Tafel Plots Research Articles

Simulation of aluminium electrodeposition on complex geometry: Influence of input parameters and electrodeposition conditions

It is necessary to improve the current efficiency and thickness distribution of the electrodeposition of Al coatings on a Mg alloy from ionic liquids. To accomplish this, finite element method is presented here to help experimental processes to refine various electrodeposition conditions for improving efficiency and economy. However, the simulation of Al deposition from ionic liquids is hindered by the lack of initial parameters in existing works. In this paper, the initial kinetic parameters used in the model were obtained precisely using Tafel plots and cyclic voltammograms. The cathodic and anodic transfer coefficients were calculated to be 0.136 and 0.864 at 318.15 K. The exchange current density for Al2Cl7−/AlCl4− redox process was calculated as 4.6A/m2 at 318.15 K. Subsequently, the multiphysics model in this work combined secondary current distribution, laminar flow, and transport of diluted species. The results of the Al coating thicknesses from finite element method agree well with the experimental method. Hence, the finite element model can precisely predict the Al coating thickness, which provides a positive outlook to analyze the thickness of Al coating and promotes its utilization in industry.

A New Supramolecular Tetraruthenated Cobalt (II) Porphyrazine Displaying Outstanding Electrocatalytical Performance in Oxygen Evolution Reaction.

A new supramolecular electrocatalyst for Oxygen Evolution Reaction (OER) was synthesized from a central multibridging cobalt tetrapyridylporphyrazine (CoTPyPz) species by attaching four [Ru(bpy)2Cl]+ groups. Both CoTPyPz and the tetraruthenated cobalt porphyrazine species, TRuCoTPyPz, form very homogenous molecular films just by dropcasting their methanol solutions onto GCE electrodes. Such films exhibited low overpotentials for O2 evolution, e.g., 560 e 340 mV, respectively, displaying high stability, typically exceeding 15 h. The kinetic parameters obtained from the Tafel plots showed that the peripheral complexes are very important for the electrocatalytic activity. Hyperspectral Raman images taken along the electrochemical process demonstrated that the cobalt center is the primary active catalyst site, but its performance is enhanced by the ruthenium complexes, which act as electron-donating groups, in the supramolecular system.

Synthesis and Corrosion Inhibition Studies of (E)-3-(2-(4‑chloro-2-nitrophenyl)diazenyl)-1-nitrosonaphthalen-2-ol on Mild Steel dissolution in 0.5 M HCl Solution- Experimental, DFT and Monte Carlo Simulations

Corrosion process and means of eradicating it continue to gain attention amongst researchers. The use of organic corrosion inhibitors became popular owing to their macroscopic physico-chemical properties. In this study, (E)-3-(2-(4‑chloro-2-nitrophenyl)diazenyl)-1-nitrosonaphthalen-2-ol (CNN) was synthesized and characterized via FTIR, UV–Vis and NMR (1H and 13C) spectroscopy. Its corrosion inhibition efficiency measurements against mild steel corrosion were carried out in acidic condition by gravimetric and electrochemical methods. Quantum mechanical calculations and Monte Carlo (MC) simulation were used to corroborate experimental findings. Kinetic, adsorption and thermodynamics studies revealed CNN as having promising inhibitory action against 0.5 M HCl solution used especially at high dosage. The adsorption mechanism of CNN was found to be complex adsorption mechanism via the most fitted isotherm, Langmuir isotherm. The Tafel plot showed that CNN is a mixed-type inhibitor. Both weight loss measurements and electrochemical studies confirmed that the inhibition efficiency increased with increased concentration of CNN. The SEM/EDS results revealed that the mild steel was protected by the inhibitors. Theoretical results obtained are well in agreement with the experimental results. The MC simulation showed spontaneous adsorption of CNN on Fe(110) surface in hydrochloric acid medium.

