Voltammetry measurements, room-temperature

Jan. 20, 1927, Cleveland, Ohio, USA - Aug. 10, 2004, Raleigh, NC, USA) Osteryoung received his bachelor s education at Ohio University and his Ph.D. at the University of Illinois. He was professor and Chairman of the Chemistry Department at Colorado State University, a professor at the State University of New York at Buffalo and research professor and Chair of the Department of Chemistry of North Carolina State University. He published about 225 original scientific papers, and was especially known for his papers on double potential step -> chronocoulometry, -> square-wave voltammetry, and room-temperature molten salt electrochemistry. He also initiated computer-controlled electrochemical measurements, which helped in developing and optimizing - pulse voltammetry. He served as an Associate Editor for the journal Analytical Chemistry. 

Since the electron donating feature of an oxygen atom in a methoxyethyl group weakens the cation s positive charge, the electrostatic binding between the ammonium cation and anion weakens, and an ionic liquid forms. The limiting reduction and oxidation potentials (Ered and Eoxd) on platinum of the ionic liquids were measured by cyclic voltammetry at room temperature as shown in Fig. 3. 

Electrolytes for electrochemical devices should resist reduction and oxidation and exhibit a larger electrochemical window. The electrochemical stability of RTMS is generally measured by cyclic voltammetry at room temperature recorded in a three-electrode cell configuration using a platinum, gold, or vitreous carbon electrode as the working electrode, and Ag/AgCl (saturated in solvent) for triethylanunonium formate PILs (Fig. 7.16a) or Li for DESs based on lithium salt (Fig. 7.16b) as the reference electrode. 

Figure 15.7 Logarithm of the kinetic current for the ORR in oxygen-saturated liquid electrolytes versus inverse diameter for Pt particles supported on Vulcan XC-72 (1) 0.9 V vs. RHE at 60 °C [Gasteiger et al., 2005] (2) 0.85 V vs. RHE at room temperature [MaiUard et al., 2002] (3)0.85 V vs. SHE at room temperature [Guerin etal., 2004]. For curves 1 and 2, measurements were performed with the thin-layer RDE in 0.1 M HCIO4 for curve 3, they were performed with stationary voltammetry in 0.5 M H2SO4. (Curves have been replotted from MaiUard et al. [2002] Gasteiger et al. [2005], Copyright 2002 and 2005, with permission from Elsevier and from Guerin et al. [2004], Copyright 2004 American Chemical Society.)...

Oliveri et al. (2009) presented the development of an artificial tongue based on cyclic voltammetry at Pt microdisk electrodes for the classification of olive oils according to their geographical origin the measurements are made directly in the oil samples, previously mixed with a proper quantity of a RTIL (room temperature ionic liquid). The pattern recognition techniques applied were PCA for data exploration and fc-NN for classification, validating the results by means of a cross-validation procedure with five cancellation groups. 

Linear sweep voltammetry, capacitance-voltage and automated admittance measurements have been applied to characterize the n-GaAs/room temperature molten salt interphase. Semiconductor crystal orientation is shown to be an important factor in the manner in which chemical interactions with the electrolyte can influence the surface potentials. For example, the flat-band shift for (100) orientation was (2.3RT/F)V per pCl" unit compared to 2(2.3RT/F)V per pCl" for (111) orientation. The manner in which these interactions may be used to optimize cell performance is discussed. The equivalent parallel conductance method has been used to identify the circuit elements for the non-illum-inated semi conductor/electrolyte interphase. The utility of this... 

Measurements of the open circuit potential (OCP) were performed by linear sweep voltammetry with the anode of the electrolyser set as the working electrode, and the cathode set as both counter and reference electrodes. The hydrogen reference electrode condition was created by saturating the catholyte with H2 gas at the room temperature. The measured OCP values were refered to the standard hydrogen electrode (SHE). Since the potential of the hydrogen reference electrode varied from SHE depending on the HC1 concentration used in the experiement, this correction was taken into account for all measured OCP. 

Apparatus Cyclic voltammetry and amperometric current-time curves were obtained with a Pine Instrument Inc., Model RDE4 bipotentiostat and Kipp Zonen BD 91 XYY recorder equipped with a time base module. All measurements were performed in a conventional single-compartment cell with a saturated calomel electrode as the reference electrode and a Pt mesh as the auxiliary electrode at room temperature. Chronoamperometry was made with EG G Princeton Applied Research potentiostat/galvanostat Model 273 equipped with Model 270 Electrochemical Analysis Software. 

Methods of Characterization The polymers were characterized by four-probe electrical conductivity measurements between room temperature and liquid nitrogen, electron spin resonance (Varlan E-line series), scanning electron microscopy (Hitachi 520), cyclic voltammetry (Princeton Applied Research Instruments), and uv-vlsl-ble spectroscopy (Perkin Elmer 330). 

