Influence Of Electrolyte pH Research Articles

Electrodeposition of Co-Mo Alloys and Its Applications in Electrochemical Sensing of Phosphate

Quantification of phosphate ions in water ecosystems is crucial for maintaining a healthy aquatic environment and optimizing aquaculture parameters. While cobalt (Co) thin film modified electrodes are widely used as phosphate sensors, their selectivity and stability often require improvements for on-site measurement. The present work addresses this challenge by introducing a novel phosphate sensing platform utilizing Cobalt-Molybdenum (Co-Mo) alloy film deposited on copper substrate. The developed Co-Mo thin film sensor exhibited a good thermal stability (up to 60 °C) and significantly improved the detection ranges (10−6 M to 10−2 M). The influence of electrolyte pH and temperature toward potentiometric sensing of phosphate were investigated and the conditions were optimized to improve the sensor sensitivity. The sensor showed a sensitivity of −56 mV.dec−1 with a good correlation coefficient (0.988). The detection limit was determined to be 0.987 μM and the relative standard deviation (RSD) was 1.3% (n = 3). The Co-Mo thin film sensor exhibited negligible interference even in the presence of 10-fold excess concentrations of common interfering analytes, demonstrating its robust performance in real-world environment. To validate the field practicality, the sensor’s performance was successfully tested in real shrimp culture water samples, demonstrating its compatibility with complex environmental matrices.

Recent Advances with Biomass‐Derived Carbon‐Based Catalysts for the High‐Efficiency Electrochemical Reduction of Oxygen to Hydrogen Peroxide

The oxygen reduction reaction (ORR) plays a pivotal role in electrochemical energy conversion and chemical production. Two‐electron (2e−) charge transfer for oxygen reduction is considered a promising method for the on‐site production of hydrogen peroxide (H2O2), which requires electrocatalysts with high H2O2 selectivity and ORR activity. Noble metal alloys (e.g., Pt‐Hg and Pd‐Hg) have been prevalent materials of choice due to their desirable intrinsic activity, but their scarcity and high cost seriously hinder their widespread application in practice. Self‐doped heteroatomic carbon‐based electrocatalysts, derived from abundant and inexpensive biomass, have emerged as attractive candidates for on‐site H2O2 production. This review summarizes the fundamentals and recent advances in H2O2 production via 2e− ORR, including basic catalytic mechanisms, the influence of electrolyte pH and porous structure of catalysts, selectivity assessment methods, determination of the cumulative H2O2 concentration, development of biomass‐derived carbon‐based catalyst, and electrochemical device designs. Current challenges and proposed opportunities are also presented with an emphasis on large‐scale electrochemical H2O2 synthesis.

Spotlight on the Effect of Electrolyte Composition on the Potential of Maximum Entropy: Supporting Electrolytes Are Not Always Inert.

The influence of electrolyte pH, the presence of alkali metal cations (Na+, K+), and the presence of O2 on the interfacial water structure of polycrystalline gold electrodes has been experimentally studied in detail. The potential of maximum entropy (PME) was determined by the laser‐induced current transient (LICT) technique. Our results demonstrate that increasing the electrolyte pH and introducing O2 shift the PME to more positive potentials. Interestingly, the PME exhibits a higher sensitivity to the pH change in the presence of K+ than Na+. Altering the pH of the K2SO4 solution from 4 to 6 can cause a drastic shift in the PME. These findings reveal that, for example, K2SO4 and Na2SO4 cannot be considered as equal supporting electrolytes: it is not a viable assumption. This can likely be extrapolated to other common “inert” supporting electrolytes. Beyond this, knowledge about the near‐ideal electrolyte composition can be used to optimize electrochemical devices such as electrolyzers, fuel cells, batteries, and supercapacitors.

The influence of electrolyte pH on anodic growth of Ni-Ti-O nanopores on NiTi alloy

The influence of electrolyte pH on anodic growth of Ni-Ti-O nanopores on NiTi alloy was investigated. Through manipulating HCl, NaCl, and NaOH concentrations in the electrolyte composed of 95 vol% ethylene glycol, 5 vol% H2O, and 0.15 M Cl−, the electrolyte pH was varied from 0.82 to 13.5. Although the pH has little influence on surface morphology and composition of the nanopores, it can significantly impact their growth rate. Initially, increase of the pH decreases the growth rate from 13.8 nm/s at pH = 0.82 to 5.7 nm/s at pH = 7.0. However, when the pH exceeds 7.0, its value increases with the pH and reaches up to 15.8 nm/s at pH = 13.5. The knowledge gained from this study should be valuable in the anodization of other valve metals and their alloys.

