Building Fe atom–cluster composite sites using a site occupation strategy to boost electrochemical oxygen reduction

The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic clusters to nanoparticles.Therefore,understanding the interactions among these components,especially the synergistic effects between single atomic sites and cluster sites,is crucial for improving the oxygen reduction reaction(ORR)activity of M–N–C catalysts.Accordingly,herein,we constructed a model catalyst composed of both atomically dispersed FeN4 SA sites and adjacent Fe clusters through a site occupation strategy.We found that the Fe clusters can optimize the adsorption strength of oxygen reduction intermediates on FeN4 SA sites by introducing electron-withdrawing–OH ligands and decreasing the d-band center of the Fe center.The as-developed catalyst exhibits encouraging ORR activity with halfwave potentials(E1/2)of 0.831 and 0.905 V in acidic and alkaline media,respectively.Moreover,the catalyst also represents excellent durability exceeding that of Fe–N–C SA catalyst.The practical application of Fe(Cd)–CNx catalyst is further validated by its superior activity and stability in a metalair battery device.Our work exhibits the great potential of synergistic effects between multiphase metal species for improvements of singleatom site catalysts.

Urban Landscaping Design and Carbon Reduction Planning Countermeasures

As the most significant green ecological resource in densely populated and economically developed areas,urban landscaping plays a pivotal role in carbon sink value and multiple ecosystem service functions.It is a crucial element in the advancement of green and low-carbon initiatives in China’s major cities and the realization of a carbon-neutral vision.By analyzing the relationship between carbon emission reduction and urban landscaping,the paper sorts out and summarizes the basic principles of urban landscaping design,proposes the role of landscape design in urban landscaping,and plans countermeasures for carbon reduction in urban landscaping,with a view to optimizing the construction and management of urban landscaping.

Precise and controllable tandem strategy triggering boosted oxygen reduction activity

The development of efficient and cost‐effective metal‐free electrocatalysts for oxygen reduction reaction(ORR)has become crucial for electrochemical energy systems.However,reasonably validating and precisely regulating the active sites for designing optimized materials are still challenging.Herein,we report a precise and controllable tandem strategy to boost the ORR activity based on metal‐free covalent organic frameworks(MFCOFs)comprising imine‐N,thiophene‐S,or triazine‐N.Among these MFCOFs,post‐tandem BTT‐TAT‐COF structure displayed a more positive catalytic capability and excellent electrochemical stability,indicating that the synergistic catalysis of multiple active sites induced the ORR catalytic activity through the conjugated skeleton of the structure.Density‐functional theory calculations suggest that the series‐connected backbone contained highly effective electrocatalytic active centers and provided synergistic catalysis.More importantly,this strategy highlights new opportunities for the advancement of efficient COF‐based metal‐free ORR catalysts.

Integrating Variable Reduction Strategy With Evolutionary Algorithms for Solving Nonlinear Equations Systems

Nonlinear equations systems(NESs)are widely used in real-world problems and they are difficult to solve due to their nonlinearity and multiple roots.Evolutionary algorithms(EAs)are one of the methods for solving NESs,given their global search capabilities and ability to locate multiple roots of a NES simultaneously within one run.Currently,the majority of research on using EAs to solve NESs focuses on transformation techniques and improving the performance of the used EAs.By contrast,problem domain knowledge of NESs is investigated in this study,where we propose the incorporation of a variable reduction strategy(VRS)into EAs to solve NESs.The VRS makes full use of the systems of expressing a NES and uses some variables(i.e.,core variable)to represent other variables(i.e.,reduced variables)through variable relationships that exist in the equation systems.It enables the reduction of partial variables and equations and shrinks the decision space,thereby reducing the complexity of the problem and improving the search efficiency of the EAs.To test the effectiveness of VRS in dealing with NESs,this paper mainly integrates the VRS into two existing state-of-the-art EA methods(i.e.,MONES and DR-JADE)according to the integration framework of the VRS and EA,respectively.Experimental results show that,with the assistance of the VRS,the EA methods can produce better results than the original methods and other compared methods.Furthermore,extensive experiments regarding the influence of different reduction schemes and EAs substantiate that a better EA for solving a NES with more reduced variables tends to provide better performance.

