Applied Electrochemistry

The oxidation of 4-t-butyltoluene in glacial acetic acid by hydrogen peroxide in a process catalysed by cobalt(II) acetate tetrahydrate and sodium bromide has been studied with the aim of increasing the selectivity towards 4-t-butylbenzaldehyde. The reaction mixtures were analysed by HPLC. Product identification was via the use of authentic compounds and retention times. The oxidation of 4-t-butyltoluene using hydrogen peroxide yielded five measurable products, 4-t-butylbenzaldehyde, 4-t-butylbenzoic acid, 4-t-butylphenol, 4-t-butylbenzyl bromide, and 4-t-butylbenzyl alcohol. The major product was 4-t-butylbenzaldehyde. The selectivity with respect to 4-t-butylbenzaldehyde depended upon the temperature, addition time of oxidant, oxidant type and concentration, and the cobalt(II) acetate tetrahydrate and sodium bromide concentrations. The effect of the temperature at which the reaction was operated was studied. It was found that the oxidation of 4-t-butyltoluene should be carried out at lower temperatures due to the instability of the hydrogen peroxide at the higher temperatures. The temperature 45 °C was chosen as an optimum temperature for a good yield of 4-tbutylbenzaldehyde. Hydrogen peroxide, cobalt(II) acetate tetrahydrate, sodium bromide concentrations were examined for yields and selectivity towards 4-t-butylbenzaldehyde. Finally, I dedicate this Thesis to my wife Nadifa, my family, and all friends in Australia and overseas, for their continued support and extraordinary patience throughout my Ph.D. pursuit.

The persistent contamination of aquatic environments by toxic heavy metals such as Pb²⁺, Cd²⁺, Hg²⁺, and As³⁺ has necessitated the development of rapid, sensitive, and field-deployable analytical techniques. Graphene-based electrochemical sensors have emerged as highly promising platforms due to their exceptional physicochemical properties, including a theoretical specific surface area of approximately 2630 m² g⁻¹, intrinsic carrier mobility exceeding 1.5 × 10⁵ cm² V⁻¹ s⁻¹, and excellent electrochemical stability. This review provides a comprehensive and detailed account of the development of graphene-based electrochemical sensors for heavy metal detection, emphasizing synthesis protocols, functionalization strategies, sensing mechanisms, and analytical performance metrics under realistic conditions. Detection limits as low as 0.008 µg L⁻¹ for Pb²⁺ and 0.015 µg L⁻¹ for Cd²⁺ are critically discussed alongside linear dynamic ranges extending from 0.02 to 500 µg L⁻¹. The role of deposition potential of −1.2 to −0.8 V vs. Ag/AgCl, accumulation time (120–300 s), and electrode surface modification in enhancing sensitivity is analyzed in depth. The review concludes with a critical evaluation of current limitations and future research directions toward scalable, real-time monitoring systems.

Flexible and optically active polymer nanocomposites have attracted significant attention for next-generation optoelectronic and photonic applications. In this study, PVA/Na-Alg/ITO nanocomposite films were successfully fabricated via a solution casting method, and the effect of indium tin oxide (ITO) nanoparticle incorporation (2–5 wt%) on their structural, optical, dielectric, and nonlinear optical properties was systematically investigated. X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and Raman analyses confirmed good miscibility between polyvinyl alcohol (PVA) and sodium alginate (Na-Alg), along with uniform dispersion of ITO nanoparticles with an average crystallite size of 21.7 nm. Morphological analysis revealed homogeneous films with minimal agglomeration. UV–visible spectroscopy showed a red shift in the absorption edge accompanied by a systematic reduction in optical band gap from 3.59 eV (pristine PVA) to 3.18 eV (5 wt% ITO), indicating enhanced electronic interactions and charge delocalization. The refractive index increased from 1.47 to 1.78, while the dispersion energy (Ed) improved from 8.28 eV to 12.17 eV with increasing ITO content, reflecting enhanced electronic polarizability. The dielectric constant (ε∞) also increased from 2.37 to 3.46, confirming strengthened interfacial polarization effects. Photoluminescence (PL) analysis revealed significant quenching of emission intensity with increasing ITO concentration, indicating efficient charge transfer and suppression of radiative recombination. Furthermore, the nonlinear refractive index (n₂) increased from 0.675 × 10⁻¹² to 4.83 × 10⁻¹², while the third-order nonlinear susceptibility (χ⁽³⁾) increased from 0.314 × 10⁻¹³ to 2.84 × 10⁻¹³ (esu) as ITO content increased from 0 to 5 wt%. These results demonstrate that controlled incorporation of ITO nanoparticles significantly enhances the structural disorder, optical tunability, dielectric response, and nonlinear optical performance of PVA/Na-Alg films. The developed nanocomposites show strong potential as environmentally friendly, flexible materials for advanced optoelectronic, photonic, and nonlinear optical device applications.

