/Ti molar ratio of 2:1 exhibits the best Pt dispersibility that Pt species mainly exist as Pt single atoms. The high dispersion of Pt species in the Pt/CeO_(2)-TiO_(2)catalysts would promote the catalytic activity of VOCs oxidation with low T90% values(1000 ppm, GHSV = 15,000 h^(-1)), such as for n-hexane degradation with T90% of 139℃. The characterizations reveal that the superior activity is mainly related to possessing the more Pt2+species,adsorbed oxygen species and higher low-temperature reducibility owing to the strong interaction between highly dispersed Pt species and CeO_(2)-TiO_(2)as well as the promoted migration of lattice oxygen by the formation of more Ce_(2)Ti_(2)O_(7)species. Furthermore, the Pt/CeTi-2/1 catalyst also exhibits excellent stability for chlorinated and other non-chlorinated VOCs oxidation, making it very promising for real application under various operating conditions.

Theoretical and numerical simulation investigation of deep hole dispersed charge cut blasting

Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways.With the advent of digital electronic detonators and the need for increased production efciency,the traditional blasting design is no longer suitable for deep hole blasting.In this paper,a disperse charge cut blasting method was proposed to address the issues of low excavation depth and high block rate in deep hole undercut blasting.First,a blasting model was used to illustrate the mechanism of the deep hole dispersive charge cut blasting process.Then,continuous charge and dispersed charge blasting models were developed using the smooth particle hydrodynamics-fnite element method(SPHFEM).The cutting parameters were determined theoretically,and the cutting efciency was introduced to evaluate the cutting efect.The blasting efects of the two charging models were analyzed utilizing the evolution law of rock damage,the number of rock particles thrown,and the cutting efciency.The results show that using a dispersed charge improves the cutting efciency by about 20%and the rock breakage for the deep hole cut blasting compared to the traditional continuous charge.In addition,important parameters such as cutting hole spacing,cutting hole depth and upper charge proportion also have a signifcant impact on the cutting efect.Finally,the deep hole dispersed charge cut blasting technology is combined with the digital electronic detonator through the feld engineering practice.It provides a reference for the subsequent deep hole cutting blasting and the use of electronic detonators in rock roadways.

A Dynamic Bayesian-Based Comprehensive Trust Evaluation Model for Dispersed Computing Environment

Dispersed computing is a new resourcecentric computing paradigm.Due to its high degree of openness and decentralization,it is vulnerable to attacks,and security issues have become an important challenge hindering its development.The trust evaluation technology is of great significance to the reliable operation and security assurance of dispersed computing networks.In this paper,a dynamic Bayesian-based comprehensive trust evaluation model is proposed for dispersed computing environment.Specifically,in the calculation of direct trust,a logarithmic decay function and a sliding window are introduced to improve the timeliness.In the calculation of indirect trust,a random screening method based on sine function is designed,which excludes malicious nodes providing false reports and multiple malicious nodes colluding attacks.Finally,the comprehensive trust value is dynamically updated based on historical interactions,current interactions and momentary changes.Simulation experiments are introduced to verify the performance of the model.Compared with existing model,the proposed trust evaluation model performs better in terms of the detection rate of malicious nodes,the interaction success rate,and the computational cost.

Well-Dispersed Graphene Enhanced Lithium Complex Grease Toward High-Efcient Lubrication

Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the infuence of graphene dispersion on the thickening efect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modifed graphene ([P_(66614)][DEHP]-G). Then lithium complex grease was prepared by saponifcation with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefn (PAO20) as base oil and the modifed-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modifed-graphene lithium complex grease ofered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefcient and wear volume up to 18.84% and 67.34%, respectively. With base oil overfow and afux, well-dispersed [P_(66614)][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition flm. The synergy of deposited graphene-flm, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.

