Nickel/mesoporous silica (SBA-15) modified electrode: An effective porous material for electrooxidation of methanol

Detection of paracetamol by a montmorillonite-modified carbon paste sensor: A study combining MC simulation, DFT computation and electrochemical investigations

This study aims to develop a suitable electrochemical electrode through the incorporation of potassium montmorillonite (MMTK10)clay into the carbon matrix for the direct and sensitive determination of paracetamol (PAR) in pharmaceutical formulations. Electrochemical characterization of the electrodes involves the use of techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The results reveal that the voltammetric response of PAR is linear over a wide concentration range (1.0-15 μM), with a low detection limit of 0.46 μM. Analytically, PAR recovery results were around 94%, indicating that the developed electrode is highly suitable for PAR detection in pharmaceutical formulation. Additionally, density functional theory (DFT) is employed to investigate the reactivity of PAR and explain the interaction process of PAR on the electrode surface at different pH values. A Monte Carlo simulations model is developed to provide a deeper understanding of the adsorption mechanism, particularly to comprehend molecular interactions and preferential orientations of PAR with MMT fractions at the electrode surface. Reduced Density Gradient is calculated and discussed using techniques such as Multiwfn and Visualization of Molecular Dynamics. The developed CPE-MMTK10 sensor provided a simple preparation method, rapid response, high sensitivity, reproducibility, strong selectivity, and extended stability. Moreover, there is a good correlation between most parameters calculated by DFT and experimental results, thereby reinforcing the validity of the theoretical approach in this study.

Structure-activity relationship and cytotoxicity of the new thiosemicarbazide derivatives and their Cu(II) complexes against prostate and melanoma cancer cells

In this study, eighteen new ligands (B1-B18) containing a thiosemicarbazide core were synthesized and characterized in terms of physicochemical properties, molecular docking and in vitro biological activity. The structures of eleven ligands were investigated using X-Ray diffraction and Hirschfeld Surface analysis. To study the structure-activity relationship, the organic ligands contained pyridin-2-ylmethyl, pyridin-3-ylmethyl or pyridin-4-ylmethyl moieties and various substituents. Their pharmakokinetic profiles and molecular docking results suggest high potential as new drug candidates. The complexing ability of the selected organic ligands was also evaluated, yielding five new Cu(II) complexes (Cu(B1)Cl2, Cu(B4)Cl2, Cu(B10)Cl2, Cu(B17)Cl2, Cu(B18)Cl2). The obtained results suggest the formation of the polymeric structures. All organic ligands and Cu(II) complexes were tested for anticancer activity against prostate and melanoma cancer cells (PC-3, DU-145, LNCaP, A375, G-361, SK-MEL-28) and normal fibroblasts (BJ), as well as antimicrobial activity against six selected bateria strains. Among B1-B18 compounds, B3, B5, B9, B10, B12 and B14 exhibited cytotoxic activity. The studied Cu(II) complexes were in general more active, with Cu(B1)Cl2 exhibiting antincancer activity agains all three prostate cancer cells and Cu(B10)Cl2 reaching the IC50 value equal to 88 μM against G-361 melanoma cells. Several compounds also exhibited antimicrobial activity against gram-positive and gram-negative bacteria. It was found that the type of specific substituents, especially the presence of -chloro and -dichloro substituents had a greated impact on the cytotoxicity than the position of the nitrogen atom in the pyridylacetyl moiety.

Electro-Oxidation Reaction of Methanol over La2-xSrxNi1-y(Mn/Fe/Co)yO4+δ Ruddlesden-Popper Oxides