Experimental work carried out in this work has investigated the scale-up of microbial fuel cell (MFC) technology by studying the stacking of single microbial fuel cells, paying attention to the electric and hydraulic connections between each unit. To do this, the performance of three stacks (which were set up with different configurations) was studied for more than three months. The first stack (two hydraulically non-connected cells) was operated for 80 days without any electric connection between them, in order to determine the reproducibility of the performance of a single MFC, and then it was electrically connected in parallel for 20 days to determine if the electricity produced by each single cell was added when they were joined in the stack. The other two stacks (with five and ten cells, hydraulically connected) were connected electrically in series during the first 80 days and in parallel during the last 20 days. The results confirmed that connection in parallel allows higher current intensities and power to be obtained, and that the total electrode surface area attained with the stack is directly related to the production of electricity and to the removal of COD, although not in a linear way.

Silicon (Si) anodes offer a high specific capacity (> 3,500 mA h g-1), but severe volume changes during cycling and poor intrinsic conductivity hinder commercialization. Carbon nanotubes (CNTs) are commonly incorporated to improve the electronic conductivity of Si electrodes, but their tendency to aggregate in polar solvent-based slurries leads to non-uniform electrodes. To address this, we synthesize polyacrylamide-grafted CNTs (PAM-g-CNTs) by covalently attaching hydrophilic acrylamide monomers to CNT surfaces. The PAM chains provide steric hindrance that minimizes van der Waals interactions between PAM-g-CNTs and interacts effectively with polar solvents, thus promoting uniform dispersion and forming a stable electron-conductive network within the electrode. Furthermore, PAM-g-CNTs establish hydrogen bonds with Si particles and binder matrices, enhancing the structural integrity of the electrode. The cycling performance of Si half cells incorporating PAM-g-CNTs shows substantial durability after 200 cycles. Moreover, in high-energy-density Si electrode configurations with reduced binder and conductive agent ratios (active material > 70%), PAM-g-CNT-based cells preserved 70% of their initial capacity after 100 cycles, compared to only 20% retention in Super P-based cells. The functionalization of CNTs with hydrophilic PAM thus proves effective in improving dispersion stability and conductivity while reinforcing electrode cohesion. This strategy presents a promising path for developing durable Si anodes for high-energy-density lithium-ion batteries.

Electro-catalytic reduction of carbon dioxide has been studied with cobalt 5,10,15,20 tetrakis(4-aminophenyl)porphyrin forming a conducting polymer on an indium tin oxide electrode, using an ionic liquid as a novel reaction media. Electrocatalytic reduction of CO2 has been carried out, the potential at which this occurs has been reduced from −2.4 V vs. Ag/AgCl reported before, to −0.8 V vs. Ag/AgCl which means a significant energy gain regarding the electrochemical fixation of CO2. Electrochemical impedance spectroscopy (EIS) experiments have been carried out in order to understand the electrical behavior of the modified electrode in ionic liquid medium. Spectroelectrochemical evidence suggests that the reactive species which promotes the reaction is an electrochemically generated Co(I) porphyrin species which can be detected in an inert atmosphere but not in the carbon dioxide saturated medium.

Background: Extracellular polymeric substances (EPS) extracted from waste activated sludge (WAS) have previously shown its potential in corrosion inhibition. The aim of this study is to design a synthetic EPS formulation as a surrogate of natural WAS EPS to overcome the corrosion inhibition inconsistency in WAS EPS. The adsorption behavior of the designed inhibitor was studied by kinetic and thermodynamic analyses. Methods: Synthetic EPS is a bio-inspired material that was formulated based on the most typical chemical compositions of natural WAS EPS, that is, proteins, carbohydrates, humic substances, nucleic acids, and uronic acids, which was not optimized for corrosion inhibition performance. It is a mixture of glutamic acid, carboxymethylcellulose, humic acid, thymine, and alginic acid. Its corrosion inhibition performance was tested with carbon steel in 3.64% NaCl saturated with CO2, using the potentiodynamic polarization scanning technique. The resulted electrochemical paramete...

