Electrocatalysis最新文献

The unusual electrochemical, catalytic, and electronic properties of conductive polymer composites with metal oxides, owing to their synergistic effects, have attracted continued interest in the past decade for diverse applications in electroanalysis and electrocatalysis. Herein, we present a novel method for indirect determination of diclofenac (DCF) sodium using a PANI|In₂O₃ composite. A glassy carbon electrode (GCE) modified with a thin PANI|In₂O₃ layer was synthesized by cyclic voltammetry (CV) from a 0.3 M H₂SO₄ solution. Electrochemical impedance spectroscopy (EIS) measurements demonstrated that the PANI|In₂O₃ composite has a significantly higher R_ct value 624.0 Ω than the pure polyaniline film (14.0 Ω). CVs of bare GCE demonstrated the irreversible oxidation of diclofenac, characterized by an anodic peak at a potential of 0.6 V. Differential pulse voltammograms (DPVs) of DCF on a GCE|PANI electrode showed two pronounced anodic peaks (j_pa), which were responsible for the electrochemical oxidation of polyaniline (I) and oxidation of DCF (II). Modification with In₂O₃ dramatically decreased the current density of peak II by inhibiting the oxidation of DCF, and on the contrary, it increased the intensity of peak I tens of times. The GC|PANI|In₂O₃ electrode can be used as an electrochemical sensor for the determination of diclofenac at low concentrations between 1 × 10^–6 M to 1 × 10^–4 M, and j_pa – C_DCF has a correlation coefficient of 0.95. The GC|PANI|In₂O₃ material exhibited a limit of detection of 181 nM and a linear range of 1–100 µM for the DCF sensor.

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The reliance of carbon black as catalyst support for Pt in PEM fuel cell has posed a major challenge in its durability as carbon blacks are highly prone to corrosion. As an alternative, CNTs, CNFs, and graphene are explored as catalyst support, however at the expense of tedious synthesis procedure and production cost. So to combat this issue, a facile flame pyrolysis route was adopted to produce carbon nano-onions using eco-friendly corn oil. Further modification in the carbon nano-onions exhibited better corrosion resistance in comparison to carbon black (Vulcan XC-72R). Also, a systematic approach was adopted towards developing a durable electrocatalyst which was designed to withstand harsh fuel cell operating conditions. The electrocatalyst was successfully analyzed using stringent standard testing protocols (< 40% ECSA loss). Among all the electrocatalyst studied, Pt/fOC exhibited only 37.1% loss in electrochemical active surface area (ECSA) after 5000 cycles, thus indicating its excellent durability. A full cell was also constructed with Pt/fOC as cathode electrocatalyst which showed a maximum power density of 365 mW cm⁻², comparable to commercial Pt/C (367 mW cm⁻²). To the best of our knowledge, this is the first study on the application of corn oil derived carbon nano-onions as catalyst support for PEM fuel cells.

Enhancement of the oxygen reduction reaction (ORR) activity is an important subject for the development of fuel cells. In this study, we prepared the n(111)-(111) series of Pt₃Co single crystal electrodes using an induction heating furnace and investigated the ORR in 0.1 M HClO₄ using the rotation disk electrode (RDE). The specific activity of the ORR (j_k) increased monotonously with increasing terrace width n on the n(111)-(111) series of Pt₃Co, showing the highest activity on Pt₃Co(111). The value of j_k of Pt₃Co(111) was 59-fold higher than that of Pt(111) at 0.95 V(RHE). This trend was different from those of the same series of Pt, Pt₃Co, and Pt₃Ni reported previously. Furthermore, the ORR activity was improved on all electrodes by adding melamine to the electrolytic solution. Melamine was preferentially adsorbed at the terrace edge. Pt₃Co(553) n = 5 showed the highest activity. The values of j_k at 0.95 V(RHE) were 23- and 3.3-fold higher than those of Pt(553) n = 5 and Pt₃Co(553) n = 5 without melamine modification, respectively. The durability of Pt₃Co(553) n = 5 with melamine was improved 8.0-fold.