Solution combustion-synthesized Ruddlesden-Popper oxides La1.4Sr0.6Ni0.9(Mn/Fe/Co)0.1O4+δ were explored for the methanol electro-oxidation reaction. With optimal doping of Sr2+ in the A site and Co2+ in the B site, Ni3+ with t2g6 d x 2 - y 2 1 configuration in La1.4Sr0.6Ni0.9Co0.1O4+δ exhibited a tetragonal distortion with compression in axial bonds and elongation in equatorial bonds. This structural modification fostered an augmented overlap of d z 2 orbitals with axial O 2p orbitals, leading to a heightened density of states at the Fermi level. Consequently, this facilitated not only elevated electrical conductivity but also a noteworthy reduction in the charge transfer resistance. These effects collectively contributed to the exceptional methanol oxidation activity of La1.4Sr0.6Ni0.9Co0.1O4+δ, as evidenced by an impressive current density of 21.4 mA cm-2 and retention of 95% of initial current density even after 10 h of prolonged reaction. The presence of Ni3+ further played a pivotal role in the creation of NiOOH, a crucial intermediate species, facilitated by the presence of surface oxygen vacancies. These factors synergistically enabled efficient methanol oxidation. In summary, our present study not only yields substantial insights but also paves the way for a novel avenue to fine-tune the activity of Ruddlesden-Popper oxides for the successful electro-oxidation of methanol.

Electro-oxidation Reaction of Methanol over Reducible Ce1-x-yNixSryO2-δ: A Mechanistic Probe of Participation of Lattice Oxygen

Methanol oxidation reaction crucially depends on the formation of -OOH species over the catalyst's surface. Ni-based catalysts are by far the choice of materials, where the redox couple of Ni²⁺/Ni³⁺ facilitates the formation of -OOH species by surface reconstructions. However, it is challenging to oxidize Ni²⁺ as it generates charge-transfer orbitals near the Fermi energy level. One possible solution is to substitute Ni²⁺ with a reducible oxide support, which will not only facilitate the Ni²⁺ → Ni³⁺ oxidation but also adsorb oxygenated species like -OOH at a lower potential owing to its oxophilicity. This work shows with the help of structural and surface studies that the reducible CeO₂ support in Ni and Sr co-doped Ce_1-x-yNi_xSr_yO_2-δ solid solution can easily facilitate Ni²⁺ → Ni³⁺ oxidation as well as evolution of lattice oxygen during the methanol oxidation reaction. While the Ni³⁺ species helped in formation of -OOH surface intermediates, the evolved lattice oxygen eased the CO oxidation process in order to bring out the better CO-tolerant methanol oxidation activity over Ce_1-x-yNi_xSr_yO_2-δ. The study shows the unique importance of the electronic interactions between the active site and support and involvement of lattice oxygen in the methanol oxidation reaction.

Electrochemical and Catalytic Properties of Carbon Dioxide-Activated Graphite Felt

The commercial graphite felt GFA 10 was subjected to an activation process with the use of CO₂ at 900 °C for 35 and 70 min. Pristine and heat-treated materials were characterized using various methods: low-temperature N₂ adsorption, SEM, and EDS. Voltammetric measurements of GFA samples (before and after activation) as the working electrode were carried out. Voltammograms were recorded in aqueous solutions of 4-chlorophenol and sodium sulfate as supporting electrolyte. The catalytic activity of GFA samples in the process of 4-chlorophenol oxidation with the use of H₂O₂ was also investigated. The influence of graphite felt thermal activation in the CO₂ atmosphere on its electrochemical and catalytic behavior was analyzed and discussed. Results of the investigation indicate that GFA activated in CO₂ can be applied as an electrode material or catalytic material in the removal of organic compounds from industrial wastewater. However, the corrosion resistance of GFA, which is decreasing during the activation, needs to be refined.

Ultrasonically Surface-Activated Nickel Foam as a Highly Efficient Monolith Electrode for the Catalytic Oxidation of Methanol to Formate

