Gold Anode Research Articles

Glass separation processing using crack generation by application of reverse voltage to gold / glass anodic joint and gold migration induced

Glass separation processing using crack generation by application of reverse voltage to gold / glass anodic joint and gold migration induced

Nanoporous gold electrode prepared from gold compact disk as the anode for the microbial fuel cell

The electrodes (anode and cathode) have an important role in the efficiency of a microbial fuel cell (MFC), as they can determine the rate of charge transfer in an electrochemical process. In this study, nanoporous gold electrode, prepared from commercially available gold-made compact disk, is utilized as the anode in a two-chamber MFC. The performance of nanoporous gold electrode in the MFC is compared with that of gold film, carbon felt and acid-heat-treated carbon felt electrodes which are usually employed as the anode in the MFCs. Electrochemical surface area of nanoporous gold electrode exhibits a 7.96-fold increase rather than gold film electrode. Scanning electron microscopy analysis also indicates the homogeneous biofilm is formed on the surface of nanoporous gold electrode, while the biofilm formed at the surface of acid-heat-treated carbon felt electrode shows rough structure. Electrochemical studies show although modifications applied on carbon felt electrodes improve its performance, nanoporous gold electrode, due to its structure and better electrochemical properties, acts more efficiently as the MFC’s anode. The maximum power density produced by nanoporous gold anode is 4.71 mW m−2 at current density of 16.00 mA m−2, while this value for acid-heat-treated carbon felt anode is 3.551 mW m−2 at current density of 9.58 mA m−2.

Power-on-paper: Origami-inspired fabrication of 3-D microbial fuel cells

Abstract We demonstrate that fabricating low-cost microbial fuel cells (MFCs) can be done efficiently by using a paper substrate and origami techniques. A 3-D MFC was developed from a 2-D sheet of paper by integrating the anode, reservoir, cation exchange membrane (CEM) and air-cathode. The cell was easily formed by folding the paper along pre-defined creases. The entirely paper-based all-printed MFC developed in this work rapidly generated power with a small amount of bacteria-containing liquid through rapid adsorption and instant attachment of the bacteria cells to the anode. A graphite-polymer composite and graphite ink with activated carbon were readily applicable as novel anodic materials on paper and enhanced performance better than a conventional graphite ink or gold anode. The hydrophobic wax-based CEM was readily built with a commercially available wax printer and using heat to control how deep the wax penetrated the paper. This work will create a novel platform for paper-based power source, stepping toward batch-fabricable flexible papertronics.

Microbial activity influences electrical conductivity of biofilm anode

This study assessed the conductivity of a Geobacter-enriched biofilm anode in a microbial electrochemical cell (MxC) equipped with two gold anodes (25 mM acetate medium), as different proton gradients were built throughout the biofilm. There was no pH gradient across the biofilm anode at 100 mM phosphate buffer (current density 2.38 A/m2) and biofilm conductivity (Kbio) was as high as 0.87 mS/cm. In comparison, an inner biofilm became acidic at 2.5 mM phosphate buffer in which dead cells were accumulated at ∼80 μm of the inner biofilm anode. At this low phosphate buffer, Kbio significantly decreased by 0.27 mS/cm, together with declined current density of 0.64 A/m2. This work demonstrates that biofilm conductivity depends on the composition of live and dead cells in the conductive biofilm anode.

Electrosynthesis of gold nanoparticles mediated by methylviologen using a gold anode in single compartment cell

Methylviologen mediated reduction of Au i ions generated in situ by dissolution of a gold anode in single compartment cell has been used for the electrosynthesis of spherical gold nanoparticles (Au-NPs) stabilized by poly(N-vinylpyrrolidone). The size of Au-NPs was from 15±6 to 27±9 nm, depending on the electrosynthesis conditions. Au-NPs were characterized by cyclic voltammetry, UV-VIS spectroscopy, dynamic light scattering, scanning and transmission electron microscopy.

