Supporting electrolyte

About: Supporting electrolyte is a research topic. Over the lifetime, 5011 publications have been published within this topic receiving 104172 citations.

Electrochemical oxidation of CoCp(CO)2: radical-substrate reaction of a 17 e-/18 e- pair and production of a unique dimer radical.

Abstract: Anodic oxidation of the important half-sandwich compound CoCp(CO)2, 1, has been studied under gentle electrolyte conditions, e.g., chlorinated hydrocarbons with weakly coordinating anion (WCA) supporting electrolyte anions. The 17-electron cation 1+ produced at E(1/2)(1) = 0.37 V vs FeCp2(0/+) undergoes a surprising reaction with neutral 1 to form the dimer radical cation [Co2Cp2(CO)4] +, 2+, which has a metal-metal bond unsupported by bridging ligands. The dimer radical is oxidized at a slightly more positive potential (E(1/2) = 0.47 V) to the corresponding dication 2(2+). Observation of the oxidation of 2+ is without precedent in confirming a radical-substrate (R-S) dimerization process by direct voltammetric detection of the R-S intermediate, K(eq) = 3 x 10(4) M(-1) for [2+]/[1][1+]. The R-S mechanism and the reaction products have been characterized by voltammetry, electrolysis, fiber-optic IR spectroscopy, and ESR measurements. DFT calculations indicate that removal of an electron from 1 results in rehybridization in 1+, thereby opening the metal center for interaction with the neutral compound 1, which has a relatively basic metal center. The LUMO of the dimer dication 2(2+) is metal-metal antibonding, and its half-occupancy in 2+ results in lengthening of the Co-Co bond from 2.64 A to 3.14 A. Inclusion of solvent in the (COSMO) calculations shows that solvation effects are necessary to account for the fact that E(1/2)(2) > E(1/2)(1). These results show the importance of medium effects in probing the fundamental redox chemistry of half-sandwich metal complexes.

Sensitive voltammetric determination of bromate by using ion-exchange property of a Sn(II)-clinoptilolite-modified carbon paste electrode

Abstract: A modified carbon paste electrode with Sn(II)-exchanged clinoptilolite nanoparticles (CNP-Sn(II)-CPE) showed voltammetric current (in cyclic voltammetry (CV)) for Sn(II)/Sn(IV) in sulfuric acid electrolyte (pH 2). The peak current was decreased when bromate was added to the solution. Hence, this decrease was used for indirect voltammetric determination of bromate. In designed experiments using response surface methodology (RSM) approach in square-wave voltammetry (SqW), strong acidic pH values (pH 1.8–2.5) caused an increased SqW voltammetric response, because such pH values bring sufficient Sn(II) as the electroactive species at the electrode surface via ion-exchange process. The optimal variables obtained are sulfuric acid as supporting electrolyte at pH 1.80, modifier% at 25, amplitude at 498.4 mV, step potential at 5.4 mV, and frequency at 25 Hz. The peak current of Sn(II)/Sn(IV) redox pair was inversely proportionate to the concentration of bromate. Hence, ΔI (difference in peak current in the absence and presence of bromate) was proportionally increased with increasing the concentration of bromate in the range of 5.00 to 100.00 μmol L−1 with a detection limit of 0.06 μmol L−1 bromate. The effect of some strong oxidizing agents was studied, and the results showed that when such agents are present at levels of 2.5 to 5 times greater than the bromate in the solution, they can cause a maximum error of 3% in the determination of bromate in sulfuric acid electrolyte at pH 2.5.

Electrochemical detection of Cr(VI) with carbon nanotubes decorated with gold nanoparticles

Abstract: A nanocomposite consisting of gold nanoparticles deposited on the side walls of functionalised multi-walled carbon nanotubes, Ox-MWCNT-Aunano, was prepared using a simple chemical reduction. The nanoparticles were well dispersed with a mean diameter of 7.5 nm and had a face-centred cubic structure and a gold loading between 2.0% and 2.6% by weight. These gold decorated nanotubes were cast onto a gold electrode to form a uniform and homogeneous sensor. Using cyclic voltammetry, the reduction of Cr(VI) was observed at a peak potential of 0.52 V versus SCE in an acidified H2SO4 solution, pH 2.0. A linear calibration curve with a sensitivity of 0.28 mA mM− 1 and a LOD of 7.2 × 10− 7 M was obtained using constant potential amperometry coupled with rotating disc voltammetry. The electrochemical detection of Cr(VI) was also observed at a MWCNT-modified gold substrate but with a higher LOD, illustrating the advantage of combining the gold nanoparticles with MWCNTs. The sensor showed good selectivity for the detection of Cr(VI) in the presence of Cu(II), chloride and nitrates and in a real water sample. This was attributed to the electropositive reduction potentials of Cr(VI), the acidic H2SO4 supporting electrolyte that provides a well-known cleaning effect at gold, and the size and good dispersion of the gold nanoparticles that minimise particle agglomeration.