Electrocatalysis最新文献

In this study, the nucleation and growth mechanisms of copper on a glassy carbon (GC) electrode from mixed acetonitrile–water (AN/H₂O) solutions were investigated using cyclic voltammetry (CV), chronoamperometry (CA) and scanning electron microscopy (SEM). The mechanism of copper nucleation in the AN and 70:30 AN/H₂O solutions is progressive, whereas for the 50:50, 60:40 and 80:20 AN/H₂O solutions, it is close to the mixed mechanism. The nucleation parameters, including the nucleation rate, nucleation density and average radius of active nuclei centres, were calculated using a three-dimensional electrochemical nucleation model developed by Scharifker-Hills, in accordance with the identified mechanism. The experimental results demonstrated that the average radius of electrodeposited particles could be reduced from 10.8 to 3.2 µm by shifting the applied potential to the negative region, from −0.43 to −0.48 V in a solution of 0.01 M CuCl₂ + 0.5 NaClO₄ + 70:30 AN/H₂O. SEM images of the obtained coatings demonstrated the formation of uniformly distributed “monanthes-like” structures of copper particles. The catalytic activity of the Cu electrocatalysts were determined by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) methods in a 0.5 M NaHCO₃ solution saturated with CO₂ under bulk electrolysis conditions. LSV shows that the Cu catalyst electrodeposited from 50:50 AN/H₂O mixture exhibited the best performance for electrochemical CO₂ reduction reaction (eCO₂RR) with a Tafel slope of 168 mV dec⁻¹, exchange current density of 6.81 (times) 10⁻⁴ A cm⁻² and charge transfer resistance of 9.4 Ω cm². This study may provide an economical approach for developing low-cost and efficient copper-based electrocatalysts for CO₂ electroreduction.

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Energy storage has become an essential need for today’s applications. Thus, the development of capacitors and their materials has gotten great attention. In this study, a high mass loading (2 mg cm⁻²) NiMn₂O₄/carbon felt (CF-NMO) was fabricated using a hydrothermal process and used as a new material for a pseudo-capacitive electrode having a potential window of 0.65 V. Several analytical techniques were employed to confirm the structure, such as X-ray diffraction (XRD), and X-ray photon spectroscopy (XPS). The spinel oxide distribution and surface morphology were studied using scanning electron microscopy (SEM), and transmitted electron microscopy (TEM). The activity of the modified CF-NMO was investigated in 1.0 M NaOH. The prepared electrode reached a capacitance of 301 F g⁻¹ at the current density of 1 mA g⁻¹. Furthermore, the electrode’s durability was investigated for 2000 cycles at 5 mA g⁻¹, and the provided capacitance retention was ~ 85% compared to the 1st cycle. Also, the rate capability was estimated to be 69% in the current range from 1 to 5 mA cm⁻².

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Electrolysis of ethanol to produce green hydrogen, with less electrical energy than for water electrolysis, is potentially an attractive sustainable energy technology. However, more efficient anode catalysts are required, and the production of acetic acid and acetaldehyde by-products must be considered. PtRhM (M = Sn, Ni, Ru) catalysts can potentially combine the high activities of PtM catalysts with the enhanced selectivity of PtRh for breaking the ethanol C–C bond, which increases hydrogen production. The purpose of this work was to compare these catalysts in a proton exchange membrane (PEM) cell and measure stoichiometries and product distributions. The results show that although Sn, Ni, and Ru all enhance the activity of PtRh at low potentials for cyclic voltammetry in H₂SO₄(aq), only Ru had a significant effect in the PEM cell. However, Ni enhanced selectivity for breaking the C–C bond, while Ru and Sn both decreased selectivity. Consequently, PtRhNi appears to be most suitable for production of hydrogen from ethanol oxidation, because it provides the optimum balance between the electrical energy required, current density, and hydrogen/ethanol ratio (higher stoichiometry).