Effects of Ce, Sm and Yb on cavitation erosion of NAB alloy in 3.5% NaCl solution

The influences of Ce, Sm and Yb on cavitation erosion of NAB alloy in 3.5% NaCl solution are evaluated using mass loss, SEM, 3D morphology and Tafel plot, respectively. The results show that the addition of Ce or Sm or Yb enhances the mechanical property of NAB alloy, and the sizes of κⅠ and κⅡ phases within NAB alloy decrease with adding Ce or Sm or Yb, resulting in the prevention of the propagation of the cracks caused by cavitation erosion initially originated at the phase boundaries between α and κ phases, and finally the cavitation erosion damage significantly decreases with adding Ce or Sm or Yb. The corrosion of NAB alloy in 3.5% NaCl solution can promote the cavitation erosion of NAB alloy, while the corrosion resistance of NAB alloy increases with the addition of Ce or Sm or Yb, and then the cavitation erosion resistance is accordingly improved with the addition of rare earth element.

Study of synergistic effects and compositional dependence of hydrogen evolution reaction on MoxNiy alloy thin films in alkaline media

In this paper hydrogen evolution reaction (HER) on the molybdenum-nickel thin films has been studied. The MoxNiy thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A change in the crystal structure of the samples prepared at different temperatures was observed. The structure of the samples prepared at 25 °C are bcc or amorphous. The structure of alloys sputtered at 800 °C changed to fcc. Tafel plots were constructed for each MoxNiy alloy sample. The mechanism of HER was determined from Tafel slope analysis. Values of charge transfer resistance were also determined by impedance spectroscopy. The compositional dependence of activity and the stability of MoxNiy thin films in 1 M NaOH were determined by cycling and chronoamperometry. Our results demonstrate that MoxNiy thin films prepared at 800 °C show significantly improved activity compared to pure Mo and Ni metals. On the other hand, MoxNiy thin films sputtered at 25 °C do not show increased activity in comparison to pure Ni metal. This points to a synergistic effect between fcc Mo and fcc Ni in thin films sputtered at elevated temperatures. Mo63Ni67 thin films alloy prepared at 800 °C shows the best values of catalytic activity for HER from all investigated compositions.

Corrosion Resistance of 3D Printed Ti6Al4V Gyroid Lattices with Varying Porosity.

Corrosion of medical implants is a possible failure mode via induced local inflammatory effects, systemic deposition and corrosion related mechanical failure. Cyclic potentiodynamic polarisation (CPP) testing was utilized to evaluate the effect of increased porosity (60% and 80%) and decreased wall thickness in gyroid lattice structures on the electrochemical behaviour of LPBF Ti6Al4V structures. The use of CPP allowed for the landmarks of breakdown potential, resting potential and vertex potential to be analysed, as well as facilitating the construction of Tafel plots and qualitative Goldberg analysis. The results indicated that 60% gyroid samples were most susceptible to the onset of pitting corrosion when compared to 80% gyroid and solid samples. This was shown through decreased breakdown and vertex potentials and were found to correlate to increased lattice surface area to void volume ratio. Tafel plots indicated that despite the earlier onset of pitting corrosion, both gyroid test groups displayed lower rates of corrosion per year, indicating a lower severity of corrosion. This study highlighted inherent tradeoffs between lattice optimisation and corrosion behaviour with a potential parabolic link between void volume, surface area and corrosion being identified. This potential link is supported by 60% gyroid samples having the lowest breakdown potentials, but investigation into other porosity ranges is suggested to support the hypothesis. All 3D printed materials studied here showed breakdown potentials higher than ASTM F2129′s suggestion of 800 mV for evaluation within the physiological environment, indicating that under static conditions pitting and crevice corrosion should not initiate within the body.

