Insight into coupled Ni-Co dual-metal atom catalysts for efficient synergistic electrochemical CO_(2)reduction

The development of highly active,selective,and stable electrocatalysts can facilitate the effective implementation of electrocatalytic CO_(2)conversion into fuels or chemicals for mitigating the energy crisis and climate problems.Therefore,it is necessary to achieve the goal through reasonable material design based on the actuality of the operational active site at the molecular scale.Inspired by the stimulating synergistic effect of coupled heteronuclear metal atoms,a novel Ni-Co atomic pairs configuration(denoted as NiN_(3)?CoN_(3)-NC)active site was theoretically screened out for improving electrochemical CO_(2)reduction reaction(CO_(2)RR).The structure of NiN_(3)?CoN_(3)-NC was finely regulated by adjusting Zn content in the precursors Zn/Co/Ni-zeolite imidazolate frameworks(Zn/Co/Ni-ZIFs)and pyrolysis temperature.The structural features of NiN_(3)?CoN_(3)-NC were systematically confirmed by aberration-corrected HAADF-STEM coupled with 3D atom-overlapping Gaussian-function fitting mapping,XAFS,and XRD.The results of theoretical calculations reveal that the synergistic effect of Ni-Co atomic pairs can effectively promote the*COOH intermediate formation and thus the overall CO_(2)RR kinetic was improved,and also restrained the competitive hydrogen evolution reaction.Due to the attributes of Ni-Co atomic pairs configuration,the developed NiN_(3)?CoN_(3)-NC with superior catalytic activity,selectivity,and durability,with a high turnover frequency of 2265 h^(-1)at-1.1 V(vs.RHE)and maximum Faradaic efficiency of 97.7%for CO production.This work demonstrates the great potential of DACs as highly efficient catalysts for CO_(2)RR,provides a useful strategy to design heteronuclear DACs,exploits the synergistic effect of multiple metal sites to facilitate complex CO_(2)RR catalytic reactions,and inspires more efforts to develop the potential of DACs in various fields.

D-band center coordination modulated enzyme-like activity in Fe-Cu dual-metal single-atom nanozymes

After explorations in a diversity of single-atom nanozymes(SAzymes),developing dual-centered SAzymes becomes a promising approach for superior catalytic performance.But confusing mechanisms including atomic coordination,spatial configuration,and metal–metal atom interaction hinder the development and design of SAzymes.Herein,a dual-centered Fe-Cu-N_(x)SAzyme exhibits excellent peroxidase(POD)-and catalase(CAT)-like activities with d-band center(ε_(d))coordination of Fe and Cu in multiple reaction stages,which plays a critical role in the adsorption of H_(2)O_(2)molecule and H_(2)O and O_(2)release.Therefore,the dband center coordination,which can be represented byε_(d)(Fe)–ε_(d)(Cu)shifts,leads to the competition between one-side and bilateral adsorption,which determines the favorable reaction path with lower energy barriers.Based on experimental statistics,simulated formation energies,and reaction barriers,3 configurations,Fe-Cu-N6-I,Fe-Cu-N_(8)-II,and Fe-Cu-N_(8)-III,are modeled and validated.Impressively,configuration-dependent catalytic selectivity and the competition between one-side and bilateral adsorption can be unveiled by d-band center coordination paradigm analysis.Theoretical simulations suggest that the unsymmetrical charge distribution over the three Fe-Cu configurations could tune the adsorption strength compared with the counterparts FeN_(4)and CuN_(4).The present work provides a potential route for optimizing enzyme-like catalysis by designing the dual-or even triple-metal SAzymes,which demonstrates the large space to modulate the metal atomic configuration and interaction.

Atomic design of carbon-based dual-metal site catalysts for energy applications

Carbon-based dual-metal sites catalysts(DMSCs)have emerged as a new frontier in the field of sustainable energy due to their unique coordination environments,electronic structure,the maximized atom utilization.The reasonable utilization of carbonbased DMSCs provides new possibilities to achieve the outstanding catalytic performance,remarkable selectivity,recyclability in energy-related catalysis.Based on this,this review intends to summarize the recent breakthroughs in carbonbased DMSCs for the energy catalysis.Firstly,the definition and classifications of DMSCs are proposed,mainly dividing into three types(isolated dual-metal site pairs,binuclear homologous dual-metal sites pairs,binuclear heterologous dual-metal sites pairs).Subsequently,we discuss the potential of DMSCs targeting on energy conversion reactions,such as electrocatalytic hydrogen evolution reaction(HER),oxygen evolution reaction(OER),oxygen reduction reaction(ORR),CO_(2)reduction reaction(CO_(2)RR),N_(2) reduction reaction(NRR).Finally,we predict the remaining challenges and possible opportunities on the unique carbon-based DMSCs for energy applications in the future.