A Group Additivity Based-Thermodynamic Analysis of a Conceptual Glycerol/Ferric Redox Flow Battery

The electrochemical oxidation of glycerol has been studied and known to be a source of several chemicals of premium industrial value and has also been utilized in the concept of direct glycerol fuel cells to produce electrical energy additionally[1]. In the current study however, this concept is extended to cover both electrochemical oxidation and reduction of glycerol as a substitute for the hydrogen ion in redox flow battery with a Fe2+/Fe3+ couple as cathode [2]. A predictive thermodynamic analysis has been developed and applied to the study and proof of this conceptual glycerol redox flow battery. Reactions toward electrochemical formation of several partial oxidation and reduction products of glycerol in acidic media under discharge and charging conditions of the proposed glycerol flow battery are presented. Free energy values of the reaction species as estimated by the Group Additivity Value (GAV) method were used to determine the feasibility of these proposed reaction towards cogeneration of electricity and commodity chemicals. The equilibrium voltages representing the maximum electrical work under these conditions are also computed. Experimental validation of this theoretical concept has also been investigated using electrochemical methods to study the electro-catalytic activity of electrolessly deposited NiCuSnP supported on carbon towards glycerol oxidation in acidic medium as anode in a proton exchange membrane-glycerol redox flow battery. Li W., Xin L., Zhang Z., Wang Z.,. (2012) Simultaneous Generation of Mesoxalic Acid and Electricity from Glycerol on a Gold Anode Catalyst in Anion-Exchange Membrane Fuel Cells ChemCatChem Vol 4 1105-1114Khalid Fatih K, Wilkinson D., Moraw F., Ilicic A and Girarda F Advancements in the Direct Hydrogen Redox Fuel Cell Electrochemical and Solid-State Letters, 11 2 B11-B15 (2008) Figure 1

On Gold(I) Complexes and Anodic Gold Dissolution in Sulfite–Thiourea Solutions

Processes involving gold(I) complexes were studied in sulfite–thiourea (TU) solutions. It is shown that at pH >5 the complex [\( {\text{AuTU}}_{2}^{ + } \)] undergoes irreversible decomposition followed by deprotonation and formation of a solid phase. From the data of pH in mixed solutions, the equilibrium constants were evaluated: \( {\text{Au}}({\text{SO}}_{3} )_{2}^{3 - } + i{\text{TU}} \rightleftharpoons {\text{Au}}({\text{SO}}_{3} )_{2 - i} {\text{TU}}_{i}^{2i - 3} + i{\text{SO}}_{3}^{2 - } \), log10 β 1 = −1.2, log10 β 2 = −3.6. Some aspects of the anodic dissolution of gold in mixed sulfite–thiourea solutions are considered. With the help of the carbonate buffer system the change of the anodic current density j a was studied at high pH; j a (pH) has a maximum at pH 11.6–11.9 for E a = 0.3–0.6 V (vs. NHE). At pH > 12.0, the j a values decrease sharply. Possible mechanisms of anodic gold dissolution, as well as the role of sulfite, are discussed.

In Situ Atomic-Scale Observation of Electrochemical Delithiation Induced Structure Evolution of LiCoO2 Cathode in a Working All-Solid-State Battery.

We report a method for in situ atomic-scale observation of electrochemical delithiation in a working all-solid-state battery using a state-of-the-art chip based in situ transmission electron microscopy (TEM) holder and focused ion beam milling to prepare an all-solid-state lithium-ion battery sample. A battery consisting of LiCoO2 cathode, LLZO solid state electrolyte and gold anode was constructed, delithiated and observed in an aberration corrected scanning transmission electron microscope at atomic scale. We found that the pristine single crystal LiCoO2 became nanosized polycrystal connected by coherent twin boundaries and antiphase domain boundaries after high voltage delithiation. This is different from liquid electrolyte batteries, where a series of phase transitions take place at LiCoO2 cathode during delithiation. Both grain boundaries become more energy favorable along with extraction of lithium ions through theoretical calculation. We also proposed a lithium migration pathway before and after polycrystallization. This new methodology could stimulate atomic scale in situ scanning/TEM studies of battery materials and provide important mechanistic insight for designing better all-solid-state battery.

