尿素调控纳米多孔合金NiFeCoMgCN的电催化性能

制备高效、稳定的析氧反应(OER)电催化剂是工业制氢的关键所在。使用尿素作为造孔剂和活性C/N源,基于纳米级柯肯达尔效应,通过高温烧结制备了纳米多孔合金NiFeCoMgCN,并分析了其作为电极的电催化性能。结果表明:在1 M KOH溶液中,NiFeCoMgCN电极在10 mA·cm^(-2)下的过电位为199 mV,Tafel斜率为41.7 mV·dec^(-1),优于IrO_(2)/Ni foam电极(10 mA·cm^(-2)下的过电位为215 mV,Tafel斜率为76.3 mV·dec^(-1)),并且在1 A·cm^(-2)的大电流密度下能够持续工作至少100 h。NiFeCoMgCN电极优异的催化活性归功于其连续的纳米多孔结构和本质活性的提高。

不同去合金化法对制备纳米多孔合金微观结构的影响

采用电弧熔炼与真空甩带制备出前驱体合金,通过化学和电化学2种去合金化方法制备出纳米多孔合金,用XRD,SEM等方法分析合金的相组成和微观结构.研究去合金化过程中,不同腐蚀方法、腐蚀电位、腐蚀时间对纳米多孔合金结构的影响.结果表明:Cu25Ni5Al70合金化学去合金化可得到均匀的纳米多孔合金,其平均孔径尺寸约125nm,孔骨架尺寸约150nm,但剩余相中有少量Al相,难以完全去合金化;而在w(NaOH)=20%的溶液中电化学去合金化可得到均匀的、双连续的三维网状纳米多孔合金,孔径尺寸约为100nm.

PtEr纳米多孔合金的氧还原反应性能研究

将Pt和稀土合金化是提高氧还原电催化性能的最有效方法之一.然而,由于稀土极易被氧化,因此采用传统自下而上的溶液法制备Pt-稀土合金纳米材料非常困难.本文采用自上而下的去合金化法制备了PtEr纳米多孔合金,对其晶体结构、形貌、电子结构进行表征,并研究了其对氧还原反应的电催化性能.PtEr纳米多孔合金的晶体结构为面心立方结构,其形貌呈分级的纳米多孔结构.PtEr催化剂在酸性条件下的质量活性达到了0.21 A·mg^(-1),远高于商业Pt/C(0.10 A·mg^(-1)).加速耐久性测试表明PtEr催化剂的稳定性也优于Pt/C.

脱合金化法制备纳米多孔铂合金的研究进展

纳米多孔金属由纳米尺度的孔隙和金属韧带组成,具有三维双连通的网络状结构,兼具纳米材料和金属材料的双重特性,在催化、传感和药物输送等领域具有广阔的应用前景。脱合金化法操作简单,工艺流程短,成本相对较低,是制备纳米多孔金属的常用方法。目前,利用脱合金化法制备的纳米多孔Pt合金因其对甲醇氧化和氧还原反应具有优异的催化活性而备受关注,有望在燃料电池等相关领域实现应用。近年,研究学者不断丰富纳米多孔Pt合金的合金体系,通过优化合金成分和脱合金化工艺对其结构和性能进行调控,发展出多种形态的纳米多孔Pt合金,系统调查了前驱体的结构和成分、脱合金工艺参数对纳米多孔Pt合金的组织结构、形貌和性能的影响,并对纳米多孔形成和优异性能的机理进行了广泛的研究。利用脱合金化法制备的纳米多孔Pt合金具有多种形态,如低维的纳米颗粒、纳米花、纳米线和薄膜以及三维的纳米多孔带材等。低维的纳米多孔Pt合金因其更大的比表面积和纳米尺寸效应而具有更为突出的催化活性,而三维的纳米多孔带材具有均匀的纳米多孔结构,且克服了低维合金易团聚的问题。通过调整前驱体合金的化学成分和组织结构,改变脱合金化工艺参数,以及对纳米多孔合金进行退火处理等手段实现了对纳米多孔Pt合金的结构和形貌的有效控制。纳米多孔Pt合金对甲醇氧化和氧还原反应的催化性能相比于商用负载型Pt/C具有较大程度的改善。磁性纳米多孔Pt合金可将催化和磁分离相结合,易实现催化剂的回收再利用。此外,磁性纳米多孔Pt合金在过滤和药物输送等方面也具有巨大应用潜力。本文主要从脱合金工艺及其机制、制备与结构调控,以及性能与应用等方面简述了近年脱合金化法制备的纳米多孔Pt合金的研究进展,并探讨了目前存在的问题和今后的发展方向。

