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Richard G Compton - One of the best experts on this subject based on the ideXlab platform.
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comparative Chronoamperometry spheres discs cylinders and bands
Journal of Electroanalytical Chemistry, 2020Co-Authors: Haonan Le, Richard G ComptonAbstract:Abstract A parameter, the diffusion indicator α, introduced in this work, is derived from chronoamperometric current responses to obtain comparative information about the diffusion of an electrochemically active species from/to an electrode. The α values are used to investigate the diffusion to four electrodes with different geometries: microsphere, microdisc, microcylinder, and microband electrodes based on literature analytical and empirical equations for their chronoamperometric currents and the associated concentration profiles extracted from new simulations. The values of α and their time evolution show the contrasting contribution of planar and convergent/divergent diffusion in the different geometries.
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influence of reaction induced thermal convection on the electrical currents measured in Chronoamperometry and cyclic voltammetry
Journal of Physical Chemistry C, 2016Co-Authors: Javor K Novev, Shaltiel Eloul, Richard G ComptonAbstract:Electrochemical reactions invariably occur with a change in the molar volume between reactant and product, as well as a change in enthalpy. These factors give rise to convective flows driven respectively by concentration and temperature and affect the mass transport in the system, but the latter has received very little attention in the scientific literature. The present study attempts to fill this gap by quantifying the effect of thermal convection on the electrical currents in Chronoamperometry and cyclic voltammetry, using the electrochemical oxidation of hexacyanoferrate (II) to hexacyanoferrate (III) as a model reaction. To this end, finite element numerical simulations of both electroanalytical techniques have been performed over a broad range of electrode radii (0.25 to 25 mm). The results presented here indicate that for Chronoamperometry, convection has a substantial overall effect on the current, but thermal convection in particular is practically negligible for the studied systems. In contrast,...
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measurement of the diffusion coefficients of ru nh3 6 3 and ru nh3 6 2 in aqueous solution using microelectrode double potential step Chronoamperometry
Journal of Electroanalytical Chemistry, 2011Co-Authors: Yijun Wang, Juan G Limonpetersen, Richard G ComptonAbstract:Abstract Microelectrode double potential step Chronoamperometry is reported which allows the measurement of the diffusion coefficients of [Ru(NH3)6]3+ and [Ru(NH3)6]2+ in aqueous solutions containing various concentrations of the supporting electrolyte, KCl, KNO3 or K2SO4. In the case of K2SO4, ion-pairing of hexaammineruthenium cations is inferred where for KCl and KNO3 no such effects were noted. The triply charged ion was found to have a significantly lower diffusion coefficient than the doubly charged ion with a ratio of ∼0.71 in the KCl and KNO3 media.
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Chronoamperometry on ring ring recessed and disk electrodes and their arrays the sensitive measurement of diffusion coefficients independent of a knowledge of concentration or number of electrons transferred
Journal of Electroanalytical Chemistry, 2010Co-Authors: Denis Menshykau, Aoife M Omahony, Montserrat Cortinapuig, Javier F Del Campo, Francesc Xavier Munoz, Richard G ComptonAbstract:Theory of Chronoamperometry on ring-recessed microelectrodes and their arrays is presented. Analysis of the current transients measured at thin rings and their arrays shows that Chronoamperometry at such devices is an excellent method of simultaneous measurement of the diffusion coefficient D and the product n[A], where n is the number of electrons transferred and [A] is the concentration of electroactive analyte. A generic, accurate and easy to use method of experimental chronoamperometric data analysis is proposed. It is shown that the method can be applied to the simultaneous measurement of D and n[A] in solution. The method is shown to be applicable to an analysis of data recorded at single disk and ring electrodes as well as arrays of these electrodes even in the case of diffusional non-independence of electrodes in the array.