Recent progress in research and design concepts for the characterization,testing,and photocatalysts for nitrogen reduction reaction

The reduction of molecular nitrogen(N_(2))to ammonia(NH_(3))under mild conditions is one of the most promising studies in the energy field due to the important role of NH_(3)in modern industry,production,and life.The photocatalytic reduction of N_(2)is expected to achieve clean and sustainable NH_(3)production by using clean solar energy.To date,the new photocatalysts for photocatalytic reduction of N_(2)to NH_(3)at room temperature and atmospheric pressure have not been fully developed.The major challenge is to achieve high light-absorption efficiency,conversion efficiency,and stability of photocatalysts.Herein,the methods for measuring produced NH_(3)are compared,and the problems related to possible NH_(3)pollution in photocatalytic systems are mentioned to provide accurate ideas for measuring photocatalytic efficiency.The recent progress of nitrogen reduction reaction(NRR)photocatalysts at ambient temperature and pressure is summarized by introducing charge transfer,migration,and separation in photocatalytic NRR,which provides a guidance for the selection of future photocatalyst.More importantly,we introduce the latest research strategies of photocatalysts in detail,which can guide the preparation and design of photocatalysts with high NRR activity.

Indirect Carbon Reduction Path from the Perspective of Urban Climate Adaptation Planning

Since the 21^(st)century,the problem of global warming has been prominent,and the problem of climate change has attracted worldwide attention.All countries have issued urban climate adaptation planning policy documents to address the current climate problem.At the same time,the proposal of the“double carbon”vision allows us to focus on the carbon emission reduction of cities and buildings.In addition to the implementation of the direct carbon reduction approach in the whole life cycle of construction,the functional role of indirect carbon reduction cannot be underestimated.By analyzing the domestic and foreign urban climate adaptation planning policy documents,summarizing the indirect carbon reduction approaches,and analyzing the feasibility of the indirect carbon reduction and emission reduction methods from the perspective of urban climate adaptation planning,the indirect carbon reduction adaptation strategy is proposed,which provides a reference for the implementation of urban climate adaptation planning and the target completion of reaching the carbon neutralization and peak on time.

Propagation form of internal cracks induced by continuous casting soft reduction and control strategy for internal quality

The propagation form of internal cracks induced by continuous casting soft reduction and the control strategy for enhancing the internal quality of 45 steel through industrial trials and a three-dimensional flow-heat transfer-solidification coupling model were investigated.The results showed that the internal cracks induced by soft reduction exhibited a characteristic of being"coarse in the middle and fine at both ends",and displayed an elliptical arc distribution on the loose side of the strand cross section.The cracks originated within the brittle temperature range and propagated inward to the liquid impenetrable temperature and outward to the zero ductility temperature or below.The control strategy for enhancing the internal quality of the 45 steel strand through soft reduction is to adjust the casting speed or the reduction zone appropriately,ensuring that the central solid fraction of the reduction zone falls within the range of 0.33-0.99.At this point,a reasonable reduction amount is allocated to eliminate the center shrinkage cavities and center segregation,even if it results in minor reduction-induced cracks.

Co-evolutionary cloud-based attribute ensemble multi-agent reduction algorithm

In order to improve the performance of the attribute reduction algorithm to deal with the noisy and uncertain large data, a novel co-evolutionary cloud-based attribute ensemble multi-agent reduction（CCAEMR） algorithm is proposed.First, a co-evolutionary cloud framework is designed under the M apReduce mechanism to divide the entire population into different co-evolutionary subpopulations with a self-adaptive scale. Meanwhile, these subpopulations will share their rewards to accelerate attribute reduction implementation.Secondly, a multi-agent ensemble strategy of co-evolutionary elitist optimization is constructed to ensure that subpopulations can exploit any correlation and interdependency between interacting attribute subsets with reinforcing noise tolerance.Hence, these agents are kept within the stable elitist region to achieve the optimal profit. The experimental results show that the proposed CCAEMR algorithm has better efficiency and feasibility to solve large-scale and uncertain dataset problems with complex noise.

