金属纳米晶体电催化剂的电化学合成:原理、应用与挑战

金属纳米晶体催化剂由于其独特的电子性质,在电化学能源转化反应中表现出优异的催化性能。为了提升催化剂的活性和耐久性,需要精确调控其晶体结构和形貌。然而,传统的制备方法往往需要严苛的条件,如高温、高压和特定的有机物,以控制晶体的生成和生长过程。这限制了能够合成的金属基催化剂的种类,并导致清洗复杂和有机物残留的问题。电化学方法通过电化学响应获取体系过程信息,并可以通过调控参数来调节晶体的生长。特别是非水体系的电化学方法为活泼的过渡金属催化剂提供了可行的途径。然而,电化学方法自身对体系变化的敏感性使得从小面积电极制备催化剂扩展到电极级别的催化层制备面临挑战。这涉及许多机理和方法上的变化,对相关研究提出了较大的挑战。本文基于晶体生长机理,探讨了电化学制备金属晶体的可行性,并综述了电化学沉积制备纳米级金属电催化剂的研究。最后,对电化学制备纳米级金属晶体催化剂面临的挑战进行了分析,并提出了实现更广泛应用的建议。通过电化学方法制备金属纳米晶体催化剂在提高制备的可控性、减少有机物残留等方面具有潜在的优势,但也需要克服相关技术和方法上的难题,以实现其在能源转化等领域的应用。

Ultrafine ordered L1_(2)-Pt-Co-Mn ternary intermetallic nanoparticles as high-performance oxygen-reduction electrocatalysts for practical fuel cells

The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.

Potential-dependent insights into the origin of high ammonia yield rate on copper surface via nitrate reduction:A computational and experimental study

Focusing on revealing the origin of high ammonia yield rate on Cu via nitrate reduction(NO3RR),we herein applied constant potential method via grand-canonical density functional theory(GC-DFT)with implicit continuum solvation model to predict the reaction energetics of NO3RR on pure copper surface in alkaline media.The potential-dependent mechanism on the most prevailing Cu(111)and the minor(100)and(110)facets were established,in consideration of NO_(2)_(−),NO,NH_(3),NH_(2)OH,N_(2),and N_(2)O as the main products.The computational results show that the major Cu(111)is the ideal surface to produce ammonia with the highest onset potential at 0.06 V(until−0.37 V)and the highest optimal potential at−0.31 V for ammonia production without kinetic obstacles in activation energies at critical steps.For other minor facets,the secondary Cu(100)shows activity to ammonia from−0.03 to−0.54 V with the ideal potential at−0.50 V,which requires larger overpotential to overcome kinetic activation energy barriers.The least Cu(110)possesses the longest potential range for ammonia yield from−0.27 to−1.12 V due to the higher adsorption coverage of nitrate,but also with higher tendency to generate di-nitrogen species.Experimental evaluations on commercial Cu/C electrocatalyst validated the accuracy of our proposed mechanism.The most influential(111)surface with highest percentage in electrocatalyst determined the trend of ammonia production.In specific,the onset potential of ammonia production at 0.1 V and emergence of yield rate peak at−0.3 V in experiments precisely located in the predicted potentials on Cu(111).Four critical factors for the high ammonia yield and selectivity on Cu surface via NO3RR are summarized,including high NO3RR activity towards ammonia on the dominant Cu(111)facet,more possibilities to produce ammonia along different pathways on each facet,excellent ability for HER inhibition and suitable surface size to suppress di-nitrogen species formation at high nitrate coverage.Overall,our work provides comprehensive potential-dependent insights into the reaction details of NO3RR to ammonia,which can serve as references for the future development of NO3RR electrocatalysts,achieving higher activity and selectivity by maximizing these characteristics of copper-based materials.

