Water pollution has badly affected human health, aquatic life, and the ecosystem. The purity of surface water can be measured in terms of dissolved oxygen (DO) measurements. Hence, it is desirable to have a portable and simple-to-use dissolved oxygen sensor. One possible remedy is an electrochemical sensor. Thus, we proposed an ITO-IrOx electrocatalyst for an effective and interference-free DO sensor utilizing the principle of oxygen reduction reaction (ORR). The ITO-IrOx was characterized using cyclic voltammetry (CV), scanning electron microscopy (SEM), electrochemical impedance spectrometry (EIS), X-ray photoelectron spectroscopy (XPS), and reflectance spectroscopy-based techniques. Reflectance spectra of the ITO-IrOx electrode showed the photoresist capability. The EIS spectra revealed lower charge transfer resistance for the ITO-IrOx electrode in ORR. The IrOx film on ITO exhibited a quick (one electron, α = 1.00), and reversible electron transfer mechanism. The electrode demonstrated high stability for oxygen sensing, having a limit of detection (LOD) of 0.49 ppm and interference-free from some common ions (nitrate, sulphate, chloride etc.) found in water.

<jats:title>Abstract</jats:title>
<jats:p>Ascorbic acid (vitamin C) is recognized as a viable alternative fuel for alkaline direct liquid fuel cells (DLFCs). After the potential anode catalyst was prepared by incorporating palladium nanoparticles (Pd NPs) into reduced graphene oxide (rGO) and multiwall carbon nanotube (MWCNT) hybrid nanocomposite (Pd/rGO/MWCNT) through a chemical reduction method, it was applied for electrooxidation of ascorbic acid (AA) in the alkaline condition. For AA electrooxidation, the Pd/rGO/MWCNT modified glassy carbon electrode (Pd/rGO/MWCNT/GCE) exhibited the highest current density of 5.18 mA cm<jats:sup>-2</jats:sup>: much higher than a bare glassy carbon electrode (0.6 mA cm<jats:sup>-2</jats:sup>). The Pd/rGO/MWCNT/GCE also demonstrated excellent stability for AA oxidation in the alkaline condition.</jats:p>

Recently, ascorbic acid (AA) has been studied as an environment-friendly fuel for energy conversion devices. This review article has deliberated an overview of ascorbic acid electrooxidation and diverse ion exchange types of AA-based fuel cells for the first time. Metal and carbon-based catalysts generated remarkable energy from environment-friendly AA fuel. The possibility of using AA in a direct liquid fuel cell (DLFC) without emitting any hazardous pollutants is discussed. AA fuel cells have been reviewed based on carbon nanomaterials, alloys/bimetallic nanoparticles, and precious and nonprecious metal nanoparticles. Finally, the obstacles and opportunities for using AA-based fuel cells in practical applications have also been incorporated.

In this study, we construct composite structures of CoPt multilayer alloy nanowires by electrodeposition using a polycarbonate template membrane (PT). The holes in PT are subsequently filled with CoPt multilayer alloy films to form nanowires. The composition of the films can be controlled by modifying the potential to produce high anisotropy CoPt alloy multilayer nanowires. The CoPt multilayer nanowires have a periodic structure like bamboo with a chemical composition of (Co80Pt20/Co30Pt70)n. Polycrystalline and ferromagnetic characteristics were visible in a single layer of Co80Pt20 nanowire. A vertical 3D magnetic domain wall memory has a ferromagnetic bit layer and a domain wall layer. Thus (Co80Pt20/Co30Pt70)n multilayer nanowires can be used in domain wall controlled 3D memory devices like racetrack memory.

The authors developed the electrodeposition technique for CoPt thin films applicable to three-dimensional domain motion memory (3D-DWMM). CoPt films with perpendicular magnetic anisotropy (PMA) were obtained in a wide range of the Co composition which was controlled by adjusting the potential during electrodeposition. The magnetic properties of the CoPt films were controlled via the Co composition. The pulse electrodeposition method was conducted to obtain smooth morphology of the Co₆₈Pt₃₂ films. Ultra-thin Co₆₈Pt₃₂ films with smooth surface morphology and an excellent squareness ratio were obtained. This study promises the electrodeposition of the artificial ferromagnetic multilayers for the magnetic pillar of the 3D-DWMM can be achieved.

Chlorazol yellow (CY) is a commonly used anionic, toxic, mutagenic, and potentially carcinogenic azo dye, which is menacing to the environment, aquatic system, food chain, and human health as well. To remove CY dye molecules from an aqueous medium, a series of Ce, Bi, and N co-doped TiO2 photocatalysts were prepared by varying the composition of the dopants. Under sunlight irradiation, the resultant 5 wt% (Ce-Bi-N) co-doped TiO2 composite catalyst was found to show the best catalytic activity. Hence, the required characterization of this catalyst was performed systematically using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. From the thorough investigation, it is revealed that the CY molecules reached adsorption–desorption equilibrium onto the surface of the catalyst within 30 min following second-order kinetics. Herein, the catalyst attained 97% degradation when exposed to sunlight at neutral (pH ~ 7, [CY] = 5 mg L−1) medium. The developed catalyst can destruct CY molecules with a maximum rate of 23.1 µg CY g−1 min−1 and the photodegradation kinetics follows first-order kinetics below 23.5 mg L−1, a fractional order between 23.5 and 35.0 mg L−1, and a zeroth order above 35.0 mg L−1 of CY concentration. Finding from scavenging effect implies that O2- and OH ∙ radicals have significant influence on the degradation. A suitable mechanism has been proposed with excellent stability and verified reusability of the proposed photocatalyst.

