Electrocatalytic Oxidation of Glucose at Nickel Phosphate Nano/Micro Particles Modified Electrode

Abd El-Lateef H, Dao VD, Mohamed IMA. Electrocatalysis of Methanol Oxidation in Alkaline Electrolytes over Novel Amorphous Fe/Ni Biphosphate Material Prepared by Different Techniques

In this work, novel phosphate materials based on bimetallic character (Fe and Ni) were introduced by different chemical fabrication methods, the reflux method (FeNiP-R) and the sol-gel technique (FeNiP-S), and evaluated as non-precious electrodes for methanol electrooxidation in KOH electrolytes. The designed FeNiP-R and FeNiP-S samples were investigated using different characterization techniques, namely TEM, SEM, XPS, BET, DLS, and FT-IR, to describe the impact of the fabrication technique on the chemistry, morphology, and surface area. The characterization techniques indicate the successful fabrication of nanoscale-sized particles with higher agglomeration by the sol-gel technique compared with the reflux strategy. After that, the electrochemical efficiency of the fabricated FeNiP-R and FeNiP-S as electrodes for electrocatalytic methanol oxidation was studied through cyclic voltammetry (CV) at different methanol concentrations and scan rates in addition to impedance analysis and chronoamperometric techniques. From electrochemical analyses, a sharp improvement in the obtained current values was observed in both electrodes, FeNiP-R and FeNiP-S. During the MeOH electrooxidation over FeNiP-S, the current value was improved from 0.14 mA/cm² at 0.402 V to 2.67 mA/cm² at 0.619 V, which is around 109 times the current density value (0.0243 mA/cm² at 0.62 V) found in the absence of MeOH. The designed FeNiP-R electrode showed an improved electrocatalytic character compared with FeNiP-S at different methanol concentrations up to 80 mmol/L. The enhancement of the anodic current density and charge transfer resistance indicates the methanol electrooxidation over the designed bimetallic Fe/Ni-phosphates.

Structural and Adsorptive Characteristics of 2D Multilayer Nanoflakes of NiCo Phosphates for Chromium(VI) Removal: Experimental and Monte Carlo Simulations

Metal phosphates are efficient adsorbent materials for heavy elements present in industrial effluents because of their promising properties. Hexachromium ions are among the most dangerous contaminants owing to their harmful properties and non-degradability. Accordingly, the present work offers a simplified study of the preparation of bimetallic phosphate materials from nickel cobalt phosphate (NiCo-Ph) based on the sol-gel method in an equimolar ratio. Characterization of the bulk, crystal phase, texture profile, and nanosize of NiCo-Ph was carried out using various techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption isotherm measurements, field emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. In this regard, the adsorption performance of NiCo-Ph was exemplified through six batch experiments, elucidating the impacts of the sorbent dose, initial concentration of pollutants, sorption time, temperature, pH, and shaking rate. According to UV/vis spectrophotometry measurements and their related calculations of NiCo-Ph, the maximum removal efficiency (RE %) of 92% and adsorption capacity (q _m) of 37 mg/g were achieved at pH = 6, a dose of 5.0 g/L, 100 mg/L of [Cr(VI)], 300 rpm, adsorption time of 60 min, and 298 K. Monte Carlo simulations were also carried out to correlate the experimental data with theoretical calculations that provided a higher negative value (-911.62 kcal mol^-1) for the adsorption energy of Cr(VI) in acidic medium. The adsorbent NiCo-Ph prepared by this direct method is therefore recommended for the quantification of Cr(VI) under slightly acidic solutions and at room temperature, which can maintain its efficiency even up to six cycles.