纳米多孔PtHo合金对乙醇的电催化氧化性能研究

采用脱合金法制备了纳米多孔PtHo合金,用X射线衍射、X射线光电子能谱、扫描电子显微镜、透射电子显微镜对其晶体结构和微结构进行表征,并研究了材料对乙醇氧化的电催化性能.经脱合金后制备得到的纳米多孔PtHo合金具有双连续的三维纳米多孔结构,孔径约5 nm.纳米多孔PtHo催化剂在酸性条件下对乙醇电催化氧化的质量活性达到了1.5 A·mg^(-1),远高于商业Pt/C(0.30 A·mg^(-1)).此外,其稳定性也优于商业Pt/C.纳米多孔PtHo合金以其优异的电催化性能有望在直接醇类燃料电池上应用.

脱合金化制备纳米多孔Ni-Fe合金及其电催化性能

采用真空熔炼与固溶相结合的方法获得原子分数为Ni_(30-x)Fe_xMn_(70)(x=0,10,20)的前驱体合金,通过脱合金化方法制备纳米多孔Ni及Ni-Fe合金,采用X射线衍射(XRD)、扫描电子显微镜(SEM)分析合金相组成和微观结构,运用线性扫描伏安法、交流阻抗、方波电位法及计时电位法研究电极的析氢电催化性能。结果表明:加入Fe获得了片状结构的纳米多孔Ni-Fe合金,提高了纳米多孔Ni的表面积,且Fe与Ni产生协同效应,能够有效提高合金的析氢电催化活性。当Fe含量为10%(原子分数)时,脱合金化得到的纳米多孔Ni-Fe合金表面积最大,析氢电催化性能最好,在0.1A/cm^2电流密度下,析氢过电位仅56mV,经10h连续电解,表现出良好的电催化活性和电化学稳定性。

纳米多孔PdAl合金的制备和电催化性能研究

采用熔体快淬结合去合金化法的方法制备了多孔PdAl合金纳米线,并对其晶体结构、形貌和电催化性能进行研究.结果表明,制备得到的材料具有纳米多孔的纳米线结构,纳米线直径约40 nm,孔径约5 nm.电化学测试表明,多孔PdAl纳米线对乙二醇电催化活性和稳定性均优于商业Pd/C.电催化性能的提高是由于其特殊的纳米多孔一维结构和PdAl的合金效应.

具有高产氢反应催化活性的纳米多孔Ni基合金电极

为制备具有高催化活性的纳米多孔Ni基合金电极用于碱性电解水产氢,首先制备了Ni、NiCo、NiCu和NiFe 4种Ni基合金条带;基于NiCu和NiCo合金体系,利用脱合金化法制备了纳米多孔NiCu和NiCo合金;采用XRD、BET、TEM、LSV等方法分析Ni基合金的晶体结构、形貌结构和电化学性能.结果表明:Ni基合金均为面心立方晶型的单相固溶体;纳米多孔NiCo合金具有均匀的多孔结构,孔径分布为3~6 nm;与原Ni基合金相比,纳米多孔NiCu和NiCo合金的过电势和塔菲尔(Tafel)斜率大幅降低,催化活性明显提高,纳米多孔NiCo合金在电流密度20 m A/cm^2下过电势为140 m V,Tafel斜率为60 m V/dec),接近于Pt.因此,选择具有协同作用的掺杂元素和构建纳米多孔结构是提高Ni基合金电极产氢反应催化活性的有效途径.