Dual-metal single-atomic catalyst:The challenge in synthesis,characterization,and mechanistic investigation for electrocatalysis

Dual-metal single-atom catalysts(DACs),featuring high atomic utilization efficiency,excellent selectivity,and stability originating from the atomically dispersed nature,have emerged as a new frontier in heterogeneous electrocatalysis due to the synergistic effect between diversified metal active sites in promoting their catalytic activity.In this review,the recent progress and development on the syntheses,characterizations,theoretical uniqueness,and applications for various catalytic reactions and devices(oxygen reduction reaction,oxygen evolution reaction,hydrogen evolution reaction,CO_(2) reduction reaction,N2 reduction reaction,proton exchange membrane fuel cells)are summarized and reviewed.Specifically,the synergistic effect between the two metal centers and electronic structures of catalysts is systematically discussed.Moreover,the future challenges and prospects in developing practical DACs are proposed as a possible direction for further investigation.

Dual-metal precursors for the universal growth of non-layered 2D transition metal chalcogenides with ordered cation vacancies

Two-dimensional(2D)transition metal chalcogenides(TMCs)are promising for nanoelectronics and energy applications.Among them,the emerging non-layered TMCs are unique due to their unsaturated dangling bonds on the surface and strong intralayer and interlayer bonding.However,the synthesis of non-layered 2D TMCs is challenging and this has made it difficult to study their structures and properties at thin thickness limit.Here,we develop a universal dual-metal precursors method to grow non-layered TMCs in which a mixture of a metal and its chloride serves as the metal source.Taking hexagonal Fe_(1-x)S as an example,the thickness of the Fe_(1-x)S flakes is down to 3 nm with a lateral size of over 100 μm.Importantly,we find ordered cation Fe vacancies in Fe_(1-x)S,which is distinct from layered TMCs like MoS_(2) where anion vacancies are commonly observed.Low-temperature transport measurements and theoretical calculations show that 2D Fe_(1-x)S is a stable semiconductor with a narrow bandgap of60 meV.In addition to Fe_(1-x)S,the method is universal in growing various non-layered 2D TMCs containing ordered cation vacancies,including Fe_(1-x)Se,Co_(1-x)S,Cr_(1-x)S,and V_(1-x)S.This work paves the way to grow and exploit properties of non-layered materials at 2D thickness limit.

基于双流YOLOv4的金属表面缺陷检测方法

目前有许多学者使用深度学习进行表面缺陷检测研究,由于这些研究大都沿用主流目标检测算法的思路,注重高级语义特征,而忽视了低级语义信息(色彩、形状)对表面缺陷检测的重要性,因此导致缺陷检测效果不够理想。为解决上述问题,提出了一种金属表面缺陷检测网络——双流YOLOv4网络,骨干网络分成两个分支,输入分为高分辨率图像和低分辨率图像,浅分支负责从高分辨率图像中提取低级特征,深分支负责从低分辨率图像中提取高级特征,通过削减两分支的层数和通道数来减少模型总参数量;为了强化低级语义特征,提出了一种树形多尺度融合方法(Tree-structured Multi-scale Feature Fusion Me-thod,TMFF),并设计了一个结合极化自注意力机制和空间金字塔池化的特征融合模块(Feature Fusion Module with Polarized Self-Attention Mechanism and Spatial Pyramid Pooling,FFM-PSASPP)应用到TMFF中。在东北大学热轧带表面缺陷数据集NEU-DET、金属表面缺陷数据集GC10-DET和伊莱特电饭煲内胆缺陷数据集Enaiter的测试集上对所提算法进行了测试,测得的map@50结果分别为0.80,0.66和0.57,相比大部分主流的用于缺陷检测的目标检测算法均有提升,且模型参数量仅为原YOLOv4的一半,速度与YOLOv4接近,可满足实际使用需求。

基于国产ZYNQ的裸机双核设计

当ZYNQ芯片裸机读写嵌入式多媒体存储卡(eMMC)时,CPU会被大量占用,从而导致CPU性能严重消耗,某些对CPU性能要求较高的场景无法正常使用。通过对ZYNQ芯片处理系统(PS)端内部的组成架构进行研究,并结合其运行模式特点,提出了一种基于国产ZYNQ架构的裸机双核运行方式,在没有操作系统参与的条件下,可同时对PS端的双核进行资源调度并实现eMMC的读写等功能,并可在此基础上扩展到四核,极大提高了国产ZYNQ芯片在无操作系统参与的情况下对资源的利用率,并在实际项目中得到了实践验证。