Determination of Carbendazim by an Ionic Liquid-Modified Carbon Paste Electrode

ABSTRACTA new method for the electroanalytical determination of carbendazim is reported using a novel ionic liquid-based carbon paste electrode. 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl-sulfonyl)imide were used as additives in the paste for electrode fabrication. The electrodes were characterized by cyclic voltammetry of the couple and scanning electron microscopy. The carbon paste electrode containing 19% 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was selected for the electrochemical determination of carbendazim by differential pulse adsorptive stripping voltammetry. The influence of electrolyte pH, accumulation potential and time, and the presence of selected pesticides on electrochemical behavior of carbendazim were characterized. The optimal conditions for differential pulse adsorptive stripping voltammetry of carbendazim were determined to be a pH 5.0 Britton–Robinson buffer, an accumulation potential of −0.05 V, an accumulation time of 120 s, a start potential of −0.10 V vs. the reference; an end potential of +1.30 V, and a scan rate of 0.050 V s−1. The linear dynamic range of the method was from 0.010 to 0.247 mg L−1 with a correlation coefficient of 0.9995. The recovery was 104.1% in fortified tap water, demonstrating its suitability for the analysis of water.

Synthesis and electrochemical detection of a thiazolyl-indole natural product isolated from the nosocomial pathogen Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen, capable of surviving in a broad range of natural environments and quickly acquiring resistance. It is associated with hospital-acquired infections, particularly in patients with compromised immunity, and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. P. aeruginosa is also of nosocomial importance on dairy farms and veterinary hospitals, where it is a key morbidity factor in bovine mastitis. P. aeruginosa uses a cell-cell communication system consisting of signalling molecules to coordinate bacterial secondary metabolites, biofilm formation, and virulence. Simple and sensitive methods for the detection of biomolecules as indicators of P. aeruginosa infection would be of great clinical importance. Here, we report the synthesis of the P. aeruginosa natural product, barakacin, which was recently isolated from the bovine ruminal strain ZIO. A simple and sensitive electrochemical method was used for barakacin detection using a boron-doped diamond (BDD) and glassy carbon (GC) electrodes, based on cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The influence of electrolyte pH on the peak potential and peak currents was also investigated. At pH 2.0, the peak current was linearly dependent on barakacin concentration (in the range used, 1-10μM), with correlation coefficients greater than 0.98 on both electrodes. The detection limit (S/N = 3) on the BDD electrode was 100-fold lower than that obtained on the GC electrode. The optimized method using the BDD electrode was extended to bovine (cow feces) and human (sputum of a CF patient) samples. Spiked barakacin was easily detected in these matrices at a limit of 0.5 and 0.05μM, respectively. Graphical abstract Electrochemical detection of barakacin.

The role of electrolyte pH on phase evolution and magnetic properties of CoFeW codeposited films

In this research, nanocrystalline Co–Fe–W alloy coatings were electrodeposited from a citrate-borate bath. The influence of electrolyte pH on the morphology, microstructure and magnetic properties of these films was also studied. By increasing pH value, the amount of iron content increased from 30 to 55wt.% which indicates anomalous fashion at higher pH electrolytes. X-ray diffraction patterns showed that the structure of these films depend on electrolyte pH effectively. However, two-phase structure coatings showed smaller average grain size compared with one- phase solid solutions. Vibrating sample magnetometer measurements indicated that the coercivity of the coatings was in the range of 21–76Oe. However, the highest pH value produced coating with superior magnetic behaviour. Microhardness of the coatings reached its maximum value at about 260HV which is referred to the highest tungsten content.

