HCl Electrolyte Research Articles

Cornstalk-derived porous carbon as a high-performance and low-cost cathode for photoelectrochemical cell

Considering agricultural wastes as carbon source to be utilized for the preparation of porous carbon (PC), in particular with the advantages of low cost and abundant active sites, we construct a one-compartment membraneless photoelectrochemical cell use cornstalk-based PC as cathode instead of commercial carbon paper. The addition of as-prepared PC with high surface area at cathode is beneficial to provide a large number of reaction sites for H2O2 storing compared with commercial carbon paper. The maximum power density of this H2O2 fuel cell with PC/ITO-based cathode achieves 1.68 mW cm−2 under AM 1.5G solar light (1 sun, 100 mW cm−2) in 0.1 M HCl electrolyte at air atmosphere, which presents around 21.3- and 3.3-times enhancement compared to the cell with bare ITO-based cathode (0.079 mW cm−2) and the cell with carbon paper-based cathode (0.51 mW cm−2), respectively. Consequently, the calculated solar-to-electricity conversion efficiency (SECE) is as high as 1.04%. Furthermore, the cell can produce H2O2 from g-C3N4 on the photoanode side through photocatalytic H2O oxidation, and adsorptively store H2O2 on the cathode side by using of hierarchical nanostructures of PC with the disconnection of electrodes. After 0.5 h of light irradiation, the cell using H2O2 as the fuel operated by connecting the electrodes in the dark can form a specific capacitance of 19451.3 mF cm−2. We propose a pathway to utilize biomass-based PC as the cathode instead of commercial carbon paper in a one-compartment H2O2 fuel cell for the first time, which is unquestionably more promising for high-value use of agricultural wastes and the development of high-performance and low-cost fuel cells.

Moisture-Stable CsSnBr2Cl Halide Perovskite: Electrochemical Insights in Aqueous Environments.

In this investigation, moisture-stable CsSnBr2Cl nanoparticles were synthesized by incorporating Cl into CsSnBr3 halide perovskite using the hot injection method. Various analyses including XRD, XPS, UV-vis absorbance, photoluminescence, and Mott-Schottky have confirmed that the structural properties, chemical states, optical properties, and electronic band structure of CsSnBr2Cl nanoparticles remain intact even after 75 days of water immersion, thereby conclusively demonstrating their moisture stability. In a three-electrode system, the comparative electrochemical performance of pristine CsSnBr3 nanoparticles and moisture-stable Cl-incorporated CsSnBr2Cl nanoparticles was evaluated in various aqueous electrolytes, including HCl, Na2SO4, and KOH. The results indicate that the CsSnBr2Cl electrode material exhibits superior electrochemical properties, such as a larger integrated cyclic voltammetry (CV) area, a wider potential window, longer charge-discharge times, and lower impedance parameters compared to the pristine CsSnBr3 nanoparticles. The electrochemical performance of CsSnBr2Cl nanoparticles was evaluated for potential applications in batteries, supercapacitors, fuel cells, and water splitting, with a focus on reaction kinetics, charge storage mechanisms, and impedance parameters. The electrochemical properties of the nanoparticles were assessed using a three-electrode configuration across various 0.5 M aqueous electrolytes (HCl, Na2SO4, and KOH). In HCl, the nanoparticles demonstrated impressive charge storage capability, achieving a capacitance of 474 F g-1 at 1 A g-1, affirming their suitability for energy storage devices. In Na2SO4(aq.), the nanoparticles exhibited excellent stability for supercapacitors, operating up to 1.6 V without significant oxygen evolution. Notably, in KOH, they demonstrated potential as effective water-splitting electrodes. The practical applicability of the nanoparticles was evaluated using a symmetric two-electrode configuration with HCl and Na2SO4 electrolytes. The capacitance values were 117 F g-1 in HCl and 70 F g-1 in Na2SO4 at 1 A g-1. Notably, after 5000 GCD cycles in HCl(aq.), the nanoparticles retained 93% of their capacitance and maintained 91% Coulombic efficiency. They also demonstrated stable operation across a temperature range of 3 to 60 °C, achieving an energy density of 5.83 W h kg-1 at a power density of 600 W kg-1. This study emphasizes the considerable potential of CsSnBr2Cl nanoparticles in advancing electrochemical energy storage technologies and sets a solid foundation for future research and development in metal halide perovskites.