Bimetallic nickel/manganese phosphate–carbon nanofiber electrocatalyst for the oxidation of formaldehyde in alkaline medium

The development of earth-abundant transition metal-based catalysts, supported by a conductive carbonaceous matrix, has received great attention in the field of conversion of formaldehyde derivatives into toxic-free species. Herein, we report a comprehensive investigation of bimetallic electrocatalyst activity towards the electrooxidation of formaldehyde. The bimetallic phosphate catalyst is prepared by co-precipitation of Ni and Mn phosphate precursors using a simple reflux approach. Then the bimetallic catalyst is produced by mixing the Ni/Mn with carbon fibres (CNFs). The structural properties and crystallinity of the catalyst were investigated by using several techniques, such as scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Brunauer Emmett−Teller theory. The system performance was studied under potentiostatic conditions. Some theoretical thermodynamic and kinetic models were applied to assess the system performance. Accordingly, key electrochemical parameters, including surface coverage (Γ) of active species, charge transfer rate (k_s), diffusion coefficient of the formaldehyde (D), and catalytic rate constant (k_cat) were calculated at Γ = 1.690 × 10⁻⁴ mmol cm⁻², k_s = 1.0800 s⁻¹, D = 1.185 × 10⁻³ cm² s⁻¹ and k_cat = 1.08 × 10⁵ cm³ mol⁻¹ s⁻¹. These findings demonstrate the intrinsic electrocatalytic activity of formaldehyde electrooxidation on nickel/manganese phosphate- CNFs in alkaline medium.

The catalytic performance of bimetallic Ni/Mn phosphate–carbon nanofiber composite catalyst is better than mono metallic catalysts toward electrooxidation of formaldehyde.

Electrochemical degradation of oxytetracycline by Ti-Sn-Sb/γ-Al2O3 three-dimensional electrodes

In this work, Ti-Sn-Sb/γ-Al₂O₃ particle electrodes were prepared and employed for the degradation of oxytetracycline (OTC) by three-dimensional electrocatalytic technology. Factors associated with the preparation of Ti-Sn-Sb/γ-Al₂O₃ particle electrodes were investigated. The effects of initial concentration, conductivity, pH value, aeration intensity, current density, plate spacing, and particle electrode dosage on OTC removal were studied. The removal rate of OTC and total organic carbon were achieved approximately 92.0% and 41.0% under the optimal operating condition, respectively. In addition, Ti-Sn-Sb/γ-Al₂O₃ particle electrode was analyzed by Fourier Transform Infrared spectroscopy (FT-IR), scanning electron microscope (SEM), energy dispersive spectrum analysis (EDX), X-Ray Fluorescence Spectrometer (XRF), and X Ray Diffraction analysis (XRD), which indicated that a significant amount of TiO₂, SnO₂, and Sb₂O₃ were formed on the surface of Ti-Sn-Sb/γ-Al₂O₃ particle electrode. It was also observed that the primary function of Ti-Sn-Sb/γ-Al₂O₃ particle electrode in the three-dimensional electrode electrolysis process is the strong oxidizing function of ·OH for degrading OTC. Consequently, the analysis of degradation products of oxytetracycline (OTC) demonstrates. In addition, the results and conclusions of this study provide a methodological basis and engineering practice basis for removing the low concentration of antibiotics in water.

Electrocatalytic oxidation of tetracycline by Bi-Sn-Sb/γ-Al2O3 three-dimensional particle electrode

In this work, highly efficient Bi-Sn-Sb/γ-Al₂O₃ particle electrodes were prepared for effectively degrading tetracycline. The effects of a mass ratio (Sn: Sb), the mass ration of Bi:(Sn + Sb), impregnation times, calcination temperature, and calcination time on the electrocatalytic oxidation capacity of Bi-Sn-Sb/γ-Al₂O₃ particle electrode was investigated. Conditions in which mass ratio of (Sn: Sb) = 10:1, the mass ratio of Bi:(Sn/Sb) = 1:1, impregnation times 2 h, calcination temperature 500 °C., and calcination time 3 h were considered as optimal preparation conditions for Bi-Sn-Sb/γ-Al₂O₃ particle electrode. It was cherecterized by infrared spectroscopy (IR), scanning electron microscope (SEM), energy dispersive X-ray detector (EDX), X-Ray Diffraction (XRD), and X-ray fluorescence (XRF) techniques to conforming that the triclinic Bi₂O₃ formed in the preparation conditions has superior electrocatalytic activity. The electrocatalytic oxidation mechanism of tetracycline by Bi-Sn-Sb/γ-Al₂O₃ particle electrode is proposed by determining degradation intermediates through LC-MS detection. Electrocatalytic oxidation experiments by adding tert-butyl alcohol indicate that the formation of OH is the primary responsibility for degradating tetracycline. Electrocatalytic degradation of tetracycline at different initial concentration shows that the degradation of tetracycline meets the pseudo first-order kinetics. Results suggest that the three-dimensional electrochemical reactor with Bi-Sn-Sb/γ-Al₂O₃ particle electrodes could be an alternative for the pretreatment of antibiotic wastewater before biological treatment.