The“Top 50 High Impact Researches of Traditional Medicine”published in 2021

In recent years,significant progress has been achieved in both basic and clinical research within the field of traditional medicine,garnering increasing attention worldwide.To further promote a high-quality and international development of traditional medicine,the editorial board of Acupuncture and Herbal Medicine provided a collection of the“Top 50 High-impact Researches of Traditional Medicine”published in 2021 through objective indicators and a strict selection process.The findings of the selected articles have a significant academic influence and possess considerable academic value both nationally and internationally.The selected articles cover a wide range of topics,including clinical research,acupuncture,pharmacology,chemistry,biosynthesis,medicinal plant resources,and new formulation and drug delivery system research on traditional medicine.Therefore,this article outlines the selection process of the top 50 high-impact research articles,analyzes their research characteristics,and provides a brief summary of their new findings and perspectives in the field of traditional medicine.

Regulating the synergy coefficient of composite materials for alleviating self-discharge of supercapacitors

Supercapacitor is an efficient energy storage device,yet its wider application is still limited by self-discharge.Currently,various composite materials have been reported to have improved inhibition on self-discharge,while the evaluation of the synergistic effect in composite materials is challenging.Herein,pairs of intercalation type pseudocapacitive niobium oxides are pre-lithiated and coupled to construct conjugatedly configured supercapacitors,within which the cathode and anode experience identical reaction environment with single type of charge carrier,thus providing ideal platform to quantify the synergistic effect of composite materials on the self-discharge process.By using titanium dioxide as the stabilizer,we have compared how the modes of forming composite would influence the selfdischarge performance of the active composite materials with similar ratio of the constituent materials.Specifically,core@shell Nb_(2)O_(5)@TiO_(2) composite using TiO_(2) as the shell shows significantly higher synergy coefficient(μ=0.61,defined as the value that evaluates the synergistic effect between composite materials,and can be quantified using the overall performance of the composite,performance of individual component as well as the ratio of the component.) than other control group samples,which corresponds to the highest retained energy of 63% at 100 h.This work is expected to provide a general method for quantifying the synergistic effect and guide the design of composite materials with specific mode of forming the composite.

分散溶剂对PEMFC催化层中超薄Nafion离聚物质子传导的影响

质子交换膜燃料电池(PEMFC)商业化应用的瓶颈仍然是贵金属催化剂导致的成本问题。然而,目前对于催化层中纳米尺度全氟磺酸离聚物(以Nafion为代表)薄膜中质子传导的问题研究不足,无法完善三相界面的成型规律,进而指导催化层设计。在催化层浆料制备过程中,分散溶剂对Nafion的分散形态有直接影响,可能对催化层成型后附着在催化剂颗粒表面Nafion薄膜的微观结构有潜在影响,进而影响Nafion薄膜的质子传导能力。因此,在本文中利用分子自组装技术模拟催化层离聚物薄膜的聚集过程,于模型基底上制备厚度精确可控的纳米尺度Nafion薄膜,并通过微观测试表征技术探索并建立纳米尺度Nafion离聚物的微观结构模型,阐明分散溶剂对Nafion薄膜微观结构及质子传导的影响。研究发现Nafion薄膜在纳米尺度下的质子电导率比体相膜的质子电导率低一个数量级,使用介电常数较小的醇类溶剂可以使Nafion薄膜形成更有利于质子传导的微观结构,使Nafion薄膜的质子电导率得到提高。相关研究结果为优化PEMFC催化层结构,改善PEMFC催化层中质子传导问题提供给了依据。

Review of the characteristics and graded utilisation of coal gasification slag

The characteristics of the energy structure of rich coal,less oil and less gas,coupling with a high external dependence on oil and natural gas and the emphasis on the efficient and clean utilisation of coal,have brought opportunities for coal chemical industry.However,with the large-scale popularisation of coal gasification technology,the production and resulting storage of coal gasification slag continue to increase,which not only result in serious environmental pollution and a waste of terrestrial resources,but also seriously affect the sustainable development of coal chemical enterprises.Hence,the treatment of coal gasification slag is extremely important.In this paper,the production,composition,morphology,particle size structure and water holding characteristics of coal gasification slag are introduced,and the methods of carbon ash separation of gasification slag,both domestically and abroad,are summarised.In addition,the paper also summarises the research progress on gasification slag in building materials,ecological restoration,residual carbon utilisation and other high-value utilisation,and ultimately puts forward the idea of the comprehensive utilisation of gasification slag.For large-scale consumption to solve the environmental problems of enterprises and achieve high-value utilisation to increase the economic benefits of enterprises,it is urgent to zealously design a reasonable and comprehensive utilisation technologies with simple operational processes,strong adaptability and economic benefits.