HLADH-catalyzed synthesis of β-amino acids, assisted by continuous electrochemical regeneration of NAD+ in a filter press microreactor

This work focuses on the use of electrochemical microreactors, applied to the direct electroregeneration of nicotinamide dinucleotide (NAD+) used in-situ for the enzymatically-assisted oxidation of the β-alanine. Mechanistic and chemical/electrochemical reactor approaches were investigated, to achieve satisfactory conversions (>80%) of the substrate in reasonable (1–2 days) reaction times; no fouling observed of the gold anode. An original method was proposed to limit the complexation effect of the produced β-alanine to the enzyme. Simulations of the overall system were achieved and an estimation of the required kinetic and Michaelis constants was proposed.

Mechanism of the anodic dissolution of gold in solutions of 6-alkyl-1,5-diazabicyclo[3.1.0]hexanes

The electrochemical corrosion of gold in solutions of 6,6-dimethyl-1,5-diazabicyclo[3.1.0]hexane (I) and 6-methyl-1,5-diazabicyclo[3.1.0]hexane (II) on a gold electrode is studied via cyclic voltammetry. It is shown that the galvanostatic electrolysis of weakly basic aqueous solutions of I and II on gold anodes results in the corrosion of Au electrodes, probably with the formation of organic complexes of gold that are reduced to form a gold mirror on the inner surface of an electrochemical cell during electrolysis. A mechanism is proposed for the investigated processes.

Electrochemical Lithiation Cycles of Gold Anodes Observed by In Situ High-Energy X-ray Diffraction

Significant developments of Li-ion batteries will be necessary to cope with the growing demands in electromobility or home storage of (sustainable) electrical energy. A detailed knowledge on the microscopic processes during battery cycling will be increasingly crucial for improvements. Involved phase changes at ambient temperature often involve metastable intermediate states, making both experimental observation and theoretical prediction of process pathways difficult. Here we describe an in situ high energy X-ray diffraction study following the initial alloying and dealloying of Li with an Au thin-film model anode using ionic liquid electrolyte. Six different crystalline alloy phases were observed to be involved in the cyclic phase transitions. Apart from the highest lithiated phase determined in this study, Li3Au, none of the observed phases could be related to known, thermodynamically stable Li–Au phases. Structural search calculations following the minima hopping method (MHM) allowed the assignment of...

Electrochemical Synthesis of Hydrogen with Depolarization of the Anodic Process

World experience defines hydrogen as the most perspective energy carrier. Producing hydrogen by electrolysis helps effectively solve the problem of peak loads and failures arising from the different structure of energy consumption during the day . Thermoelectrochemical cycles of producing hydrogen are intensively studied in Kharkov Polytechnic Institute, Kharkov, Ukraine. Further development of hydrogen production by electrolysis of water associated with implementation of Hybrid Sulfur cycle or "Westinghouse cycle") [1]. It is a two–step process, first a low–temperature electrochemical step (1): 2H2O + SO2 H2 + H2SO4 (1) and second a high temperature (2): H2SO4 H2O + SO2 + 0,5 O2 (2) The clear advantage of the Hybrid Sulfur Cycle process is that the standard reversible voltage E0 of the net cell reaction (2) is only 0.17 V. For comparison, conventional water electrolysis requires E0 = 1.23 V. In laboratory–scale tests, the realized cell voltage of SO2 depolarization electrolysis has been 0.5¼1.3 V, depending on the current density and other operational parameters compared with the 1.8¼2.0 V of commercial alkaline water electrolysis. Thus, SO2 depolarization electrolysis would require 25¼60 % of the electrical energy required for direct water splitting by conventional electrolysis. The electrochemical process is far from technical implementation and intensively studied in recent years.Hybrid Sulfur cycle was intensively studied for practical implementation with using platinum, gold and palladium anodes . Further investigation is connected with using more affordable anode materials. According to the E–pH diagram, ruthenium, molybdenum, tungsten and their oxides are defined to be most perspective catalytic materials. Active porous anode was obtained by covering the graphite basis by active carbon, Pt, MoO3, RuO2, WO3. Covering with active carbon was prepared by impregnating the graphite basis in sugar solution, followed by drying and thermal decomposition. The other composite coatings were prepared by impregnating a sugar solution and brine H2[PtCl6], (NH4)6Mo7O24·4H2O, (NH4)4W5O17, followed by drying and thermal decomposition at 600...650 K. The cylindrical anodes have diameter 20 mm and thickness 5 mm. They were inserted into a special current source, consisting of a current–conducting tubes with welded sample holder (Fig. 1). Samples were fixed in a holder nut. Current supply material – titanium coated PTFE. Current–voltage measurements were carried out in plastic cell with anode and cathode separation space cation exchange membrane. Electrode potentials were measured relative to a mercury sulfate reference electrode and converted to the normal hydrogen electrode.