The electrodeposition of copper onto AISI 1010 steel using an alkaline electrolyte based on glycerol has been studied. The influence of NaOH concentration and the addition of sulfate as supporting electrolyte were investigated by voltammetric techniques. For a NaOH concentration ≥ 0.6 M the plating bath was stable and immersion deposition onto steel was avoided. Voltammetric studies and SEM analysis indicated that the reduction process occurs through two different copper(II) species. The copper films were golden in colour, even in the high hydrogen evolution region, indicating that glycerinate anions prevent the copper deposits becoming darker. The presence of the sulfate anions affected the morphology of the copper films, acting as brighteners.

The focus of this project was to design and construct a model controlled-flow apparatus to study electropolishing of one cm 2 niobium coupons at surface flow rates typical of cavity processing. A simulation of the apparatus was constructed using CFDesign, a flow and thermal simulation software, to ensure that the selected dimensions may be expected to provide steady-state, laminar flow across the surface of the niobium coupon. Based on these dimensions, a sample system and apparatus was produced to determine the correct reservoir elevation heights for the desired flow rates for fluid viscosities represented in the mixed acid electrolyte. From the CFDesign simulations, it was found that the flow channel supplied laminar flow rates when the center of the niobium coupon was located 40 mm downstream from the inlet stream. The corresponding system, based on the CFDesign simulations, showed that the reservoir elevation heights for flow rates of 0 cm/s to 5 cm/s ranged from 0 to 1.27 cm. T...

The influence of CsHSO 4 inorganic solid acid was evaluated as a possible proton conductor in the catalyst layer of ABPBI (poly(2,5-benzimidazole))-based hightemperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Gas diffusion electrodes (GDEs) were prepared with fixed polytetrafluoroethylene (PTFE) and polyvinylidene diflouride (PVDF) binder content, while the CsHSO 4 loading was varied. Porosimetry data showed that the addition of 10 % CsHSO 4 to the PVDF GDE increased the porosity across all the pore regions, whereas the addition of 10 % CsHSO 4 to the PTFE GDE decreased the GDEs porosity. The CsHSO 4 MEAs showed good proton transfer dynamics and low resistance for fuel cell operation. An optimum loading of 10 % CsHSO 4 in conjunction with either of the binders was observed, with CsHSO 4 -PVDF GDE achieving peak power of 498.2 mW cm -2 at a cell voltage of ?352 mV. Higher CsHSO 4 loadings increased the charge transfer resistance and lowered the cell performance of these GDEs.

One of the ways to protect aluminum metal from corrosion in polymer electrolyte membrane (PEM) hydrogen fuel cells is through the use of the chemical inhibition method. In this work, we present unsubstituted (NiPc) and tetrasubstituted nickel phthalocyanines (TNNiPc) as corrosion inhibitors for aluminum (Al) metal in 1 mol•L -1 hydrochloric acid (HCl) solution. The synthesized inhibitors were characterized using several techniques. The XRD patterns demonstrated that NiPc was more crystalline than TNNiPc (a nitro group at a peripheral position). The FTIR spectra for all the inhibitors showed a similar vibration band at around 730 cm -1 , which was due to C-H deformations. The TNNiPc inhibitor showed additional asymmetric and symmetric NO2 vibrations around 1336 and 1525 cm -1 , respectively. The UVvis spectrum of NiPc showed an intense Q-band at around 774 nm in 1 mol•L -1 H2SO4, whereas TNNiPc resulted in a blue shift of the Q-band due to the electron-withdrawing properties of the NO2 group. The TGA supported the presence of NO2 by the degradation step as indicative of decomposition of NO2 group in the TNNiPc inhibitor. Electrochemical studies showed that the inhibitors prevent Al metal sheet corrosion by adsorbing on Al surface to form a pseudocapacitive interface. The inhibitive effect of NiPc and TNNiPc inhibitors increased with increasing concentration. Furthermore, potentiodynamic polarization measurements revealed that the dyes are mixed-type corrosion inhibitors.

This work describes a method for synthesizing sodium peroxocarbonate by electoxidation of carbonate on conductive-diamond thin film electrodes in a sodium carbonate solution at room temperature. The effect of several parameters including: electrolyte concentration, current intensity, addition of Na 2 SiO 3 as a stabilizing agent, and increments in temperature for sodium peroxocarbonate formation has been studied in an electrochemical H cell of two compartments separated by a cationexchange membrane. The oxidant formation has been confirmed by cyclic voltammetry and in situ reduction during water electrolysis. The optimal experimental conditions are: the current density of 34.3 mAcm -2 , an electrolyte concentration of 1M, and the addition of 4 g/L of sodium metasilicate in the two compartments of the electrochemical cell.

