Electroanalytical applications based on carbon nanotube/prussian blue screen-printable composite

A single step fabrication process of carbon nanotube/Prussian Blue (CNT/PB) paste electrodes based on screen printing technology has been studied as an amperometric sensor for the determination of hydrogen peroxide and free chlorine. Compared to the classical carbon paste (CP) electrode, the CNT paste electrode greatly enhanced the response in the presence of hydrogen peroxide due to the electrocatalytic activity of the CNT. Based on the CNT/binder paste, PB was also incorporated into a network of CNT paste and characterized. The best electroanalytical properties of PB-mixed sensors to hydrogen peroxide were obtained with PB ratio of 10 wt % composition, which showed fast response tμMe (t 90 ≤ 5 s; 0.2 - 0.3 mM), low detection lμMit of 1.0μM, good linear response in the range from 5.0 × 10 -5 - 1.0 × 10 -3 mol L -1 (r 2 = 0.9998), and high sensitivity of -8.21 μA mM -1. In order to confirm the enhanced electrochemical properties of CNT/PB electrode, the sensor was further applied for the determination of chlorine in water which exhibited a linear response behavior in the range of 50 - 2000 ppb for chlorine with a slope of 1.10 μA ppm -1 (r 2 = 9971)

Carbon-supported palladium sub-nanometer particle catalyst for oxygen reduction reaction in acid media

Pd nanoparticles (Pd NPs) on a carbon support (Pd/C) were synthesized in ethylene glycol containing poly(1-vinyl- 2-pyrrolidone) (PVP) at various PVP/Pd precursor ratios. The sizes of the Pd NPs were controlled by varying the PVP concentration. Smaller Pd NPs were obtained at higher PVP concentrations. Indeed, the mean sizes of the Pd NPs with PVP/Pd precursor ratios of 0, 40, and 80 (Pd/C-0, -40, and -80) were 2.8 (±1.2), 1.5 (±0.3), and 0.8 (±0.3) nm, respectively, by TEM analysis. The electrocatalytic activities of the Pd/C catalysts toward the oxygen reduction reaction (ORR) were examined in a 0.1M HClO4 solution using rotating disk electrode voltammetry. The smaller Pd NPs exhibited more efficient ORR properties, such as a more positive ORR onset potential (or half-wave potential, E1/2) and increased number of electrons (n) transferred in the ORR. In particular, the Pd/C-80 catalyst with a lower metal content (7.9 wt% Pd) showed desirable ORR performance in terms of the onset potential, n value, mass activity, and methanol tolerance. © 2011 The Chemical Society of Japan

Porous Pd layer-coated au nanoparticles supported on carbon: Synthesis and electrocatalytic activity for oxygen reduction in acid media

This paper reports the simple synthesis and characterization of carbon-supported Pd layer-coated Au nanoparticles (AuPd/C). A series of AuPd/C with various Pd/Au weight percentage ratios were prepared by the spontaneous deposition of a Pd shell on a Au nanoparticle core using different Pd precursor concentrations (0.5, 5, 10, 20 mM PdCl2). Au nanospheres encapsulated by the porous Pd shells are confirmed by transmission electron microscopy (TEM), UV-vis absorption spectroscopy, and scanning TEM. The catalytic activity of the AuPd/C for the oxygen reduction reaction (ORR) was investigated by rotating disk electrode voltammetry in 0.5 M H2SO4. In particular, a AuPd/C with a Pd/Au ratio of 0.61 shows superior ORR activity along with satisfactory stability and methanol tolerance under acidic conditions. © 2011 American Chemical Society

A dual electrochemical microsensor for simultaneous imaging of oxygen and pH over the rat kidney surface

In this study, a dual microsensing electrochemical probe for measuring oxygen (O2) and pH levels was developed based on a dual recessed Pt disk electrode (each disk diameter, 10 μm) with the use of two Ag/AgCl reference electrodes (one for each disk of the dual electrode). One of the recessed Pt disks of the dual electrode was electrodeposited with a porous Pt layer and then coated with a hydrophobic photocured polymer (partially fluorinated epoxy diacrylate, abbreviated as FED). The Pt-FED covered disk was used as an amperometric O2 sensor and exhibited a linear current increase that was proportional to the PO2 level (partial O 2 pressure) with high sensitivity (168.4 ± 33.8 pA mmHg -1) and fast response time (t90% = 0.17 ± 0.05 s). The other recessed Pt disk was electrodeposited with an IrO2 layer. The potential between the IrO2 deposited electrode and the Ag/AgCl reference electrode produced a reliable Nernstian response to pH changes (58.3 ± 1.5 mV pH-1) with a t90% of 0.43 ± 0.09 s. The sensor displayed high stability in the in vitro organ tissue measurements for at least 2.5 h. By using the developed dual O2/pH microsensor as a probe tip for scanning electrochemical microscopy, the two-dimensional images of the location-dependent PO2 and pH levels were simultaneously acquired and could be used to assess the surface of a rat kidney tissue slice. When compared to the corresponding medullary levels, both PO2 and pH were observed to be higher in the cortex area, while the modest level gradient was observed near the cortex-medulla border. This finding suggests that there is a direct relationship between the tissue O2 supply/consumption and pH, which is mainly determined by metabolite, such as CO2, production. © 2013 The Royal Society of Chemistry