MoS2-rGO hybrid architecture as durable support for cathode catalyst in proton exchange membrane fuel cells

Carbon black is utilized as a conventional electrocatalyst support material for proton exchange membrane fuel cells. However, this support is prone to corrosion under oxidative and harsh environments, thus limiting the durability of the fuel cells. Meanwhile, carbon corrosion would also weaken the linkage between Pt and the support material, which causes Pt agglomeration, and consequently, deterioration of the cell performance. To overcome the drawbacks of a Pt/C electrocatalyst, a hybrid support material comprising molybdenum disulfide and reduced graphene oxide is proposed and synthesized in this study to exploit the graphitic nature of graphene and the availability of the exposed edges of MoS2. TEM results show the uniform dispersion of Pt nanoparticles over the MoS2-rGO surface. Electrochemical measurements indicate higher ECSA retention and better ORR activity after 10000 potential cycles for Pt/MoS2-rGO as compared to Pt/C, demonstrating the improved durability for this hybrid support material.

Closed-loop cobalt recycling from spent lithium-ion batteries based on a deep eutectic solvent (DES) with easy solvent recovery

Efficient recycling technology for the rapid growth of spent lithium-ion batteries(LIBs)is essential to tackle the resources and environmental crisis.Hydrometallurgical approach has attracted extensive research due to its potential to reduce the consumption of energy and threat to the environment.However,the simultaneous realization of green,efficient and closed-loop recycling is still challenging.Herein,we report a closed-loop and highly efficient approach to recycle lithium cobalt oxide from spent LIBs based on a choline chloride:oxalic acid(ChCl:OA)type deep eutectic solvent(DES).An ultrafast leaching process is observed at 180°C for 10 s with no observable residues.The energy barrier during leaching is calculated to be 113.9 kJ/mol.Noteworthy,the solubility of cobalt ions can be reversibly tuned by simply adding/evaporating deionized water,thus avoiding the addition of precipitant and enabling the easy recovery of the leaching solvent for realizing a closed-loop recycling process.The simultaneous realization of high efficiency,green and closed-loop process is expected to push the DES into practical application for recycling the electrodes of LIBs.

First-principles study of catalytic activity of W-doped cobalt phosphide toward the hydrogen evolution reaction

In this study,we investigated the hydrogen evolution reaction(HER)on the(101)facet of pristine and W-doped CoP using the density functional theory.Two types of Co atoms are identified on the catalyst surface:the Co atoms that present the higher d band center are marked as valid sites,whereas the others are marked as invalid sites owing to their weaker H adsorption ability.It is further revealed that W-doping can decrease the d band center of the surface Co atoms,which is beneficial for the HER;however the exposure to W weakens the desorption of H.To address the strong adsorption effect of W,the doping sites and dopant content are analyzed,and the results indicate that 8.4 wt%W doping at the invalid surface Co sites is preferred;moreover,the optimal W content increases to 16.8 wt%when W is inserted into the subsurface.The effect of W doping is weakened when the doping site is far away from the surface.