Degradable Foam Tray Based on High-concentration Dispersed Cellulose Fibers Obtained by a Hot-press Baking Process

Degradable industrial packaging foam trays made from cellulose fibers were fabricated using a hot-press baking process.Bleached softwood pulp fibers with a concentration of 30%were dispersed at a high speed under the action of a dispersant.The effects of the dispersant dosage of the fibers on the porosity,foam density,and static compression characteristics were discussed.Furthermore,the effects of the reinforcing adhesive including polyvinyl alcohol(PVA),and cassava starch on the physical and mechanical properties of the foam trays were studied,as well as the relationship between these properties and the microstructure of the foam trays.The dispersant enhanced the rheological and blistering properties of the fiber dispersion.As the dispersant dosage increased from 2%to 4%,the foam density gradually increased and the compressive strain performance and residual compressive strain of the foam trays decreased.Under the condition of constant dosage of dispersant,increasing the fiber proportion from 67%to 77%improved the porosity and foam density and slightly reduced the static compression performance.In additioton,the static compression resistance of the foamed materials was improved by increasing the PVA dosage since PVA was beneficial for improving the strength of the foam trays.

Experimental Determination of the Vibrational Constants of FeS（X5 △） by Dispersed Fluorescence Spectroscopy

Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels up to v＂=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS（X5 △） （518±5 cm-1） agrees well with that reported in a recent PES measurement （520±30 cm-1） [J. Phys. Chem. A 107, 2821 （2003）] which is the only one prior experimental vibrational frequency value for the 5 △ state of FeS. Careful comparisons of our experimental results and those documented in the literature （mainly from theoretical predictions） suggest that the ground state of FeS is 5 △ state.

A Fe-N-C catalyst with highly dispersed iron in carbon for oxygen reduction reaction and its application in direct methanol fuel cells

Exploring non‐precious metal catalysts for the oxygen reduction reaction （ORR） is essential for fuel cells and metal–air batteries. Herein, we report a Fe‐N‐C catalyst possessing a high specific surface area （1501 m2/g） and uniformly dispersed iron within a carbon matrix prepared via a two‐step pyrolysis process. The Fe‐N‐C catalyst exhibits excellent ORR activity in 0.1 mol/L NaOH electrolyte （onset potential, Eo=1.08 V and half wave potential, E1/2=0.88 V vs. reversible hydrogen electrode） and 0.1 mol/L HClO4 electrolyte （Eo=0.85 V and E1/2=0.75 V vs. reversible hydrogen electrode）. The direct methanol fuel cells employing Fe‐N‐C as the cathodic catalyst displayed promising per‐formance with a maximum power density of 33 mW/cm2 in alkaline media and 47 mW/cm2 in acidic media. The detailed investigation on the composition–structure–performance relationship by X‐ray diffraction, X‐ray photoelectron spectroscopy and Mo-ssbauer spectroscopy suggests that Fe‐N4, together with graphitic‐N and pyridinic‐N are the active ORR components. The promising direct methanol fuel cell performance displayed by the Fe‐N‐C catalyst is related to the intrinsic high catalytic activity, and critically for this application, to the high methanol tolerance.

Laser-induced Fluorescence and Dispersed Fluorescence Spectroscopy of NiB： Identification of a New 2П State in 19000-22100 cm^-1

The laser-induced fluorescence excitation spectra of jet-cooled NiB radicals have been recorded in the energy range of 19000-22100 cm-1. Eleven bands have been assigned to the [20.77]2П-X2∑＋ transition system for the first time. The dispersed fluorescence spectra related to most of these bands have been investigated. Vibrationally excited levels of the ground electronic state, with v＂ up to 6, have been observed. In addition, the lifetimes for almost all the observed bands have also been measured.