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In modern era, air pollution arises from various human activities and natural processes. Several studies have revealed that automobile exhaust monitoring sensors are indispensable tools for ensuring compliance with emissions regulations, protecting public health, reducing environmental impact, optimizing engine performance, and facilitating diagnostic and maintenance activities in the automotive industry. This study introduces a green synthesis of pure CuO using Calotropis giantea (CG) leaf extract. The synthesized CuO with CG leaf extract was characterized through numerous analytical techniques to understand the basic properties of the synthesized material. The novelty of this work lies in the fabrication of the electrode material of CuO based nanoparticles for sensing applications. The Calotropis gigantea leaf extract enhances the surface activity area of CuO and leads to achieving good electrochemical performance. In the amperometric mode, the fabricated sensor device was applied with a constant bias voltage of + 1 V at the CuO nanoparticle–based anode relative to the fixed lanthanum strontium cobaltite La_0.5Sr_0.5CoO₃ (LSC) cathode. Utilizing LaGaO₃ (LSGMN) as the solid electrolyte, this electrochemical device achieved a remarkable sensitivity of 586 μA/decade at 550 °C. The fabricated sensor structure was tested for detecting ammonia (NH₃) concentrations ranging from 3 to 40 ppm in a base gas (mixture of 5% O₂ and N₂), in the temperature range of 300 to 650 °C. This testing configuration was designed for exhaust gas monitoring applications. Notably, the sensor demonstrated a rapid response time of 20 s and a recovery time of 90 s, while detecting ammonia, making it effective for real-time monitoring in various environmental conditions.

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Patients undergoing treatment with nonsteroidal anti-inflammatory drugs (NSAIDs), such as aceclofenac (ACF), primarily aimed at managing conditions like rheumatoid arthritis, face potential risks associated with overdosage, impacting organs like the kidney, liver, gastrointestinal tract, and blood cells. Hence, accurate quantification of ACF in real samples becomes paramount. In this investigation, we propose an innovative voltammetric approach for the determination of ACF in urine specimens. The working electrode employed herein consisted of a glassy carbon electrode (GCE) modified with boron nitride quantum dots doped bismuth cerium oxide nanocomposite (Bi₂O₃/CeO₂@B-NQds/GCE). Comprehensive characterization of the Bi₂O₃/CeO₂@B-NQds/GCE was conducted utilizing various techniques, followed by photoelectrochemical (PEC) analysis. These photosensors exhibited commendable sensitivity and reproducibility, and their preparation was deemed facile, rapid, and cost-effective. The impact of diverse interfering species was scrutinized, alongside calibration procedures to ascertain analytical performance. Remarkably, the results unveiled a high degree of linearity within the range of 0.6 to 13.8 µM, with exceptional values for the limit of detection 4.2 nM. Moreover, the constructed photoelectrode demonstrated stability and reproducibility, showcasing promising potential for reliable ACF detection in urine samples upon successful validation. In addition to its potential for clinical diagnostics, this novel light-assisted voltammetric technique holds promise for enhancing patient care by enabling precise monitoring of ACF levels in urine, facilitating personalized treatment regimens for individuals undergoing NSAID therapy. Furthermore, its ease of use and cost-effectiveness make it a practical tool for routine screening in medical settings, offering a valuable asset for healthcare professionals striving to optimize patient outcomes.

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The efficiency of photoelectrochemical (PEC) water splitting is considerably controlled by the recombination of photogenerated electron/hole charge carriers at the interface. Herein, the correlation between composition and photoelectrochemical activity is studied by utilizing molybdenum-modified tungsten oxide electrodes. Molybdenum tungsten mixed oxides (Mo_xW_1−xO₃) were synthesized by spray-freeze/freeze-drying approach by varying x from 0 to 1 and studied as a photoanode. The structural changes after Mo substitution in tungsten oxide (Mo_xW_1−xO₃; 0 ≤ x ≤ 1.0) were observed as a function of the composition. In binary oxides, monoclinic structure (ℽ-phase) was observed until Mo substitution (x) reached 0.2. A coexistence of both monoclinic and orthorhombic phases was observed for x varying from 0.2 to 0.8. All synthesized n-semiconducting materials were photoelectrochemically active in water splitting under the acidic condition of HClO₄. The highest PEC activity was observed for the sample with low Mo content (x = 0.05) for which the narrowest band gap was determined. The overall activity decrease encountered for Mo-rich materials can be related to a higher tendency to photoinduced proton insertion facilitated by rhombohedral structure. The insight into the mechanism was determined by differential electrochemical mass spectrometry (DEMS). Oxygen (m/z 32) and hydrogen peroxide (m/z 34) were identified as main products. The material with small variation in compositions (x = 0.05) significantly influenced catalytic activity and selectivity, highlighting the importance of the material’s design.