Tribological and corrosion behaviour of non-equiatomic magnetic FeCoNiMnAl high entropy alloy

High entropy alloys (HEAs) have promise as new materials for functional and structural applications. Researchers have focused on fabricating a novel material with improved resistance to wear and corrosion. This study investigates the potential of FeCoNiMn0.25Al0.25 magnetic HEA in tribological and corrosion environments. Since dry sliding is a common mode of wear for many engineering applications. The tribological properties of HEA are investigated under dry conditions under three different normal loads (10 N, 20 N, and 30 N) and three different frequencies (5 Hz, 10 Hz, and 15 Hz) at ambient temperature. Our findings indicate that the coefficient of friction (COF) and specific wear rate (SWR) significantly declined by 8.33 % and 20.71 %, respectively, as the load increased from 10 N to 30 N and the frequency increased from 5 Hz to 15 Hz. Additionally, an ANOVA analysis is performed to understand which process parameters (normal loads and frequencies) affect our response parameters (COF and SWR) the most. The corrosion performance of fabricated HEA is further investigated in three different electrolytes, such as 3.5 wt% NaCl, 1 M HCl, and 1 M NaOH, at room temperature. It is observed that the HEA behaves differently in different electrolytes and exhibits good corrosion resistance (COR) in a sequence of NaOH > NaCl > HCl which is also supported by Nyquist analysis. Furthermore, it has been found that the HEA is seriously corroded in NaCl and HCl electrolytes due to the strong pitting corrosion of Cl- ions.

Enhanced supercapacitor performance through synergistic electrode design: Reduced graphene oxide-polythiophene (rGO-PTs) nanocomposite

In this investigation, we introduce an innovative method for the fabrication of a 2D/2D nanocomposite, involving the in-situ functionalization of graphene oxide (GO) with thiophene monomer. This approach employs a modified surfactant-based bi-solvent swollen liquid crystalline lamellar mesophase (SLCLM) nanoreactor system, utilizing dimethyl sulfoxide and water as primary solvents. The nanocomposite is formed via simultaneous reactions at both the edge and basal plane of GO with thiophene monomers, resulting in polymerization and reduction to generate graphene oxide-polythiophene (rGO-PTs) nanocomposite.We assess the pseudocapacitive properties of rGO-PTs in a 2 M HCl electrolyte. The cyclic voltammetry (CV) investigations reveal distinctive redox curves, indicative of the materials capacitive behaviour. In the galvanostatic charge–discharge (GCD) study, the rGO-PTs exhibits a discharge duration of 169.50 s within a potential window of −0.2 to 1 V at a current density of 7.5 A/g. This performance corresponds to a significantly higher specific capacitance of 1412 F/g, sustained over 10000 cycles as asymmetric capacitor. Notably, the rGO-PTs nanocomposite retains 106 % of its initial capacitance even after a number cycles, tested at a scan rate of 50 mV/s. The exceptional durability and electrochemical performance of the rGO-PTs nanocomposite position it as a promising alternative to conventional materials such as metals, metal oxides, pure carbonaceous substances, and polymers. The simplicity of the synthesis process, coupled with the nanocomposites outstanding electrochemical characteristics, underscores rGO-PTs potential for advancing in the field of energy storage and supercapacitor technology.

Inhibition performance of a novel quinoxaline derivative for carbon steel corrosion in 1 M HCl

In this work, the effect of a new quinoxaline derivative, 2-phenyl-3-(prop-2-yn-1-yloxy) quinoxaline (PYQX), was evaluated as a corrosion inhibitor for carbon steel (CS) in 1 M HCl electrolyte. Weight loss measurement, atomic absorption spectroscopy, potentio­dynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, and UV-vis spectroscopy were employed to assess the inhibitory activity. The electronic properties of the interaction between the inhibitor molecule and the CS substrate were studied using molecular dynamics (MD) simulation, density functional theory (DFT), and Fukui functions. According to AC impedance experiments, the inhibitor under consideration showed a maximum level of 98.1 % inhibition efficiency at 1 mM and 30 °C. The Langmuir adsorption isotherm model explains the adsorption of PYQX on the CS surface. A slope of 1 denotes a strong molecule-substrate interaction, suggesting that the binding occurs at specific surface locations. To understand the functioning of the adsorption mechanism, various thermodynamic and activation parameters were evaluated. PDP tests demonstrated that PYQX functions as a mixed-type inhibitor. Computational correlations (DFT, MD, and Fukui indices) supported the experimental findings.