Electrodeposition of Catalytically Active Ni-Mo Alloys / Elektroosadzanie Aktywnych Katalitycznie Stopów Ni-Mo

The work presents results of researches over the deposition of Ni-Mo alloys through the electrolysis conducted in galvanostatic conditions. In order to improve adhesion and aesthetic properties of the deposited alloys, SLS was added to the bath as a surface active agent. The influence of electrolyte pH was tested as well as concentrations of particular components on the composition, structure, cathodic current efficiency of the electrolysis process and catalytic activity of alloys in the process of hydrogen evolution. A positive influence of addition of molybdenum on catalytic activity was observed occurring in lowering the Tafel’s slope within the activation control range from 122 mV/dec (Ni) to 21 mV/dec (Ni-28.5Mo) for a reaction of water molecules reduction in 8 M NaOH at 90°C.

Influence of electrolyte pH on composition, corrosion properties and surface morphology of electrodeposited Cu–Ni alloy

Cu–Ni alloys were electrodeposited by the brush plating technique from sulphate/citrate electrolyte at various pH values. The effects of pH on composition and surface morphological properties of alloys were investigated by X-ray fluorescence and atomic force microscopy. The Cu content increased in the composition of Cu–Ni alloy at electrolyte pH 2. The deposition mechanisms of Cu, Ni and Cu–Ni were investigated by cyclic voltammetry. The lower electrolyte pH leads to the higher reduction current density. The corrosion behaviours of the deposits at different pH values were investigated by Tafel analysis and electrochemical impedance spectroscopy. The corrosion studies indicate that the Cu–Ni alloy exhibits better corrosion resistance at higher pH values than at lower pH values. The surface roughness decreases with increasing solution pH and this observation was confirmed by atomic force microscopy measurements.

Morphology, structure, and magnetic properties of electrodeposited Ni films obtained from different pH solutions

Nanocrystalline nickel (Ni) films were obtained by electrodeposition from chloride aqueous solution with different pH values. The influence of electrolyte pH on the morphological, structural, and magnetic properties is studied, using scanning electron microscopy (SEM), X-ray diffraction (XRD), and alternating gradient force magnetometry (AGFM) techniques. SEM studies revealed a granular and compact structure of the surface of the electrodeposited Ni layers, and the variation of film roughness with bath pH is established. XRD analysis gives evidence of strongly textured Ni films along the (111) direction, with the face-centered cubic (fcc) structure for all baths pH. Magnetic properties such as coercivity, remanence, saturation magnetization, and squareness showed strong dependence on the baths pH and crystallite size. High coercivity was attributed to the presence of the small crystallite size of deposits. The properties of the deposit are greatly influenced by the solution pH.

Contribution of electrolyte pH and deposition potentials to the magnetic anisotropy of electrodeposited nickel films

The influence of electrolyte pH and cathode potential on the magnetic properties of single layer Nickel films electrodeposited on polycrystalline titanium substrates was studied. The films were deposited at the electrolyte pH=3.5±0.1, 2.5±0.1 and 2.1±0.1 by varying the deposition potentials (−1.2, −1.5 and −1.8 V vs saturated calomel electrode, SCE) applied in continuous waveform. The structural analysis by X-ray diffraction revealed that the films have face-centred cubic structure. Results of the magnetic measurements obtained by vibrating sample magnetometer (VSM) indicated that the magnetic properties were affected by the electrolyte pH and the cathode potentials in terms of magnetic anisotropy. At the highest pH the films deposited at the lowest potential had in-plane magnetic anisotropy. As the electrolyte pH decreased from the high (pH=3.5±0.1) to low (pH=2.5±0.1), which is aided by increasing the potentials, resulted in an almost magnetic isotropy in the films. However, isotropic magnetic behaviour was observed for the film deposited at the low pH combined with the high potential (−1.8 V vs SCE). Magnetic thickness profile of the samples obtained by VSM revealed that the isotropic films have a smoother magnetic variation across the film from one edge than the anisotropic ones. This is also verified with a microscopic observation by an optical microscope and the surface of the isotropic films is observed to be smoother than that of the anisotropic ones. Furthermore, all films were found to have planar magnetic anisotropy irrespective of the pH’s and the potentials.