Cooperative extended rough attribute reduction algorithm based on improved PSO

Particle swarm optimization （PSO） is a new heuristic algorithm which has been applied to many optimization problems successfully. Attribute reduction is a key studying point of the rough set theory, and it has been proven that computing minimal reduc- tion of decision tables is a non-derterministic polynomial （NP）-hard problem. A new cooperative extended attribute reduction algorithm named Co-PSAR based on improved PSO is proposed, in which the cooperative evolutionary strategy with suitable fitness func- tions is involved to learn a good hypothesis for accelerating the optimization of searching minimal attribute reduction. Experiments on Benchmark functions and University of California, Irvine （UCI） data sets, compared with other algorithms, verify the superiority of the Co-PSAR algorithm in terms of the convergence speed, efficiency and accuracy for the attribute reduction.

Carbon-supported ultrafine Pt nanoparticles modified with trace amounts of cobalt as enhanced oxygen reduction reaction catalysts for proton exchange membrane fuel cells

To accelerate the kinetics of the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells,ultrafine Pt nanoparticles modified with trace amounts of cobalt were fabricated and decorated on carbon black through a strategy involving modified glycol reduction and chemical etching.The obtained Pt36Co/C catalyst exhibits a much larger electrochemical surface area(ECSA)and an improved ORR electrocatalytic activity compared to commercial Pt/C.Moreover,an electrode prepared with Pt36Co/C was further evaluated under H2-air single cell test conditions,and exhibited a maximum specific power density of 10.27 W mgPt^-1,which is 1.61 times higher than that of a conventional Pt/C electrode and also competitive with most state-of-the-art Pt-based architectures.In addition,the changes in ECSA,power density,and reacting resistance during the accelerated degradation process further demonstrate the enhanced durability of the Pt36Co/C electrode.The superior performance observed in this work can be attributed to the synergy between the ultrasmall size and homogeneous distribution of catalyst nanoparticles,bimetallic ligand and electronic effects,and the dissolution of unstable Co with the rearrangement of surface structure brought about by acid etching.Furthermore,the accessible raw materials and simplified operating procedures involved in the fabrication process would result in great cost-effectiveness for practical applications of PEMFCs.

Atomic Level Dispersed Metal–Nitrogen–Carbon Catalyst toward Oxygen Reduction Reaction: Synthesis Strategies and Chemical Environmental Regulation

For development and application of proton exchange membrane fuel cell(PEMFC) energy transformation technology, the cost performance must be elevated for the catalyst. At present, compared with noble metal-based catalysts, such as Pt-based catalysts, atomically dispersed metal–nitrogen–carbon(M–N–C) catalysts are popularity and show great potential in maximizing active site density, high atom utilization and high activity,making them the first choice to replace Pt-based catalysts. In the preparation of atomically dispersed metal–nitrogen–carbon catalyst, it is difficult to ensure that all active sites are uniformly dispersed, and the structure system of the active sites is not optimal. Based on this, we focus on various approaches for preparing M–N–C catalysts that are conducive to atomic dispersion, and the influence of the chemical environmental regulation of atoms on the catalytic sites in different catalysts. Therefore, we discuss the chemical environmental regulation of the catalytic sites by bimetals, atom clusters, and heteroatoms(B, S, and P). The active sites of M–N–C catalysts are explored in depth from the synthesis and characterization, reaction mechanisms, and density functional theory(DFT)calculations. Finally, the existing problems and development prospects of the current atomic dispersion M–N–C catalyst are proposed in detail.

Main group metal elements for ambient-condition electrochemical nitrogen reduction

Electrocatalytic N_(2) reduction under ambient-condition is considered to be the most appealing strategy to the conventional Haber-Bosch process for synthetic ammonia to alleviate greenhouse emissions and reduce environmental pollution, mainly powered by renewable energy. Recent years, rapid advances have been gained in this attractive research field, and numerous electrocatalysts have been exploited. However, its conversion efficiency is still far behind the requirement of industrial applications owing to the breakage of the N≡N triple bond, which is an energetically challenging kinetically complex multistep reaction and the strong competing reaction of hydrogen evolution reaction. Recently, main group metal-based catalysts have been demonstrated promising application prospect for ammonia production, significantly boosting their further application in this field. However, a comprehensive review of main group metal-based catalysts towards electrochemical ammonia production applications is still lacking. In this review, the fundamentals of N_(2) reduction, such as the reaction pathways, the reaction potential and the challenges of N_(2) reduction have been comprehensively discussed. And then, the role, mechanism, and effect of each main group element-based catalysts used for N_(2) reduction (Li, K, Al, Ga, Sn, Sb, Bi, and their compounds) are systematically summarized. Finally, several state-of-the-art strategies to promote their NRR catalytic performance, as well as the existing problems and prospects are put forward. This review is expected to guide the design and establishment of more efficient electrocatalytic N_(2) reduction systems based on main group metal elements in the future.