Direct Electrochemical Detection of Glutamate, Acetylcholine, Choline, and Adenosine Using Non-Enzymatic Electrodes

Non-electroactive neurotransmitters such as glutamate, acetylcholine, choline, and adenosine play a critical role in proper activity of living organisms, particularly in the nervous system. While enzyme-based sensing of this type of neurotransmitter has been a research interest for years, non-enzymatic approaches are gaining more attention because of their stability and low cost. Accordingly, this focused review aims to give a summary of the state of the art of non-enzymatic electrochemical sensors used for detection of neurotransmitter that lack an electrochemically active component. In place of using enzymes, transition metal materials such as those based on nickel show an acceptable level of catalytic activity for neurotransmitter sensing. They benefit from fast electron transport properties and high surface energy and their catalytic activity can be much improved if their surface is modified with nanomaterials such as carbon nanotubes and platinum nanoparticles. However, a general comparison reveals that the performance of non-enzymatic biosensors is still lower than those that use enzyme-based methods. Nevertheless, their excellent stability demonstrates that non-enzymatic neurotransmitter sensors warrant additional research in order to advance them toward becoming an acceptable replacement for the more expensive enzyme-based sensors.

Nanostructured Nickel on Porous Carbon-Silica Matrix as an Efficient Electrocatalytic Material for a Non-Enzymatic Glucose Sensor

Nanostructured nickel on porous carbon-silica matrix (N-CS) has been synthesized using a sol gel process and subsequent pyrolysis treatment at a temperature of 650 °C. The morphology and microstructure of the N-CS sample has been investigated using XRD (X-ray Diffraction), SEM-EDS (Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy), and BET (Brunauer-Emmett-Teller) analysis. The synthesized nanocomposite has been used for developing NCS-modified screen-printed electrodes (NCS-SPCEs) and was applied in the electrochemical monitoring of glucose. After electrochemical activation, via cycling the modified electrode in a potential window from 0 to 0.8 V in 0.1 M KOH solution, the fabricated NCS-SPCEs electrodes were evaluated for the voltammetric and amperometric determination of glucose. The developed sensors showed good sensing performance towards glucose, displaying a sensitivity of 585 µA/mM cm−1 in the linear range from 0.05 to 1.5 mM, a detection limit lower than 30 µM with excellent selectivity.

Facile Synthesis of Ultrathin Nickel-Cobalt Phosphate 2D Nanosheets with Enhanced Electrocatalytic Activity for Glucose Oxidation

Two-dimensional (2D) ultrathin nickel-cobalt phosphate nanosheets were synthesized using a simple one-step hydrothermal method. The morphology and structure of nanomaterials synthesized under different Ni/Co ratios were investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Moreover, the influence of nanomaterials' structure on the electrochemical performance for glucose oxidation was investigated. It is found that the thinnest nickel-cobalt phosphate nanosheets synthesized with a Ni/Co ratio of 2:5 showed the best electrocatalytic activity for glucose oxidation. Also, the ultrathin nickel-cobalt phosphate nanosheet was used as an electrode material to construct a nonenzymatic electrochemical glucose sensor. The sensor showed a wide linear range (2-4470 μM) and a low detection limit (0.4 μM) with a high sensitivity of 302.99 μA·mM^-1·cm^-2. Furthermore, the application of the as-prepared sensor in detection of glucose in human serum was successfully demonstrated. These superior performances prove that ultrathin 2D nickel-cobalt phosphate nanosheets are promising materials in the field of electrochemical sensing.