Smart contact lens and smart eye glasses

Event Abstract Back to Event Smart contact lens and smart eye glasses Sei Kwang Hahn1 and Do Hee Keum1* 1 Pohang University of Science and Technology, Materials Science and Engineering, Korea Introduction: Contact lens has been widely investigated for biosensing and drug delivery applications to ocular diseases. Here, we developed a smart contact lens containing biosensor and drug delivery system, and a smart eye glasses for the treatment of diabetes as a model disease. Materials and Methods: For the diagnosis of diabetes, tear glucose content was measured as a non-invasive alternative for the blood glucose content monitoring. The Ti electrode of biosensor was immobilized with glucose oxidase. When glucose binds to glucose oxidase, hydrogen peroxide is produced and oxidized on the electrode generating electrical current. For the drug delivery system, we fabricated Au membrane coated drug reservoirs on contact lens. Each reservoir was sealed at one end with a thin membrane of gold anode. When we applied electrical current, Au membrane was dissolved into AuCl4- in NaCl solution. This flexible, biocompatible and miniaturized device was wirelessly powered by the WiTricity system of transmitter coils in smart eyeglasses and receiver coils in smart contact lens. Results: The electrical current from the glucose sensor increased from 10 microA to 200 microA with increasing tear glucose level ranging from 0.05 mM to 0.8 mM. Glucose sensor could be repeatedly used for 3 weeks in tear solution without lens corrosions and big current decrease. The thin gold anode was dissolved immediately in PBS solution by applying electrical voltage, triggering the release of drug from the reservoir. The transmitter circuit generated sine wave signals and MOSFET driver in SOIC8 package drived coils up to 60 V peaks on sine wave. For the power density calculation, the measured absolute value of the optical power was divided to the detector active area (1 cm2). A proper power was transferred to the receiver and sufficient energy was available to power the glucose sensor, drug delivery system, and communication circuitry. Discussion: Biosensor can transmit the detected ocular signals to the smart eyeglasses for future processing and diagnostics applications. A miniaturized ocular drug-delivery system was also automatically controlled using the smart eyeglasses by user voice command. The efficient wireless power transfer system and the miniaturized microelectronic integrated circuit using CMOS and NEMS technologies will introduce a new alternative platform for future diagnostic and therapeutic applications, and human-machine interface healthcare applications. This novel smart contact lens can be further developed as a platform for the futuristic nano clinic systems. Conclusions: We successfully developed smart contact lens which is composed of glucose biosensor, on-demand drug delivery MEMS system, and remote power systems. Biosensor could measure tear glucose level in real-time for the diagnosis of diabetes, electrically controllable pulsatile DDS was applicable to deliver the drugs into the eyes, and miniaturized electrical power system made possible to drive flexible portable devices. This smart contact lens can be further developed for various theranostic applications.