Influence of different Fe doping strategies on modulating active sites and oxygen reduction reaction performance of Fe, N-doped carbonaceous catalysts

Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity in fuel cells and/or metal-air batteries.However,post-treatments (acid washing,second pyrolysis,and so on) are unavoidable to improve ORR catalytic activity and stability.The method for introducing Fe^(3+) sources (anhydrous Fe Cl_(3)) into the MOF structure,in particular,is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-N_(x) active sites.Herein,three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance.Fe-NC(Zn^(2+)),synthesized by one-step pyrolysis of Fe doped ZIF-8 (Zn^(2+)) precursor which was obtained by adding the anhydrous Fe Cl_(3)source into the Zn(NO_(3))_(2)·6H_(2)O/methanol solution before mixing,possessed the highest Fe-N_(x)active sites due to the high-efficiency substitution of Zn^(2+)ions with Fe^(3+) ions during ZIF-8 growth,the strong interaction between Fe^(3+) ions and N atoms of 2-Methylimidazole (2-MIm),and ZIF-8’s micropore confinement effect.As a result,Fe-NC(Zn^(2+)) presented high ORR activity in the entire p H range (p H=1,7,and 13).At p H=13,Fe-NC(Zn^(2+)) exhibited a half-wave potential (E1/2) of 0.95 V (vs.reversible hydrogen electrode),which was 70 m V higher than that of commercial Pt/C.More importantly,Fe-NC(Zn^(2+)) showed superior ORR stability in neutral media without performance loss after 5,000 cycles.A record-high open-circuit voltage(1.9 V) was obtained when Fe-NC(Zn^(2+)) was used as a cathodic catalyst in assembled Mg-air batteries in neutral media.The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn^(2+)) has enormous potential for use in flexible and wearable Mg-air batteries.

Synergy of staggered stacking confinement and microporous defect fixation for high‐density atomic Fe^(Ⅱ)‐N_(4)oxygen reduction active sites

The development of high‐performance nonprecious metal catalysts(NPMCs)to supersede Pt‐based catalysts for the oxygen reduction reaction(ORR)in polymer electrolyte membrane fuel cells is highly desirable but remains challenging.In this paper,we present a pyrolysis strategy for spatial confinement and active‐site fixation using iron phthalocyanine(FePc),phthalocyanine(Pc)and Zn salts as precursors.In the obtained carbon‐based NPMC with a hierarchically porous nanostructure of thin‐layered carbon nanosheets,nearly 100%of the total Fe species are Fe^(Ⅱ)‐N_(4) active sites.In contrast,pyrolyzing FePc alone forms Fe‐based nanoparticles embedded in amorphous carbon with only 5.9%Fe^(Ⅱ)‐N_(4) active sites.Both experimental characterization and density functional theory calculations reveal that spatial confinement through the staggeredπ–πstacking of Pc macrocycles effectively prevents the demetallation of Fe atoms and the formation of Fe‐based nanoparticles via aggregation.Furthermore,Zn‐induced microporous defects allow the fixation of Fe^(Ⅱ)‐N_(4) active sites.The synergistic effect of staggered stacking confinement and microporous defect fixation results in a high density of atomic Fe^(Ⅱ)‐N_(4) active sites that can enhance the ORR.The optimal Fe^(Ⅱ)‐N_(4)‐C electro‐catalyst outperforms a commercial Pt/C catalyst in terms of half‐wave potential,methanol toler‐ance,and long‐term stability in alkaline media.This modulation strategy can greatly advance efforts to develop high‐performance NPMCs.