聚合物纳米纤维-多孔镁合金双层支架的构建及对成骨细胞活性的影响

目的 制备一种聚合物纳米纤维-多孔镁合金双层支架,并考察其体外降解性能及对MC3T3-E1Q前成骨细胞生物活性的影响.方法 使用热致相分离法(TIPS)在多孔镁合金支架外层覆盖一层聚合物纳米纤维,将PLA聚合物纳米纤维-多孔镁合金双层支架和PLA聚合物纳米纤维-TCP复合支架进行对比,采用电子天平称重、荧光显微细胞计数、MTT法、钙黄绿素染色分别测定两种支架的失重率、对MC3T3-E1Q前成骨细胞黏附、增殖和分化的影响.结果 PLA聚合物纳米纤维-多孔镁合金双层支架的失重率、黏附的MC3T3-E1Q前成骨细胞数量、MC3T3-E1Q前成骨细胞增殖数量、钙化结节数量及面积较PLA聚合物纳米纤维-TCP复合支架均有显著优势,差异均具有统计学意义(P<0.05).结论 成功制备了一种具有良好生物学功能及快降解速率的PLA聚合物纳米纤维-多孔镁合金双层支架,具有广泛的应用前景.

纳米多孔Pd-Cu/Pd-Ag催化剂的制备及其电催化性能

针对直接甲醇燃料电池(direct methanol fuel cell,DMFE)对高效阳极催化剂的需求,设计研发Ca-Mg-Pd-M(M=Cu,Ag)非晶合金前躯体体系,并采用去合金化制备系带-孔道双连续结构的纳米多孔Pd-Cu/Pd-Ag合金。通过设计前驱体合金比例可调节多孔结构的元素比例和尺寸,Pd元素可与Cu,Ag元素形成连续固溶体,在去合金化过程中可以降低Cu,Ag元素的扩散,进而细化纳米多孔的系带尺寸(由100 nm减小到10 nm)。相较于纳米多孔Pd,纳米多孔Pd-Cu/Pd-Ag合金表现出更优异的甲醇催化活性(催化电流强度:45 mA/mg)和抗毒化能力(J f/J b值为1.56),还具有低成本的优点,在直接甲醇燃料电池阳极催化剂方面有着良好的应用前景。

不同Co含量对纳米多孔Ni-Co结构及析氢催化性能的影响

通过真空熔炼和快速凝固的方法制备了不同Co含量的Ni-Co-Al合金,经脱合金化后得到纳米多孔Ni-Co。采用XRD、SEM、TEM、N2吸附-脱附研究了所得纳米多孔Ni-Co结构特征,以线性扫描伏安法(LSV)、交流阻抗(IMP)等手段对纳米多孔Ni-Co/GCE电极析氢性能进行了测试。结果表明:纳米多孔Ni-Co合金骨架表面存在尺寸更为细小的5~10nm的小孔,Co含量(质量分数)在40%~60%时,析氢催化性能较好。

Ni-Cu合金的脱合金制备及其析氢电催化性能

通过真空熔炼与固溶处理相结合的方法获得Ni_(30)Mn_(70)和Ni_(20)Cu_(10)Mn_(70)前驱体合金,经电化学脱合金化法制备纳米多孔Ni及Ni-Cu合金,采用X射线衍射(XRD)、扫描电子显微镜(SEM)分析合金相组成和微观结构,运用线性扫描伏安法、交流阻抗、方波电位法及计时电位法研究电极的析氢电催化性能.结果表明:纳米多孔Ni-Cu合金电极具有较高的电催化析氢性能,在0.1 A/cm^2电流密度下,析氢过电位仅19 mV,具有较好的电化学稳定性.

Facile synthesis of 3D nanoporous Pd/Co_2O_3 composites with enhanced catalytic performance for methanol oxidation

To simultaneously reduce noble metal Pd usage and enhance electrocatalytic performance for methanol oxidation,Pd/Co2O3 composites with ultrafine three-dimensional(3D)nanoporous structures were designed and synthesized by simple one-step dealloying of a melt-spun Al-Pd-Co alloy with an alkaline solution.Their electrocatalytic activity in alkaline media was determined by a Versa-STAT MC workstation.The results indicate that the typical sizes of the ligaments and pores of the composites were approximately 8-9 nm.The Co2O3 was uniformly distributed on the Pd ligament surface.Among the as-prepared samples,the nanoporous Pd/Co2O3 composite generated from dealloying of the Al84.5Pd15Co0.5 alloy had the best electrocatalytic activity,and its activity was enhanced by approximately 230%compared with the nanoporous Pd from dealloying of Al85Pd15.The improvement of the electrocatalytic performance was mainly attributed to the electronic modification effect between Pd and Co as well as the bifunctional mechanism between Pd and Co2O3.

