Journal of Electroanalytical Chemistry最新文献

The adsorption of organic molecules on gold electrodes serves as a model to understand the organic/inorganic electrified interface, which is relevant to the study of molecular electronics and organic thin film semiconductors. Our previous study on terthiophene (TT) adsorption on an Au(1 1 1) electrode shows that immersing Au(1 1 1) crystals in a TT ethanol dosing solution installs an ordered TT adlayer on the sample. The current study addresses the adsorption of 3′,4′-bis(hexylthio)-2,2′:5′,2′'-terthiophene (DTDST), a molecule with a TT backbone attached with two thiolhexyl chains, on an ordered Au(1 1 1) electrode. High-quality STM images were obtained to reveal the internal and 2D spatial structures of DTDST admolecules. The potential greatly influenced the organization of DTDST on the ordered Au(1 1 1) electrode. Although the pristine DTDST adlayer was disordered, it transformed into ordered Au(1 1 1) - (3√3 × 9) and (5√3 × 26) structures after applying a potential more negative than 0 V (vs. Ag/AgCl) in 0.1 M H₂SO₄ and HClO₄, respectively. Shifting the potential more positive than 0.25 V resulted in coadsorption of bisulfate anions and restructuring of the DTDST adlayer. High-quality molecular resolution STM images were collected to reveal the azimuthal orientation of the DTDST admolecule on the Au(1 1 1) electrode. The thiolhexyl chains of DTDST admolecules could arrange in such a way that allowed intermolecular van der Waals interactions. Oxidation of adsorbed DTDST molecules to yield oligomers was also revealed by in situ STM.

The electrodeposition process of tin films on copper electrodes in ethaline and reline deep eutectic solvents (DES) was studied in the 303 – 353 K range. Voltammetric data indicate the presence of underpotential and overpotential electrodeposition processes. While the former occurs under surface-reaction control, the latter proceeds under mass transport control. Electrochemical impedance spectroscopy shows two capacitive contributions during the underpotential process and a single capacitive contribution at high frequencies and a Warburg contribution at low frequencies, when the electrodeposition process takes place in the overpotential region. Tin deposits obtained in ethaline exhibit blunt particles with ordered structures whereas in reline facetted particles with no preferential order are observed as electrodeposition time is increased. The electrocrystallization mechanism under overpotential conditions in ethaline and reline corresponds to an instantaneous nucleation and a 3D growth process. For underpotential conditions in ethaline, an instantaneous nucleation and 2D growth coupled to an adsorption process occurs. XRD spectra shows the formation of Cu₃Sn and Cu₆Sn₅ intermetallics due to the diffusion of Sn atoms into the Cu lattice during the electrodeposition process. From rotating disk electrode measurements, the diffusion coefficient of Sn(II) ions in both DES at different temperatures, and the diffusion activation energy, were determined.

In vitro diagnostics (IVD) is aimed at ensuring human welfare and life security. Electrochemical sensors have been utilized in different applications, such as environmental contaminant detection and food safety, especially in the field of IVD, due to their excellent properties such as high sensitivity, simple to use, and cost-effectiveness. However, reluctant reproducibility and accuracy are among the most insurmountable hindrances for electrochemical IVD sensors, especially bioaffinity-based ones essential in disease biomarker detection and infection prognoses. In recent years, inspired by the ratiometric strategy from fluorometry, electrochemically ratiometric biosensors have been increasingly developing. This review highlights recent advances in bioaffinity based electrochemically ratiometric sensors (BERS) for IVD applications. Their signal generation strategies and analysis applications, especially for potential applications in the real world, are introduced. Finally, we enlighted several thoughts and insights into the design and application of BERS in IVD and provided the challenges and perspectives in this domain.

NiO/Fe₂O₃ modified glass carbon (GCE) electrode was prepared by electrodeposition of NiO nanoparticles on Fe₂O₃/GCE. The electrochemical characteristics of NiO/Fe₂O₃/GCE have been examined using cyclic voltammetry. The enhanced electrocatalytic activity of NiO/Fe₂O₃/GCE modified electrode for nitrite oxidation may be related to the synergistic effect of NiO and Fe₂O₃ nanoparticles, which may not only modify the electronic structure of the composite materials but also favor the increase of active sites in NiO/Fe2O3 and help to adsorb more active materials. To detect nitrite, the NiO/Fe₂O₃/GCE modified electrode was employed as an electrochemical sensor. There is a strong linear correlation between concentration and peak current (R = 0.9993) in the 5–500 μM range, and a detection limit of 0.05 μM (S/N = 3) was established. NiO/Fe₂O₃ sensors have excellent selectivity and stability as well. The sensor performs well analytically in determining nitrite in tap water, indicating that it has the possibility for efficient application in nitrite detection. This simple, low-cost, stable and highly sensitive nitrite electrochemical sensor provides a promising method for the detection of nitrite in practical samples.

Temperature is an important variable in electrochemistry, increasing the operating temperature has the capacity to provide significant increases in mass transport and electron transfer rates. In the case of electrodeposition, it can also allow the deposition of crystalline material which would otherwise be amorphous when grown at lower temperatures. In this work we exploit a high boiling point, weakly coordinating solvent, o-dichlorobenzene, to electrodeposit the p-block semiconductors antimony and antimony telluride at temperatures up to 140 °C. The effect of the temperature on the morphology and crystallinity of the deposits is investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and optical microscopy. An attempt is also made to rationalise the role of temperature in electrodeposition and its influence on the aforementioned properties.

