镍铜合金立方体纳米晶的脉冲电沉积及电催化析氢性能

以泡沫镍(NF)为基体, 采用常规脉冲伏安法合成了独立分相的金属Ni, Cu为主晶相、 平均粒径为70 nm的规则立方体结构镍铜合金电催化剂(NiCu/NF). 在电催化析氢反应中, NiCu/NF表现出优良的催化活性和优异的催化稳定性, 在电流密度为10 mA/cm ²时, 在1.0 mol/L KOH溶液中需要的析氢过电位仅为86 mV, 催化24 h的电位波动仅为12 mV. 二级复合纳米立方体结构使NiCu/NF展现出15.5倍于空白NF的电化学活性面积(ECSA), 为电催化反应提供了大量催化活性位点, 也为电极表面的电荷传输、 物质传递提供了充足的通道; Cu的引入以及NiO/Ni异质结的形成改善了邻近Ni原子的活性, 使镍基材料本征析氢活性得以改善, 三者协同促进了NiCu/NF电催化活性的提升. NiCu/NF电极在析氢过程中遵循Volmer-Heyrovsky机理, 反应速率由电极表面吸附氢原子的电化学脱附过程决定.     

Hydrogen evolution kinetics on Ni cathodes modified by spontaneous deposition of Ag or Cu

Nickel modification by spontaneous deposition of transition metals such as Ag and Cu is shown as an economic and simple alternative for the activation of hydrogen evolution reaction(HER) on cathodes in alkaline media. The kinetics of HER is studied on Ni/Ag and Ni/Cu catalysts by cyclic voltammetry and electrochemical impedance spectroscopy(EIS) using a rotating disk electrode(RDE). Freshly synthesized catalysts, as well as catalysts subjected to a short chronoamperometric ageing procedure, are analyzed and the kinetic and thermodynamic parameters of the HER are obtained. The nickel surface modified with transition metals with an outer shell electronic configuration [xd~(10)(x+1)s~1], such as Cu(3d~(10)4s~1)and Ag(4d~(10)5s~1), shows an improved activity for the HER compared to bare nickel. Furthermore, the Ni/Cu catalyst presents a decreased onset potential. The hydrogen evolution rate, measured as current density at –1.5 V(vs. SCE), is similar on Ni/Cu and Ni/Ag electrodes.     

电沉积纳米镍合金在海水溶液中的析氢性能

采用电沉积法获得Ni、Ni-Fe和Ni-Fe-C合金镀层电极, 在90 °C模拟海水(0.5 mol·L-1 NaCl, pH=12)的稳态极化曲线表明Ni-Fe-C合金电极具有最好的析氢催化性能. 通过扫描电子显微镜(SEM)观察电极表面形貌、X射线衍射(XRD)与透射电子显微镜(HRTEM)分析合金的晶体结构, 发现电极材料的晶粒尺寸影响析氢催化性能, 晶粒尺寸越小析氢催化活性越好. 用电化学阻抗方法(EIS)研究电极析氢催化性能的本质原因, 结果表明电极表面活性点数目和电极的本质电催化活性对合金电极析氢催化活性有重要的影响.     

Mercury meniscus on solid silver amalgam electrode as a sensitive electrochemical sensor for tetrachlorvinphos

The in-house prepared mercury meniscus modified solid silver amalgam electrode (m-AgSAE) was successfully applied for the detection of organophosphate pesticide tetrachlorvinphos in pH 7 buffer solution. The electrochemical performance of m-AgSAE for the reduction of tetrachlorvinphos was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV), respectively. The surface morphology of solid silver electrode (AgE), as-amalgamated solid silver amalgam electrode (AgSAE), and polished solid silver amalgam electrode (p-AgSAE) was examined by field emission scanning electron microscopy (FESEM). Among the applied techniques, DPV and SWV analysis showed a remarkable increase in the reduction peak current and provided a simple, fast, and sensitive method for the determination of tetrachlorvinphos. The electrochemical impedance spectroscopy (EIS) was used to correlate the electrocatalytic activity of AgSAE, p-AgSAE and m-AgSAE with their interfacial charge transport capabilities. Under the optimized experimental conditions, the DPV and SWV responses were linear over the 1–9 μM and 10–50 μM concentration ranges with a detection limit of 0.06 μM for DPV and 0.04 for SWV. The estimation of tetrachlorvinphos in the ground and waste water samples with the proposed method was in good agreement with that of the added amount. The proposed electrochemical method not only extends the application of non-toxic m-AgSAE, but also offers new possibilities for fast and sensitive analysis of tetrachlorvinphos and its structural analogs in environmental samples.     