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theory for double potential step Chronoamperometry for any potential values at spherical electrodes simultaneous determination of the diffusion coefficients of the electroactive species
Electrochimica Acta, 2009Co-Authors: Angela Molina, Richard G Compton, Carmen Serna, Francisco Martinezortiz, Eduardo LabordaAbstract:Abstract We present a general and explicit analytical solution for double potential step Chronoamperometry with any applied potential values ( E 1 , E 2 ) corresponding to a reversible charge transfer process at spherical electrode. This solution is essential to analyze double pulse electrochemical techniques such as RPV and DPV. We consider unequal diffusion coefficients, initial presence of both electroactive species and that the reaction product can dissolve in the electrolytic solution or in the electrode. From the analytical equation obtained it is possible to deduce interesting simplified expressions for some particular cases: both species soluble in the electrolytic solution with equal diffusion coefficients, planar electrodes, ultramicroelectrodes when both species are soluble in the electrolytic solution, and double potential step Chronoamperometry with limit current potentials ( E 1 − E ° ′ → − ∞ , E 2 − E ° ′ → + ∞ ). In this last case, when reaction product is not initially present it is pointed that planar electrodes and ultramicroelectrodes cannot be used for determining both diffusion coefficients. This interesting practical consequence can be demonstrated by means of the analytical expression deduced here, which represents a notable advantage in front of numerical results.
Anil Kumar Sinha - One of the best experts on this subject based on the ideXlab platform.
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Photo-electrochemical hydrogen evolution over FTO/Ni0.98Si0.02O2-Ni electrode induced by visible and UV light irradiation
Journal of Applied Electrochemistry, 2019Co-Authors: Rajkumar Yadav, Sandhya Saini, Bijoy Biswas, Avnish Kumar, Hari Singh, Anil Kumar SinhaAbstract:Photo-electrochemical properties of fluorine-doped tin oxide (FTO)/nickel oxide-nickel (Ni0.98Si0.02O2-Ni) with isolated Si sites are discussed. The Ni0.98Si0.02O2-Ni photo-electrocatalyst without any noble metal was prepared using a one-step chemical reduction precipitation method. Photo-electrochemical properties were investigated by cyclic voltammetry and Chronoamperometry techniques in aqueous alkaline solution at pH 8.0. The photo-electrochemical response of the catalyst showed sensitivity to visible and UV light. The catalyst produced hydrogen from water at a rate of 0.5 mmol g−1 h−1 with the reduction of CO2 into CO under visible light in the absence of any light sensitizer or a noble metal. The metallic Ni amount in the catalyst system was optimized to obtain the best photo-electrocatalyst. The first principle DFT study showed that the incorporation of Si sites allowed absorbance of visible light. The catalyst was characterized by powder x-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Brunauer–Emmett–Teller (BET), cyclic voltammetry, and Chronoamperometry. The products were analyzed by gas chromatography- thermal conductivity detector (GC-TCD).Graphic Abstract
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Photo-electrochemical hydrogen evolution over FTO/Ni_0.98Si_0.02O_2-Ni electrode induced by visible and UV light irradiation
Journal of Applied Electrochemistry, 2019Co-Authors: Rajkumar Yadav, Sandhya Saini, Bijoy Biswas, Avnish Kumar, Hari Singh, Anil Kumar SinhaAbstract:Photo-electrochemical properties of fluorine-doped tin oxide (FTO)/nickel oxide-nickel (Ni_0.98Si_0.02O_2-Ni) with isolated Si sites are discussed. The Ni_0.98Si_0.02O_2-Ni photo-electrocatalyst without any noble metal was prepared using a one-step chemical reduction precipitation method. Photo-electrochemical properties were investigated by cyclic voltammetry and Chronoamperometry techniques in aqueous alkaline solution at pH 8.0. The photo-electrochemical response of the catalyst showed sensitivity to visible and UV light. The catalyst produced hydrogen from water at a rate of 0.5 mmol g^−1 h^−1 with the reduction of CO_2 into CO under visible light in the absence of any light sensitizer or a noble metal. The metallic Ni amount in the catalyst system was optimized to obtain the best photo-electrocatalyst. The first principle DFT study showed that the incorporation of Si sites allowed absorbance of visible light. The catalyst was characterized by powder x-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Brunauer–Emmett–Teller (BET), cyclic voltammetry, and Chronoamperometry. The products were analyzed by gas chromatography- thermal conductivity detector (GC-TCD). Graphic Abstract
Yongzhe Zhang - One of the best experts on this subject based on the ideXlab platform.
