Beibei Yang

Facile synthesis of PdNi nanowire networks supported on reduced graphene oxide with enhanced catalytic performance for formic acid oxidation

This paper reports a simple method, in which Ni nanoparticles act as seeds for the formation of reduced graphene oxide (RGO) supported PdNi nanowire networks. The as-prepared catalysts were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements proved that the PdNi-NNs/RGO catalyst has superior electrocatalytic activity towards the formic acid oxidation reaction with much larger electrochemically active surface area and mass activity as well as higher long term-stability in comparison with the Pd/RGO and commercial Pd/C catalysts. The optimized ratio of Pd and Ni is 1 : 1, tuned by simply adjusting the feed ratio of the precursors as well. It is proposed that the improvement of the catalytic performance is attributed to the special nanostructure and the synergistic effect between Pd and Ni. These findings highlight the facile synthesis of the PdNi nanowire networks on RGO sheets and their promising application as electrocatalysts for fuel cells.

Electrochemical synthesis of gold nanoparticles decorated flower-like graphene for high sensitivity detection of nitrite

In this paper, the spherical Au nanoparticles and 3D flower-like structure graphene were successively deposited on glassy carbon electrode (GCE) (Au/f-GE/GCE) via a facile and two-step electrodeposition method for the detection of nitrite ions (NaNO2). The morphology and composition elements were confirmed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction measurements (XRD). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to evaluate the electrochemical behaviors of NaNO2 on the as-prepared electrode. Compared to f-GE/GCE and Au/GCE, Au/f-GE/GCE showed a sharp and obvious oxidation peak at 0.78V. The oxidation peak current of NaNO2 was linearly proportional to its concentration in the range from 0.125 to 20375.98μM, with a detection limit of 0.01μM (at S/N=3). Furthermore, the experiment results also showed that the as-prepared electrode exhibited excellent reproducibility and long-term stability, as well as good recovery when applied to the determination of NaNO2 in pickled pork samples.

A three dimensional Pt nanodendrite/graphene/MnO2 nanoflower modified electrode for the sensitive and selective detection of dopamine

An electrochemical sensor using a novel three dimensional (3D) ternary Pt nanodendrite/reduced graphene oxide/MnO2 nanoflower (Pt/RGO/MnO2) modified glassy carbon electrode was proposed for the selective and sensitive determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to evaluate electrochemical behaviors of DA on the as-prepared electrode. The oxidation peak current of DA is linearly proportional to its concentration in the range from 1.5-215.56 μM, with a detection limit of 0.1 μM (at S/N = 3). Compared to bare RGO, Pt nanodendrite/RGO and MnO2 nanoflower modified electrodes, the 3D hierarchical ternary Pt/RGO/MnO2 composites displayed the highest electrocatalytic activity for the selective detection of DA. Moreover, the 3D Pt/RGO/MnO2 modified electrode can be reused with no obvious deterioration in the electrocatalytic performance. This work paves the way for developing a novel 3D nanostructure and offers new opportunities for improving the performance of electrochemical sensors with excellent sensitivity, repeatability and anti-interference.

Facile synthesis of PVP-assisted PtRu/RGO nanocomposites with high electrocatalytic performance for methanol oxidation

In this paper, we report a facile approach for the synthesis of polyvinylpyrrolidone (PVP)-stabilized PtRu/RGO nanocomposites (PtRu/RGO/PVP) by the one-pot method. The structure, morphology and composition of the as-prepared catalysts were characterized by Raman, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX), respectively. It was found that PVP plays an important role in controlling the size of PtRu nanoparticles (NPs) as well as their dispersion stability. TEM images show that as-prepared PtRu NPs with a mean particle size of about 3.09 nm are uniformly dispersed on the RGO surface in the presence of PVP. The electrocatalytic properties of the as-prepared catalysts were evaluated by cyclic voltammetry (CV) and chronoamperometry (CA). Compared to PtRu/RGO and PtRu/PVP catalysts, our PtRu/RGO/PVP hybrids exhibited enhanced electrocatalytic activity and stability for the methanol oxidation reaction. Moreover, our multicomposites also showed higher electrocatalytic performance than the commercial PtRu/C catalysts. The PtRu/RGO/PVP nanostructures with an optimized molar ratio of Pt/Ru (1 : 1) displayed 1.96 times greater stability than the commercial PtRu/C nanospecies. These findings indicated that PtRu/RGO catalysts show a promising future of potential applications in direct methanol fuel cells with the assistance of PVP stabilized.

Design of PdAg Hollow Nanoflowers through Galvanic Replacement and Their Application for Ethanol Electrooxidation

In this study, galvanic replacement provides a simple route for the synthesis of PdAg hollow nanoflower structures by using the Ag-seeds as sacrificial templates in the presence of l-ascorbic acid (reductant) and CTAC (capping agent). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and EDS mapping were used to characterize the as-prepared PdAg hollow nanoflower catalysts, where they were alloyed nanoflower structures with hollow interiors. By maneuvering the Pd/Ag ratio, we found that the as-prepared Pd1 Ag3 hollow nanoflower catalysts had the optimized performance for catalytic activity toward ethanol oxidation reaction. Moreover, these as-prepared PdAg hollow nanoflower catalysts exhibited noticeably higher electrocatalytic activity as compared to pure Pd and commercial Pd/C catalysts due to the alloyed Ag-Pd composition as well as the hollow nanoflower structures. It is anticipated that this work provides a rational design of other architecturally controlled bimetallic nanocrystals for application in fuel cells.