In this research work, a preliminary potentiodynamic polarization performance testing was carried out on a new environmentally friendly proposed composite coating. The proposed composite coating was developed by: (a) hot sulfuric anodizing to produce an Al 2 O 3 conversion film followed by an (b) organic electrodeposited chitosan-sodium alginate blended film. Posteriorly, the conversion and organic films were microstructurally characterized by scanning electron microscopy. Finally, the polarization resistance technique was used to measure the corrosion resistance of the uncoated and coated AA6063 alloy in a simulated marine environment and the polarization tests were compared to samples immersed during 30 days in same electrolyte solution. The obtained inhibition corrosion efficiency of the proposed coating system was measured comparing the Rp of the uncoated alloy to the coated samples, showing an efficiency about 99% for a 3% NaCl electrolyte for some of the samples. Therefore, the experimental results obtained during this research demonstrates the feasibility of using the developed anticorrosive composite coating to protect aluminum alloys against chloride corrosive ions species and to further continue with the corresponding research.

The consumption of critical raw materials, especially those in permanent magnets of Nd–Fe–B and Sm–Co-type, has significantly grown in the past decade. With predictions on further electrification growing exponentially the demand for these materials will even increase. This implies that efforts in assuring sustainability must involve recycling from secondary resources. In recent years the electrochemical approaches in recycling have been extensively investigated and applied owing to their advantages of high efficiency and selectivity, easy operation, low energy consumption, and environmental friendliness. In this paper, we investigate the Sm 2 (Co,Fe,Cu,Zr) 17 permanent magnet leaching process using the anodic oxidation to be paired with the metal deposition on the cathode. Linear sweep voltammetry was performed from − 0.15 to 1 V versus Pt quasi reference electrode that indicated current peaks that would correspond to some preferential leaching of the crystal phases contained in the...

An epoxy-functionalized beta type nanozeolite (BEA)/graphene oxide nanocomposite modified glassy carbon electrode (GCE/BEA/APTMS/GA/GO/NF) has been created for the differential pulse voltammetric determination of bisphenol E (BPE). The modified electrode presented an enhanced current response in comparison with bare GCE. A linear dependence of anodic peak current (Ip) and scan rate (ν) was observed, which showed that the electrochemical process was adsorption-controlled. Differential pulse voltammetry (DPV) was employed and optimized for the sensitive determination of BPE. Under the optimized conditions, the anodic peak current was linearly proportional to BPE concentration in the range between 0.07 and 4.81 µM, with a correlation coefficient of 0.995 and limit of detection 0.056 μM (S/N = 3). The electrode showed good repeatability and storage stability, and a low response to interfering compounds. Comparison was made to the determination of bisphenol A. To confirm the electrode an...

High energy consumptian in the production of magnesium by molten salt electrolysis is mainly due to the recombination of magnesium and chlorine. The large interelectrode distance used, in conventional techniques, to reduce the extent of 'back reaction', results in a significant potential drop. A laboratory cell that enables the operation with smaller interelectrode distance and easy separation of electrode products has been used to study electrolytic magnesium production. The cell features a top inserted grap hite anode and a Mg-Pb alloy cathode at the bottom. Current efficiency and power consumptian were determined at 690°C using a current density of 0.48 A cm-2. Experiments were performed to study the effects of MgCl2 concentration and anode-cathode distance (a.c.d.) on cell operation. Results indicated that an electrolyte containing 20% MgCl2 (equiweight NaCl: KCl and 1% NaF) with a 3 cm a.c.d. reduced the cell voltage to 3.72 V. This value corresponds to an energy consumptian of 11.3kWh kg-1 including the refining of Mg-Pb alloy produced at the cathode. This cell performance is more energy efficient compared to conventional magnesium cells.

We present a robust and facile method to produce metal nanoparticle (NP) alloys in a one-step synthesis using direct electrodeposition onto highly oriented pyrolytic graphite (HOPG). Precursor salts, H 2 PtCl 6 and Pd(NO 3 ) 2 , were dissolved in a 1 mM sodium dodecylsulfate (SDS) water droplet with 1× phosphate buffered saline solution and suspended in a dichloroethane (DCE) continuous phase. Tetrabutylammonium perchlorate was added to the DCE continuous phase to maintain charge balance during electrodeposition. NP fabrication via electrodeposition was driven by droplet collisions onto HOPG, which was biased at a potential where the metal precursor salts would reduce to their respective zero-valent atoms. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were used to study the size, coverage, and morphology of the NPs as well as the atomic stoichiometry. EDX mapping indicated homogeneous distribution of Pd and Pt at the single NP level. Homogeneously alloyed PdPt NPs were realized from this study with demonstrated control over metal composition, surface coverage, and NP size.