Preparation and electro-catalytic activity of nanoporous palladium by dealloying rapidly-quenched Al_(70)Pd_(17)Fe_(13) quasicrystalline alloy

The formation of nanoporous Pd was studied by electro-chemical dealloying a rapidly-quenched Al70Pd17Fe13 quasicrystal alloy in dilute NaCl aqueous solution,and the electro-catalytic activity of the nanoporous Pd towards methanol electro-oxidation was evaluated by cyclic voltammetry in 1 mol/L KOH solution.XRD and TEM analyses revealed that nano-decomposition of quasicrystal grains occurred in the initial stage of dealloying,and the fully dealloyed sample was composed of FCC-Pd phase.Scanning electron microscopy observation indicated that a maze-like nanoporous pattern was formed in the dealloyed sample,consisting of percolated pores of 5.20 nm in diameter in a skeleton of randomly-orientated Pd nano-ligaments with a uniform thickness of^5 nm.A retention of^12 at.%Al in the Pd nano-ligments was determined by energy dispersive X-ray spectroscopy(EDS).The nanoporous Pd demonstrated obvious electro-catalytic activity towards methanol electro-oxidation in alkaline environment.

Degradation efficiency of Mg_(65)Cu_(25-x)Ag_(x)Y_(10) nanoporous dealloyed ribbons on pesticide wastewater

Dealloyed ribbons with a layer of networked nanoporous structure of different pore sizes were fabricated by dealloying the as-spun Mg_(65)Cu_(25-x)Ag_(x)Y_(10)(x=0,5,10,at.%)ribbons in dilute H_(2)SO_(4) solution in order to enhance the degradation efficiency of pesticide wastewater.Compared to the as-spun ribbons,it is found that the dealloyed ribbons with the networked nanoporous structure exhibit higher degradation efficiency due to their large specific surface areas and enough active sites for the degradation process.Both the average pore sizes of the nanoporous structure and the degradation efficiency of the pesticide wastewater increase with the increase of Ag addition in the dealloyed ribbons.The maximum degradation efficiency up to 95.8%is obtained for the Mg_(65)Cu_(15)Ag_(10)Y_(10)dealloyed ribbon under the optimal conditions of pH being 3,the initial cis-cypermethrin concentration being 500 mg/L,and the dosage of dealloyed ribbon being 1.33 g/L.

Ni-Co合金的制备及其析氢电催化性能

通过真空熔炼与固溶处理相结合的方法获得Ni30Mn70和Ni20Co10Mn70前驱体合金，利用电化学脱合金化法制备纳米多孔Ni及M-Co合金，采用X射线衍射（XRD）、扫描电子显微镜（SEM）分析合金相组成和微观结构，运用线性扫描伏安法、交流阻抗、方波电位法及计时电位法研究电极的析氢电催化性能。结果表明：Co的加入与Ni形成协同效应，能够有效提高合金电催化活性，且在一定程度上提高了纳米多孔Ni的电化学稳定性。Ni20Co10Mn70制得的纳米多孔Ni-Co合金表面积是纳米多孔Ni的1．609倍，在0．1A／em2电流密度下，析氢过电位仅128mV，经10h连续电解，表现出良好的析氢电催化活性及电化学稳定性。

Electrochemical synthesis of silver nanoparticles-coated gold nanoporous film electrode and its application to amperometric detection for trace Cr(VI)

A simple and rapid approach for the electrochemical synthesis of Ag nanoparticles-coated gold nanoporous film (AgGNF) on a gold substrate was reported. The solid gold electrode (SGE) was directly anodized under a high potential of 5 V, and then reduced to obtain gold nanoporous film (AuNF) by freshly prepared ascorbic acid. The Ag nanoparticles (AgNPs) were grown on the AuNF electrode by potential-step electrodeposition. The resulting AgGNF composites electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and cyclic voltammetry (CV). As-prepared AgGNF electrode was used as a kind of superior sensor for Cr(VI) detection, which exhibited better electrocatalytic behavior than those of AuNF and SGE under identical conditions. Such a designed AgGNF nanocomposites electrode showed outstanding sensitivity (about 0.15 nA/ppb) and favorable reproducibility for Cr(VI) detection. The dependence of reduction current on Cr(VI) concentration is linear from 2 to 370 ppb with a low detection limit of 0.65 ppb. Interferences from other heavy metals ions (Cr3+, Cu2+, Pb2+, As3+ and Hg2+) associated with Cr(VI) analysis could be effectively diminished. The present method proves to be rapid, reliable, sensitive and low-cost.