A novel blended polymer membrane is prepared by a facile route for using as the diaphragm in vanadium redox flow batteries (VRFBs). The polymers polyvinylchloride (PVC) and polyvinylpyrrolidone (PVP) are first blended in a 1.2:1 mol ratio to give a PVP-PVC mixture, and the PVC in the mixture is then functionalized with 1-(3-aminopropyl)-imidazole (APIm). The functionalized polymers are impregnated into the porous polytetrafluoroethylene (PTFE) to fabricate membranes. The obtained membranes possess superior affinity to sulfuric acid mainly due to acid-base interactions between APIm groups and sulfuric acid molecules. The presence of hydrophobic PTFE restricts the deterioration of mechanical strength of membranes by doped acids. Moreover, the prepared membranes exhibit high oxidation stability and low vanadium permeability. The VRFB assembled with the proposed diaphragm displays energy efficiency above 82 % at a current density range of 20 to 120 mA cm⁻². The membrane-based VRFB demonstrates stable performance after over 50 charge–discharge cycles.

The anion exchange membrane fuel cell (AEMFC) represents a promising avenue in clean energy equipment. However, its practical application is limited due to the high cost of Pt-based catalysts. Therefore, it is necessary to develop cheap and efficient non-precious metal catalysts. Here in, we employed a simple one-step thermal strategy to synthesize N-doped porous carbon encapsulated Fe and Ni bimetal catalysts (FeNi-N-C-1-1-Ts, T = 900, 950, 1000, 1050 and 1100 ℃). Among these catalysts, FeNi-N-C-1-1-1000 exhibited the highest half-wave potential of 0.885 V, 5 mV higher than 20 wt% Pt/C (0.880 V). Furthermore, it demonstrated a dominant 4e^- reduction pathway, exceptional durability and high resistance to methanol. These excellent performances were attributed to the synergistic effect of FeNi bimetallicaction, increased graphitic content, higher Fe/Ni-N₄ content, larger BET surface area and the presence of mesoporous structures. Moreover, FeNi-N-C-1-1-1000 exhibited higher half-wave potential than Ni-N-C-1000 and Fe-N-C-1000 owing to the smaller particle size and larger BET surface area of FeNi-N-C after the doping of Ni into Fe-N-C. Finally, FeNi-N-C-1-1-1000 was employed as the cathode in the AEMFC with a loading of 2.0 mg·cm⁻², resulting in the highest peak power density of 545 mW·cm⁻², surpassing that of 20 wt% Pt/C (375 mW·cm⁻²) by 170 mW·cm⁻².

Vanadium Pentoxide (V₂O₅) has good ion storage capacity and weak anodic electrochromism. Since the V₂O₅ and Tungsten Trioxide (WO₃) films were used as the auxiliary and major color-changing layers, respectively, then they were combined with heat-cured gel (LiClO₄ + PC) + PMMA electrolyte as an complementary all-solid-state electrochromic device (ECD). Also, the V₂O₅ films were prepared at different oxygen flows and annealing temperatures. These results exhibited that oxygen flow of 4 sccm and annealing temperature of 400 °C can enable the optimal optical contrast (ΔT) to reach 38.7%@550 nm. The response time of the coloring(tc) and the bleaching(tb) were 5 and 4 s, respectively. Raman spectrum showed the stable phase of V⁵⁺ and specific element ratio of 2.52 and X-ray photoelectron spectroscopy (XPS) had the red shift phenomenon. However, the performance of ITO/V₂O₅/gel-electrolyte/WO₃/ITO device, the best working voltage was measured as ±2.5 V, the optical contrast was ΔT = 42% and the response time of tc and tb were 6.5 and 5.5 s, respectively. These results demonstrate that ECD has the advantages of fast response time and low voltage stable startup.

The development and improvement of new transition metal-based catalysts to replace Pt/C electrodes in electrolytic water hydrogen evolution has attracted much attention. In this work, we used ammonium citrate as additive, mixed with cobalt nitrate, through hydrothermal and phosphating methods to get supported on carbon cloth catalyst with new morphology (referred to as E380-CoP/CC, E380 stands for ammonium citrate). Benefit from the dense and fine nanosheet structure, compared with cobalt phosphating alone, the catalyst E380-CoP/CC has a significant improvement in hydrogen evolution performance. In 1 M KOH, the overpotential is 57 mV at the current density of 10 mA cm⁻², and the Tafel slope is only 40 mV dec^-1, which is very close to the hydrogen evolution performance of Pt/C electrode. In addition, the catalyst has favorable stability and superior hydrogen evolution performance after undergoing CV 2000 cycles and 48 h i-t test. This work offers a reliable idea for realizing electrolytic water hydrogen evolution technology with high efficiency and energy saving.

The effects of a thin Ni-flash coating, tens of nanometers thick, on hydrogen evolution, ad/absorption, and permeation of advanced high-strength steel were examined for a deeper understanding of the hydrogen infusion behavior in the steel substrate during electro-Zn plating. The electrochemical permeation technique and impedance spectroscopy were used under cathodic polarization in a step-up manner. In addition to the electrochemical analyses, the hydrogen microprinting technique was employed to identify the distribution of Ag particles (locating hydrogen atoms) in the electro-Zn plated steels with and without a thin intermediate Ni-layer. The results revealed that despite the higher hydrogen evolution rate on Ni-flash coating layer than on bare steel, the intermediate Ni-layer decreased the hydrogen infusion considerably in the steel substrate during electro-Zn plating, due primarily to the lower hydrogen ad/absorption rate on the Ni-flash coating layer, and the predominant hydrogen trapping at the multi-interfacial areas of the Zn-layer/Ni-layer/steel substrate. These results could provide insights into the precise role of a thin (tens of nanometers) Ni-flash coating on the resistance to hydrogen embrittlement of ultra-high-strength steel alloys during electro-Zn plating.