(Digital Presentation) Synergistic Effect of Cobalt and Nitrogen on the Spent Coffee Grounds Derived Carbon As an Efficient Catalyst for Alkaline Hydrogen Evolution

Due to global electricity demand and ecological issues, eco-friendly and sustainable energy resource is becoming a hot topic in energy production and future economic development. On this point, efficient catalytic materials for electrochemical hydrogen evolution reaction (HER) are crucial in the research area. HER in alkaline medium has several advantages, including its lower vapor pressure, which helps produce pure hydrogen gas and provides better stability than acidic medium to metal contents by reducing catalyst’s corrosion. Primarily, carbon-based electrocatalytic materials such as hetero-atomic-doped carbon, transition metal-doped carbon, and co-doped carbon show off an effective HER performance. Because it has a large surface area, good chemical stability, it is inexpensive and earth-abundant.Additionally, spent coffee grounds (SCG) contain a high amount of carbohydrates, melanoidins, and lipids that are given a possibility to be suitable carbon precursors for carbon catalyst synthesis. Moreover, SCG is becoming an environmental issue that produces many tons of waste worldwide each year due to the proliferation of global coffee consumption.Here, we present cobalt nanoparticles embedded on nitrogen (N)-doped carbon catalyst, synthesized from SCG. Initially, SCG-derived nanoporous carbon was obtained by pyrolysis under high temperatures with KOH and urea. After that, carbon materials were functionalized with cobalt and nitrogen with the simple method.Cobalt-embedded N-doped carbon catalyst has a high surface area and highly distributed nano-sized pores. Polarization measurement, Tafel plot, electrochemical impedance spectroscopy, chronopotentiometry, and cyclovoltammetry have tested the electrochemical performance. Even though the catalyst contained a negligible amount of cobalt (0.56 at. %), HER catalytic activity in alkaline medium has better resulted than non-functionalized carbon catalysts and was comparable to higher activity benchmark electrocatalysts such as RuO2 and 20% Pt/C. Also, experimental results demonstrate that excellent long-term stability for the alkaline hydrogen evolution. So, synergistic effects of cobalt nanoparticles content and N-doping on the SCG-derived carbon were indicated for efficient catalyst in the alkaline hydrogen evolution application.

(Invited) Solar CO2 Conversion into Liquid Fuels By Photoelectrochemical Approaches

