Electrocatalysis最新文献

In this work, NiMnFe oxide catalyst materials were prepared by electrodeposition for the oxygen evolution reaction (OER) in an alkaline solution. Incorporation of Fe into these catalyst structures was carried out using galvanic replacement of Mn within the electrodeposited NiMn alloy to produce more surface Fe sites, which led to the leaching of Mn from the NiMn alloy, resulting in surface defects. The electrocatalysts were studied by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) and X-ray photoelectron spectroscopy (XPS). They were electrochemically characterized for OER by cyclic voltammetry and electrochemical impedance spectroscopy. SEM–EDX demonstrated an increase in Fe content in the catalyst due to the galvanic exchange and the incorporation of Fe from the KOH solution onto the Ni disc. XPS showed that after OER experiments, the surface is highly oxidized, dominated by Fe³⁺ and Ni³⁺ species. During the OER studies in 1 M KOH, the NiMnFe material demonstrated an overpotential of 321 mV at a current density of 10 mA cm⁻² and a Tafel slope of 41 mV dec⁻¹, showing a 15 mV overpotential improvement over the bare Ni disc. The difference of the overpotential grew to 24 mV when moving to an OER current density of 100 mA cm⁻².

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NiMn was electrodeposited on Ni discs. Employing galvanic exchange of Mn by Fe on electrodeposited NiMn film led to a 42 mV oxygen evolution reaction overpotential decrease at a current density of 100 mA cm⁻². An overpotential of 368 mV was observed for the best-performing material, achieved through the galvanic exchange.

Herein, for the first time, a gold digital video disc (GDVD) platform was modified layer by layer with the graphitic carbon nitride (g-C₃N₄) nanosheets and gold-platinum nanoparticles (Au–PtNPs), and it was used as an efficient nanocatalyst for the electrocatalytic oxidation of the methanol molecules. The graphitic carbon nitride nanosheets were synthesized through the pyrolysis method, and they were employed as a substrate for the distribution of the Au–PtNPs. The change in the electrochemical behavior of the GDVD surface was investigated in each modification step. The electrocatalytic oxidation of the methanol molecules at the surface of different modified GDVDs was evaluated using cyclic voltammetry (CV) and chronoamperometry techniques. The experimental results indicated that the Au–Pt/g-C₃N₄/GDVD has a higher electrocatalytic activity for the oxidation of methanol under the optimized experimental conditions in comparison with the other studied GDVDs. The kinetic study of the electro-oxidation of methanol was also investigated, and the exchange current density (J₀) values revealed a better kinetic in the presence of graphitic carbon nitride and Au–PtNPs.

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New energy storing technologies must be developed immediately because of the serious issues brought by global energy crisis. For supercapacitor applications, the development of effective, stable and sustainable electrode materials with high specific capacitance (C_sp) is necessary. The current investigation highlights the use of CoMoO₃/g-CN electrode materials to enhance supercapacitive properties. The physical and chemical properties hydrothermally developed materials were studied utilising a number of characterisation test. In 3 M KOH solution, electrochemical characteristics of produced electrode materials were observed by galvanostatic charge and discharge (GCD) analysis and cyclic voltammetry. Electrochemical results exposed that CoMoO₃/g-CN nanocomposite exhibited specific capacitance of 964.93 F/g, specific energy (S_E) 44.09 Wh/kg and specific power (S_P) 288.15 W/kg at current density (C_d) 1 A/g. Furthermore, after 3000th cycles, the material exhibits superior cyclic stability compared to the pure material and reduced charge transfer resistance of 0.13 Ω. Addition of graphitic carbon nitride (g-CN) caused high specific capacitance, quick charging discharging and stability of active electrode material, attributed to bigger surface area and excellent electrical conductivity. Moreover, N-enrich structure of g-CN caused a quick ion transport and higher specific surface area. These results demonstrated that advanced CoMoO₃/g-CN can be applied to next-generation supercapacitors.

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This study explored the potential for performance enhancement using a Ru(III) salophen-type Schiff base complex as a co-catalyst in conjunction with PtSn/C for ethanol electro-oxidation. This type of compound is recognized as a cost-effective synthetic catalyst for oxidation reactions, which can improve the electrocatalytic activity of platinum-based catalysts while remaining less expensive. The ligand and complex were synthesized and characterized using various techniques, including FTIR and UV–vis spectroscopies, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. Electrocatalytic experiments revealed that the mixed catalyst PtSn/C:[Ru(ndsp)(Cl)(H₂O)] at a mass ratio of 4:1—comprising 20% of the catalyst mass—outperformed pure PtSn/C. It achieved a peak current density of 32.5 mA/cm², approximately 1.7 times higher than that of pure PtSn/C, and the onset potential for the ethanol oxidation reaction occurred at a less positive value. Maximum catalytic efficiency was observed at a pH of 0.3 and increased with higher ethanol concentrations. These results indicate that the addition of the Ru(III) complex significantly enhances the catalytic activity of PtSn/C, making it a promising and cost-effective candidate catalyst system for direct ethanol fuel cell (DEFC) applications.