A perspective on influences of cathode material degradation on oxygen transport resistance in low Pt PEMFC

A large-scale industrial application of proton exchange membrane fuel cells(PEMFCs)greatly depends on both substantial cost reduction and continuous durability enhancement.However,compared to effects of material degradation on apparent activity loss,little attention has been paid to influences on the phenomena of mass transport.In this review,influences of the degradation of key materials in membrane electrode assemblies(MEAs)on oxygen transport resistance in both cathode catalyst layers(CCLs)and gas diffusion layers(GDLs)are comprehensively explored,including carbon support,electrocatalyst,ionomer in CCLs as well as carbon material and hydrophobic polytetrafluoroethylene(PTFE)in GDLs.It is analyzed that carbon corrosion in CCLs will result in pore structure destruction and impact ionomer distribution,thus affecting both the bulk and local oxygen transport behavior.Considering the catalyst degradation,an eventual decrease in electrochemical active surface area(ECSA)definitely increases the local oxygen transport resistance since a decrease in active sites will lead to a longer oxygen transport path.It is also noted that problems concerning oxygen transport caused by the degradation of ionomer chemical structure in CCLs should not be ignored.Both cation contamination and chemical decomposition will change the structure of ionomer,thus worsening the local oxygen transport.Finally,it is found that the loss of carbon and PTFE in GDLs lead to a higher hydrophilicity,which is related to an occurrence of water flooding and increase in the oxygen transport resistance.

The effect of catalyst layer design on catalyst utilization in PEMFC studied via stochastic reconstruction method

Catalyst utilization is an important determinant of proton exchange membrane fuel cell performance,and increasing the catalyst utilization is one of the most critical approaches to reducing the catalyst loading in PEMFC.4-phase stochastic reconstruction method based on the variable-resolution Quartet Structure Generation Set(QSGS)algorithm is utilized to elucidate the influence of different parameters of electrode preparation,including the porosity,the dispersion degree of carbon agglomerate,ionomer content,and carbon support size,on the catalyst utilization in the catalyst layer.It was found that there exist optimal values for the porosity,dispersion degree of carbon agglomerate,ionomer content,and carbon support sizes in CLs and any deviations from these optimal values would lead to transport issues of electron,proton and mass within CLs.Taking electron,proton and mass transport into consideration simultaneously,the optimal Pt utilization is 46.55%among 48 cases in this investigation,taken at the carbon support diameter of 40 nm,the porosity of 0.4,the agglomerate spatial density of 25μm^(−3) and I/C at 0.7.The selection of porosity,ultrasonic dispersion technique and ionomer content for conventional electrode preparation requires compromises on mass,electron and proton transport,leading to catalyst utilization in CLs hardly exceeding 50%.Therefore,the next generation of catalyst layer design and preparation technology is desired.

Medical micro-and nanomotors in the body

Attributed to the miniaturized body size and active mobility,micro-and nanomotors(MNMs)have demonstrated tremendous potential for medical applications.However,from bench to bedside,massive efforts are needed to address critical issues,such as cost-effective fabrication,on-demand integration of multiple functions,biocompatibility,biodegradability,controlled propulsion and in vivo navigation.Herein,we summarize the advances of biomedical MNMs reported in the past two decades,with particular emphasis on the design,fabrication,propulsion,navigation,and the abilities of biological barriers penetration,biosensing,diagnosis,minimally invasive surgery and targeted cargo delivery.Future perspectives and challenges are discussed as well.This review can lay the foundation for the future direction of medical MNMs,pushing one step forward on the road to achieving practical theranostics using MNMs.

Exploration of the oxygen transport behavior in non-precious metal catalyst-based cathode catalyst layer for proton exchange membrane fuel cells