Photoelectrochemical (PEC) system for the reduction of CO2 into liquid fuels of formaldehyde/acetaldehyde, methanol and ethanol with trace amount of hydrogen gas bubbling have been described in the aspect of thermodynamics and kinetics of the CO2 reduction reaction to have efficient method by lowering activation energy of CO2 reduction on the electron transfer reaction and to do reduction potential tuning of CO2 reduction reaction for the selective reduction products. Ca/Fe doped TiO2 photoanode oxidizes water and generates the large amount of O2, electrons and protons. On the other side, rGO(reduced graphene oxide)/PVP(poly(4-vinyl)pyridine)/Nafion multi-layers have been coated and fabricated on the surface of Cu foil cathode to reduce CO2 into formaldehyde and acetaldehyde. When solar light was irradiated on the surface of photoanode, electrons get excited to the conduction band of Ca/Fe doped TiO2 and transported to the cathode via external wire with low external bias potential. rGO on Cu foil has been used for the dual functions of reduction potential tuning and multi-electron shuttling process of CO2 reduction reaction. The multi-electron shuttling function was illuminated by larger number and longer life-time of excited electrons and generating electron cloud, which have been confirmed by time-resolved photoluminescence (TR-PL) decay curves and 2D time-resolved photoluminescence (TR-PL) mapping images of Cu/rGO electrode. This allows the sequential multi-electron transport process from Cu/rGOcathode to CO2, which was studied with time-resolved chronoamperometry. N-heterocyclic poly(4-vinyl)pyridine (PVP) helps to capture and do chemical activation of reactant CO2 molecule by complexation as [PVP-CO2*] complex via charge separation and lowering transition state energy level of the electron transfer for the formation of anion radical of carbon dioxide complex with PVP as [e- + PVP-CO2*]≠ complex via electron delocalization, which is basically possible due to high basicity of lone pair electrons of nitrogen atoms of N-heterocyclic PVP compounds. These functions result in the lowered activation energy for the CO2 reduction reaction to have faster kinetics. The decreased amount of activation energy was determined with Tafel plots by measuring the slopes of it and semicircles of the electrochemical impedance spectroscopy (EIS) Nyquist plots at different temperatures. Nafion film coated on the surface of cathode assists the faster transport of H+ ions to CO2 reduction reaction sites for the simultaneous one-pot reaction of proton coupled electron transfer reactions. In the photocataytic system with semi-conducting polymers, CO2 was conversed into liquid solar fuels like formaldehyde and alcohols with solar to fuel efficiency over 2.5% to produce liquid fuel products over mM concentration for 4 hour reaction. Chang Woo Kim, So Jin Yeob, Hui-Ming Cheng, Young Soo Kang*, Selectively Exposed Crystal Facet-Engineered TiO2 Thin Film Photoanode for the Higher Performance of Photoelectrochemical Water Splitting Reaction, Energy and Environmental Sciences. 2015, 8, 3646.Amol U.Pawar, Chang WooKim, Myung Jong Kang, Young Soo Kang*, Crystal facet engineering of ZnO photoanode for the higher water splitting efficiency with proton transferable nafion film, Nano Energy 2015, 20, 156.Chang Woo Kim, Young Seok Son, Myung Jong Kang, Do Yoon Kim, Young Soo Kang*, (040)-Crystal Facet Engineering of BiVO4 Plate Photoanode for Solar Fuel Production, Energy Mater., 2016, 6, 1501754.Jin You Zheng, Amol Uttam Pawar, Chang Woo Kim, Yong Joo Kim, Young Soo Kang*, Highly enhancing photoelectrochemical performance of facilely-fabricated Bi-induced (002)-oriented WO3 film with intermittent short-time negative polarization, Applied Catalysis B 2018, 233, 88.Chang Woo Kim, Myung Jong Kang, Sohyun Ji, and Young Soo Kang*, Artificial Photosynthesis for Formaldehyde Production with 85% of Faradaic Efficiency by Tuning the Reduction Potential, ACS Catalysis 2018, 82, 968-974.Myung Jong Kang, Chang Woo Kim, Amol U. Pawar, Hyun Gil Cha, Sohyun Ji, Wen-Bin Cai, and Young Soo Kang*, Selective Alcohol on Dark Cathode by Photoelectrochemical CO2 Valorization and Their in-situ Characterization, minor revision, ACS Energy Lett. 2019, 4, 1549.Hong Ryeol Park, Amol Uttam Pawar, Umapada Pal, Tierui Zhang, Young Soo Kang, Enhanced solar photoreduction of CO2 to liquid fuel over rGO grafted NiO-CeO2 heterostructure nanocomposite, Nano Energy, 2021, 79, 105483.Amol U. Pawar, Umapada Pal, Jin You Zheng, Chang Woo Kim and Young Soo Kang*, Dynamics controlled CO2 reduction on Cu/rGO/PVP/Nafion multi-layered cathode for selective production of Acetaldehyde and Formaldehyde, Applied Catalysis B: Environmental, 2022, 303, 120921.

(Digital Presentation) OER Catalysts Supported on Layered Zirconium Phosphate Nanomaterials

Learning from nature, instead of using expensive catalysts such as platinum for splitting water, cheaper alternatives (such as cobalt, iron, or nickel) could be used for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Hydrogen solar fuel produced in artificial photosynthesis schemes for water splitting could be used in fuel cells. However, obtaining efficient catalysts based on earth-abundant materials is still difficult, particularly for the OER. Recent theory has shown that nanoscopic confinement of catalysts increases the stability and efficiency of catalysts for OER. We have designed and develop earth-abundant electrocatalysts for oxygen reduction and water splitting using nanostructured layered inorganic materials of zirconium phosphate (ZrP). We have demonstrated improved electrocatalytic activity of ZrP nanomaterials loaded with metal ions suitable for the OER of water splitting. Adsorbing Co or Ni catalysts on the ZrP nanoparticles surface proved to improved OER activity compared to intercalated catalysts. A comparison between adsorbed Co or Ni catalysts and those catalysts on exfoliated ZrP hexagonal nanoplatelets proved that those on exfoliated nanoplatelets were more active, with diminished overpotentials and reduced Tafel plot slopes as well as higher mass activities. More recently, comparison between Co and Ni catalyst on ZrP particles with different morphologies (hexagonal platelets, rods, cubes, and spheres) revealed that the more active Co catalysts are those on hexagonal ZrP platelets, whereas the best Ni catalysts are those on ZrP spheres. Finally, encouraging recent results with a cobalt porphyrin catalyst and bimetal catalysts will be presented, as well as recent XAS operando results. These results demonstrate that ZrP nanoparticles are suitable supports for electrocatalysis of the OER and water splitting.Sponsored by the NSF-PREM Center for Interfacial Electrochemistry for Energy Materials (CIE2M) grant DMR-1827622.