双源CT虚拟单能量成像去除椎弓根螺钉金属伪影的应用研究

目的双源CT虚拟单能量成像(VMI)技术在消除椎弓螺钉金属伪影方面具有显著的应用价值,本研究选择伪影最严重层面上四个不同的位置,从伪影指数和对比度噪声比方面探讨双源CT虚拟单能量成像技术消除椎弓螺钉金属伪影的应用价值。方法纳入48例行双源CT检查椎弓根螺钉植入情况的患者,获得14组(60~190keV,间隔10keV)虚拟单能量图像和1组(140kVp)混合能量图像,测量金属植入物周围的4个兴趣区和同一层面1个脂肪兴趣区的CT值和标准差,并算出伪影指数和对比度噪声比。针对伪影严重程度及金属周围组织清晰度进行主观评分。比较不同图像伪影指数、对比度噪声比和主观评分差异,评估VMI去除金属伪影的价值。结果随着keV的增加,各感兴趣区的伪影指数减小,而对比度噪声比增加。能级110~190keV时伪影指数均低于140kVp图像,且差异有统计学意义(P<0.05)。能级110~190keV时各个感兴趣区的对比度噪声比均高于140kVp混合式能量图像,且差异有统计学意义(P<0.05)。主观评分方面,110~150keV图像评分高于140kVp图像,且差异有统计学意义(P<0.05)。结论双源CT单能量成像技术可有效减少脊柱螺钉内固定后金属伪影的影响,能级110~150keV的单能量图像伪影指数低和对比度噪声比高,并且主观评价显示伪影消除效果良好,是消除椎弓根螺钉金属伪影的最佳单能量值。

基于功能化金属有机骨架材料的比率电化学传感器在检测领域的应用进展

比率电化学传感器将电流信号的比值作为输出信号,通过电流信号比值的变化实现目标物的定量检测,具有可靠性好、重复性高等优点。金属有机骨架(MOFs)材料是一种多孔配位聚合物,因比表面积、孔隙率、孔径等结构和性能优势备受学者关注。目前,基于MOFs材料的比率电化学传感器已广泛用于多种物质的检测,成为传统检测方法的潜在替代方法。为此,对比率电化学传感器的原理、分类、常用信号物质以及不同MOFs材料的性能进行总结,重点综述了基于功能化MOFs材料的比率电化学传感器在检测领域的应用进展(引用文献60篇)。

分步负载金属法制备铁钴双金属位点高效氧还原电催化剂

过渡金属和氮掺杂的碳(M-N-C)由于优异的电催化活性以及较低的生产成本,成为铂基催化剂的替代。然而,目前的M-N-C催化剂通常涉及金属盐、含氮物质和碳载体的结合,在经过热处理和酸洗过程后得到的催化剂在活性位点密度和传质能力上性能不足。采用分步负载金属法制备了Fe、Co双金属掺杂的M-N-C催化剂。利用Zn2+和Co2+的竞争效应,成功合成了小尺寸且均匀的Zn-Co-ZIFs双金属沸石咪唑骨架。随后,在不形成金属团簇的前提下将最大量的Fe原子嵌入C-Zn-Co-ZIFs-H+前体结构中,使其在热解后能产生大量的FeCo—Nx活性位点。这种改进显著增加了FeCo-N-C-2催化剂中Fe活性位点的含量(1.9%,质量分数),并深度优化了其微孔和介孔结构(860 m^(2)·g^(-1))。该催化剂在0.1 mol·L^(-1) HClO_(4)和0.1 mol·L^(-1) KOH溶液中,氧还原反应(ORR)活性展现出了0.806 V和0.921 V的半波电位,并分别在50000、45000 s恒定电位测试后保持了91.21%和95.32%的活性。将其组装于质子交换膜燃料电池(PEMFCs)和碱性锌-空气液流电池(ZAFBs)中,峰值功率密度分别达到了746、164 mW·cm^(-2),显示出优越的性能。

Preparation of sodium alginate gel microspheres catalysts and its high catalytic performance for treatment of ciprofloxacin wastewater