Hydrogen bubble dynamic template synthesis of porous gold for nonenzymatic electrochemical detection of glucose

Gold (Au) films with open interconnected macroporous walls and nanoparticles have been successfully sculptured using the hydrogen bubble dynamic template synthesis followed by a galvanic replacement reaction. Copper (Cu) films with open interconnected macroporous walls and nanoparticles were synthesized using the electrochemically generated hydrogen bubbles as a dynamic template. Then through a galvanic replacement reaction between the porous Cu sacrificial templates and KAu(CN)₂ in solution, the porous Cu films were converted to porous Au films with the similar morphologies. Additional electrochemical dealloying process was introduced to remove the remaining Cu from the porous Au films. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and electrochemical methods were adopted to characterize the porous Au films. The resulted porous Au films show excellent catalytic activity toward the electrooxidation of glucose. A nonenzymatic glucose sensor based on those Au film electrodes shows a linear range from 2 to 10 mM with a sensitivity of 11.8 μA cm⁻² mM⁻¹, and a detection limit of 5 μM.     

Disposable paper-based electrochemical sensor based on stacked gold nanoparticles supported carbon nanotubes for the determination of bisphenol A

This work reports a new type of disposable electrochemical sensor for the determination of bisphenol A (BPA). The working electrodes were fabricated by sputtering gold nanoparticles on commercial art paper and then modifying the gold layer with multi-walled carbon nanotubes (MWCNTs). The electrode in their intermediated and final stage was characterized by atomic force microscope, scanning electron microscope and electrochemical techniques. To perform electrochemical analysis, the resulting electrode was integrated with a homemade paper-based analytical device, which could also ensure the immobilization of MWCNTs on the electrode surface without any functionalization. The determination of BPA was investigated by linear sweep voltammetry (LSV). A wide linearity in the range from 0.2 to 20 mg/L with a detection limit of 0.03 mg/L (S/N = 3) was obtained. The between-sensor reproducibility was 5.7% (n = 8) for 0.5 mg/L BPA. The proposed sensor showed good resistance against interferences and was applied to detect BPA leached from real plastic samples with satisfying results. This disposable sensor is readily mass-produced and has been verified to serve as an attractive alternative to screen-printed electrodes for practical applications.     

Highly enhanced electrocatalytic oxidation of glucose on Cu(OH)2/CuO nanotube arrays modified copper electrode

A highly sensitive and fast-response biosensor based on cupric hydroxide/oxide (Cu(OH)₂/CuO) nanotube arrays (CNA) was successfully fabricated in this work. CNAs were prepared on copper electrode surface by simply immersing copper electrode in an aqueous solution of NaOH and (NH₄)₂S₂O₈. The morphology and the composition of the CNAs were characterized by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD), respectively. The electrocatalytic activity of the CNA modified copper electrodes (CNA/Cu) towards glucose oxidation was investigated by cyclic voltammetry and amperometry. The CNA/Cu showed good non-enzymatic electrocatalytic responses to glucose in alkaline media and can be used for the development of enzyme-free glucose sensors.     

Modification of a glassy carbon surface with amine-terminated dendrimers and its application to electrocatalytic hydrazine oxidation

Amine-terminated polyamidoamine (PAMAM) dendrimers were immobilized on glassy carbon electrodes (GCEs) via electrochemical oxidation of the terminal amine groups of dendrimers. The electrochemical immobilization of dendrimers was confirmed by cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The immobilized dendrimer films were robust and behaved as charge-selective electrochemical gates for oppositely charged redox molecules. The immobilization approach was applied to assemble Au dendrimer-encapsulated nanoparticles (Au DENs, dia. 1.5 ± 0.3 nm) on GCEs, and the resulting Au DEN films showed electrocatalytic activity to hydrazine oxidation.     

