Synergistic Effect of Allium-like Ni9 S8 & Cu7 S4 Electrodeposited on Nickel Foam for Enhanced Water Splitting Activity.

This study explores a water-splitting activity using a biphasic electrodeposited electrode on nickel foam (NF). The *Ni9 S8 /Cu7 S4 /NF electrode with citric acid reduction exhibits superior OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) performance with reduced overpotential and a steeper Tafel slope. The *Ni9 S8 /Cu7 S4 /NF electrode displays the ultra-low overpotential value of 212 mV for OER and 109 mV for HER at the current density of 10 mA cm-2 . The Tafel slope of 25.4 mV dec-1 for OER and 108 mV dec-1 for HER was found from that electrode. The maximum electrochemical surface area (ECSA), lowest series resistance and lowest charge transfer resistance are found in citric acid reduced electrode, showing increased electrical conductivity and quick charge transfer kinetics. Remarkably, the *Ni9 S8 /Cu7 S4 /NF electrode demonstrated excellent stability for 80 hours in pure water splitting and 20 hours in seawater splitting. The synergistic effect of using bimetallic (Cu&Ni) sulfide and enhanced electrical conductivity of the electrode are caused by reduction of metal sulfide into metallic species resulting in improved water splitting performance.

Phytochemical-assisted green synthesis of CuFeOx nano-rose electrocatalysts for oxygen evolution reaction in alkaline media.

This study represents a green synthesis method for fabricating an oxygen evolution reaction (OER) electrode by depositing two-dimensional CuFeOx on nickel foam (NF). Two-dimensional CuFeOx was deposited on NF using in situ hydrothermal synthesis in the presence of Aloe vera extract. This phytochemical-assisted synthesis of CuFeOx resulted in a unique nano-rose-like morphology (petal diameter 30-70 nm), which significantly improved the electrochemical surface area of the electrode. The synthesized electrode was analyzed for its OER electrocatalytic activity and it was observed that using 75% Aloe vera extract in the phytochemical-assisted synthesis of CuFeOx resulted in improved OER electrocatalytic performance by attaining an overpotential of 310 mV for 50 mA cm-2 and 410 mV for 100 mA cm-2. The electrode also sustained robust stability throughout the 50 h of chronopotentiometry studies under alkaline electrolyte conditions, demonstrating its potential as an efficient OER electrode material. This study highlights the promising use of Aloe vera extract as a green and cost-effective way to synthesize efficient OER electrode materials.

Effect of Graphene Concentration on the Electrochemical Properties of Cobalt Ferrite Nanocomposite Materials.

A two-step process was applied to synthesize the cobalt ferrite-graphene composite materials in a one-pot hydrothermal reaction process. Graphene Oxide (GO) was synthesized by a modified Hummer's method. The synthesized composite materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The XRD and FTIR results were in good agreement with the TGA/DTG observations. SEM and TEM disclosed the spherical shape of the nanoparticles in 4-10 nm. The optimized CoFe2O4-G (1-5 wt.%) composite materials samples were tried for their conductivity, supercapacity, and corrosion properties. The CV results demonstrated a distinctive behavior of the supercapacitor, while the modified CoFe2O4-G (5 wt.%) electrode demonstrated a strong reduction in the Rct value (~94 Ω). The highest corrosion current density valves and corrosion rates were attained in the CoFe2O4-G (5 wt.%) composite materials as 5.53 and 0.20, respectively. The high conductivity of graphene that initiated the poor corrosion rate of the CoFe2O4-graphene composite materials could be accredited to the high conductivity and reactivity.

Magnetic/Polyetherimide-Acrylonitrile Composite Nanofibers for Nickel Ion Removal from Aqueous Solution.

In this study, a magnetic/polyetherimide-acrylonitrile composite nanofiber membrane with effective adsorption of nickel ions in an aqueous solution was created using a simple electrospinning method. Iron oxide nanoparticles (NPs) were stirred and ultrasonically dispersed into a polyetherimide-acrylonitrile solution to create a homogenous NPs suspension, which was placed in an electrospinning machine to produce a uniform and smooth nanofiber composite membrane. Nanoparticle incorporation into this membrane was confirmed using scanning electron microscope, energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and NPs aqueous stability from a leaching test. The high adsorption capability of the membrane on nickel ions was attributed to the combination of magnetic NPs, polyetherimide-acrylonitrile matrix, and the nanostructure of the membrane. A membrane containing magnetic NPs demonstrated the maximum adsorption capabilities (102 mg/g) of nickel ions in an aqueous solution. Various kinetic and isotherm models were applied to understand the adsorption behavior, such as pseudo-second-order kinetic and Langmuir isotherm models. A polyetherimide-acrylonitrile composite nanofiber membrane containing magnetic NPs could be used as an environmentally friendly and nontoxic adsorbent for the removal of nickel ions in an aqueous medium due to its ease of preparation and use and stability in aqueous mediums.

Computational Approach to Understanding the Electrocatalytic Reaction Mechanism for the Process of Electrochemical Oxidation of Nitrite at a Ni-Co-Based Heterometallo-Supramolecular Polymer.

Here, we report a semiempirical quantum chemistry computational approach to understanding the electrocatalytic reaction mechanism (ERM) of a metallic supramolecular polymer (SMP) with nitrite through UV/vis spectral simulations of SMP with different metal oxidation states before and after interactions with nitrite. In one of our recent works, by analyzing the electrochemical experimental data, we showed that computational cyclic voltammetry simulation (CCVS) can be used to predict the possible ERM of heterometallo-SMP (HMSMP) during electrochemical oxidation of nitrite (Islam T.ACS Appl. Polym. Mater.2020, 2( (2), ), 273-284). However, CCVS cannot predict how the ERM happens at the molecular level. Thus, in this work, we simulated the interactions between the repeating unit (RU) of the HMSMP polyNiCo and nitrite to understand how the oxidation process took place at the molecular level. The RU for studying the ERM was confirmed through comparing the simulated UV/vis and IR spectra with the experimental spectra. Then, the simulations between the RU of the polyNiCo and various species of nitrite were done for gaining insights into the ERM. The simulations revealed that the first electron transfer (ET) occurred through coordination of NO2 - with either of the metal centers during the two-electron-transfer oxidation of nitrite, while the second ET followed a ligand-ligand charge transfer (LLCT) and metal-ligand charge transfer (MLCT) pathway between the NO2 species and the RU. This ET pathway has been proposed by analyzing the transition states (TSs), simulated UV/vis spectra, energy of the optimized systems, and highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) interactions from the simulations between the RU and nitrite species.

Superior Mechanical Performance of Inductively Sintered Al/SiC Nanocomposites Processed by Novel Milling Route.

This paper explores new routes for flake powder metallurgy, with the aim of designing an effective route for fabricating metal matrix nanocomposites, combining high strength and good ductility. A new route that uses three speeds, instead of the two speeds characterizing the shift-speed ball milling (SSBM) route, has been suggested and implemented. The mechanisms of these routes were illustrated based on the intensity of ball-powder-ball collisions and the morphology evolution. The ball milled powder were characterized using filed emission scanning electron microscope (FESEM), X-ray diffractometer (XRD) and Energy dispersive spectroscopy (EDS) to investigate the morphology evolution of the composites powder and the homogenous distribution of the SiC nanoparticles within the Al matrix. The reinforcing adequacy and interfacial bonding of 2 wt.% SiC nanoparticles in an inductively sintered composite has been investigated. Mechanical testing of the produced bulk composites resulted in achieving superior mechanical properties, characterized by 92% higher hardness, 180% higher yield strength, 101% higher ultimate strength, and 0% loss in uniform elongation, compared with those of regular SSBM. This is attributed to the homogeneous dispersion of the reinforcement into the Al matrix.

WS2: A New Window Layer Material for Solar Cell Application.

Radio frequency (RF) magnetron sputtering was used to deposit tungsten disulfide (WS2) thin films on top of soda lime glass substrates. The deposition power of RF magnetron sputtering varied at 50, 100, 150, 200, and 250 W to investigate the impact on film characteristics and determine the optimized conditions for suitable application in thin-film solar cells. Morphological, structural, and opto-electronic properties of as-grown films were investigated and analyzed for different deposition powers. All the WS2 films exhibited granular morphology and consisted of a rhombohedral phase with a strong preferential orientation toward the (101) crystal plane. Polycrystalline ultra-thin WS2 films with bandgap of 2.2 eV, carrier concentration of 1.01 × 1019 cm-3, and resistivity of 0.135 Ω-cm were successfully achieved at RF deposition power of 200 W. The optimized WS2 thin film was successfully incorporated as a window layer for the first time in CdTe/WS2 solar cell. Initial investigations revealed that the newly incorporated WS2 window layer in CdTe solar cell demonstrated photovoltaic conversion efficiency of 1.2% with Voc of 379 mV, Jsc of 11.5 mA/cm2, and FF of 27.1%. This study paves the way for WS2 thin film as a potential window layer to be used in thin-film solar cells.