Influence of electrolyte pH on TiO 2 nanotube formation by Ti anodization

This paper investigates the effect of pH and anodization time on the formation of titania (TiO 2) nanotubes. Well-organized TiO 2 nanotubes were electrochemically prepared by anodizing titanium foil in 1 M Na 2SO 4 containing 0.3 g of NH 4F. It was found that TiO 2 nanotubes with uniform pore diameters can be produced by manipulating electrochemical conditions. This study showed that nanotube lengths ranging from ∼0.7 to 2.5 μm could be formed by altering the electrolytes pH. The rate of formation depends upon the specific pH level applied as shown in the following results: pH 3 at a rate of 23 nm min −1, 0.7 μm; pH 5 at a rate of 15 nm min −1, 0.6 μm; pH 7 at a rate of 8 nm min −1, 0.5 μm. In the as-anodized condition, the nanotubes had an amorphous structure. Annealing the nanotube arrays promoted the formation of anatase and rutile phases depending upon the temperature. Furthermore, the sample annealed at 500 °C showed better photocatalytic activity. The activity is also believed to be closely related to the degree of crystallinity and the crystallography structure of the nanotube, which consists of the anatase (76%) and rutile (24%) phases.

Electrodeposition of Au/nanosized diamond composite coatings

Ultra-dispersed diamond UDD particles were codeposited in gold matrix coatings from a sulphite electrolyte, changing bath load and key operating parameters. The influence of electrolyte pH, current density and bath load on current efficiency, particle co-deposition, surface morphology and microhardness of composite coatings was investigated. UDD incorporation is mainly affected by bath load; however, particle embedding is specifically sensitive to electrolyte pH and deposition current density. The maximum mass fraction of carbon in the coating, about 0.55%, is obtained by depositing from ultrasonically pre-treated electrolytes with UDD concentration 20 g l−1, pH 9.5 and 3 mA cm−2 . Au/UDD composites are characterised by an increased microhardness and improved wear resistance. When compared to pure gold coatings which are notoriously weak, Au/UDD electrodeposits from sulphite electrolytes represent a significant improvement.

Influence of Surface Protonation on the Sensitization Efficiency of Porphyrin-Derivatized TiO2

The influence of electrolyte pH on the sensitization efficiency of porphyrin-derivatized TiO2 was studied by photoelectrochemical and transient absorption measurements. The porphyrins 5-(4-carboxyphenyl)-10,15,20-trimesitylporphinatozinc(II) (1), 5-(4-carboxyphenyl)-10,15,20-trimesitylporphine (2), 5-(4-carboxyphenyl)-10,15,20-trimesitylporphinatoplatinum(II) (3), and 5-(4-dihydroxyphosphorylphenyl)-10,15,20-trimesitylporphinatozinc(II) (4) were anchored to low-surface-area and nanocrystalline TiO2 films. The TiO2 conduction band edge potential (ECB) shifted 59 ± 2 mV/pH, from −0.43 V vs Ag/AgCl(aq) at pH 12 to +0.16 V vs Ag/AgCl(aq) at pH 2. Excited-state potentials (E1/2(P+/*)) of 1−4 ranged from −1.58 to −0.91 V vs Ag/AgCl(aq), well negative of ECB. Despite the thermodynamic favorability of electron injection, a 10-fold increase in sensitized photocurrent was measured for 1−4 upon acidification of the electrolyte from pH 10 to 4. Transient absorption data revealed that sensitization of nanocrystalline TiO2 by 1−4 depended on pH in an identical manner. A mechanism is proposed wherein protonation of a surface site is required for charge compensation of injected electrons. Thus, the magnitude of sensitized photocurrent is determined by surface protonation-deprotonation equilibria.

Separation of organic and inorganic arsenic species by capillary electrophoresis using direct spectrophotometric detection.