Evaluation of crude methanolic mangrove leaves extract for antibiofilm efficacy against biofilm-forming bacteria on a cooling tower wastewater system

The present study demonstrated microbial corrosion protection of MS 1010 on cooling tower water using plant-based inhibitors derived from methanolic extraction of dry mangrove leaves (R.mangle and A.marina), and its assessment of antibacterial activity against corrosive bacteria (B.megaterium) was investigated. FT-IR and GC–MS analyzed the inhibitors component and corrosion behavior of MS 1010 on cooling water, with and without inhibitors were analyzed by EIS and Tafel studies. GC–MS spectra confirmed the presence of Myo-Inositol, 4-C-methyl and chromene as major constituents presented on the R.mangle whereas Lupeol, trifluoroacetate and beta-amyrin compounds were found on the A.marina. In the cooling water, these two inhibitors demonstrated outstanding antibacterial activity and controlled biofilm growth. As plant-based inhibitors were used in cooling water systems, EIS data showed a significant increase in Rct value when compared to the control system. Tafel plot indicates inhibitors have mixed inhibitory effects and for the systems with and without inhibitors, the icorr value was 1.5649A and 2.0875A, respectively. At the optimal dose of 25 ppm, the inhibitory efficiency of MERM and MEAM was 81% and 80%, respectively. The overall discussion reveals that inhibitor substances can be absorbed on the metal surface and then act as a dual role in inhibiting corrosive bacterial growth and barrier to the corrosion process in the cooling water system.

Protecting Oil Flowlines from Corrosion Using 5-ACETYL-2-ANILINO-4-DIMETHYLAMINOTHIAZOLE

Oil flow lines are used to transport oil and its derivatives from a well over long distances, and because oil wells produce other potentially corrosive products, such as carbon dioxide and Hydrogen sulfide, it is necessary to take methods to protect the pipeline from corrosion. One of these methods is the use of corrosion inhibitors in this study. Prepare 5-acetyl-2-anilino-4-dimethylaminothiazole and test it as a corrosion inhibitor on a sample of the Rumaila flow line at a constant temperature 25°C in (3.5%) NaCl and (3.5%) KCl solution in the absence and presence of different concentrations of inhibitor (0 mM, 0.01 mM, 0.03 M, 0.05 mM). by using liner polarization (Tafel slope). The inhibiter exhibited the best performance at high concentration giving 94% in NaCl solution and 88% in KCl solution and solution, the inhibitor gave It was used FT-IR to find out the effective aggregates in the inhibitor, Tafel plot reveals that Ecorr for flowline in the presence the inhibitors shift to a higher (noble) position compared with blank solution, implying that the protection acts as an anodic protection. Keywords: corrosion inhibiter, oil flowline, leaks.

Corrosion studies and thermogravimetric analysis performed on activated tungsten inert gas and hot wire tungsten inert gas welded super austenitic stainless steel AISI 904L