Simultaneous determination of dopamine, uric acid and ascorbic acid using a glassy carbon electrode modified with reduced graphene oxide

A facile and cost-effective approach has been developed towards electrochemical fabrication of a reduced graphene oxide (RGO) modified glassy carbon electrode (RGO/GCE). Scanning electron microscopy (SEM) images show that RGO is covered completely on the surface of glassy carbon electrodes. The RGO/GCE is used to detect dopamine (DA), uric acid (UA) and ascorbic acid (AA) simultaneously via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. Compared with bare GCE, RGO/GCE exhibits much high electrocatalytic activities toward the oxidation of DA, UA and AA, and three well-defined fully resolved anodic peaks were found in the CV curve at RGO/GCE. The GCEs modified with different amounts of RGO have an obvious influence on the determination of DA, UA and AA. By changing the concentrations of DA, UA and AA in the three substances coexisting system, the linear response ranges for the determination of DA, UA and AA were 0.1–400 μM, 2–600 μM, and 0.7–100 μM with the limit of detection (LOD) (S/N = 3) were estimated to be 0.1 μM, 1 μM and 0.7 μM, respectively. Moreover, it is found that RGO/GCE displays high reproducibility and selectivity for the determination of DA, UA and AA.

Highly sensitive electrochemical determination of Sunset Yellow based on the ultrafine Au-Pd and reduced graphene oxide nanocomposites.

A sensitive and novel electrochemical sensor with Au-Pd and reduced graphene oxide (RGO) nanocomposites modified glassy carbon electrode (Au-Pd-RGO/GCE) was successfully fabricated by one-step synthesis method for the detection of Sunset Yellow. The as-prepared composites were uniformly dispersed on the surface of electrode with an average diameter of approximately 3.44nm, and the ultrafine nanoparticles effectively enhanced the electrochemical active surface area of GCE. The modified electrode had been characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and electrochemical tests. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed high stability and outstanding electrocatalytic activity of Au-Pd-RGO/GCE for the detection of SY with low detection limits (1.5 nM, S/N=3) and wide concentration ranges (0.686-331.686μM). The Au-Pd-RGO/GCE was further applied to detect SY in real samples with good recovery. Herein, the fabricated Au-Pd-RGO/GCE showed excellent sensitivity, stability and repeatability for the detection of SY and will be a promising application in electrochemical sensor.

Au–Cu–Pt ternary catalyst fabricated by electrodeposition and galvanic replacement with superior methanol electrooxidation activity

A series of Au–Cu–Pt ternary catalysts were fabricated on glassy carbon electrode (GCE) by a two-step method. Au–Cu nanoparticles were formed by initial electrodeposition of Au–Cu layers onto GCE and then followed by the partial replacement of Cu by Pt. The morphology and composition of Au–Cu–Pt catalysts were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), EDX element mapping and X-ray photoelectron spectroscopy (XPS). It was found that the alloying micro-structures existed in the catalysts among Au, Cu and/or the partially replaced Pt. Moreover, electrochemical measurements revealed that despite low loading of Pt, the Au–Cu–Pt/GCE-10 catalyst presented superior electrocatalytic activity and stability to that of the other comparative electrodes toward methanol electrooxidation (MEO). It indicated that this two-step method can efficiently decrease the amount of Pt loading in the catalyst. These findings also suggested that the prepared Au–Cu–Pt catalyst has a great potential for use in the direct methanol fuel cell (DMFC).

Rutin detection using highly electrochemical sensing amplified by an Au–Ag nanoring decorated N-doped graphene nanosheet

A hybrid nanostructure of Au–Ag nanorings prepared by decorating the surface of N-doped graphene (NG) was utilized as an electrocatalyst to construct a novel electrochemical sensor. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-prepared composites. The Au–Ag nanorings/NG modified electrode exhibited a much better electrochemical response of rutin than that of Au/NG, Ag/NG and NG due to the synergetic catalytic effect between the Au–Ag nanorings and NG. Under optimal conditions, the electrochemical sensor of the Au–Ag nanorings/NG exhibited a wide linear range from 0.05 μM to 241.2 μM (S/N = 3) with a low detection limit of 0.01 μM. In addition, the proposed sensor also displayed good anti-interference ability and long-term stability, which had promising applications in bioassay analysis.

A seed-mediated method to design N-doped graphene supported gold-silver nanothorns sensor for rutin detection

In this paper, a novel Au-Ag nanothorns (NT) composite has been synthesized through a seed-mediated mild chemical route, and then assembled on N-doped graphene (NG). The composite (Au-Ag NTs/NG) was characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Furthermore, electrochemical activity of as-prepared Au-Ag NTs/NG was investigated by cyclic voltammetry (CV) and different pulse voltammetry (DPV). In CVs of Au-Ag NTs, NG, and Au-Ag NTs electrodes recorded in 0.1 M PBS (pH = 3.0) containing 0.1 mM rutin, a remarkably large peak current (55 μA) was obtained on Au-Ag NTs/NG compared to those for NG (25 μA) and Au-Ag NTs (6.2 μA) demonstraing the remarkably enhanced electrochemical activity of the Au-Ag NTs/NG as compared to Au-Ag NTs/NG and NG modified onto a glassy carbon electrode. Electrochemical measurements indicated that the sensors made by Au-Ag NTs/NG electrode are very sensitive and selective for rutin detection due to the NT structure and effects of NG and Au-Ag NTs. In the DPV, Au-Ag NTs/NG electrode was found to have a linear response in the range of 0.1-420 μM and a comparable low detection limit of 0.015 μM (S/N = 3). These results demonstrate that Au-Ag NTs/NG has great potential in extending application in sensor field as the efficient material.