Achieving efficient N_(2)electrochemical reduction by stabilizing the N2H*intermediate with the frustrated Lewis pairs

Electrocatalytic nitrogen reduction reaction(eNRR)with sustainable energy under ambient conditions represents an attractive approach to producing ammonia,but the design of the-state-of-the-art electrocatalyst with high efficiency and selectivity still faces formidable challenges.In contrast to traditional eNRR catalyst design strategies focusing on N≡N triple bond activation,we herein theoretically proposed an alternative strategy to improve eNRR performance via stabilizing the N_(2)H^(*)intermediate using catalysts with the frustrated Lewis pairs(FLPs),i.e.,transition metal(TM)atoms and boron(B)atom co-doped 2D black phosphorus(TM-B@BP).Our density functional theory(DFT)results reveal that the TM atom donates electrons to the adsorbed N_(2)molecule,while B atom provides empty orbital to stabilize the adsorption of N_(2)H^(*)intermediate.This framework successfully identifies five promising candidates(i.e.,Ti-B@BP,V-B@BP,Cr-B@BP,Mn-B@BP and Fe-B@BP)with low theoretical limiting potentials(−0.60,−0.41,−0.45,−0.43 and−0.50 V,respectively)and high selectivity for eNRR.We believe that the intermediate stabilization strategy introduced in current work offers a new opportunity to achieve accelerated and cost-effective ammonia synthesis with electrocatalysis.

Variations in the natural 13C and 15N abundance of plants and soils under long-term N addition and precipitation reduction:interpretation of C and N dynamics

Background:The nitrogen isotope natural abundance(δ^(15)N)provides integrated information on ecosystem N dynamics,and carbon isotope natural abundance(δ^(13)C)has been used to infer how water-using processes of plants change in terrestrial ecosystems.However,howδ^(13)C andδ^(15)N abundances in plant life and soils respond to N addition and water availability change is still unclear.Thus,δ^(13)C andδ^(15)N abundances in plant life and soils were used to investigate the effects of long-time(10 years)N addition(+50 kg N·ha^(−1)·yr^(−1)and precipitation reduction(−30%of throughfall)in forest C and N cycling traits in a temperate forest in northern China.Results:We analyzed theδ^(13)C andδ^(15)N values of dominant plant foliage,litterfall,fungal sporophores,roots,and soils in the study.The results showed thatδ^(15)N values of foliage,litterfall,and surface soil layer’s(0–10 cm)total N were significantly increased by N addition,whileδ^(15)N values of fine roots and coarse roots were considerably decreased.Nitrogen addition also significantly increased theδ^(13)C value of fine roots and total N concentration of the surface soil layer compared with the control.The C concentration,δ^(13)C,andδ^(15)N values of foliage andδ^(15)N values of fine roots were significantly increased by precipitation reduction,while N concentration of foliage and litterfall significantly decreased.The combined effects of N addition and precipitation reduction significantly increased theδ^(13)C andδ^(15)N values of foliage as well as theδ^(15)N values of fine roots andδ^(13)C values of litterfall.Furthermore,foliarδ^(15)N values were significantly correlated with foliageδ^(13)C values,surface soilδ^(15)N values,surface soil C concentration,and N concentrations.Nitrogen concentrations andδ^(13)C values of foliage were significantly correlated withδ^(15)N values and N concentrations of fine roots.Conclusions:This indicates that plants increasingly take up the heavier 15N under N addition and the heavier 13C and 15N under precipitation reduction,suggesting that N addition and precipitation reduction may lead to more open forest ecosystem C and N cycling and affect plant nutrient acquisition strategies.

Secondary reduction strategy synthesis of Pt-Co nanoparticle catalysts towards boosting the activity of proton exchange membrane fuel cells