Most of the current electrocatalysts for the methanol oxidation reaction are precious group metals such as Pt, Pd, and Ru. However, their use is limited due to their high cost, scarcity, and issues with carbon monoxide poisoning. We developed a simple method to prepare a nickel foam (NF)-based monolith electrode with a NiO nanosheet array structure as an efficient electrocatalyst toward the oxidation of methanol to produce formate. By a simple ultrasonic acid treatment and air oxidation at room temperature, an inert NF was converted to NiO/NF as a catalytically active electrode due to the uniform NiO nanosheet array that was rapidly formed on the surface of NiO/NF. In alkaline electrolytes containing methanol, the as-prepared NiO/NF catalysts exhibited a lower methanol oxidation reaction (MOR) potential of +1.53 V vs RHE at 100 mA cm^-2 compared to that of inert NF samples. The difference in potentials between the E_MOR and the E_OER at that current density was found to be 280 mV, indicating that methanol oxidation occurred at lower potentials as compared to the oxygen evolution reaction (OER). We also observed that the NiO/NF could also efficiently catalyze the oxidation of CO without being poisoned by it. NiO/NF retained close to 100% of its initial activity after 20,000 s of methanol oxidation tests at high current densities above 200 mA cm^-2. Because of the simple synthesis method and the enhanced catalytic performance and stability of NiO/NF, this allows methanol to be used as an OER masking agent for the energy-efficient generation of value-added products such as formic acid and hydrogen.

Evaluating the Effect of WO3 on Electrochemical and Corrosion Properties of TiO2-RuO2-Coated Titanium Anodes with Low Content of RuO2

The electrochemical and corrosion characterization of Ti0.97Ru0.03O2/Ti electrodes modified with WO3 was reported. Modification of Ti0.97Ru0.03O2/Ti electrodes with WO3 was previously described as improving the effectiveness of an azo dye degradation in a photoelectrochemical treatment. Thus, the effect of WO3 introduction to oxide film on electrode surface on electrochemical behaviour and stability of the modified electrodes was investigated. Moreover, corrosion behaviour of Ti0.97Ru0.03O2/Ti electrodes modified with WO3 was evaluated with the application of potentiodynamic polarization sweep method and open circuit potential measurement. Electrodes modified with WO3 revealed higher anodic and cathodic peak currents in K4[Fe(CN)6] solution (by 35% for 6%WO3 content) indicating higher electroactive surface area and faster electron transfer reaction. An increase in WO3 amount in the oxide layer caused an increase in the number of active sites determined in Na2SO4 and most of them (more than 80%) were located in the outer and more accessible surface. The investigation of the tested electrodes at high potentials at which oxygen evolution is observed, allowed their classification in the following order showing an increase in their activity towards oxygen evolution reaction: Ti0.97Ru0.03O2/Ti < Ti0.94Ru0.03O2-W0.03O3/Ti < Ti0.91Ru0.03O2-W0.06O3/Ti. Although the electrode modification with WO3 resulted in lower resistance to corrosion in Na2SO4 solution regarding corrosion potential, corrosion current densities were clearly lower in comparison with the non-modified electrode, especially after longer immersion in the solution. ASTs showed that even a small addition of WO3 increased the lifetime of the electrodes. The Ti0.97Ru0.03O2/Ti electrode modification with WO3 seemed to be advantageous for their application in electrochemical and photoelectrochemical degradation of organic pollutants.

NiSn nanoparticle-incorporated carbon nanofibers as efficient electrocatalysts for urea oxidation and working anodes in direct urea fuel cells

Synthesis of NiSn alloy nanoparticle-incorporated carbon nanofibers was performed by calcining electrospun mats composed of nickel acetate, tin chloride and poly(vinyl alcohol) under vacuum. The electrochemical measurements indicated that utilization of tin as a co-catalyst could strongly enhance the electrocatalytic activity if its content and calcination temperature were optimized. Typically, the nanofibers prepared from calcination of an electrospun solution containing 15 wt% SnCl2 at 700 °C have a current density almost 9-fold higher than that of pristine nickel-incorporated carbon nanofibers (77 and 9 mA/cm2, respectively) at 30 °C in a 1.0 M urea solution. Furthermore, the current density increases to 175 mA/cm2 at 55 °C for the urea oxidation reaction. Interestingly, the nanofibers prepared from a solution with 10 wt% of co-catalyst precursor show an onset potential of 175 mV (vs. Ag/AgCl) at 55 °C, making this proposed composite an adequate anode material for direct urea fuel cells. Optimization of the co-catalyst content to maximize the generated current density resulted in a Gaussian function peak at 15 wt%. However, studying the influence of the calcination temperature indicated that 850 °C was the optimum temperature because synthesizing the proposed nanofibers at 1000 °C led to a decrease in the graphite content, which dramatically decreased the catalyst activity. Overall, the study opens a new venue for the researchers to exploit tin as effective co-catalyst to enhance the electrocatalytic performance of the nickel-based nanostructures. Moreover, the proposed co-catalyst can be utilized with other functional electrocatalysts to improve their activity toward oxidation of different fuels.