Efficient green combustion production of pure nickel oxide (NiO) and silver-doped NiO nanoparticles using Aloe Vera gel extract: Its supercapacitors applications

This study employs the synthesis of pure NiO and Ag-doped NiO with varying concentrations (1, 3, 5, 7 and 9 mol%) of Ag2O nanoparticles by solution combustion method. The Structural and morphology of nanomaterials were elucidated by analytical spectroscopic methods. XRD revealed alterations in physical properties, such as crystallite size and lattice parameters, of NiO nanoparticles due to the presence of Ag2O. UV-Vis spectroscopy demonstrated a reduction in the bandgap from 3.41 eV (pure NiO) to 3.21 eV for 1, 3, 5, 7 and 9 mol% Ag2O-doped NiONPs. To assess their viability as active electrode materials in supercapacitors, the synthesized samples were subjected to analysis in a 0.1 M HCl electrolyte. Electrochemical studies done through various tests, including Electrochemical-Impedance, Cyclic-Voltammetry and Galvanic Charge-Discharge. Remarkably, the 5 mol% Ag2O-doped NiO in a 3-electrode system exhibited a notable capacitance value of 248 Fg−1 at a scan rate of 5 Ag−1. Additionally, it demonstrated robust cycling stability, maintaining over 90% of the original capacitance after 2000 cycles in GCD studies. The potential chemical interaction between nanoscale Ag2O and NiO could be responsible for the enhanced capacitance. These findings offer valuable insights for researchers exploring the development of novel electrode materials for energy-storage devices.

Atom-Pd catalysts supported by hollow N-doped carbon nanospheres for ultra-efficient nitrogen reduction reaction

Electrochemical N2 reduction reaction (eNRR) presents a promising alternative to the Haber-Bosch process, owing to its mild preparation conditions, absence of costly reagents, and high energy conversion efficiency. However, the process poses significant challenges due to its poor selectivity and low yield. Here, single atom Pd is successfully anchored on N-doped hollow carbon nanospheres via a simple wet impregnation method under relatively mild loading temperature, anhydrous and anaerobic environments. Our experiment demonstrates that SA-Pd/N@C exhibits outstanding catalytic performance in comparison to Pd nanoparticles which is consistent with the results of the DFT calculations, achieving an NH3 yield rate of 132.8 μg·h − 1·mgcat−1 and a corresponding FE of 6 % at -0.2 V versus RHE in HCl electrolyte (pH=1), as well as superior stability with only 5 % decrease after 10 consecutive cycles of electrochemical testing at room temperature, positioning it as one of the most effective catalyst materials reported for eNRR. The exceptional eNRR activity and stability can be attributed to the abundant active sites resulting from the relatively mild loading temperature, as well as electronic effects and structural engineering, which further diminish *H adsorption and efficiently suppress hydrogen evolution reaction. This work will provide a novel approach to enhance the eNRR performance through the effective design of Pd single-atom catalyst

High‐performance BCN‐C heterostructured electrocatalyst derived from covalent triazine frameworks for nitrogen reduction

AbstractDesigning and synthesizing heterostructure‐based catalysis combining two‐dimensional (2D) materials has attracted enormous attention in materials chemistry, especially for electrocatalysis, due to their tunable electronic properties and structure. In this work, a boron carbon nitride (BCN)‐coupled carbon (BCN‐C) heterostructure with improved electronic performance was synthesized starting from C‐ and N‐enriched 2D covalent triazine frameworks (CTFs) via a simple thermal transformation process using NaBH4 as the B source. The characterizations results showed that the B released from NaBH4 reacted with N and C in CTF, forming the BCN‐C heterostructure coupling the BCN and carbon with a strong interfacial effect. The electrocatalytic NRR experiments and density functional theory (DFT) calculation revealed that the interfacial electronic properties and large numbers of active sites of the BCN‐C heterostructure benefited the NRR. The BCN‐C‐1 catalyst showed a high Faradaic efficiency of 27.8% and an NH3 yield of 4.3 μg h−1 mgcat.−1 in 0.1 M HCl electrolyte, owing to its high specific surface area (288 m2/g) with a large number of exposed active sites and the Mott–Schottky effect from the BCN‐C heterostructure. This work highlights the design and synthesis of metal‐free catalysts with high activity and selectivity and makes them excellent candidates for electrocatalytic applications.