Phase transfer catalysis: Synthesis of monodispersed FePt nanoparticles and its electrocatalytic activity

Using dibenzo-24-crown-8-ether (DB24C8) as phase transfer catalyst, the monodispersed iron–platinum (FePt) alloy nanoparticles with size of ∼17 nm were synthesized by reduction of H₂PtCl₆·6H₂O and FeCl₂·4H₂O in the solvothermal system. The structure, magnetic property and electrocatalytic activity of FePt nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction system (XRD), vibration sample magnetometer (VSM) and CHI 820 electrochemical analyser (three electrodes system, the reference electrode is saturated calomel electrode (SCE), the counter electrode is platinum electrode and the glassy carbon electrode is used as working electrode (GCE)), respectively. The results show that the as-synthesized FePt nanoparticles have a chemically disordered fcc structure and can be transformed into chemically ordered fct structure after annealing treatment above 400 °C, simultaneously accompanying with the coercivity changed from 5 to 2400 Oe. CVs of 0.5 M H₂SO₄/0.5 M CH₃OH on GCE modified with FePt nanoparticles monolayer illustrate that the as-synthesized FePt nanoparticles have strong electrocatalytic activity toward the oxidation of CH₃OH in aqueous solution.     

Determination of formal potential of NADH/NAD+ redox couple and catalytic oxidation of NADH using poly(phenosafranin)-modified carbon electrodes

The electrochemical regeneration of NADH/NAD⁺ redox couple has been studied using poly(phenosafranin) (PPS)-modified carbon electrodes to evaluate the formal potential and catalytic rate constant for the oxidation of NADH. The PPS-modified electrodes were prepared by electropolymerization of phenosafranin onto different carbon substrates (glassy carbon (GC) and basal-plane pyrolytic graphite (BPPG)) in different electrolytic solutions. The formal potential was estimated to be ? 0.365 ± 0.002 V vs. SHE at pH 7.0. As for the bare carbon electrodes, the oxidation of NADH at the BPPG electrode was found to be enhanced compared with the GC electrode. For the PPS-modified electrodes, it was found that the electrocatalysis of PPS-modified electrodes for the oxidation of NADH largely depends on the carbon substrate and electrolyte solution employed for their preparation, i.e., the PPS-modified BPPG electrode prepared in 0.2 M NaClO₄/acetonitrile solution exhibits an excellent and persistent electrocatalytic property toward NADH oxidation in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of about 740 and 670 mV compared with those at the bare GC electrode and the PPS-modified GC electrode prepared in 0.2 M H₂SO₄ solution, respectively. A quantitative analysis of the electrocatalytic reaction based on rotating disk voltammetry gave the electrocatalytic reaction rate constants of the order of 10³–10⁴ M^?1 s^? 1 depending on the preparation conditions of the PPS-modified electrodes.     

Electrodeposited fabrication of highly ordered Pd nanowire arrays for alcohol electrooxidation

Highly ordered Pd nanowire arrays (NWAs) are prepared using a porous aluminum oxide template by pulse electrodeposition. The obtained Pd nanowire arrays with the diameter of 50 nm and length of 850 nm have been characterized by scanning electron microscopy, energy dispersive X-ray analysis, and high resolution transmission electron microscope. Meanwhile, the electrocatalytic activity of Pd NWAs electrodes for methanol and isopropanol oxidation in alkaline media is studied. It is found that the obtained nanostructures exhibit excellent catalytic activity for alcohol electrooxidation. The isopropanol oxidation shows the higher activity on Pd NWAs electrode than methanol in alkaline medium.     