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Miltefosine is an alkyllylosophospholipid analogue used to treat visceral leishmaniasis. Recently, reports have been made of suspected counterfeit miltefosine on the Indian market. With the risk counterfeit drugs pose to drug resistance development, quality control of antileishmanial drugs has become important. Hence, in this study, amino-functionalized multi-walled carbon nanotubes (MWCNT-NH₂) were synthesised and characterised using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Also, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the electrochemical properties of the synthesised MWCNT-NH₂. A complex was formed between MWCNT-NH₂ and miltefosine (Mil-MWCNT-NH₂). Five microliters of Mil-MWCNT-NH₂ was drop-cast on glassy carbon electrode, and differential pulse voltammetry studies were carried out to assess the performance of the sensor. Using [Fe(CN)₆]^-3/-4 as a redox couple, a calibration study was carried out at different concentrations (0–250 µM) to establish the concentration range of the sensor. A linear response was established. With a detection limit of 1 µM, the fabricated sensor is a viable tool for detecting antileishmanial drug miltefosine in urine samples and possible application in quality control of miltefosine against counterfeiting.

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Pesticide (glyphosate) monitoring has become a focal point of concern as the unregulated application of pesticides puts both human health and the ecosystem at serious risk. Effective tracking of glyphosate levels is essential to mitigate its adverse effects and ensure the safety of the ecosystem and the human population. This study develops a novel electrochemical (EC) sensor using a nickel-metal organic framework (Ni-MOF) modified electrode to detect ultra-low concentrations of glyphosate pesticide. A one-pot solvothermal approach to synthesize Ni-MOF and a one-step sensor fabrication approach were adopted to modify the electrode surface of an electrochemical sensor. The Ni-MOF material coating on the working electrode surface increases the electrode’s electroactive surface area, promotes electron transport between the electrodes, and demonstrates selectivity and sensitivity towards glyphosate. This electrochemical sensor has a detection limit of 1.9 parts per billion (ppb) or 0.0113 nM, over an extensive concentration range of 0.166–0.666 µM/L. Further, the proposed sensor exhibits excellent stability and reproducibility with a standard deviation of around 2.8% in relative peak current. It shows excellent selectivity against various interfering substances with approximately ≤ 5% change in the current response. Finally, to showcase its practical applicability, the sensor was assessed by a glyphosate-spiked real sample.

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The development of active bifunctional electrocatalysts is crucial in reducing dependence on precious-metal-based materials for energy production and storage. In this work, we present the synthesis of novel nanocomposites of XCoFe₂O₄ (where X represents Pr or Nd) integrated with graphene oxide (GO) using a hydrothermal method for light-induced hydrogen evolution reaction (HER) and supercapacitor functions. Among the synthesized electrocatalysts, NdPr-CoFe₂O₄/GO exhibits superior HER performance, characterized by a minimal overpotential at photocurrent density of 10 mA cm⁻² in 1 M KOH solution. Additionally, the composite shows a high specific capacitance of 1590.5 F/g at 3 A/g, maintaining approximately 97.6% of its capacitance after 1000 cycles. The enhanced performance is attributed to the synergistic effects of optimal bimetallic substitution, maximized electrochemical surface area, reduced particle size, and minimized charge transfer resistance. This study opens new pathways for the design of spinel ferrite-GO composites for efficient energy conversion and storage applications.

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Graphical abstract presenting applications of synthesized catalysts.