Asymmetric empty orbitals in ZrO2-BCN for enhancing electrocatalytic hydrogenation of nitrogen to ammonia

Electrocatalytic nitrogen reduction reaction (NRR) provides an environment-friendly and sustainable approach for nitrogen fixation at ambient conditions. However, simultaneously activating N≡N triple bond and suppressing the competitive hydrogen evolution reaction (HER) in aqueous electrolytes remain challenges. Herein, we construct ZrO2-BCN hetero-catalyst with tunable Zr-B-N interfacial structure for efficiently improving selectivity of the NRR. The asymmetric electron acceptance and back-donation capacity of the empty orbitals of Zr and B favors the activation of the N≡N triple bond during the NRR. The optimal ZrO2-BCN catalyst exhibits excellent NRR performance with a high ammonia yield of 17.8 μg mg-1cat. h−1 at −0.65 V vs. reversible hydrogen electrode (RHE) and a faradaic efficiency of 23.1 % at −0.45 V vs. RHE in 0.1 M HCl electrolyte, surpassing most previous reports. In-situ electrochemical attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy demonstrates the effect of the Zr-B-N interface on activating N2. This study paves a new way for hetero-interface catalyst design that would accelerate the implementation of NRR technology.

Experimental and theoretical investigation of two thioether-based Schiff bases as anti-corrosion agents for carbon steel in HCl electrolyte

PurposeThe main purpose of the present work is to introduce two new Schiff bases as corrosion inhibitors (CIs) for carbon steel (CS). The anti-corrosion performance of these Schiff bases having N and S heteroatoms in their structures was investigated and compared in 2 M HCl electrolyte. The inhibitory activity of these Schiff bases was also assessed.Design/methodology/approachCommon electrochemical assays like potentiodynamic polarization and electrochemical impedance measurements were used to evaluate the ability of compounds in reduction of the rate of corrosion. Quantum chemical calculations (QCCs) were also used to examine the corrosion inhibitive and the process related to the electrical and structural characteristics of the molecules acting as CIs.FindingsThe electrochemical measurements indicate that both Schiff bases acted as the efficient CIs of CS in 2 M HCl electrolyte. The adsorption of the Schiff base on the surface of the CS caused the corrosion to be inhibited. The change of Gibbs energies indicated that both physical and chemical interactions are involved in the adsorption of NNS and SNS on CS surfaces. The predicted QCCs of the CIs neutral and positively charged versions were well-aligned with those obtained by electrochemical experiments.Originality/valueUsing electrochemical experiments and quantum chemical modelings, two new Schiff bases, N-2-((2-nitrophenyl)thio)phenyl)-1-(pyrrole-2-yl)methanimine (NNS) and N-2-((2-nitrophenyl)thio)phenyl)-1-(thiophen-2-yl)methanimine (SNS), were evaluated as anti-corrosion agents for CS in 2 M HCl electrolyte. The DFT calculations were considered to compute the quantum chemical parameters of the inhibitors.

Evaluation of physiochemical and electrochemical behaviour of reduced grapheme functionalized copper nanostructure as an effective corrosion inhibitor