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Methanol has potential to replace conventional fuels. But its popularity is hindered by lower kinetics of electrode reactions, lower surface area, CO poisoning of catalysts, and higher cost of platinum-based catalysts. It is rare to find electrocatalysts for methanol oxidation in acidic media because its mechanism is not fully understood yet. In this research, HNO₃ exfoliated graphite powder and iron oxide composites have been synthesized by facile, single-step hydrothermal method. This procedure replaces the long and hazardous route of synthesizing graphene oxide. These composites not only provide large surface area for electrode reactions but also utilize catalytic and electrical capabilities of graphene and iron synergistically. Samples were characterized with FTIR, XRD, and SEM analyses while electrocatalytic efficiencies were studied with cyclic voltammetry and electrochemical impedance spectroscopy. Composites have shown remarkable efficiencies for oxidation of methanol in acidic media.

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In the field of sustainable and renewable energy, developing highly active electrode materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a significant challenge. Herein, we have used novel M-type hexaferrites, SrCo_xNi_xFe_12−2xO₁₉ materials, prepared using sol-gel auto-combustion (SGAC) route, for water splitting, in which Co and Ni elements were used as doping materials. Six different compositions of hexaferrites were prepared by varying the concentrations of Co and Ni elements. The fabricated electrode materials were then well characterized by various advanced analytical tools such as XPS, PXRD, BET, FTIR, FE-SEM, and HR-TEM to evaluate their chemical composition, oxidation state, crystallinity, porosity, functional groups and morphology. These prepared electrocatalysts were used as electrode materials for OER and HER application. The rich heterostructural interfaces and unique morphology effectively accelerate the transition of electrons and expose highly active sites for chemical reactions. Among the prepared electrocatalysts, the one with x = 1.0 (SrNi6) shows better OER activity in terms of potential and kinetic activity. ECSA and EIS studies were also conducted to support the electrochemical observations, and the results were found to be consistent with the OER and HER results. Therefore, the fabricated electrocatalysts are suitable for electrochemical applications.

A new glass sample (BNiLi) was prepared by melt-quenching method. The physical nature of the glass sample was investigated via X-ray diffraction, while the atomic structure was studied via density and infrared spectroscopy. The existence of main structure units such as ({text{BO}}_{3}) and ({text{BO}}_{4}) was confirmed. Furthermore, the optical absorbance was measured, and the electronic transitions of nickel ions were revealed. Optical band gap energy was estimated for the BNiLi glass sample. The prepared BNiLi glass was used to modify a carbon paste electrode (CPE) with a polymer film of l-alanine (Ala). The obtained p-Ala@BNiLi/CPE was employed to determine linezolid (LIN) by cyclic voltammetric, linear sweep voltammetric, differential pulse voltammetric, and chronoamperometric methods. The proposed sensor achieves a low limit of detection (0.23 nM), good repeatability, and high stability. The fabricated sensor was applied to detect LIN in pharmaceutical and human serum samples.

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The elucidation of potential molecular structures and metabolites of pharmaceutical drugs remains a key area of research in medicinal chemistry, particularly due to drug-induced toxicity reactions. In this study, the electrochemical degradation of mefenamic acid (MFA) was conducted, leveraging biomimetic electron-transfer mechanisms. A carbon black (CB)–modified glassy carbon electrode (GCE) was employed as a biomimetic system to facilitate the in situ electrochemical conversion of MFA-drug into redox-active hydroxylated MFA metabolite (MFA-Redox). The chemically modified electrode (CME) demonstrated a surface-confined electronic feature of MFA-Redox, with a surface excess of 14.1 × 10⁻⁹ mol cm⁻² under physiological conditions. Various physicochemical and chemical characterization techniques, including liquid chromatography-mass spectrometry (LC–MS/MS) analysis, confirmed the hydroxylated metabolite of MFA (M_w = 305.05 g/mol). Furthermore, the CME was used for the mediated oxidation of thiol groups, using cysteine (CySH)—a biomarker for cellular redox balance in physiologically neutral pH—as a model compound. This resulted in a well-defined, diffusion-controlled oxidation peak current. The Michaelis–Menten (MM) enzymatic kinetics model was applied to describe the oxidation process, yielding key kinetic parameters: the MM rate constant (K_M) of 0.060 mM, the first-order catalytic rate constant (k_c) of 0.4 s⁻¹, and the heterogeneous electron-transfer rate constant (k'_ME) of 9.7 × 10⁻² cm s⁻¹. In a separate electroanalytical study, the performance of the CME for CySH detection was evaluated using amperometric i-t curves. The CME demonstrated a linear concentration range from 100 µM to 1 mM, with a sensitivity of 1.045 nA/µM and a detection limit of 3 µM. Importantly, the CME showed excellent selectivity, with no interference from uric acid, ascorbic acid, dopamine, glucose, and creatinine.