Redox potential (V) measured in CH3CN versus the saturated calomel electrode (SCE), determined by cyclic voltammetry at the platinum electrode, 0.1 M (nC4H9)4N. BF4 room temperature under argon scan rate, 100 mV s" the systems are reversible except in a few cases indicated by qrev (quasi reversible) and irr (irreversible). 

Mix fsDNA solution and H33258 at a final concentration of 1 pM in 50mM PBS and pipet an aliquot (20 pL) of this mixture on the gold or carbon SPE surface. Measure immediately using linear sweep voltammetry (LSV) after an equilibration time of 10s, with a sample interval of lmV, and a scan rate of 0.1 V/s from 0 to IV (Fig. 5). Alternatively, cyclic voltammetry (CV) can be applied with a scan range between 0 and 1V at a sweep rate of 0.1 V/s. For differential pulse voltammetry (DPV) measurements, the potential is scanned from 0 to 0.90V with a step potential of 4mV, pulse amplitude of 50mV, and a pulse period of 0.20s at a scan rate of lOmV/s. The current height is recorded at the peak potential (-0.6V) for analytical evaluation of the measurements. All measurements should be carried out at room temperature. 

For the electrochemical measurements, the copper-2% zinc alloy was mounted into epoxy (Buehler epoxide resin) by curing at room temperature for about 10 h. The finished metal surface had 1 cm2 exposed. The reference electrode probe and both high-density graphite counter electrodes were also positioned into the beaker. The working electrodes were immersed in the solutions for up to 0.5 h prior to the cyclic voltammetry for monitoring the open circuit potential. 

Physical Measurements. For the electrolyses, a Wenking potentiostat model 70TS1 and a Koslow Scientific coulometer model 541 were used. Voltammetry with wax-impregnated graphite and rotating platinum electrodes was performed as described elsewhere (7, 8). IR and electronic spectra were measured on Perkin-Elmer 225 and Cary 14 instruments. X-band ESR spectra were recorded at room temperature on a JEOL MES-3X spectrometer. Phosphorus-31 NMR spectra were recorded in the pulse mode on a Varian XL-100 instrument at 40.5 MHz using a deuterium lock, or on a Bruker HFX-90 instrument at 36.43 MHz using a fluorine lock. 

Cyclic voltammetry studies reveal striking differences between complex 13 and the analogous complex [HFe(depp)(dmpm)(CH3CN)f (17) in which the NMe group of 13 has been replaced by a methylene group. At normal scan rates the Fe " couple is reversible for complex 17, but irreversible for 13. Scan rate dependence measurements and potential step experiments indicated that this difference in behavior arises from a rapid transfer of the proton of the Fe hydride to the N atom of the pendant base with a rate constant of 1.1 x 10 s at room temperature. This proton transfer results in an irreversible Fe " " couple at low scan rates. A similar process cannot occur for 17, and the Fe " " couple remains reversible, even at slow scan rates in the presence of an external base. These results indicate that pendant bases in the second coordination sphere can facilitate the coupling of electron and proton transfer reactions. 

The partial support of this study by the University of Missouri through the Missouri Research Assistance Act and of Toshio Maruo through a Mallinckrodt Research Fellowship is gratefully acknowledged. Also acknowledged is the help of Dr. David Pipes of the Mallinckrodt Co. who kindly made the cyclic voltammetry measurements. Also gratefully acknowledged is the help of Professor Bernard Feldman of the Department of Physics at the University of Missouri-St. Louis who made the room-temperature electrical conductivity measurements. 

A PAR Model 173 Potentiostat and a PAR Model 179 Digital Coulometer were used for controlled- potential electrolysis experiments. The potentiostat was connected to a PAR Model 175 Universal Programmer and a Houston Instruments Model 2000 X-Y Recorder for cyclic voltammetry experiments. A Perkin-Elmer Model 1710 FTIR Spectrophotometer and Varian Model E-9 ESR Spectrometer were used in spectroscopic measurements. For the ESR spectra taken in vacuum, the samples were filled in ESR tubes, pumped down to 10 torr for one hour, and sealed on a vacuum line. The ESR spectra were t en at room temperature. A Gammacell Model 220 Co gamma ray source was used for irradiation. 

The cyclic voltammetry of poly(3 (2-methyl>I>buto >4>metylthiophene)[2P] (PMBMT), a polymer that can be obtained either in a pkmar or non-planar form at room temperature, is drown in Figure 11. The planar (violet) form has an oxidation potential of +0.70 V vs SCE while the non-planar (yellow) form has an oxidation potential of +0.88 V vs SCE. At a potential of +0.65 V, there is almost a 200-fold increase in the measured current giving rise to a very simple way of quantifying electrochemically the different field-induced chromic transitions of regioregular polythiophene derivatives[45]. 

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