Feasibility of measuring arsenic and selenium in human skin using in vivo x-ray fluorescence (XRF)—a comparison of methods

In recent years, in vivo measurement systems of arsenic in skin by K-shell x-ray fluorescence (XRF) have been developed, including one which was applied in a pilot study of human subjects. Improved tube-based approaches suggest the method can be further exploited for in vivo studies. Recently, it has been suggested that selenium deficiency is correlated with arsenic toxicity. A non-invasive measurement of both elements could therefore be of potential interest. The main aim of this current study was to evaluate and compare the performance of an upgraded portable XRF system and an advanced version of the benchtop XRF system for both selenium and arsenic. This evaluation was performed in terms of arsenic and selenium Kα detection limits for a 4W gold anode Olympus InnovX Delta portable analyzer (40 kVp) in polyester resin skin-mimicking phantoms. Unlike the polychromatic source earlier reported in the literature, the benchtop tube-based technique involves monochromatic excitation (25 W silver anode, manufactured by x-ray optics, XOS) and a higher throughput detector type. Use of a single exciting energy allows for a lower in vivo dose delivered and superior signal-noise ratio. For the portable XRF method, arsenic and selenium minimum detection limits (MDLs) of 0.59 ± 0.03 ppm and 0.75 ± 0.02 ppm respectively were found for 1 min measurement times. The MDLs for arsenic and selenium using the benchtop system were found to be 0.35 ± 0.01 ppm and 0.670 ± 0.004 ppm respectively for 30 min measurement times. In terms of a figure of merit (FOM), allowing for dose as well as MDL, the benchtop system was found to be superior for arsenic and the two systems were equivalent, within error, for selenium. We shall discuss the performance and possible improvements of each system, their ease of use and potential for field application.

Features of Sulfite Oxidation on Gold Anode

Electrochemical oxidation of sulfite ions on gold was studied by means of voltammetry with the electrode renewed by cutting off a thin layer. It was demonstrated that two different kinds of voltammograms can be recorded on gold, depending on experimental conditions. Voltammograms of the first kind, with current maximum at 0.8V, is typical for the fresh gold surface. The second one, with current maximum at 0.6V, is observed on gold surface modified during sulfite oxidation. Modification of gold surface is likely to be due to the formation of “sulfur adlayer” in the reduction of adsorbed products of sulfite oxidation. Attention is attracted to the fact that the characteristics of the oxidation of sulfite and sulfur dioxide on gold have many common features.

Selective Oxidation of 1,2-Propanediol in Alkaline Anion-Exchange Membrane Electrocatalytic Flow Reactors: Experimental and DFT Investigations

Electrocatalytic oxidation of polyhydric alcohols represents an important route for coproduction of biorenewable chemicals and energy. However, the governing factors leading to high product selectivity remain unclear. Herein, we investigate the selective oxidation of 1,2-propanediol (PDO) to pyruvate or lactate in electrocatalytic reactors over carbon-supported platinum (Pt/C) and gold (Au/C) anode catalysts. PDO-fed alkaline anion-exchange membrane fuel cells successfully cogenerated electricity and valuable chemicals with peak power densities of 46.3 mW cm–2 on Pt/C and 10.0 mW cm–2 on Au/C. Pt/C was highly selective for primary alcohol group oxidation to lactate (86.8%) under fuel cell conditions, but Au/C yielded significant amounts of pyruvate, a product that has previously eluded heterogeneous catalytic studies on Au. Sequential oxidation of lactate to pyruvate was not observed on Au/C but did occur slowly on Pt/C. The electrode potential dependent product distribution was investigated, and it was r...

Role of anode material on the electrochemical oxidation of methyl orange

The anodic oxidation of methyl orange (MO, 5-(4-nitrophenylazo)salicylic acid) has been studied by cyclic voltammetry and bulk electrolysis, using a range of electrode materials such as Ti–Ru–Sn ternary oxide, lead dioxide and boron-doped diamond (BDD), glassy carbon (GC) and gold anodes. The results of voltammetries show that with all the electrode materials, in the potential region before oxygen evolution, the oxidation of MO involves simple electrode transfer that produces a polymeric film that deactivates the electrode surface, as confirmed by Fourier Transform Infrared Reflection-Absorption Spectroscopy (FTIRRAS) analysis. A very different behaviour was observed among the electrodes in the region of water decomposition. While BDD and PbO2 regained their initial activity by simple polarisation at 2.3 V vs. saturated calomel electrode (SCE) due to the production of high amount of hydroxyl radicals that destroy the polymeric film, TiRuSnO2, GC and gold cannot be completely reactivated, because they have a low overpotential for oxygen evolution, and this secondary reaction is favoured over polymer mineralization. The results of bulk electrolysis showed that after 3 h of polarisation at 10 mA cm−2, complete colour and chemical oxygen demand (COD) removal were obtained only with BDD anode. Using PbO2 MO was oxidised but a residual COD remains in the solution, while TiRuSnO2 permitted only a partial oxidation of MO.