This study examines the physicochemical properties and corrosion resistance of hydrothermally produced copper oxide-reduced graphene oxide nanocomposite (CuO/rGO). The CuO/rGO nanocomposite has a well-defined and homogeneous structure, decreased crystal size, and uniformly distributed CuO nanoparticles tethered to the rGO. X-Ray diffraction confirms the fabrication of 15.1 nm crystalline monoclinic CuO nanoparticles. EDX confirms the composite's composition by detecting Cu, O, and C components. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (LSV) tests evaluate the CuO/rGO nanocomposite's corrosion resistance. A mild steel plate under an HCl electrolyte with corrosion in the PPM ratio treats the nanocomposite-coated substrate. The composite's synergistic effect is assessed by comparing its corrosion performance to CuO/rGO concentrations in ppm. The corrosion resistance data demonstrate that the CuO/rGO composite improves with inhibitor concentrations of 0, 25, 50, 75, and 100 ppm. Adding rGO to the composite protects it and speeds up charge transfer, reducing corrosion and improving stability. The composite's synergistic effect of CuO and rGO provides excellent corrosion resistance regardless of concentration, making it a viable material for corrosion-prone applications. The research develops novel and effective anti-corrosion methods to preserve materials in the food, automotive, and large-scale energy industries.
 KEY WORDS: CuO/rGO nanocomposite, Tafel plot, Corrosion protection, Surface analysis
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 269-280. DOI: https://dx.doi.org/10.4314/bcse.v38i1.20

Fabrication of a low-cost efficient novel Ti3AlC2 MAX phase / Polyvinyl alcohol / Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) polymer nanocomposite film for symmetric supercapacitor

ABSTRACT This work reports a systematic study of the electrochemical performance of the Ti3AlC2 MAX phase/PVA-PEDOT: PSS + DMSO polymer nanocomposite (PPM) films fabricated by the facile solution cast technique. A varying weight percentage of Ti3AlC2 MAX phase nanoparticles were dispersed in the polyvinyl alcohol (PVA)-[poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) + dimethyl sulfoxide)] (PEDOT: PSS + DMSO) polymer blend to fabricate the polymer nanocomposite films. The structural, morphological, optical, thermal, electrical, and electrochemical properties of the nanocomposite films were studied meticulously. The structural and morphological studies were done by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction technique (XRD), and field emission scanning electron microscopy (FESEM). The optical properties of the PPM films were analyzed using the UV-Visible (UV-Vis) spectra. The thermal analysis of the PPM films was done from the thermogravimetric analysis (TGA) curves. The ac conductivity and dynamic mechanical analysis (DMA) were done to evaluate the electrical conductivity and mechanical properties of the PPM films. The performance enhancement of the polymer blend film by loading Ti3AlC2 MAX phase nanofiller was investigated. The nanocomposite film having the highest conductivity and the greatest mechanical strength was further considered for the electrochemical characterization. The nanocomposites reported a specific capacitance of 52.8 F/g and 1500 mF/g in 0.1 M HCl electrolyte at a scan rate of 20 mV/s in the 3-electrode system and 2-electrode system, respectively. The Nyquist plots and Bode plots were plotted from the electrochemical impedance spectroscopy (EIS) data. The Nyquist plots were analyzed from the simulated equivalent circuits. The facile fabrication method of the supercapacitor electrode with improved thermal and mechanical properties will be beneficial for their commercial electrochemical applications in the future.

Electrochemical and Morphological investigations of Elettaria cardamomum pod extract as a green corrosion inhibitor for Mild steel corrosion in 1 N HCl

The corrosion inhibition performance of an ethanolic extract from Elettaria cardamomum pod (ECPE) as a corrosion inhibitor for Mild Steel (MS) in 1 N Hydrochloric acid (1 N HCl) electrolyte was investigated via gravimetric analysis and electrochemical studies like Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) studies. Qualitative technique such as Gas Chromatography-Mass Spectrometry (GC–MS) was used to identify the main phytochemical components of the ECPE, such as phenolic chemicals, tannins, flavonoids, amino acids, carbohydrates, proteins, and terpenoids. With increasing in inhibitor concentrations (50-250 ppm), it was discovered that the efficiency of the inhibition increased to a maximum inhibition of 60.6% with 250 ppm at 303 K after 1hr. The influence of four distinct temperatures (303-333 K) were also examined where the inhibition efficiency decreased with temperature. The inhibitors were adsorbed onto the MS surface via physisorption. The adsorption of inhibitor appears to function through Freundlich adsorption isotherm more appropriately. EIS study showed that the values of resistance due to charge transfer (Rct) increased with concentration of ECPE where the PDP plots indicate that the extract functions as a mixed inhibitor affecting both the anodic and cathodic partial reactions of the corrosion process. Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and Atomic Force Microscope (AFM) investigated the surface morphology and topology of the MS which confirmed the adsorption of inhibitor molecules on the metal surface. The contact angle method predicted the hydrophobic nature of the MS in the presence of inhibitor. The results of Ultraviolet-Visible Spectroscopy (UV-Vis) provide evidence of iron/inhibitor interaction, which is responsible for the inhibition of corrosion. From all these investigations, it can be concluded that the ECPE acted as a good corrosion inhibitor for MS in a 1 N HCl electrolyte.