High-efficiency purification of sulforaphane from the broccoli extract by nanostructured SBA-15 silica using solid-phase extraction method

Sulforaphane, a promising phytochemical, has received much attention in recent decades as a potential anticarcinogenic compound. In this research work, a novel, specific and affordable method has been developed for the separation and purification of natural sulforaphane from broccoli extract using SBA-15 mesoporous silica. SBA-15 was found to be the most efficient in the purification of sulforaphane compared to some of the conventionally used adsorbents and zeolites. The nanoparticles of SBA-15 mesoporous silica were synthesized using the hydrothermal method from natural amorphous silica extracted from rice husk ash with a silica purity of 96%. Structural and morphological analysis of the synthesized SBA-15 mesoporous silica were performed by the XRD, FT-IR, FE-SEM, and BET techniques. The method includes the primary immiscible solvent extraction of autolyzed broccoli sample with dichloromethane, followed by purification of the extract by SBA-15 mesoporous silica using solid-phase extraction (SPE) method. The recovery of the purified sulforaphane from broccoli extract was >98% using SBA-15 mesoporous silica, which is higher compared to that obtained using current purification methods. The highest purity of sulforaphane product was measured 94% based on the results of analytical HPLC chromatograms. Moreover, the effects of different parameters on the sulforaphane purification by using SBA-15 were studied and optimized.

Voltammetric detection of trifluralin in tap water, fruit juice, and vegetable extracts in the presence of surfactants

This study describes a novel electrochemical method to determine the herbicide trifluralin in samples of water, fruit juice, and vegetable extracts in the presence of surfactants, using a glassy carbon electrode (GCE). In acidic media, trifluralin was irreversible on the glassy carbon electrode surface at -0.5 V vs. Ag/AgCl. Surfactant presence on the electrode-solution interface modified current intensities and shifted the reduction peak potential of trifluralin. Different types of surfactant and their concentrations were investigated. The anionic surfactant significantly enhanced the peak current intensity of trifluralin. Under optimal analytical conditions, an analytical curve was obtained in the concentration range of 0.48-32.20 µM. The limits of detection and quantification were estimated at 0.031 and 0.104 µM, respectively. The method was successfully applied to quantify trifluralin in samples of water, orange and tomato juice, and green pepper, carrot, and onion extracts, with recovery rates of 97.9-102.1%. The results were in good agreement with those obtained using high-performance liquid chromatography, indicating that the proposed electrochemical method can be employed to quantify trifluralin in various types foods, with sensitivity, specificity, selectivity and reproducibility.

A Pd nanocatalyst supported on multifaceted mesoporous silica with enhanced activity and stability for glycerol electrooxidation

The current density of glycerol electrooxidation on Pd/SiO₂reached twice the values found for Pd/C. Mesosporous silica support works as a trap that confines the reactant.

Microwave-assisted synthesis of NaA nanozeolite from slag and performance of Ag-doped nanozeolite as an efficient material for determination of hydrogen peroxide

A new amperometric sensor is prepared based on a Ag doped NaA nanozeolite modified carbon paste electrode (Ag/ACPE) in order to detect hydrogen peroxide (H₂O₂) in phosphate buffer solution (PBS, pH 7.0).

In situ growth of nickel selenide nanowire arrays on nickel foil for methanol electro-oxidation in alkaline media

NiSe nanowire arrays solvothermally grown on nickel foil behave as an efficient 3D anode for electro-catalytic oxidation of methanol in alkaline media with strong durability.