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High-entropy alloys (HEAs) have attracted significant interest because of the materials structural and thermal stabilities, tailorable compositions, and unique functional properties. The present study synthesizes for the first time a noble metals-free HEA of Cu, Fe, Zn, Ni, and Co (CFZNC) supported on activated carbon powder (ACP) by the suspension polymerization of a phenol–formaldehyde precursor, followed by thermal treatment (carbonization, steam-activation, and H₂-reduction), and ball milling. Metal salts were in situ added to the polymerization reaction mixture. The electrochemical activity tests reveal a good hydrogen evolution rate (169 μmol.L⁻¹.h⁻¹) over the synthesized CFZNC-HEA/ACP, with an overpotential of 139 mV at the current density of 10 mA.cm⁻² in alkaline medium. The tests also show the Faradaic efficiency of 90.5% and the materials stability up to 30 h. This study has provided a new approach to synthesize the non-noble metals-based HEA in bulk quantity as an efficient electroctalyst for environmental and energy applications including hydrogen storage, and carbon dioxide and nitrate reductions.

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Data-driven approaches have the potential to make a priori predictions. However, there are very few models that have been explored for the prediction of nanocomposite electrocatalysts under testing conditions. Here we report for the first time the parametric optimization coupled with data-driven approaches of efficient electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. The parametric optimization suggests that the porous Ni- or Fe-based nitride composites, with combinatorial structures or thin films with average d-electrons between 5 and 8 and catalyst loading between 1 and 10 mg cm⁻² will exhibit the best OER activity. Machine learning classification of OER overpotential grades (η₁₀, overpotential at 10 mA cm⁻²) of transition metal oxynitrides (TMONs) and transition metal oxides (TMOs) is achieved using random forest (RF) and CatBoost algorithms. η₁₀ is classified as grade ‘A’ if η₁₀ < 351 mV, else grade ‘F’. We note that 80–85% of electrocatalysts containing nickel foam (NF) have been in grade A, implying NF is a prospective hindrance against true activity determination of the electrocatalyst but suitable for achieving grade ‘A’ electrocatalyst for electrolysers. RF and CatBoost models achieved an accuracy of 78.09% on the TMON dataset and RF model achieved 72.88% on the TMO dataset. This work aims to reduce the experimental time for the design and development of an electrocatalyst using a data-driven paradigm.

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In the present work, the four Fe-based structures were prepared from the phyto-synthetic approaches and their subsequent calcinations. The aqueous extracts of Salsola sp. and Heliotropium bacciferum plants were used as the bio-reductant and stabilizer in these approaches. The green synthesized structures were characterized using FT-IR, XRD, FESEM, EDX, and VSM techniques. The characterization results showed that calcination created a cubic γ-Fe₂O₃ phase with spherical morphology. The preparation of Pd-Fe composites was completed by reducing palladium ions on iron-containing samples using Salsola sp. aqueous extract. The effect of calcination and the type of extract used in the synthesis of Pd-Fe composites on their electrocatalytic activity towards the electrooxidation of ethylene glycol by voltammetry technique. The catalyst prepared with Salsola sp. (2.35 mA.cm⁻²) extract had better catalytic activity than the one Heliotropium bacciferum (1.67 mA.cm⁻²) for 0.28 M ethylene glycol oxidation. The catalytic activity of iron in the not-calcined form was higher than in the calcined due to the transformation in the electronic structure, confirmed by the change in the magnetic behavior of the sample. This work highlights the importance of green synthesis methodologies in electrochemistry applications. In summary, the main advantages of this work are the principles of green chemistry followed by an eco-friendly approach, sustainable resource utilization, cost-effectiveness, and enhanced catalytic properties.

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Herein, an electrochemical sensor based on antimony oxide/graphitic carbon nitride nanocomposite (Sb₂O₃/GCN) was applied for bisphenol A (BPA) electroanalysis in a water sample. This composite and its components were characterized with X-ray diffraction (XRD) spectroscopy, UV–visible spectroscopy, Raman spectroscopy, Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX). Electrochemical characterization of a pencil graphite electrode (PGE) modified with Sb₂O₃/GCN, Sb₂O₃ nanoparticles (Sb₂O₃ NPs) and graphitic carbon nitride (GCN) show that the Sb₂O₃/GCN modified pencil graphite electrode (PGE/Sb₂O₃/GCN) has the highest electroactive surface area and electronic conductivity. Theoretical calculation of the adsorption energies of BPA/GCN complex and its variants revealed that hydrogen bonding and π- π interaction between GCN and BPA contributed to the electrocatalytic oxidation of BPA at the proposed sensor. The limit of detection of BPA at PGE/Sb₂O₃/GCN was estimated to be 5.61 μM. The calibration curve depicting the changes in peak current with BPA concentration showed two linear ranges at 8–60 μM and 60–140 μM. Also, the proposed sensor offered a percentage recovery of 102.43% for BPA in spiked bottled water. These figures of merit as well as the outstanding selectivity, remarkable repeatability and good reproducibility of the proposed sensor are indications that PGE/Sb₂O₃/GCN is a useful analytical tool for BPA electroanalysis in water samples.

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Development of active electrocatalyst for CO₂ reduction to useful chemicals would be essential factor to achieve the carbon neutral society. The Co poly-4-vinyl-pyridine (P4VPy)/Ketjenblack (KB) activated thermally was found for an active electrocatalyst in the electroreduction of CO₂ with water by the solid-polymer-electrolyte, SPE, electrolysis cell. Various carbon supports were applied instead of KB. Contents of CoN₄C_x, CoO and Co⁰ compounds on activated electrocatalysts were determined by linear combination fitting, LCF, of X-ray absorption near edge structure, XANES. Pyrolysis of the catalyst precursor for activation was essential and kinds of carbon supports strongly influenced formation of the Co compounds. It was revealed that the content of CoN₄C_x related to the current efficiency of the CO formation and that of CoO and Co⁰ related the H₂ formation.

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Relation between Faraday efficiency to CO and content of CoN₄C_x