High cost has undoubtedly become the biggest obstacle to the commercialization of proton exchange membrane fuel cells(PEMFCs),in which Pt-based catalysts employed in the cathodic catalyst layer(CCL)account for the major portion of the cost.Although nonprecious metal catalysts(NPMCs)show appreciable activity and stability in the oxygen reduction reaction(ORR),the performance of fuel cells based on NPMCs remains unsatisfactory compared to those using Pt-based CCL.Therefore,most studies on NPMC-based fuel cells focus on developing highly active catalysts rather than facilitating oxygen transport.In this work,the oxygen transport behavior in CCLs based on highly active Fe-N-C catalysts is comprehensively explored through the elaborate design of two types of membrane electrode structures,one containing low-Pt-based CCL and NPMCbased dummy catalyst layer(DCL)and the other containing only the NPMC-based CCL.Using Zn-N-C based DCLs of different thickness,the bulk oxygen transport resistance at the unit thickness in NPMC-based CCL was quantified via the limiting current method combined with linear fitting analysis.Then,the local and bulk resistances in NPMC-based CCLs were quantified via the limiting current method and scanning electron microscopy,respectively.Results show that the ratios of local and bulk oxygen transport resistances in NPMCbased CCL are 80%and 20%,respectively,and that an enhancement of local oxygen transport is critical to greatly improve the performance of NPMC-based PEMFCs.Furthermore,the activity of active sites per unit in NPMCbased CCLs was determined to be lower than that in the Pt-based CCL,thus explaining worse cell performance of NPMC-based membrane electrode assemblys(MEAs).It is believed that the development of NPMC-based PEMFCs should proceed not only through the design of catalysts with higher activity but also through the improvement of oxygen transport in the CCL.

质子交换膜燃料电池超低铂化过程中物质传输的分析与展望

居高不下的成本已成为车用质子交换膜燃料电池商业化的最大阻碍.其中,用于阴极氧还原反应的Pt基贵金属催化剂的成本占比最高,降低Pt用量是控制燃料电池成本的关键.然而,一方面,Pt载量的降低会引起阴极氧气传质阻力明显加大,包括催化层纳米孔道内氧气扩散引起的体相传质阻力和氧气跨越Pt表面超薄离子树脂薄膜导致的局域传质阻力,从而引起电池性能的急剧恶化.另一方面,超低Pt膜电极中的质子传导问题也会降低电池的性能.这是由于离子树脂薄膜的限域作用削弱了离子树脂内部的亲疏水相分离,减少了质子的传输通道和传递效率,造成了较大的欧姆阻抗.本文详细分析了Pt载量不断降低时,阴极催化层内的氧气体相、局域传输以及质子传导规律,及其对电池性能的影响,并针对其作用机制提出了应对策略.

Li2FeSiO4/C hollow nanospheres as cathode materials for lithium-ion batteries

Undoubtedly, it is imperative to figure out two stubborn issues concerning low electronic conductivity and sluggish lithium ion diffusion to promote the practical application of Li2FeSiO4 materials in lithium-ion battery (LIB) cathode. Herein, we report an innovative and simple strategy that combines a hydrothermal process with subsequent annealing to synthesize highly uniform Li2FeSiO/C hollow nanospheres. During the hydrothermal process, polystyrenen anospheres are employed not only as the template but also, more tactfully, as carb on source to form amorphous carbon layers, which will function to enhance the electronic conductivity and restrict particle aggregations. The use of the LIB Li2FeSiO4/C hollow nano spheres as a LIB cathode delivers a desired stable capacity at each rate stage, and eve n at a high rate of 10 C, the hollow nano sphere cathode can prese nt a specific discharge capacity as high as 50.5 mAh·g^-1. After 100 cycles, the capacity rete ntions at 1 and 10 C remain as high as 93% and 72%, respectively. The superior electrochemical performance is believed to be related to special architectures of the Li2FeSiO4/C hollow nano sphere cathode.

途径特异性调控因子介导的链霉菌来源天然产物的产量提升

链霉菌是活性天然产物的重要来源。基因组学研究揭示了链霉菌有巨大的生物合成潜力,平均每株菌拥有20-40个生物合成基因簇。在常规的实验室条件下,大多数链霉菌来源的天然产物产量较低,影响了对其进一步研究和产业化开发。由于链霉菌中天然产物的生物合成受到严格的调控,对于这些调控因子和调控网络的深入研究将有力地促进链霉菌来源的天然产物的发现和开发利用。文中主要综述了近5年来链霉菌来源天然产物生物合成中途径特异性调控因子的研究进展,重点介绍其在提高相应天然产物产量中的应用。