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understand the degradation mechanism of electrochromic wo3 films by double step Chronoamperometry and chronocoulometry techniques combined with in situ spectroelectrochemical study
Electroanalysis, 2017Co-Authors: Kailing Zhou, Hao Wang, Yongzhe ZhangAbstract:In this paper, we demonstrate that the double-step Chronoamperometry and chronocoulometry techniques are efficient tools for characterizing the basic electrochromic performance of WO3 films (i. e., coloration/bleaching conversion, charge capacity and coloration efficiency). In combination with in situ spectroelectrochemical study, the variations in the optical modulation and charge capacity of the WO3 film under different potential windows were attributed to different ion diffusion depths and the quantity of WO3 sites participating in the redox reaction. Moreover, the double-step techniques have distinctive advantages for analyzing the cyclic mechanism of the WO3 film. When the inserted Li+ ions in the coloration process cannot be completely extracted from the film in the next bleaching process, these ions accumulate in the film upon cycling, leading to the degradation of the electrochromic performance. Here the accumulated ions are referred to as “unrecoverable ions”. The abundant formation of unrecoverable ions may be due to incomplete reduction of a portion of LixWO3, which is caused by collapse of the Li+ ion diffusion channels in the deep of film after repeated cycles. All these results support that the double-step Chronoamperometry and chronocoulometry techniques have significant advantages to analyze the cyclic stability and explore the degradation mechanism of electrochromic WO3 films.
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Understand the Degradation Mechanism of Electrochromic WO3 Films by Double‐step Chronoamperometry and Chronocoulometry Techniques Combined with in situ Spectroelectrochemical Study
Electroanalysis, 2017Co-Authors: Kailing Zhou, Hao Wang, Yongzhe ZhangAbstract:In this paper, we demonstrate that the double-step Chronoamperometry and chronocoulometry techniques are efficient tools for characterizing the basic electrochromic performance of WO3 films (i. e., coloration/bleaching conversion, charge capacity and coloration efficiency). In combination with in situ spectroelectrochemical study, the variations in the optical modulation and charge capacity of the WO3 film under different potential windows were attributed to different ion diffusion depths and the quantity of WO3 sites participating in the redox reaction. Moreover, the double-step techniques have distinctive advantages for analyzing the cyclic mechanism of the WO3 film. When the inserted Li+ ions in the coloration process cannot be completely extracted from the film in the next bleaching process, these ions accumulate in the film upon cycling, leading to the degradation of the electrochromic performance. Here the accumulated ions are referred to as “unrecoverable ions”. The abundant formation of unrecoverable ions may be due to incomplete reduction of a portion of LixWO3, which is caused by collapse of the Li+ ion diffusion channels in the deep of film after repeated cycles. All these results support that the double-step Chronoamperometry and chronocoulometry techniques have significant advantages to analyze the cyclic stability and explore the degradation mechanism of electrochromic WO3 films.
Rajkumar Yadav - One of the best experts on this subject based on the ideXlab platform.