Capillary electrophoresis (CE) with UV detection was used for the determination of arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, p-aminophenylarsonic acid, 4-hydroxy-3-nitrobenzenearsonic acid, 4-nitrophenylarsonic acid, phenylarsonic acid, and phenylarsine oxide. The electrophoretic mobilities of these anionic species were determined in a 20 mM phosphate buffer in a pH range from 4 to 11, which established pH 10 as the optimum for the separation. The target analytes were then separated in a fused-silica capillary using 20 mM NaHCO(3)-Na(2)CO(3) buffer, pH 10, as electrolyte and detected at 192 nm. Both normal- and reversed electroosmotic flow (EOF) separation modes were investigated and in the latter case, poly(diallydimethylammonium chloride) (PDDAC), was used for dynamic coating of the capillary and to provide a stable and reproducible reversed EOF (relative standard deviation RSD, 0.39%). The influence of electrolyte pH and composition, applied voltage, as well as EOF reversal protocols upon the method performance criteria were investigated. The optimised method provided limits of detection for the target analytes of 1.62, 6.22, 1.45, 1.83, 0.34, 0.40, 0.40, 0.18, and 0.30 mg/L As, respectively. Linearity was obtained in the range of 0.5-40 mg/L As (for aryl compounds) and from 5-100 mg/L As (for the remaining analytes). Reproducibility of peak areas was in the range of 0.8-5.5% RSD. The method was applied to the determination of four aryl arsenic compounds used as additives in animal feed. Analytes were extracted with 40 mM hydrochloric acid - acetonitrile 4:1 v/v, and then cleaned up by passing through a C(18) solid-phase extraction cartridge before analysis by CE with detection at 200 nm. Recoveries for the four analytes were in the range of 78.8-108.3%.

Influence of electrolyte pH on the electrochemical synthesis of poly(O-anisidine) thin films

Abstract The influence of electrolyte pH on the optical absorption and morphology of electrochemically synthesized poly( O -anisidine) (POA) thin films has been investigated. The optical absorption spectrum of the films deposited at higher pH indicates predominant formation of pernigraniline base, whereas at lower pH the spectrum shows exclusive formation of the conducting emeraldine salt phase. A clear transition from insulator to conductor has been observed between pH 1 and 2. The morphology of the films is found to strongly depend on electrolyte pH.

The influence of electrolyte pH on the surface morphology of polypyrrole

Cyclic voltammetric studies of the aqueous synthesis of polypyrrole (PPy) with p-toluenesulfonic acid (pTSA) supporting electrolyte over a range of pH values, from pH 4 to pH 11, have been made. The optimum system pH for the p-toluene sulfonate (pTS) dopant anion is approximately 11. Synthesis of polypyrroles in electrolytic systems with a pH in the optimum region has been observed to produce a more uniform surface morphology with fewer and smaller surface defects. Electrolytic systems with pH values less than the optimum suffer from mixed oxidation mechanisms. The oxidation of the pyrrole monomer was found to compete with the oxidation of water to evolve O 2(g), which adsorbs at the anode/polymerization surface to act as a nucleation or polymerization focal point. The resultant polymer morphology is irregular with large cup- or bell-like surface defects due to gas adsorption.

Direct measurements of flat-band potential shifts under illumination of the semiconductor-electrolyte interface by electrolyte electroreflectance

Direct measurements of flat-band potential shifts produced by illumination of the semiconductor-electrolyte interface can be performed by means of the electrolyte electroreflectance technique. The method has been applied for the first time to monitor the flat-band potential shifts occurring during photooxidation of water at an n-TiO 2 single crystal. The influence of electrolyte pH, applied bias, light intensity and time of illumination has been studied. Two main mechanisms seem to be responsible for the band-edge shifts measured: on the one hand the accumulation of photogenerated holes at OH 0 surface radicals, on the other hand the changes in the local pH at the TiO 2-electrolyte interface. Experimental evidence is given that in a basic electrolyte holes are mainly trapped by chemisorbed OH − groups of basic character, while in acid medium photogenerated holes mainly react with adsorbed water molecules. We estimate the OH 0 surface radical density under steady state working illumination conditions to be of the order of 10 13 cm −2.

Photosynthetic production of H 2O 2 from water at n-TiO 2 electrodes in a photoelectrochemical cell: influence of electrolyte pH AND Pt electrodeposition

The electroreduction of photogenerated and/or dissolved oxygen to H 2O 2 at n-TiO 2 polycrystalline electrodes in a photoelectrochemical cell has been studied by means of photocurrent transients and the rotating ring-disk electrode technique. The photoproduction of H 2O 2 from water under open circuit (photocatalytic mode), in a basic medium, reaches an efficiency η (defined as the ratio between the generation rates of H 2O 2 and “effective” h + +- e − pairs) of ~1%. By contrast, under external polarization (photoelectrochemical mode) η reaches maximum values of about 10%. This value decreases drastically at acidic pHs because of the high overpotential for O 2 electroreduction at n-TiO 2. The effect of Pt overlayers on η has also been analysed.