Bimetallic CuO−ZnO Hybrid Nanocomposite Materials for Efficient Remediation of Environmental Pollutants

AbstractPure CuO and 2‐Dimentional CuO−ZnO nanocomposites (NCs) were effectively prepared by an ultrasound‐assisted probe sonication route for different ratios of CuO and ZnO, and the multifunctional properties were investigated by the application of the advanced methods. XRD (X‐ray diffraction) patterns revealed a crystallite size (D) range of 25 to 31 nm for pure CuO and CuO−ZnO NCs. According to calculations, the energy band gap value (Eg) for the NCs is between 2.15 and 2.48 eV. Under UV light irradiation, the photocatalytic degradation of pure CuO and CuO−ZnO NCs on Direct Green (DG) and Fast Blue (FB) dyes was assessed. 60 mg of the catalyst was added to 20 ppm solutions of DG and FB dye. The stock solution of the dyes was prepared 10, 15, 20 and 25 ppm of 250 ml dye solution. Electrochemical analysis using cyclic voltammetry revealed improved redox potential output in the electrode crafted with graphite powder in 0.1 N HCl electrolyte solution. These NCs were used because of their capacity to detect an extremely dangerous chemical like arsenic. The constructed electrode‘s lowest limit of detection was determined to be 110–3 mol/L. In general, vertical linearity was seen in all of the prepared nano‐electrodes, especially above 150 ohms with real axis for pure CuO but beyond 100 ohms for doped electrodes. Based on our study, we conclude that the CuO and ZnO NCs, containing 10 % of ZnO, were the most effective photocatalyst for DG and FB dyes and electrochemical sensor for Arsenic.

W18O49 Nanowire Arrays for Plasmonic Photodetector with Electromediated Broadband Photoresponse

Plasmonic semiconductors offer significant advantages for the development of photodetectors with a tunable wide spectral response. Herein, we developed a plasmonic semiconductor photodetector based on the W18O49 nanowire array (NWA) to achieve a tunable broadband photodetector by adjusting the plasmonic absorption intensity of the W18O49 NWA. The plasmonic absorption intensity could be mediated through adjusting the free electron density of the W18O49 NWA by applying the external voltage on the W18O49 NWA-loaded electrode in HCl electrolyte. When the applied voltage decreased from +2 to −2 V, the plasmonic absorption intensity of the W18O49 NWA gradually enhanced due to the increased electron density. As a result, the responsivity and detectivity of the W18O49 NWA-based photodetector in the visible–NIR region were dramatically increased. Especially, upon 940 nm illumination, the responsivity and detectivity could reach ∼47.2 mA W–1 and ∼8.22 × 109 Jones, respectively, which is much higher than the corresponding values (∼2.9 mA W–1 and ∼4.53 × 109 Jones) obtained by the W18O49 NWA-based photodetector with a low plasmonic absorption. This work proposes a promising strategy to construct broadband-tunable photodetectors by using low-cost nonmetallic plasmonic nanostructures.

Effect of chemical composition on the electrochemical and wear behavior of boron carbide reinforced copper composites

ABSTRACT. In this work, the Copper composites Cu-x wt. % B4C (x = 0, 5, 10, 15, 20) were fabricated for the metallurgical and mechanical property evaluation as per ASTM standards. The metallurgical characterization tests on the samples include x-ray diffraction, optical microscopy, and scanning electron microscopy with EDX. Further, pin-on-disc apparatus was used to investigate the tribological behavior of composite specimens. An SEM micrograph of the worn surface and wear debris, along with the Gwyddion software, has been used to discuss the wear mechanisms in detail. The Artificial Neural Networks (ANN) classifier model is also constructed to describe the wear behavior in more detail. The experimental results inferred that the addition of Boron carbide particles has enhanced the Copper's corrosion resistance in a 1 M HCl electrolyte solution from 30.34% to 74.2%, 75.08%, and 83.29% with B and C ions. Also, it significantly enhance the mechanical and tribological characteristics considerably.
 