The discharge of the antibiotic wastewater has increased dramatically in our country with the development of medical science and wide application of antibiotic,resulting in serious harm to human body and ecological environment.In this work,ciprofloxacin(CIP)was selected as one of typical antibiotics and heterogeneous Fenton-like catalysts were prepared for the treatment of ciprofloxacin wastewater.The sodium alginate(SA)gel microspheres catalysts were prepared by polymerization method using double metal ions of Fe^(3+)and Mn^(2+)as cross-linking agents.Preparation conditions such as metal ions concentration,mass fraction of SA,polymerization temperature and dual-metal ions as crosslinking agent were optimized.Moreover,the effects of operating conditions such as initial concentration of CIP,pH value and catalyst dosage on CIP removal were studied.The kinetic equation showed that the effect of the initial concentration of CIP on the degradation rate was in line with second-order kinetics,and the effects of catalyst dosage and pH value on the degradation rate of CIP were in line with first-order kinetics.The SA gel microspheres catalysts prepared by dual-metal ions exhibited a high CIP removal and showed a good reusability after six recycles.The SA gel microspheres catalysts with an easy recovery performance provided an economical and efficient method for the removal of antibiotics in the future.

外加电位对X80管线钢模拟海岸土壤腐蚀的影响

为探究双相X80管线钢在沿海土壤模拟溶液环境中的腐蚀机理,采用极化曲线、慢应变速率拉伸试验(SSRT)和交流阻抗(EIS)法对不同外加电位(-750,-900和-1050 mV vs.饱和甘汞电极(SCE))下双相X80管线钢的应力腐蚀和电化学腐蚀行为进行研究。结果表明,双相X80管线钢在-1050 mV电位下对应力腐蚀(SCC)最为敏感。慢应变拉伸呈现为脆性断裂,断口可见铁素体区域圆形或椭圆形的凹坑,这是由于过度阴极反应产生的氢原子扩散进入到钢中在铁素体晶界聚集,氢气析出产生的较高氢压超过材料的强度产生圆形孔洞,在拉伸应力作用下变为椭圆形。在此电位下EIS模拟电阻最小,耐腐蚀性最差。-750 mV的外加电位可起到一定的电化学保护作用,但不足以防止X80管线钢应力腐蚀的发生。-900 mV的外加电位可有效抑制X80管线钢的阳极溶解,SSRT的强度和延展性均高于0 mV电位试样,表现出韧性断裂特征,EIS模拟电阻最高,因此双相X80管线钢在模拟海岸土壤环境下最佳的阴极保护电位约为-900 mV vs.SCE。双相X80管线钢在沿海土壤模拟环境中的应力腐蚀行为的研究可对其在实际使用过程中的安全服役提供一定理论依据,同时为腐蚀抑制与防护工作提供参考。

双金属离子调控型镍钴氧化物纳米片用于非对称超级电容器

通过水热-煅烧两步法制备了系列镍钴氧化物(NCO)纳米片。通过改变前驱体溶液中的镍、钴离子物质的量之比,进而调控NCO纳米片中的过渡金属离子比例。NCO纳米片的晶相、形貌和结构利用X射线衍射、扫描电子显微镜和X射线光电子能谱表征。此外,对NCO纳米片的电化学性能进行测试。结果表明,NCO-2(Ni_(1.95)Co_(1)O_(x))纳米片在0.5 A·g^(-1)电流密度下,比电容为1096.88 F·g^(-1),且经过5000次循环后具有78.26%的循环稳定性。以NCO-2为正极、活性碳为负极构成的非对称超级电容器,在功率密度为576 W·kg^(-1)时,能量密度为57.70 Wh·kg^(-1)。

简洁构型与馈电的宽带双极化金属锥阵列天线

本文提出了一种宽带双极化金属锥阵列天线。该阵列天线以传统的旋转体天线结构为主体,通过在锥体底部开设四道正交的直通槽,以便在锥状单元内部形成可与地板间构成匹配谐振腔的开放式空腔结构。在阵列中,任意两个相邻的锥状单元之间可形成类似于Vivaldi天线的辐射缝隙结构。馈电采用同轴馈电方式,探针无弯折结构,金属锥体无弯折过孔。每个金属锥状单元独立,可极大简化加工、装配和维护过程。该天线具有两个正交极化,分别由左右和前后相邻单元构成。仿真结果表明,在频率范围为2~8GHz内,阵列大部分有源VSWR小于2,小部分端口有源VSWR小于2.5(相对带宽为120%)。

“双碳”背景下有色金属产业发展困境与对策

有色金属产业是典型高能耗产业,又是实现“双碳”目标的关键产业。通过全面调研分析有色金属产业发展面临的问题及困境,结果显示“双碳”背景下有色金属企业存在盈利能力不强、技术设备普遍落后、人才素质不高、流动性大等突出问题。建议完善并落实相关政策的扶持及顶层设计,实施强化校企合作及人才精准培养等举措,解决人才断层及技术落后问题,提升企业管理水平、产品竞争力及盈利能力。