Bottom-up fabrication of three-dimensional nanoporous gold from Au nanoparticles using nanowelding

Three-dimensional(3D)nanoporous gold(NPG)shows promising applications in various fields.However,its most common fabrication strategy(i.e.,dealloying)faces the problems of high energy consumption,resource waste,the use of corrosive solvent,and residue of the sacrificial component.Here,we report a general bottom-up nanowelding strategy to fabricate high-purity NPG from Au nanoparticles(NPs),accomplished via interfacial self-assembly of the Au NPs into monolayer Au NP film,its subsequent layer-by-layer transfer onto a solid substrate,and direct current(DC)nanowelding.We show that the DC nanowelding process can gradually evolve the layered Au NP film into NPG at low temperatures within 10 s,while not damaging their spherical structure.This is because during the nanowelding,electrons are preferred to be localized at the high-resistance NP/NP junctions,whose electrostatic repulsion in turn strengthens their surface atom diffusion to initiate a mild solid-state diffusion nanowelding.Furthermore,when using differently sized Au NPs as the starting building blocks,this strategy allows readily tuning the thickness,ligament size,and pore size,thereby offering great flexibility to create functional porous nanomaterials,e.g.,electrocatalyst for methanol electrooxidation.Surely,low-temperature nanowelding can play a role for the production of diverse nanoporous materials from other NPs beyond Au NPs.

Ni(OH)_2 nanoflakes supported on 3D hierarchically nanoporous gold/Ni foam as superior electrodes for supercapacitors

The increasing demand for portable electronic devices and hybrid electric vehicles stimulates the develop- ment of supercapacitors as an advanced energy storage system. Here, we demonstrate a binder-free nickel hydroxide@nano- porous gold/Ni foam （Ni（OH）2@NPG/Ni foam） electrode for high-performance supercapacitors, which is prepared by a facile three-step fabrication route including electrodeposition of Au-Sn alloy on Ni foam, chemical dealloying of Sn and electrodepostion of Ni（OH）2 on NPG/Ni foam. Such Ni（OH）2@NPG/Ni foam electrode is composed of a thin layer of conformable Ni（OH）2 nanoflakes supported on three-di- mensional （3D） hierarchically porous NPG/Ni foam substrate. The resulting Ni（OH）2@NPG/Ni foam electrode can offer highways for both electron transfer and ion transport and lead to an excellent electrochemical performance with an ultrahigh specific capacitance of 3,380 F g-1 at a current density of 2 A g-1. Even when the current density was increased to 50 A g-1, it still retained a high capacitance of 1,927 F g-1. The promising performance of the Ni（OH）2@NPG/Ni foam elec- trode is mainly ascribed to the 3D hierarchical porosity and the highly conductive network on the NPG/Ni foam composite current collector, as well as the conformal electrodeposition of Ni（OH）2 active material on the NPG/Ni foam, which induces the formation of interconnected porosity both on the top surface and on the inner surface of the electrode. This in- spiring electrochemical performance would make the as-de- signed electrode material become one of the most promising candidates for future electrochemical energy storage systems.

Room-temperature liquid metal synthesis of nanoporous copper-indium heterostructures for efficient carbon dioxide reduction to syngas

Nanoporous metals show promising performances in electrochemical catalysis.In this paper,we report a self-supporting bimetallic porous heterogeneous indium/copper structure synthesized with a eutectic gallium-indium(EGaIn)material on a copper substrate.This nanoporous copper-indium heterostructure catalyst exhibits excellent performance in the reduction of carbon dioxide to syngas.The ratio of H_(2)/CO is tunable from 0.47 to 2.0 by changing working potentials.The catalyst is highly stable,showing 96%maintenance of the current density after a 70-h continuous test.Density functional theory calculations reveal that the indium/copper interface induces charge redistribution within the copper surface,leading to the formation of two distinct active sites,namely,Cu^(δ)and Cu0,and enabling a high-performance generation of CO and H_(2).This work provides a new strategy for obtaining self-supporting nanoporous metal electrode catalysts.