 KEY WORDS: Powder metallurgy, Cu-B4C, Gwyddion, Wear, Artificial Neural Network
 
 Bull. Chem. Soc. Ethiop. 2023, 37(4), 959-972. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i4.12

Electrochemical dating of archaeological gold based on repetitive voltammetry monitoring of silver/copper in depth concentration gradients

The use of repetitive voltammetry for dating archaeological gold objects is described. The method involves the record of the gold- silver-, and copper-related voltammetric responses obtained for metal nanosamples attached to graphite electrodes immersed into HCl electrolytes. This methodology permits to characterize different electrochemical types representative of different manufacturing techniques. Age estimates are based on the assumption that decuprification/desilvering processes advance with time under reasonably uniform conditions. Age calibration curves covering a range of ca. 2500 years were obtained from a set of archaeological samples from the Mapungubwe Gold Collection at the University of Pretoria Museums, South Africa, the Rijksmuseum of Amsterdam, The Netherlands, the Rheinische Landesmuseum Trier of Mannheim (Germany), the Museu de Belles Arts de Castelló, Spain, the Museu de Segovia, Spain, and the repository of the Servei d’Investigació Arqueològica Municipal de València, Spain.

PEDOT:PSS‐bacterial cellulose bilayer actuators: From the movement of ions to deflection

AbstractHere, the role of the voltage waveform and the electrolytic ions in the actuation mechanism of Poly (3,4‐ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS)/bacterial cellulose bilayer actuator is reported. PEDOT:PSS/bacterial cellulose‐based bilayer actuator was fabricated, and its mechanism under a square and triangular wave potential at multiple frequencies was studied. The actuation was performed with HCL, KCl, and LiCl electrolytes. The deflection of the actuator was found to be dependent on the time period of the voltage waveform. The deflection for opposite biases showed frequency‐dependent asymmetry. Further, the actuator deflection was found to be related to the hydrodynamic size of cations present in electrolytes. The results indicate a cation‐dominated actuation mechanism for PEDOT:PSS/bacterial cellulose bi‐layer actuator.

Metallic MoO2 as a Highly Selective Catalyst for Electrochemical Nitrogen Fixation to Ammonia under Ambient Conditions

AbstractThe development of earth‐abundant and non‐noble based metal catalysts for electrochemical nitrogen reduction towards sustainable ammonia production from N2 and H2O in the ambient atmosphere holds immense potential in realizing an alternate route to energy‐intensive Haber‐Bosch process. Herein, we have employed highly conductive MoO2 synthesized by hydrothermal route as an electrocatalyst for ammonia generation. The MoO2 catalyst was employed for electrochemical nitrogen reduction in N2 saturated 0.1 m HCl electrolyte in a two‐compartment cell. Ammonia yield rate of 2.30 μg h−1 mg−1cat and 2.40 % Faradaic efficiency has been obtained at a potential of −0.3 V vs. RHE. The MoO2 catalyst is selective for ammonia generation without any hydrazine formation. The metallic nature of MoO2 catalyst assists in achieving comparable activity for the electrochemical nitrogen reduction. The above catalyst has the potential for providing better ammonia yield rate by combining or doping with other active elements.

Petal-like NiS-NiO/G-C3N4 Nanocomposite for High-Performance Symmetric Supercapacitor.

Graphitic carbon nitride (G-C3N4) and NiS-NiO/G-C3N4 nanocomposite have been synthesized via combustion and hydrothermal techniques, respectively. The chemical and morphological properties of these materials were confirmed using different analytical methods. SEM confirms the formation of G-C3N4 sheets containing additional petal-like shapes of NiS-NiO nanoparticles. The electrochemical testing of NiS-NiO/G-C3N4 symmetric supercapacitors is carried out from 0.6 M HCl electrolyte. Such testing includes charge/discharge, cyclic voltammetry, impedance, and supercapacitor stability. The charge/discharge time reaches 790 s at 0.3 A/g, while the cyclic voltammetry curve forms under a high surface area. The produced specific capacitance (CS) and energy density values are 766 F/g and 23.55 W.h.kg-1, correspondingly.