量子点修饰Ln-ZIF杂化材料的构筑及其对单宁酸的荧光检测

采用一步水热法制备了一种具有新型褶皱球结构的镧系金属Eu3+掺杂的金属有机骨架材料Eu/ZIF-67,并进一步通过配位键合的方式将ZnO量子点负载到Eu/ZIF-67的表面,形成了一种类沸石咪唑酯骨架的双发射荧光杂化材料Eu/ZIF-67@ZnO QDs。通过对材料的结构、形貌以及荧光传感性能表征分析,发现该荧光材料具有ZnO量子点和镧系红光铕离子的双重荧光发射。此外,进一步探究了Eu/ZIF-67@ZnO QDs对单宁酸的荧光传感性能。结果表明,单宁酸能够有效猝灭Eu/ZIF-67@ZnO QDs在ZnO QDs处的特征荧光发射,检出限为0.029 9μmol/L。同时,Eu/ZIF-67@ZnO QDs对单宁酸的荧光响应具有抗干扰能力,可作为一种经济高效的荧光传感器来特异性识别单宁酸。

双通带三维频率选择表面设计及分析

为了满足现代通信设备双频带的要求,提出了一种双通带三维频率选择表面(Three Dimensional Frequency Selective Surface,3D FSS)。所提出的3D FSS单元结构是由平行平板波导(Parallel Plate Waveguide,PPW)结构和方同轴波导(Square Coaxial Waveguide,SCW)结构组合而成。在PPW传播路径中,通过加载金属通孔和环形槽,构成2个相同的1/4波长谐振器,在电磁耦合作用下产生二阶低频通带;环形槽处不连续性引起的电磁波反射引入一个传输零点。在SCW传播路径中,通过加载环形槽,构成2个相同的短SCW谐振器,耦合产生二阶高频通带。通过对传输零极点处的电场矢量分布和设计参数进行分析,阐明了3D FSS的工作机理。仿真结果显示,该3D FSS的低频和高频通带3 dB相对带宽分别为10.74%和6.89%,通带比为1.32,单元结构的电尺寸为0.13λ_(0)×0.13λ_(0),具有双极化特性,在0°~40°具有良好的角度稳定性。

双金属原子电催化剂的研究进展

双金属原子催化剂(DACs)具有原子利用率高、选择性高、稳定性好的特点。由于各种金属的活性中心在提高其催化活性方面具有协同效应,因此在多相电催化领域得到了广泛关注。本文综述了DACs的制备方法,以及其在多种催化反应中的最新应用进展,讨论了2个金属中心的协同效应以及催化剂的电子结构,对目前面临的挑战与未来的发展方向进行了展望。

铅铋合金/硅酸锆颗粒双介质相变储热性能及演化规律数值研究

随着我国新能源电力装机容量大幅提升,大型燃煤机组迫切需要提高灵活运行和深度调峰能力,而利用高温蒸汽热量进行适时存储/释放是提高机组调峰能力的有效方法。为了提高高温储/放热过程速率及性能,本文提出了基于液态金属/硅酸锆颗粒的新型双介质储热体系,建立了铅铋合金/硅酸锆双介质储热过程数理模型,数值研究了铅铋合金与硅酸锆颗粒储热性能及其储热过程瞬态演化规律,比较了纯液态金属和不同硅酸锆颗粒填充比时相变储热过程特征。结果表明相同体积下,纯铅铋合金、29%、34%、38%、42%、50%六种填充比模型的熔化时间分别为202、167、164、161、158、151 s,储热量分别为18547、20474、20670、20845、21001、21254 J。双介质体系与纯铅铋合金相比熔化时间最大缩短25.2%,蓄热量最大提高14.6%。与纯液态金属储热相比,双介质储热体系具有吸热速度快、储热量大,成本低等优点,具有较好的经济效益和应用价值。

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金属锂是下一代高能量密度二次电池的理想负极材料。然而,循环期间不均匀的锂沉积/脱出过程和大体积形变,严重阻碍了金属锂负极的实用化。为了解决上述问题,引入三维骨架形成复合锂负极是一种有前景的策略,可以促进均匀的锂沉积/脱出并缓解负极体积形变。梯度复合锂负极可以引导锂自底向上沉积,从而最大限度地发挥复合锂负极的优势。由于碳骨架具有结构可调节性强、(电)化学稳定和重量轻等特点,碳基梯度复合锂负极受到了广泛关注。本文总结了碳基梯度复合锂负极的最新进展,将其分为梯度亲锂骨架、梯度导电骨架和双梯度骨架,讨论了各类梯度骨架的特点和研究进展。同时,对梯度复合锂负极的发展进行了展望,以望推动复合锂负极在高能量密度电池中的应用。