This paper reports a study of the neutralization of Li-SOCl 2 batteries. Immersion of these batteries in acidic seawater solutions leads to their complete discharge by short circuit, followed by corrosion of the positive pin (made of an Fe/Ni alloy). This corrosion process is desirable because it allows penetration of water into the battery, and hence, neutralization of the active mass of the batteries through their reaction with water. The most efficient corrosion of Fe/Ni electrodes is obtained in seawater containing both HCl and H 2 SO 4 in a situation of no separation between the electrode compartments, due to the reaction of the H 2 liberated at the cathode with the surface films on the anode (Fe/Ni pin electrodes). This reaction prevents passivation of the positive pin. Indeed, used Li-SOCl 2 batteries whose insulating covers were removed, corroded much quicker than regular batteries because of the impact of H 2 evolved at the case (the negative pole of the battery) on the dissolution of the positive pin.

The Schiff base N ′-[(E)-phenylmethylidene]pyridine-3-carbohydrazide (PPC) was investigated as a corrosion inhibitor for IS 2062 E250 mild steel in 0.5-M trichloroacetic acid. The inhibition performance was evaluated using weight-loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy at different inhibitor concentrations and temperatures, supported by quantum chemical calculations. The study provides a systematic evaluation of PPC as a corrosion inhibitor in an aggressive organic acid medium and establishes an experimental-theoretical correlation to elucidate its inhibition mechanism. Thermodynamic parameters such as activation energy, enthalpy, entropy, and Gibbs free energy of corrosion indicate that the adsorption of PPC on the steel surface involves both physical and chemical interactions. The inhibition efficiency reached up to 97% in 0.5-M trichloroacetic acid. Polarization studies show that PPC modifies both anodic and cathodic Tafel slopes, confirming mixed-type inhibition behavior. Electrochemical impedance results demonstrate strong adsorption through the formation of a protective surface film following the Temkin adsorption isotherm. Density functional theory calculations support the experimental observations by identifying key electrophilic (C20, C18, N15, and O28) and nucleophilic (C18, C20, and C2) active sites responsible for strong metal-inhibitor interactions. The combined results confirm PPC as an efficient corrosion inhibitor for acidic environments.

Voltamperometric studies on the indirect electrochemical a-methoxylation of Boc-Pro-Gly-OMe and Boc-Val-Gly-OMe in MeOH in the presence of NaCl or NaBr as the mediator suggested that the first reaction step was a direct N-halogenation of the dipeptide by active chlorine or bromine adsorbed on the electrode surface. The kind of mediator (NaCl or NaBr), its concentration, the current density, and the applied electric charge had a significant influence on the reaction course. In the case of Boc-Pro-Gly-OMe, the use of sodium bromide was necessary to obtain a relatively high ratio of a-monomethoxylation to a,a-dimethoxylation. For Boc-Val-Gly-OMe, the selectivity for a-monomethoxylation was close to 100%, independently of the mediator. Optimisation of the selected electrolysis parameters allowed us to significantly improve the yield and selectivity of the a-methoxylation of Boc-Pro-Gly-OMe (Kardassis et al. Tetrahedron 54:3471, 1998) and to obtain good results in the a-methoxylation of Boc-Val-Gly-OMe.

This work has been devoted to investigate the effects of using available and inexpensive cathodic materials, such as steel, Al, and Zn, beside the change of spacing between electrodes on the efficiency of the on-site electrochemical production of sodium hypochlorite using a single batch electrolysis cell. The rate of NaOCl production generally increases in the order : Zn > Al > steel at all separations except at 14 cm, where the production rate with steel cathode is found remarkably higher than that with Al cathode. While at ambient electrode separation, it is clearly evident that the electrochemical activation increases in the order: Zn > Al > steel. This may be attributed to the lowering in the electronic resistivity in the order: Zn < Al < steel. Generally, the best on-site generation of sodium hypochlorite was observed for Zn electrode having the surface area of 66.3 cm 2 , and separated from the graphite anode by 8 cm within the electrolysis time of 120 min, by applying DC voltage 9.5 V with measured current density of 176.5 mA.cm 2-at 25 o C as an ambient temperature. The best effective concentration value of sodium hypochlorite at the previous conditions was 0.054%.