Mass Transfer Enhancement of Gas Absorption by Adding the Dispersed Organic Phases

Mass transfer enhancement of gas absorption by adding a dispersed organic phase has been studied in this work. Various dispersed organic phases （heptanol, octanol, isoamyl alcohol, heptane, octane, and isooctane） were tested respectively in the experiment. According to the theoretical model and experimental data, the overall volumetric mass transfer coefficient and enhancement factor were obtained under different dispersed organic phase volume fraction and stirring speed. The experimental results indicate that gas-liquid mass transfer is enhanced at different level by adding a dispersed organic phase. The best performance of enhancement were achieved with the dispersed organic phase volumetric fraction of 5% and under an intermediate stirring speed of 670 r·min^-1. Among the organic phases tested in the experiment, alcohols show better performance, which gave 20% higher enhance-ment of overall volumetric mass transfer coefficient than adding alkanes.

Tuning Atomically Dispersed Fe Sites in Metal–Organic Frameworks Boosts Peroxidase‑Like Activity for Sensitive Biosensing

Although nanozymes have been widely developed,accurate design of highly active sites at the atomic level to mimic the electronic and geometrical structure of enzymes and the exploration of underlying mechanisms still face significant challenges.Herein,two functional groups with opposite electron modulation abilities(nitro and amino)were introduced into the metal–organic frameworks(MIL-101(Fe))to tune the atomically dispersed metal sites and thus regulate the enzymelike activity.Notably,the functionalization of nitro can enhance the peroxidase(POD)-like activity of MIL-101(Fe),while the amino is poles apart.Theoretical calculations demonstrate that the introduction of nitro can not only regulate the geometry of adsorbed intermediates but also improve the electronic structure of metal active sites.Benefiting from both geometric and electronic effects,the nitro-functionalized MIL-101(Fe)with a low reaction energy barrier for the HO*formation exhibits a superior POD-like activity.As a concept of the application,a nitro-functionalized MIL-101(Fe)-based biosensor was elaborately applied for the sensitive detection of acetylcholinesterase activity in the range of 0.2–50 mU mL−1 with a limit of detection of 0.14 mU mL−1.Moreover,the detection of organophosphorus pesticides was also achieved.This work not only opens up new prospects for the rational design of highly active nanozymes at the atomic scale but also enhances the performance of nanozyme-based biosensors.

Advances in Studies on Turbulent Dispersed Multiphase Flows

Dispersed multiphase flows,including gas-particle(gas-solid),gas-spray,liquid-particle(liquid-solid) ,liquid-bubble,and bubble-liquid-particle flows,are widely encountered in power,chemical and metallurgical,aeronautical and astronautical,transportation,hydraulic and nuclear engineering. In this paper,advances and re-search needs in fundamental studies of dispersed multiphase flows,including the particle/droplet/bubble dynamics,particle-particle,droplet-droplet and bubble-bubble interactions,gas-particle and bubble-liquid turbulence interac-tions,particle-wall interaction,numerical simulation of dispersed multiphase flows,including Reynolds-averaged modeling(RANS modeling),large-eddy simulation(LES) and direct numerical simulation(DNS) are reviewed. The research results obtained by the present author are also included in this review.

Hydrogenation Conversion of Phenanthrene over Dispersed Mo-based Catalysts

With oil-soluble molybdenum compound and sublimed sulfur serving as raw materials, two dispersed Mo-based catalysts were prepared, characterized and then applied to the hydrogenation conversion of phenanthrene. The test results showed that under the conditions specified by this study, the catalyst prepared in a higher sulfiding atmosphere was more catalytically active due to its higher content of MoS2 and stronger intrinsic catalytic activity of MoS2 unit, which demonstrated that the sulfiding atmosphere for the preparation of catalysts not only could influence the yield of MoS2 but also the structure of MoS2.The analysis on the selectivity of octahydrophenanthrene isomers revealed that the catalyst prepared in a lower sulfiding atmosphere had a relatively higher catalytic selectivity to the hydrogenation of outer aromatic ring and the structure of catalysts could be modified under the specific reaction conditions. Moreover, the selectivity between the isomers of as-octahydrophenanthrene at different reaction time and temperature was analyzed and, based on the results, a hydrogenation mechanism over dispersed Mo-based catalysts was suggested, with monatomic hydrogen transfer and catalytic surface desorption of the half-addition intermediates functioning as the key points. In addition, it is concluded that the catalyst prepared in a lower sulfiding atmosphere was more capable of adsorption than the other one.