A gas-diffusion gold-ring-tip: Fabrication,characterization, and application in electrocatalysis

A gas-diffusion gold-ring microelectrode used as scanning electrochemical microscopy tip was fabricated. Compared to the ring-tip for droplet dispensation reported before, the as-fabricated micropipette tip has a larger ring size (ca. 25 μm diameter) that is beneficial to gas dispensation and is more sensitive to electroactive species. This micropipette electrode functioned as both a normal SECM tip and a gas dispenser was demonstrated by imaging FcMeOH⁺/FcMeOH reaction and electrocatalytic oxygen reduction reaction, respectively.     

A Novel Electrochemical Method for the Analysis of Hydrogen Peroxide with the Use of a Glassy Carbon Electrode Modified by a Prussian Blue/Copper‐Gold Bimetallic Nanoparticles Hybrid Film

A novel Prussian blue/copper‐gold bimetallic nanoparticles hybrid film modified electrode was prepared by electrochemical deposition on a glassy carbon electrode (PB/Cu‐AuNPs/GCE). Morphology and electrochemistry of this electrode were studied by UV‐vis spectroscopy, scanning electron microscopy, X‐ray diffraction, cyclic voltammetry and electrochemical impedance spectroscopy. The sensor showed significantly better electrocatalytic activity for the reduction of hydrogen peroxide in comparison with the single PB/GCE and PB/AuNPs/GCE. This was attributed to the synergistic effect of PB and Cu‐Au bimetallic nanoparticles. Also, the sensor demonstrated an overall high level of performance for the analysis of H₂O₂ in the concentration range from 0.002 to 0.84 mM.     

Mesoporous silica thin film mechanized with a DNAzyme-based molecular switch for electrochemical biosensing

A novel electroanalytical strategy for copper and ascorbic acid detection was developed by using a nanostructured electrode surface mechanized with a DNAzyme-based molecular gate. This sensing interface was constructed by first electrodeposition of a mesoporous silica thin film on Au electrodes and further assembly of a Cu(II)-specific DNAzyme. The biosensing assay was based on the Cu(II) and ascorbic acid responsible activation of the DNAzyme, which acted as a molecular switch able to control the diffusion of the Fe(CN)₆^{3 −/4 −} electrochemical probe through the nanochannels of the mesoporous film.     

Enhancement of electrochemical and catalytic properties of MoS2 through ball-milling

MoS₂ nanosheets of one to few layer thickness present novel electronic and enhanced catalytic properties with respect to the bulk material. Here we show that a simple and highly scalable ball-milling procedure can lead to significant improvements of the electrochemical and catalytic properties of the bulk natural MoS₂. We characterized the material before and after the milling process by means of scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy in order to evaluate morphological and chemical features. We investigated the electrochemical properties by means of voltammetry techniques to monitor the electron transfer with [Fe(CN)₆]^{4 −/3 −} redox probe and the catalytic properties by monitoring the electrochemical hydrogen evolution reaction (HER). A significant overpotential lowering of about 210 mV is obtained for the HER by the ball-milled material when compared to bulk materials. This has a huge potential for the lowering of the energy consumption during hydrogen evolution. Ball-milling offers highly scalable dry method for large scale production of electrocatalyst with enhanced properties.     

CtrA gene based electrochemical DNA sensor for detection of meningitis

Electrochemical DNA sensor has been fabricated by immobilizing thiolated single stranded oligonucleotide (ssDNA) probe onto gold (Au) coated glass electrode for meningitis detection using hybridization with complementary DNA (CtrA) in presence of methylene blue (MB). These electrodes (ssDNA/Au and dsDNA/Au) have been characterized using atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetric (CV) technique. The DNA/Au electrode can detect the complementary DNA in the range of 7–42 ng/μl in 5 min (hybridization) with response time 60 s and electrode is stable for about 4 months when stored at 4 °C. The sensitivity of dsDNA/Au electrode is 115.8 μA/ng with 0.917 regression coefficient (R).     