Attributed to the remarkable resistance offered against various types of corrosion, AISI 904L is used for a wide range of challenging applications. In this context, this research aims to conduct an in-depth corrosion study about the base material and weldments of 10 mm thick AISI 904L plates fabricated by autogenous activated tungsten inert gas (ATIG) welding and hot wire tungsten inert gas (HWTIG) welding techniques. The pitting resistance effective number (PREN) is analyzed to evaluate pitting corrosion resistance. The Tafel plot is drawn and evaluated for the electrochemical corrosion of base metal and weldments in a 3.5% NaCl solution, while the specimens immersed in 3.5% NaCl solution at 650oC for 24 hours are evaluated for hot corrosion behavior. Thermogravimetric analysis (TGA) is performed at 300C–9000C to study material behavior at elevated temperatures. Results indicate that the base metal, ATIG weldment, and HWTIG weldment have a PREN of 34. During Tafel plot analysis, the ATIG weldment displayed a corrosion rate of 0.02792 mm/year while the HWTIG weldment recorded 0.02091 mm/year. Corrosion rates of ATIG and HWTIG weldments during hot corrosion studies are 14.93 mm/year and 12.69 mm/year, respectively. During TGA analysis, the ATIG weldment suffered a weight loss of 12.42% while the HWTIG weldment lost only 9.68% of its weight during the process. FESEM + EDS analysis confirmed the presence of unmixed flux particles in the ATIG weldment, which could be attributed to the weldment’s poor performance. In general, this research cemented the supremacy of the HWTIG weldment over the ATIG weldment with improved corrosion resistance and thermal stability. This study also contributed to a better understanding of the corrosion behavior of AISI 904L weldments under different environments that this superior grade of stainless steel alloy may encounter during its real-life applications.

Artificial neural networks modeling ethanol oxidation reaction kinetics catalyzed by polyaniline-manganese ferrite supported platinum-ruthenium nanohybrid electrocatalyst

The electrochemical and physicochemical properties of the anode catalyst used in alcohol fuel cells affect the efficiency of the fuel cell due to both its effect on the cell potential and its direct relationship with the reaction stoichiometry. It is possible to determine these parameters from polarization curves (current vs. cell potential) of the cells. At low potentials, Tafel plots offer kinetic information, whereas currents at high potentials reveal the average number of electrons released per ethanol molecule and their potential dependency. Herein, bearing the chemical engineering research and design aspects, it was aimed to model the kinetics of ethanol electrooxidation reaction catalyzed by PANI-MnFe2O4/Pt/Ru nanocomposite by an artificial neural network (ANN) approach, specifically by Differential Evolution (DE) algorithm for the first time. The different parts of the Tafel plots were condensed into a single and efficient model to illustrate the generalization potential of ANN. The findings demonstrated that the best model with a single hidden layer with 18 neurons offered the highest correlation metrics of 0.997476, and the lowest mean-square-error value of 0.000428 at the testing phase. Furthermore, the average absolute error was calculated, with 0.773% in the training phase and 0.66% in the testing phase. These outstanding results indicated that the best model is capable of accurately capturing the dynamics of all instances analyzed.

A mixed-potential type NH3 sensors based on spinel Zn2SnO4 sensing electrode

Spinel oxide Zn2SnO4 with cubic structure was synthesized by solid state reaction method. A NH3 sensor based on mixed potential mechanism were fabricated with 8% yttria stabilized zirconia electrolyte with bi-layered and Zn2SnO4 sensing electrode (SE). The influence of Zn2SnO4-SE thickness and sintering temperature on the response performance of the sensor was evaluated. The results display that the sensor using Zn2SnO4-SE with a thickness of 17 µm and sintered at 1100 °C displays better performance, which is closely related to the microstructure of the Zn2SnO4-SE. The response signals are linearly related to the logarithm of the NH3 concentrations over the operating temperature range and at 600 °C the sensor shows the highest sensitivity of − 61.8 mV/decade. The cross-sensitivity experiment results show that the cross-sensitivity of the sensor towards CO2 and H2 is hardly observed; the NH3 sensitivity decreases with the increasing of O2 content to some extent; relative humidity and NO or NO2 cause serious interference. In order to eliminate NO or NO2 interference, CuO was chosen to replace Pt as the reference electrode, and the results show that the cross-sensitivity of the sensor to NO or NO2 was significantly reduced, but the sensitivity slightly decreases. The sensor also shows a relatively good long-term stability. The polarization curve and Tafel plots verify that the sensor complies with mixed potential model.