Corrosion resistance evaluation of highly dispersed MgO–MgAl2O4–ZrO2 composite and analysis of its corrosion mechanism: A chromium-free refractory for RH refining kilns

The corrosion resistance behavior of a highly dispersed MgO-MgAl2O4-ZrO2 composite refractory material is examined by testing with high-basicity and low-basicity RH(Ruhrstahl-Hereaeus)slags.The composite material exhibits greater resistance to the RH slags than the traditional MgO-Cr2O3 composite,MgO-ZrO2 composite,and MgO-MgAl2O4-ZrO2 composite.On the basis of the microstructural analysis and mechanisms calculations,the corrosion resistance behavior of the MgO-MgAl2O4-ZrO2 composite is attributable to its highly dispersed structure,which helps protect the high activity of ZrO2.When in contact with the slag,ZrO2 reacts with CaO to form the stable phase CaZrO3,which protects MgAl2O4 against corrosion,thereby enhancing the corrosion resistance of the composite.

Atomically Dispersed Transition Metal-Nitrogen-Carbon Bifunctional Oxygen Electrocatalysts for Zinc-Air Batteries:Recent Advances and Future Perspectives

Rechargeable zinc-air batteries(ZABs)are currently receiving extensive attention because of their extremely high theoretical specific energy density,low manufacturing costs,and environmental friendliness.Exploring bifunctional catalysts with high activity and stability to overcome sluggish kinetics of oxygen reduction reaction and oxygen evolution reaction is critical for the development of rechargeable ZABs.Atomically dispersed metal-nitrogen-carbon(M-N-C)catalysts possessing prominent advantages of high metal atom utilization and electrocatalytic activity are promising candidates to promote oxygen electrocatalysis.In this work,general principles for designing atomically dispersed M-N-C are reviewed.Then,strategies aiming at enhancing the bifunctional catalytic activity and stability are presented.Finally,the challenges and perspectives of M-N-C bifunctional oxygen catalysts for ZABs are outlined.It is expected that this review will provide insights into the targeted optimization of atomically dispersed M-N-C catalysts in rechargeable ZABs.

A facile sulfur-assisted method to synthesize porous alveolate Fe/g-C3N4 catalysts with ultra-small cluster and atomically dispersed Fe sites

Heterogeneous catalysts with ultra-small clusters and atomically dispersed(USCAD)active sites have gained increasing attention in recent years.However,developing USCAD catalysts with high-density metal sites anchored in porous nanomaterials is still challenging.Here,through the template-free S-assisted pyrolysis of low-cost Fe-salts with melamine(MA),porous alveolate Fe/g-C3N4 catalysts with high-density(Fe loading up to 17.7 wt%)and increased USCAD Fe sites were synthesized.The presence of a certain amount of S species in the Fe-salts/MA system plays an important role in the formation of USCAD S-Fe-salt/CN catalysts;the S species act as a"sacrificial carrier"to increase the dispersion of Fe species through Fe-S coordination and generate porous alveolate structure by escaping in the form of SO2 during pyrolysis.The S-Fe-salt/CN catalysts exhibit greatly promoted activity and reusability for degrading various organic pollutants in advanced oxidation processes compared to the corresponding Fe-salt/CN catalysts,due to the promoted accessibility of USCAD Fe sites by the porous alveolate structure.This S-assisted method exhibits good feasibility in a large variety of S species(thiourea,S powder,and NH4SCN)and Fe salts,providing a new avenue for the low-cost and large-scale synthesis of high-density USCAD metal/g-C3N4 catalysts.