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Healthcare diagnostics and supplementary experimental research require electrochemical tools that are straightforward, inexpensive, delicate, quick, and precise. In addition to the previous reports of paracetamol sensors, we present an electrochemical sensor that customs differential pulse voltammetry (DPV) and cyclic voltammetry (CV) to determine the presence of nickel sulfide (NiS) on graphene oxide sheets (GO) (NiS@GO). Utilizing analytical methods, the composite surface morphology and structural characteristics were described. A substantial drop in overpotential was seen in the electrochemical investigation of the NiS@GO composite revised glassy carbon electrode (NiS@GO/GCE) owing to its substantial external part and high hauler agility, which demonstrated remarkable activity towards the oxidation of paracetamol (Para). Para electrochemical sensing was made more accessible by a diffusion-controlled oxidation process with an identical quantity of protons and electrons. From 3.3 µM to 125 µM the concentration of Para ornament linearly with the peak currents during the determination process 0.052 µM was the Para detection limit (3σ/S) sensitivity of the fabricated electrode was 12.14 µA µM⁻¹. In addition, the sensors demonstrated remarkable recovery with actual tablet samples over a month-long period with very little interference from common species. Commercial tablet samples demonstrate a noteworthy potential for wide-ranging applications in the electrochemical sector, with an acceptable recovery rate of 96.6 to 100.8%. An upfront, affordable quality monitoring system that can track the amount of para in tablets may be developed with the help of the suggested electrochemical sensor. Application investigations using the proposed sensor successfully detected Para in drug tabulations and biological materials.

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Preliminary experiments are reported to show quantitatively that hydrogen gas can be stored under triphasic conditions in wet nanoparticulate polymer of intrinsic microporosity (PIM-1) applied as a film to a platinum disk electrode surface. Based on chronoamperometric data, it is shown that the resulting triphasic interface is able to store hydrogen gas at apparent concentrations higher (3 orders of magnitude increase for an approx. 15 μm thick film with typically c_app,hydrogen = 80 mM; D_app,hydrogen = 1.2 × 10^–11 m²s⁻¹) than the known solubility of hydrogen gas in aqueous electrolyte (c_hydrogen = 0.08 mM; D_hydrogen = 5.0 × 10^–9 m²s⁻¹) at room temperature. Due to film roughness/heterogeneity, the apparent hydrogen concentration can only be estimated, but it increases with film thickness. At the same time the apparent diffusion coefficient is lowered considerably due to the molecularly rigid/glassy polymer host. The resulting modified electrode is investigated/proposed for energy storage applications with different amounts of PIM-1 nanoparticle deposits attached to the platinum surface.

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Graphene electrodes incorporated TiO₂/C-dots@NiO (G-TCN) nanocomposites have been successfully synthesized and investigated for their performance in detecting the pesticide diazinon (DZN). The synthesis begins with preparing a C-dots solution hydrothermally using tolaki citrus extract (Citrus sp.) as a precursor. The incorporation was continued hydrothermally between C-dots, Ni (II), and TiO₂ to obtain the TiO₂/C-dots@NiO (TCN) nanocomposites. The results of the morphological study illustrate that the TCN nanocomposite is composed of round particles with a uniform size between 180 and 200 nm. The XRD diffractogram pattern describes the overlapping interactions between the elements that make up the nanocomposites. The electrochemical performance in the Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ solution system illustrates the reversible redox reaction of G-TCN with a value of ∆E_p = 0.08 V. DZN detection showed superior results. Based on the cyclic voltammogram, DZN experienced a reduction at a potential of 0.65 V. The linearity test showed an LOD value of 0.09 μg/mL. In other tests, G-TCN showed good stability and reliability, with an RSD of 11.90% and 7.44%, respectively. The results reported in this work will be a reference for researchers in developing voltammetric sensors for pesticide residue detection.

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