Electrochemical determination of ornidazole at silver electrode: analytical application in human blood

This paper reports on the electrocatalytic and electroanalytical activity of metallic silver electrode (MSE) for ornidazole (ONZ) reduction using cyclic voltammetry (CV), square wave voltammetry (SWV), chronoamperometry, Tafel plots, and electrochemical impedance spectroscopy (EIS). Voltammetry results show an irreversible response with a significant shift to positive potentials. Based on the polarization curves, the Tafel slope is higher than 120 mV per decade indicating the Volmer step as rate determining step. The MSE presents the highest exchange current density (i0) value (6.452 µA/cm2), which further confirms their higher electrocatalytic activity towards ONZ reduction. Under the optimized conditions, MSE showed a good linearity in the concentration range from 8.0 × 10–7 mol L–1 to 6.0 × 10–5 mol L–1, with a detection limit (LOD) of 4.38 × 10–7 mol L–1. The MSE was successfully applied for the determination of ONZ in human blood.

Synthesis of Au-NiOx/ultrathin graphitic C3N4 nanocomposite for electrochemical non-platinum oxidation of methanol

The Au-NiOx/g-C3N4 (graphitic C3N4) nanocomposite is synthesized and utilized as catalyst for the electrochemical oxidation of methanol in the alkaline electrolyte. Au and Ni nanoparticles are uniformly dispersed on ultrathin g-C3N4 nanosheets by in-situ synthesis with nickel nitrate and chloroauric acid as Ni and Au resource respectively. The structure, morphology and component of the prepared nanocomposites are characterized by different techniques like transmission electron microscopy, X-ray diffraction, elemental mapping image and X-ray photoelectron spectroscopy. The results prove that the nanoparticles are well-distributed and embedded in g-C3N4 nanosheets. The electrochemical performance of different nanocomposite for methanol oxidation reaction (MOR) is tested under alkaline conditions via electrochemical technologies. Compared to the pure g-C3N4 and Au/g-C3N4, the NiOx/g-C3N4 exhibits electrochemical catalytic effect toward methanol electro-oxidation with the existence of Ni. This electrochemical catalytic performance is enhanced significantly for the Au-NiOx/g-C3N4, whose oxidation peak current density is 2.32 times higher than NiOx/g-C3N4. The slope value drew from the Tafel plots shows that the Au-NiOx/g-C3N4 owns the lowest Tafel slope (67.00 mV/dec). After the 7200 s stability test, the Au-NiOx/g-C3N4 catalyst can still maintain a high current density. Long-term stability and good anti-poisoning ability promise Au-NiOx/g-C3N4 a competitive non-Pt catalyst for the methanol oxidation.

Characterisation, hardness and corrosion behaviour of electrodeposited ZnFe and ZnFe/BN composite coatings

ABSTRACT ZnFe and ZnFe/BN composite coatings were successfully electrodeposited on 304 stainless steel substrates by pulse electrodeposition technique. The effect of various concentrations of BN particles in the plating solution on the structural, hardness and corrosion properties of electrodeposited ZnFe alloy and ZnFe/BN composites were investigated. The deposition process and electrochemical behaviour of alloy and composite coatings were analysed by the Cyclic Voltammetry (CV) method. X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used for the structural, and morphological characterisation of the coatings. Vickers micro hardness indentation was used to determine the hardness of the deposits. The corrosion behaviour of ZnFe alloy and ZnFe/BN composites was investigated by open circuit potential (OCP), Tafel plots, and electrochemical impedance spectroscopy (EIS) methods. As the BN particle content in ZnFe/BN composite coatings rose, the microhardness, and corrosion resistance of coatings increased, which was due to the function of grain refinement and changing dispersion strengthening. Meanwhile, grain sizes were strongly affected from the presence of BN particles and their content. The ZnFe/BN composite coatings with the BN particle concentration of 20 g L−1 had the highest corrosion resistance, and microhardness.