Approach and potential of replacing oil and natural gas with coal in China

China’s fossil energy is characterized by an abundance of coal and a relative lack of oil and natural gas.Developing a strategy in which coal can replace oil and natural gas is,therefore,a necessary and practical approach to easing the excessive external dependence on oil and natural gas.Based on the perspective of energy security,this paper proposes a technical framework for defining the substitution of oil and natural gas with coal in China.In this framework,three substitution classifications and 11 industrialized technical routes are reviewed.Then,three scenarios(namely,the cautious scenario,baseline scenario,and positive scenario)are developed to estimate the potential of this strategy for 2020 and 2030.The results indicate that oil and natural gas replaced by coal will reach 67 to 81 Mt and 8.7 to 14.3 Gm^3 in 2020 and reach 93 to 138 Mt and 32.3 to 47.3 Gm^3 in 2030,respectively.By implementing this strategy,China’s external dependence on oil,natural gas,and primary energy is expected to be curbed at approximately 70%,40%,and 20%by 2030,respectively.This paper also demonstrates how coal,as a substitute for oil and natural gas,can contribute to carbon and pollution reduction and economic cost savings.It suggests a new direction for the development of the global coal industry and provides a crucial reference for energy transformation in China and other countries with similar energy situations.

Facile preparation of unique three-dimensional(3D)α-MnCh/MWCNTs macroporous hybrid as the high-performance cathode of rechargeable Li-O2 batteries

Un doubtedly,there remai ns an urge nt prerequisite to achieve sign ifica nt adva nces in both the specific capacity and cyclability of Li-O2 batteries for their practical application.In this work,a series of unique three-dimensional(3D)α-MnO2/MWCNTs hybrids are successfully prepared using a facile lyophilization method and investigated as the cathode of Li-O2 batteries.Thereinto,cross-1 inkedα-MnO2/MWCNTs nano composites are first syn thesized via a modified chemical route.Results dem on strate that MnO2 nano rods in the nano composites have a length of 100-400 nm and a diameter ranging from 5 to 10 nm,and more attractively,the as-lyophilized 3D MnO2/MWCNTs hybrids is uniquely constructed with large amounts of interconnected macroporous channels.The U-O2 battery with the 3D macroporous hybrid cathode that has a mass percentage of 50%ofα-MnO2 delivers a high discharge specific capacity of 8,643 mAh·g^-1 at 100 mA·g^-1,and main tains over 90 cycles before the discharge voltage drops to 2.0 V un der a controlled specific capacity of 1,000 mAh·g^-1.It is observed that when being recharged,the product of toroidal Li2O2 particles disappears and electrode surfaces are well recovered,thus confirming a good reversibility.The excellent performanee of Li-O2 battery with the 3Dα-MnO2/MWCNTs macroporous hybrid cathode is ascribed to a syn ergistic com bination betwee n the unique macroporous architecture and highly efficient bi-fun ctionalα-MnO2/MWCNTs electrocatalyst.

Polynomial networks based adaptive attitude tracking control for NSVs with input constraints and stochastic noises

This paper proposes a backstepping technique and Multi-dimensional Taylor Polynomial Networks(MTPN)based adaptive attitude tracking control strategy for Near Space Vehicles(NSVs)subjected to input constraints and stochastic input noises.Firstly,considering the control input has stochastic noises,and the attitude motion dynamical model of the NSVs is actually modeled as the Multi-Input Multi-Output(MIMO)stochastic nonlinear system form.Furthermore,the MTPN is used to estimate the unknown system uncertainties,and an auxiliary system is designed to compensate the influence of the saturation control input.Then,by using backstepping method and the output of the auxiliary system,a MTPN-based robust adaptive attitude control approach is proposed for the NSVs with saturation input nonlinearity,stochastic input noises,and system uncertainties.Stochastic Lyapunov stability theory is utilized to analysis the stability in the sense of probability of the entire closed-loop system.Additionally,by selecting appropriate parameters,the tracking errors will converge to a small neighborhood with a tunable radius.Finally,the numerical simulation results of the NSVs attitude motion show the satisfactory flight control performance under the proposed tracking control strategy.