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Photo-electrochemical hydrogen evolution over FTO/Ni0.98Si0.02O2-Ni electrode induced by visible and UV light irradiation
Journal of Applied Electrochemistry, 2019Co-Authors: Rajkumar Yadav, Sandhya Saini, Bijoy Biswas, Avnish Kumar, Hari Singh, Anil Kumar SinhaAbstract:Photo-electrochemical properties of fluorine-doped tin oxide (FTO)/nickel oxide-nickel (Ni0.98Si0.02O2-Ni) with isolated Si sites are discussed. The Ni0.98Si0.02O2-Ni photo-electrocatalyst without any noble metal was prepared using a one-step chemical reduction precipitation method. Photo-electrochemical properties were investigated by cyclic voltammetry and Chronoamperometry techniques in aqueous alkaline solution at pH 8.0. The photo-electrochemical response of the catalyst showed sensitivity to visible and UV light. The catalyst produced hydrogen from water at a rate of 0.5 mmol g−1 h−1 with the reduction of CO2 into CO under visible light in the absence of any light sensitizer or a noble metal. The metallic Ni amount in the catalyst system was optimized to obtain the best photo-electrocatalyst. The first principle DFT study showed that the incorporation of Si sites allowed absorbance of visible light. The catalyst was characterized by powder x-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Brunauer–Emmett–Teller (BET), cyclic voltammetry, and Chronoamperometry. The products were analyzed by gas chromatography- thermal conductivity detector (GC-TCD).Graphic Abstract
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Photo-electrochemical hydrogen evolution over FTO/Ni_0.98Si_0.02O_2-Ni electrode induced by visible and UV light irradiation
Journal of Applied Electrochemistry, 2019Co-Authors: Rajkumar Yadav, Sandhya Saini, Bijoy Biswas, Avnish Kumar, Hari Singh, Anil Kumar SinhaAbstract:Photo-electrochemical properties of fluorine-doped tin oxide (FTO)/nickel oxide-nickel (Ni_0.98Si_0.02O_2-Ni) with isolated Si sites are discussed. The Ni_0.98Si_0.02O_2-Ni photo-electrocatalyst without any noble metal was prepared using a one-step chemical reduction precipitation method. Photo-electrochemical properties were investigated by cyclic voltammetry and Chronoamperometry techniques in aqueous alkaline solution at pH 8.0. The photo-electrochemical response of the catalyst showed sensitivity to visible and UV light. The catalyst produced hydrogen from water at a rate of 0.5 mmol g^−1 h^−1 with the reduction of CO_2 into CO under visible light in the absence of any light sensitizer or a noble metal. The metallic Ni amount in the catalyst system was optimized to obtain the best photo-electrocatalyst. The first principle DFT study showed that the incorporation of Si sites allowed absorbance of visible light. The catalyst was characterized by powder x-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Brunauer–Emmett–Teller (BET), cyclic voltammetry, and Chronoamperometry. The products were analyzed by gas chromatography- thermal conductivity detector (GC-TCD). Graphic Abstract
Zempachi Ogumi - One of the best experts on this subject based on the ideXlab platform.
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study of hydrogen nanobubbles in solution in the vicinity of a platinum wire electrode using double potential step Chronoamperometry
Electrochimica Acta, 2006Co-Authors: Kenji Kikuchi, Yoshinori Tanaka, Yasuhiro Saihara, Zempachi OgumiAbstract:Abstract A solution supersaturated with hydrogen around a platinum wire electrode was studied by double-potential step Chronoamperometry. The time–current curve at the hydrogen oxidation potential obtained with double-potential step increased with a shift of the hydrogen evolution potential to the cathodic potential. The initial slope of the chronoamperogram at the oxidation potential increased to zero with the shift from the hydrogen evolution potential to the cathodic potential. The increase was observed with increasing ionic strength and increasing cathodic current density. These phenomena were analyzed with numerical method using a number of assumptions.
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Influence of defects on the phase-boundary movement in a stage transformation of lithium-graphite intercalation compounds
Carbon, 1999Co-Authors: Atsushi Funabiki, Takeshi Abe, Minoru Inaba, Zempachi OgumiAbstract:The influence of defects on the phase-boundary movement in the stage transformation from random stage (dilute stage 1) to stage 4 of lithium-graphite intercalation compounds was investigated using highly oriented pyrolytic graphite (HOPG). Potential-step Chronoamperometry and in situ optical microscopy coupled with micro Raman spectroscopy were used to clarify macroscopic and microscopic influence of defects. Potential-step Chronoamperometry confirmed that the diffusion-limited rate of the phase-boundary movement in the bulk of HOPG was independent of the crystallinity of the samples. This result indicates that defects have macroscopically no appreciable influence on the phase-boundary movement. In situ optical microscopy on the basal plane of HOPG revealed that the nucleation and growth of the stage-4 phase took place quite inhomogeneously in the initial stage. The rate of the phase-boundary movement in the surface region of HOPG was roughly evaluated to be in the range of 5 to 10 μm min-1. The phase-boundary movement was seriously retarded by cracks formed on the basal plane during the stage transformation.