Influence of anode surface chemistry on microbial fuel cell operation

Self-assembled monolayers (SAMs) modified gold anodes are used in single chamber microbial fuel cells for organic removal and electricity generation. Hydrophilic (N(CH3)3+, OH, COOH) and hydrophobic (CH3) SAMs are examined for their effect on bacterial attachment, current and power output. The different substratum chemistry affects the community composition of the electrochemically active biofilm formed and thus the current and power output. Of the four SAM-modified anodes tested, N(CH3)3+ results in the shortest start up time (15days), highest current achieved (225μAcm−2) and highest MFC power density (40μWcm−2), followed by COOH (150μAcm−2 and 37μWcm−2) and OH (83μAcm−2 and 27μWcm−2) SAMs. Hydrophobic SAM decreases electrochemically active bacteria attachment and anode performance in comparison to hydrophilic SAMs (CH3 modified anodes 7μAcm−2 anodic current and 1.2μWcm−2 MFC's power density). A consortium of Clostridia and δ-Proteobacteria is found on all the anode surfaces, suggesting a synergistic cooperation under anodic conditions.

Tuning the Size of Gold Nanoparticles with Repetitive Oxidation-reduction Cycles

A simple method to control the size of gold nanoparticles (AuNP) using repetitive oxidation-reduction cycles is described. First, AuNP are shown to be readily immobilized onto an indium-doped tin oxide coated glass surface using cyclic voltammetry nanoparticle containing citrate buffer. Subsequently, the attached AuNPsize can be reduced to a desired level by potential cyclingin the range from 0 V to +1.1 V (vs. Ag/AgCl).Gradual AuNPdiameter decrease was attributed to the formation of gold oxide upon anodic potential sweep and the partial solubilization of the Au(III) species during subsequent reduction of gold oxide in the absence of gold chelator (e.g.,Cl<SUP>-</SUP>, Br<SUP>-</SUP>, or CN<SUP>-</SUP>) normally necessary for anodic gold dissolution.

Surface plasmon excitation in semitransparent inverted polymer photovoltaic devices and their applications as label-free optical sensors

Herein, we report on surface plasmon (SP)-sensitive semitransparent inverted polymer photovoltaic (PV) devices that are based on multilayered material systems consisting of poly(3-hexylthiophene): fullerene-derivative bulk-heterojunction PV layers and thin gold or silver anodes. We demonstrate that these PV devices allow the simultaneous generation of both electrical power and SPs on their anodes for photoexcitation just above the optical absorption edge of the PV layers, resulting not only in attenuated total reflection, but also in attenuated photocurrent generation (APG) under the SP resonance (SPR) condition. Moreover, we also confirm that the biomolecular interaction of biotin–streptavidin on the PV devices can be precisely detected via apparent SPR angle shifts in the APG spectra, even without the need for complex attenuated total reflection configurations. We highlight our view that APG measurements made using these PV devices show great potential for the development of future generations of compact and highly sensitive SPR-based optical sensors. Researchers investigate surface plasmon excitation in photovoltaic devices and explore their application as highly sensitive optical sensors. Byoungchoo Park and co-workers at Kwangwoon University in South Korea have developed semitransparent inverted polymer photovoltaic devices with a planar multilayer structure that are capable of simultaneously generating electrical power and surface plasmons on irradiation. When surface plasmon resonance is induced in these devices, both total internal reflection and photocurrent generation are attenuated. The researchers demonstrated that this property can be exploited to sensitively detect biological compounds. Specifically, they used apparent shifts in the surface plasmon resonance angle in attenuated photocurrent generation to detect the biomolecular interaction of biotin-streptavidin. They conclude that these devices have great potential as next-generation optical sensors that are simple, inexpensive, compact and highly sensitive.