多孔枝晶镍铜合金的制备及其电催化析氢、肼氧化性能

以镍网(NM)为基体,采用氢气泡模板法合成了独立分相金属Ni、Cu为主晶相、具有四级复合微纳结构的镍铜合金电催化剂(NiCu/NM)。在电催化析氢(HER)及肼氧化(HzOR)反应中,NiCu/NM表现出优良的催化活性,在1.0 mol·L^-1KOH(含0.5 mol·L^-1N2H4·H2O)溶液中,电流密度为10 mA·cm^-2时,其需要的HER及HzOR过电势分别为104和41 mV;在双电极体系中,电流密度为100 mA·cm^-2时,NiCu/NM的分解槽压仅为0.536 V,远低于全水分解过程所需的1.921 V,大大提高了电池的产氢效率。无论三电极体系还是双电极体系,NiCu/NM均表现出优异的催化活性及稳定性。分析认为,镍铜合金薄膜的多级复合结构使其展现出增大了近14倍的电化学活性面积(ECSA),为电催化反应提供了大量催化活性位点,也为电极表面的电荷传输、物质传递提供了充足的通道;Cu的掺入提高了材料的本征HER活性,两者协同促进了电催化活性的提升,其中NiCu/NM的结构优势对其优良的催化性能起主导作用。     

Electrocatalytic Oxidation of Paracetamol on Ni and NiCu Alloy Modified Glassy Carbon Electrode

In this study we investigated the electrocatalytic oxidation of anti‐inflammatory drug (paracetamol) on Nickel and Nickel–copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) in alkaline solution. These electrodes prepared by galvanostatic method and different electrochemical techniques such as cyclic voltammetry and chronoamperometry were used to track the oxidation process and its kinetics. From Voltammetric studies we concluded that in the presence of drugs the anodic peak current of low valences Nickel species increased, followed by a decrease in the corresponding cathodic current peak. This indicates that drugs were oxidized on the redox mediator which was immobilized on the electrode surface via an electrocatalytic mechanism. Using Laviron's equation, the values of α and k_s for the immobilized redox species were determined. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of paracetamol was found in agreement with the values obtained from CV measurements.     

Electrochemical fabrication of novel fluorescent polymeric film: Poly(pyrrole–pyrene)

We describe herein the electrochemical characterization and polymerization of 4-pyren-1-yl-butyric acid 11-pyrrol-1-yl-decyl ester (pyrrole–pyrene) in CH₃CN. The electrochemical oxidation of the pyrrole group at 0.77 V vs Ag/Ag + 10 mM in CH₃CN led to the first example of a fluorescent polypyrrole film. The mechanism of deposition on platinum electrode was studied by voltammetry and chronoamperometry. The optical properties of the polymeric films electrogenerated on ITO electrodes were examined by UV–visible spectroscopy and fluorescence microscopy indicating an increase in fluorescence properties by increased polymer thickness. The electrochemical oxidation of pyrenyl group linked to the polypyrrole backbone was carried out at 1.2 V. This additional polymerization was demonstrated by UV–visible spectroscopy and induced the loss of the fluorescence properties of the resulting polymeric film.     

Electrochemical and FTIR spectroscopic study of CO2 reduction at a nanostructured Cu/reduced graphene oxide thin film

Here we report a facile approach to synthesize a novel nanostructured thin film comprising Cu nanoparticles (NPs) and reduced graphene oxide (rGO) on a glassy carbon electrode (GCE) via the direct electrochemical reduction of a mixture of cupper and graphene oxide (GO) precursors. The effect of the applied potential on the electrochemical reduction of CO₂ was investigated using linear sweep voltammetric (LSV) and chronoamperometric (CA) techniques. Carbon monoxide and formate were found as the main products based on our GC and HPLC analysis. The electrochemical reduction of CO₂ at the Cu/rGO thin film was further studied using in situ ATR-FTIR spectroscopy to identify the liquid product formed at different applied cathodic potentials. Our experimental measurements have shown that the nanostructured Cu/rGO thin film exhibits an excellent stability and superb catalytic activity for the electrochemical reduction of CO₂ in an aqueous solution with a high current efficiency of 69.4% at − 0.6 V vs. RHE, promising for the efficient electrochemical conversion of CO₂ to valuable products.