Based on the volcanic relationship between catalytic activity and key adsorption energies,Pt-Co alloy materials have been widely studied as cathode oxygen reduction reaction(ORR)catalysts in proton exchange membrane fuel cells(PEMFCs)due to their higher active surface area and adjustable D-band energy levels compared to Pt/C.However,how to balance the alloying degree and ORR performance of Pt-Co catalyst remains a great challenge.Herein,we first synthesized a well-dispersed Pt/Co/C precursor by using a mild dimethylamine borane(DMAB)as the reducing agent.The precursor was calcined at high temperature under H_(2)/Ar mixed gas by a secondary reduction strategy to obtain an ordered Pt_(3)Co intermetallic compound nanoparticle catalyst with a high degree of alloying.The optimization of elec-tronic structure due to Pt-Co alloying and the strong metal-carrier interaction ensure the high kinetic activity of the cell membrane electrode.Additionally,the high degree of graphitization increases the electrical conductivity during the reaction.As a result,the activity and stability of the catalyst were significantly improved,with a half-wave potential as high as 0.87 V,which decreased by only 20 mV after 10000 potential cycles.Single-cell tests further validate the high intrinsic activity of the ordered Pt_(3)Co catalyst with mass activity up to 0.67 A mg_(pt)^(-1),exceeding the United States Department of Energy(US DOE)standard(0.44 A mg_(pt)^(-1)),and a rated power of 5.93 W mg_(pt)^(-1).

The Correlation Study between Thinking Styles and English-Speaking Learning Strategies of Junior School Students under the Background of “Double Reduction” Policy

Based on Cognitive Style Theory,Oxford’s Speaking Learning Theory and Communicative Competence Theory,this paper adopts questionnaire method,uses Sternberg’s Thinking Style Inventory modified by Zhang Lifang,as well as Oxford’s Learning Strategies Scale,and combines with the actual situation of junior high school students’oral learning to design the questionnaire of speaking learning strategies.Eighth graders of a junior middle school in Sichuan Province are randomly selected as the research object.The statistical tool SPSS23.0 is used to conduct the descriptive analysis and Pearson correlation analysis of the questionnaire results to explore the overall situation of junior high school students’thinking styles and the use of English-speaking learning strategies as well as their correlation.According to the research,junior high school students generally tend to executive style,liberal style,conservative style,legislative style,hierarchic style.The use of speaking learning strategies is at an average level.They tend to use memory speaking strategies,social speaking strategies,affective speaking strategies,and cognitive speaking strategies.As a whole,there is a relatively significant correlation between thinking styles and speaking learning strategies.Specifically,there is a partial correlation between thinking styles and speaking learning strategies.

Hierarchically porous N-doped carbon derived from biomass as oxygen reduction electrocatalyst for high-performance Al–air battery

Developing large-scale and highly efficient oxygen reduction reaction(ORR)catalysts acts a vital role in realizing wide application of metal–air batteries.Here,we propose a gas-foaming strategy to fabricate sustainable and 3D hierarchically porous N-doped carbon with high specific surface area and abundant defects sites derived from biomass.The obtained catalyst exhibits prominent ORR property with higher half-wave potential(0.861 V)and slightly lower kinetic current density(32.44 m A cm^-2),compared to Pt/C(0.856 V and 43.61 m A cm^-1).Furthermore,employing it as catalyst of air cathode,the Al–air battery delivers remarkable discharge performance with excellent power density of 401 m W cm^-2,distinguished energy density of 2453.4 Wh kg^-1 and extremely high open-circuit voltage of 1.85 V among the reported metal–air batteries in the literatures.This gas-foaming strategy for full utilization of biomass affords a chance to explore scalable advanced catalysts in metal–air battery.

Long-Term Poverty Reduction Strategies in China Post-2020

Poverty reduction is an eternal theme in the modernization drive of countries.After 2020,China’s poverty reduction endeavors will face new challenges and shift towards:(i)elevating poverty standards,(ii)placing equal emphasis on rural and urban poverty,(iii)preventing people in the deeply poor regions from slipping back to poverty,(iv)combining external assistance with endogenous development,and(v)enhancing social protection and targeted fiscal support for aiding the poor.Following the new trends of poverty reduction,policymakers should update their strategic approach,adopt new poverty reduction standards,target at a broader group of poor groups,promote pro-poor development,and improve poverty governance.Lastly,this paper puts forward the following policy recommendations for reducing poverty in China post-2020:(i)maintaining policy continuity and stability during the transition period;(ii)creating regular poverty relief mechanisms for urban and rural residents;(iii)improving the targeted identification and dynamic adjustment of target groups for poverty reduction;and(iv)reducing poverty through social protection and development.