Selective oxidation of amaranth dye in soft drinks through tin oxide decorated reduced graphene oxide nanocomposite based electrochemical sensor

The recent studies evaluated the extensive exploitation of azo dyes as food colorant to improve the texture of food to turn the food to be very attractive. The heavy consumption of the food colorants by the food industries in commonly consumed beverages especially in the soft drinks may become the cause of certain suspected diseases. Amaranth is an azo dye which easily cleaved into amines and is suspected to be mutagen and carcinogen. Thus, the quantification of amaranth through reliable and sensitive sensor is of great importance. The SnO2/rGO nanocomposite has been engineered to be utilized as chemically modified sensor for the low-level quantification of amaranth in soft drinks and water sample. The fabricated nanocomposite materials was characterized through XRD, FTIR, raman and TEM tools which revealed average crystalline size of 23.7 nm, different surface functionalities and internal rectangle shaped morphology. The engineered nanocomposite was electrochemically characterized through electrochemical impedance spectroscopy (EIS) and Tafel plot to evaluate the electrocatalytic properties and charger transfer kinetics of SnO2/rGO/Nafion/GCE. The resistance of bare, GO/GCE and SnO2/rGO/Nafion/GCE was calculated as 812.5 Ω, 1343 Ω and 338 Ω. Certain parameters were optimized such as PBS electrolyte pH 6, scan rate 130 mV/s and potential window (0.4–1.2 V) to carry out sensitive and fluent determination process of amaranth azo dye. For the effectiveness of proposed sensor two calibration ranges were optimized from 1 to 800 nM and 1–60 μM. The LOD for both ranges were calculated as 0.68 nM and 0.0027 μM. Moreover, the anti-interference and stability profile of developed sensor were found phenomenal that suggest the exceptional electrocatalytic performance of SnO2/rGO/Nafion/GCE for amaranth.

Development and Performance Evaluation of a Mini-potentiostat for Corrosion Experimentations

The exorbitant cost of laboratory equipment is chiefly responsible for the dearth of corrosion characterization equipment in material science laboratories of Universities from Sub-Saharan Africa and that of other developing countries across the globe. It has therefore become germane to exploit available resources for development of affordable potentiostat within the university community. In this work, detailed procedure and working principles for design, fabrication and performance evaluation of a portable and inexpensive microcontroller-based potentiostat are presented. PROTEUS® software was used for the design of the parent circuit board. Graphical User Interface (GUI) developed using Visual Studio and Origin PRO Software was used for acquisition of experimental results. Performance evaluation of the potentiostat was implemented by performing corrosion experiments in 5 wt.% NaCl solution using mild steel as a working electrode (WE). Ag/AgCl reference electrode (RE) was used as well as Platinum wire as the counter electrode (CE). The analysis of the working electrode potential against the log of current-density plot at a scan rate of 10 mV/s of the fabricated potentiostat revealed a Tafel plot that is in conformity with results from commercially available potentiostats.

Environmentally Benign Synthesis of Copper Benzenetricarboxylic Acid MOF as an Electrocatalyst for Overall Water Splitting and CO2 Reduction

As a class of porous coordination polymers, metal organic frameworks (MOFs) have potential applications in many fields. In this work, a novel synthetic method, without using toxic solvents, has been developed to prepare HKUST-1 MOF nanoparticles from coprecipitation reaction of copper (II) chloride and 1,3,5-benzenetricarboxylic acid (trimesic acid) in distilled water. The synthesized nanoparticles were first characterized by X–ray diffraction (XRD), Fourier–transform infrared spectroscopy (FT–IR), and scanning electron microscopy (SEM). The flat–band potential, conduction band, and valence band edges of HKUST-1 nanoparticles were experimentally determined in alkaline solution, and UV–Vis diffuse reflectance spectra (DRS) analysis showed the band gap energy to be 2.5 eV. Electrochemical working electrodes were prepared by electrophoretic deposition of HKUST-1 on the surface of a stainless steel electrode for electrochemical voltammetry and impedance measurements. For the first time the prepared HKUST-1 nanoparticles were investigated as multifunctional electrocatalysts for both overall water splitting and CO2 reduction in alkaline solution. The Tafel plot was used to show the relationship between the over–potential (η) and the logarithmic current density, revealing the kinetic parameters of the electrochemical reactions. Furthermore, the Tafel slope was determined to be 190 mVdec−1, indicating that the Volmer mechanism with electrochemical desorption of hydrogen acts as the rate–determining step (RDS).