Applications of porous Pt-filled micropore electrode: Direct amperometric glucose detection and potentiometric pH sensing

This paper reports the utilization of a micropore electrode as platform for the development of a nonenzymatic glucose microsensor. To facilitate direct glucose oxidation, a highly porous Pt (pPt) layer was deposited electrochemically on the Pt disk base in the pore. Compared to a pPt deposited planar Pt disk electrode, the higher sensitivity and selectivity of the pPt deposited micropore electrode could not only be attributed to the increased electrode roughness, but also to the small pore opening functioning as an efficient mass-transport resistance to the interfering species. The prepared pPt-micropore electrode also showed improved potentiometric responses to pH changes. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Nonenzymatic amperometric glucose sensor based on nanoporous gold/ruthenium electrode

Nanoporous gold/ruthenium (npAu-Ru) nanocomposite catalysts were synthesized by the incorporation of Ru on npAu, which exhibited reasonable nonenzymatic glucose sensing characteristics with good sensitivity and selectivity. The structure and electrocatalytic activities of the npAu and npAu-Ru catalysts were characterized by transmission electron microscopy, energy dispersive X-ray spectroscopy and linear sweep voltammetry. To examine the detection of glucose, npAu and npAu-Ru were loaded on a glassy carbon electrode with chitosan (CHIT) as capping agent for the nanocomposites, GC/npAu/CHIT and GC/npAu-Ru/CHIT electrode, respectively. The GC/npAu-Ru/CHIT electrode showed six fold higher sensitivity (240μAmM-1cm-2 for the linear dynamic range) for amperometric glucose detection than the GC/npAu/CHIT electrode. This could be attributed to the incorporation of Ru. Moreover the GC/npAu-Ru/CHIT electrode displayed selectivity for glucose over biological interferents, including ascorbic acid and uric acid. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

OXYGEN-REDUCTION ELECTROCATALYST BASED ON POROUS BIMETALLIC STRUCTURE, AND PREPARING METHOD OF THE SAME

본원은 팔라듐이 코팅된 다공성 금 나노입자를 포함하는 산소-환원용 전극촉매, 상기 산소-환원용 전극촉매를 포함하는 연료전지, 및 상기 산소-환원용 전극촉매의 제조방법에 관한 것이다

The effect of electrochemical pretreatment on the catalytic activity of carbon-supported gold nanoparticles for NADH oxidation

The electrochemical oxidation of nicotinamide adenine dinucleotide (NADH) is studied systematically on four types of electrodes, i.e., glassy carbon (GC), carbon (C), Au nanoparticles (AuNP), and C-supported AuNP (AuNP/C) in a 0.05 M phosphate buffer solution (pH 7.4) before and after the electrochemical pretreatment carried out by repetitive potential scanning between -0.2 V and 1.0 V (vs. SCE) for 100 cycles. This simple pretreatment improves the electrocatalytic activity of the AuNP/C toward the NADH oxidation remarkably, suggesting the key role of Au oxide layers in facilitating the NADH electrochemical oxidation. © 2012 Elsevier B.V. All rights reserved

Impact of anions on electrocatalytic activity in palladium nanoparticles supported on ionic liquid-carbon nanotube hybrids for the oxygen reduction reaction

A series of palladium nanoparticles supported on carbon nanotubes (CNTs), which were functionalized covalently with imidazolium polymer salts with different anions, Pd/polyIL(X)-CNTs (IL=ionic liquid; X=Cl, Br, I, ClO 4, BF4, PF6), were prepared to investigate the influence of imidazolim salt anions on electrocatalytic activity in the oxygen reduction reaction (ORR). The anions of the imidazolium moiety significantly impacted on the ORR kinetics in a 0.1 M solution of HClO4. The electronically active surface area results are in good agreement with the order of the ORR kinetic activity of the supported Pd/polyIL(X)-CNTs (X: Cl>ClO4>BF4>Br≈PF6≤laquo;I). In contrast, owing to the facile anion exchange of halide anions with hydroxide anions, anion-dependent catalytic activity has not been observed in 0.1 M NaOH. Iterative ORR experiments in acid-base solutions demonstrated anion exchange on the electrode. These results indicate that subtly varied structures of the IL moiety profoundly influence the performance of IL-CNT hybrid materials and molecular-level control of interfacial interactions between the support material, catalysts, and electrolytes is important in the design of supported metal nanoparticle catalysts for fuel cells. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim