The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

2022 ◽  
Vol 169 (1) ◽  
pp. 016503
Author(s):  
Md. Shafiul Islam ◽  
Alan J. Branigan ◽  
Borkat Ullah ◽  
Christopher J. Freeman ◽  
Maryanne M. Collinson
Keyword(s):  
Fold Increase ◽  
Reduction Reaction ◽  
Open Circuit ◽  
Nanoporous Gold ◽  
Pt Electrode ◽  
Electrodeposition Time ◽  
Titration Curves ◽  
Redox Sensing ◽  
Redox Molecules ◽  
Mixed Potentials

Potentiometric redox sensing in solutions containing multiple redox molecules was evaluated using in-house constructed nanoporous gold (NPG)-platinum (Pt) and unmodified NPG electrodes. The NPG-Pt electrode was fabricated by electrodepositing Pt into the nanoporous framework of a chemically dealloyed NPG electrode. By varying the concentration of the Pt salt and the electrodeposition time, different amounts of Pt were introduced. Characterization by SEM shows the pore morphology doesn’t change with the addition of Pt and XPS indicates the electrodes contain ∼2.5–24 wt% Pt. Open-circuit potential (OCP) measurements in buffer and solutions containing ascorbic acid, cysteine, and/or uric acid show that the OCP shifts positive with the addition of Pt. These results are explained by an increase in the rate of the oxygen reduction reaction with the addition of Pt. The overall shape of the potentiometric titration curves generated from solutions containing one or more bioreagents is also highly dependent on the amount of Pt in the nanoporous electrode. Furthermore, the generation of OCP vs Log [bioreagent] from the results of the potentiometric experiments shows an ∼2-fold increase in sensitivity can result with the addition of Pt. These results indicate the promise that these electrodes have in potentiometric redox sensing.

scholarly journals Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

Biosensors ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Christopher J. Freeman ◽  
Borkat Ullah ◽  
Md. Shafiul Islam ◽  
Maryanne M. Collinson
Keyword(s):  
Ascorbic Acid ◽  
Uric Acid ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Nanoporous Gold ◽  
Redox Potentials ◽  
Biologically Relevant ◽  
Redox Sensing ◽  
Redox Molecules

Potentiometric redox sensing is a relatively inexpensive and passive approach to evaluate the overall redox state of complex biological and environmental solutions. The ability to make such measurements in ultra-small volumes using high surface area, nanoporous electrodes is of particular importance as such electrodes can improve the rates of electron transfer and reduce the effects of biofouling on the electrochemical signal. This work focuses on the fabrication of miniaturized nanoporous gold (NPG) electrodes with a high surface area and a small footprint for the potentiometric redox sensing of three biologically relevant redox molecules (ascorbic acid, uric acid, and cysteine) in microliter volumes. The NPG electrodes were inexpensively made by attaching a nanoporous gold leaf prepared by dealloying 12K gold in nitric acid to a modified glass capillary (1.5 mm id) and establishing an electrode connection with copper tape. The surface area of the electrodes was ~1.5 cm2, providing a roughness factor of ~16 relative to the geometric area of 0.09 cm2. Scanning electron microscopy confirmed the nanoporous framework. A linear dependence between the open-circuit potential (OCP) and the logarithm of concentration (e.g., Nernstian-like behavior) was obtained for all three redox molecules in 100 μL buffered solutions. As a first step towards understanding a real system, the response associated with changing the concentration of one redox species in the presence of the other two was examined. These results show that at NPG, the redox potential of a solution containing biologically relevant concentrations of ascorbic acid, uric acid, and cysteine is strongly influenced by ascorbic acid. Such information is important for the measurement of redox potentials in complex biological solutions.

scholarly journals Mixed Lithium and Sodium Ion Aprotic DMSO Electrolytes for Oxygen Reduction on Au and Pt Studied by DEMS and RRDE

2021 ◽  
Author(s):  
M. Hegemann ◽  
P. P. Bawol ◽  
A. Köllisch-Mirbach ◽  
H. Baltruschat
Keyword(s):  
Oxygen Reduction ◽  
Product Distribution ◽  
Reduction Reaction ◽  
Mixed Electrolytes ◽  
Peroxide Formation ◽  
Pt Electrode ◽  
Rate Determining Step ◽  
Differential Electrochemical Mass Spectrometry ◽  
Redox Couples ◽  
Pt Electrodes

AbstractIn order to advance the development of metal-air batteries and solve possible problems, it is necessary to gain a fundamental understanding of the underlying reaction mechanisms. In this study we investigate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER, from species formed during ORR) in Na+ containing dimethyl sulfoxide (DMSO) on poly and single crystalline Pt and Au electrodes. Using a rotating ring disk electrode (RRDE) generator collector setup and additional differential electrochemical mass spectrometry (DEMS), we investigate the ORR mechanism and product distribution. We found that the formation of adsorbed Na2O2, which inhibits further oxygen reduction, is kinetically favored on Pt overadsorption on Au. Peroxide formation occurs to a smaller extent on the single crystal electrodes of Pt than on the polycrystalline surface. Utilizing two different approaches, we were able to calculate the heterogeneous rate constants of the O2/O2− redox couple on Pt and Au and found a higher rate for Pt electrodes compared to Au. We will show that on both electrodes the first electron transfer (formation of superoxide) is the rate-determining step in the reaction mechanism. Small amounts of added Li+ in the electrolyte reduce the reversibility of the O2/O2− redox couples due to faster and more efficient blocking of the electrode by peroxide. Another effect is the positive potential shift of the peroxide formation on both electrodes. The reaction rate of the peroxide formation on the Au electrode increases when increasing the Li+ content in the electrolyte, whereas it remains unaffected on the Pt electrode. However, we can show that the mixed electrolytes promote the activity of peroxide oxidation on the Pt electrode compared to a pure Li+ electrolyte. Overall, we found that the addition of Li+ leads to a Li+-dominated mechanism (ORR onset and product distribution) as soon as the Li+ concentration exceeds the oxygen concentration. Graphical abstract

Printed air cathode for flexible and high energy density zinc-air battery

MRS Advances ◽  
2016 ◽  
Vol 1 (53) ◽  
pp. 3585-3591
Author(s):  
Soorathep Kheawhom ◽  
Sira Suren
Keyword(s):  
Metal Oxides ◽  
High Energy ◽  
Reduction Reaction ◽  
Open Circuit ◽  
High Energy Density ◽  
Ohmic Loss ◽  
Screen Printing Technique ◽  
Cathode Current ◽  
Discharge Potential ◽  
Zinc Air Batteries

ABSTRACTFlexible zinc-air batteries were fabricated using an inexpensive screen-printing technique. The anode and cathode current collectors were printed using commercial nano-silver conductive ink on a polyethylene terephthalate (PET) substrate and a polypropylene (PP) membrane, respectively. Air cathodes made of blended carbon black with inexpensive metal oxides including manganese oxide (MnO2) and cerium oxide (CeO2), were studied. The presence of the metal oxides in the air cathodes enhanced the oxygen reduction reaction which is the most important cathodic reaction in zinc-air batteries. The battery with 20 %wt CeO2showed the highest performance and provided an open-circuit voltage of 1.6 V and 5 – 240 mA.cm-2ohmic loss zone. The discharge potential of this battery at the current density of 5 mA.cm-2was nearly 0.25 V higher than that of the battery without metal oxides. Finally, the battery was tested for its flexibility by bending it so that its length decreased from 2.5 to 1 cm. The results showed that the bending did not affect characteristics on potential voltage and discharging time of the batteries fabricated.

scholarly journals Effect of pH on the Electrochemical Behavior of Hydrogen Peroxide in the Presence of Pseudomonas aeruginosa

2021 ◽  
Vol 9 ◽  
Author(s):  
Javier Espinoza-Vergara ◽  
Paulo Molina ◽  
Mariana Walter ◽  
Miguel Gulppi ◽  
Nelson Vejar ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Pseudomonas Aeruginosa ◽  
Enzymatic Activity ◽  
Electrochemical Behavior ◽  
Electrochemical Techniques ◽  
Stable State ◽  
Reduction Reaction ◽  
Maximum Activity ◽  
Open Circuit ◽  
Mueller Hinton

The influence of pH on the electrochemical behavior of hydrogen peroxide in the presence of Pseudomonas aeruginosa was investigated using electrochemical techniques. Cyclic and square wave voltammetry were used to monitor the enzymatic activity. A modified cobalt phthalocyanine (CoPc) carbon electrode (OPG), a known catalyst for reducing O2 to H2O2, was used to detect species resulting from the enzyme activity. The electrolyte was a sterilized aqueous medium containing Mueller-Hinton (MH) broth. The open-circuit potential (OCP) of the Pseudomonas aeruginosa culture in MH decreased rapidly with time, reaching a stable state after 4 h. Peculiarities in the E / I response were observed in voltammograms conducted in less than 4 h of exposure to the culture medium. Such particular E/I responses are due to the catalase’s enzymatic action related to the conversion of hydrogen peroxide to oxygen, confirming the authors’ previous findings related to the behavior of other catalase-positive microorganisms. The enzymatic activity exhibits maximum activity at pH 7.5, assessed by the potential at which oxygen is reduced to hydrogen peroxide. At higher or lower pHs, the oxygen reduction reaction (ORR) occurs at higher overpotentials, i.e., at more negative potentials. In addition, and to assess the influence of bacterial adhesion on the electrochemical behavior, measurements of the bacterial-substrate metal interaction were performed at different pH using atomic force microscopy.

One-pot facile synthesis of PtCu coated nanoporous gold with unique catalytic activity toward the oxygen reduction reaction

RSC Advances ◽  
2016 ◽  
Vol 6 (46) ◽  
pp. 40086-40089 ◽  
Author(s):  
Hongjie Zhang ◽  
Baolian Yi ◽  
Yachao Zeng ◽  
Shangfeng Jiang ◽  
Yongyi Jiang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Nanoporous Gold ◽  
Facile Synthesis ◽  
One Pot ◽  
3D Nanostructure

PtCu@NPG prepared by a one-pot protocol preserved the 3D nanostructure of NPG and presented unique catalytic activity and durability towards the ORR.

scholarly journals Prussian Blue Analogue Derived Co3O4/CuO Nanoparticles as Effective Oxygen Reduction Reaction Catalyst for Magnesium-Air Battery

2022 ◽  
Author(s):  
Xiaoyang Dong ◽  
Jinxing Wang ◽  
Xiao Wang ◽  
Jingdong Yang ◽  
Ling Zhu ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Prussian Blue ◽  
Oxygen Reduction ◽  
Noble Metal ◽  
Reduction Reaction ◽  
Open Circuit ◽  
Cuo Nanoparticles ◽  
Limiting Current ◽  
Prussian Blue Analogue ◽  
Air Battery

Abstract Developing efficient, durable, and cost-effective non-noble metal catalysts for oxygen reduction reaction (ORR) is necessary to promote the efficiency and performance of Mg-air batteries. Herein, the Co3O4/CuO nanoparticles were synthesized by a low-cost and simple approach using CuCo-based prussian blue analogue (PBA) as precursor of pyrolysis at different calcination temperatures. It was found that the Co3O4/CuO nanoparticles calcined at 600ºC (CCO-600) have relatively small size and superior ORR performance. The onset potential is 0.889 V and the diffusion limiting current density achieves 6.746 mA·cm-2, as well as prominent stability in 0.1 M KOH electrolyte. The electron transfer number of the CCO-600 is 3.89 under alkaline medium, which indicates that the reaction mechanism of ORR is dominated by 4 e process, similar to commercial Pt. The primary Mg-air battery with the CCO-600 as the cathode catalyst has been assembled and possesses better discharge performance than the CuCo-based PBA. The open circuit voltage of CCO-600 arrives at 1.76 V and energy density of 1895.95 mWh/g. This work provides an effective strategy to develop non-noble metal ORR catalyst for the application of metal-air batteries

scholarly journals KCl Transport Across an Insect Epithelium: Characterization of K-Stimulated Cl Absorption and Active K Transport

1984 ◽  
Vol 111 (1) ◽  
pp. 201-223
Author(s):  
J. W. HANRAHAN ◽  
J. E. PHILLIPS
Keyword(s):  
Fold Increase ◽  
Open Circuit ◽  
Cl Transport ◽  
Kcl Transport ◽  
Low Levels ◽  
Mucosal Side ◽  
Kinetics Of ◽  
K Transport ◽  
Stimulation Of

The kinetics of 36C1 fluxes across cAMP-stimulated, short-circuited locust rectum were studied. Raising external K+ from 0 to 100 mM increased both Kt and Vmax for net Cl transport (JnetCl) by four- to six-fold. Hill plots of JnetCl indicated non-cooperative Cl interactions. The sequence for cation stimulation of JnetCl was K > Rb > Cs > Na > NH4. Low levels of K were stimulatory only when added to the mucosal side. Cyclic AMP (cAMP) caused a small active absorption of K, although this was minor compared to the four-fold increase in transepithelial K diffusion (PK). Neither cAMP stimulation of JnetK nor of PK was sensitive to Cl removal, suggesting that K-stimulated Cl absorption and K transport are not mediated by the same co-transport mechanism. Potassium is the counter-ion for electrogenic Cl transport because JnetK was less than 10% of the JnetK during cAMP exposure under Isc conditions, but JnetK equalled JnetCl at open-circuit.

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