This study provides insights into the protonation of bio-polymer blend electrolytes (BBEs) that are based on alginate (Alg)-PVA doped with various NH4NO3 compositions, which was prepared using the solution casting method. The physicochemical of BBEs were studied by using electrical impedance spectroscopy (EIS) analysis, thermogravimetric analysis (TGA), scanning electron microscope (SEM), x-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The complexation had occurred between the Alg-PVA functional groups with the H+–NH3NO3 through the shifting and changes in the intensity of the bands. The BBEs films showed the enhancement of amorphous and the presence of globules when introduced NH4NO3, which enhanced the ionic conductivity. The addition of 35 wt.% of NH4NO3 resulted in the highest ionic conductivity value of 5.20×10–4 S cm-1 and demonstrated excellent thermal property. It was found that the system's ionic conductivity was generally influenced by the charge carriers based on evaluation of the Nyquist fitting approaches.

In the present work, amorphous bio-based polymer electrolytes (BBPEs) using alginate polymer as a matrix host and doped with varying amounts of ammonium iodide (NH4I) have been developed via the solution casting technique. The physicochemical properties of alginate-NH4I BBPEs were evaluated by using X-Ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), electrical impedance spectroscopy (EIS), and transference number measurement (TNM). The BBPEs film containing 25 wt % of NH4I possessed the highest ionic conductivity of 1.29 × 10−4 S cm−1, the highest amorphous phase, and good thermal stability of up to 234 °C. Based on the Nyquist fitting approaches, the ionic conductivity of the BBPEs was primarily influenced by the ion transportation, which was due to the interplay of segmental motion between the alginate and NH4I, and also the H+ hopping mechanism, as shown by FTIR. The proton transference number (tH+ = 0.41) suggests that alginate BBPEs are promising materials in electrochemical device applications.

Nickel particles alone can oxidize hydrogen peroxide but confronts extreme stability problem which imparts a barrier to act as sensor. The porous Nafion bed on glassy carbon electrode (GCE) surface provides the sureness of incorporating of Ni particles which was further exploited as an electrochemical sensor for H2O2 detection through oxidative degradation process. The simple electrochemical incorporation of Ni particles along the pores of Nafion improves the stability of the sensor significantly. The oxidative pathway of hydrogen peroxide on GCE/Nafion/Ni was probed by analyzing mass transfer dependent linear sweep voltammograms both in static and rotating modes along with chronoamperometry. An electron transfer step determines the overall reaction rate with k°= 2.72 × 10−4 cm s−1, which is supported by the values of transfer coefficient (β) in between (0.68–0.75). Sensing performance was evaluated by recording differential pulse voltammograms (DPVs) with the linear detection limit (LOD) of 1.8 μM and linear dynamic range (LDR) of 5–500 μM. Real samples from industrial sources were successfully quantified with excellent reproducibility mark GCE/Nafion/Ni electrode as an applicable sensor.

This study investigates the structural and ionic conduction performance with the involvement of ethylene carbonate (EC) in a bio-based polymer electrolytes (BBPEs) system, based on alginate doped glycolic acid (GA). The solution casting technique was used to successfully prepare the BBPEs which were characterized with various approaches to evaluate their ionic conduction performance. It was revealed that at ambient temperature, an optimum ionic conductivity of 9.06 × 10−4 S cm−1 was achieved after the addition of 6 wt% EC, with an observed improvement of the amorphous phase and thermal stability. The enhancement of ionic conduction properties is believed to be due to the protonation (H+) enhancement, as proven by FTIR and TNM studies. The findings show that the developed alginate-GA-EC is a promising candidate for use as electrolytes in electrochemical devices that are based on H+ carriers.

Hydrogen peroxide is widely used in various industries for the synthesis of different chemicals and often applied as a fuel in fuel cells instead of oxygen. Thus, quick detection of hydrogen peroxide is important, and consequently the development of a cost-saving methodology is a time-worthy necessity. A Polycrystalline Au [Au(pc)] electrode does not show significant electrocatalytic performance concerning H2O2 oxidation reaction. The catalytic performance is improved tremendously while Au(110) and Au(100) sites of Au(pc) surface are selectively blocked with the thiol group adsorption keeping Au(111) sites unblocked in an alkaline medium. In this article, cysteine molecules were used as the source of the thiol functional group which has coverage on Au(111) with a value of 3.47 × 10−10 mol cm−2. While Cysteine molecules are partially adsorbed on Au(110) and Au(100) sites, the unblocked Au(111) sites receive a partially positive charge, which is assumed to catalyze the oxidation of anionic species(HO2−). The current response vs H2O2 concentration relationship showed a wide linear dynamic range (LDR) between 1 and 3000 µM with LOD of 0.8 µM having a sensitivity of 58.68 µA mM−1 cm−2. In this article, detailed electrochemical investigations and characterizations of the developed sensor have been attained using cyclic voltammetric (CV), square wave voltammetric (SWV), and amperometric techniques.

Covalent organic frameworks (COFs) are a novel class of crystalline porous polymers, which possess high porosity, excellent stability, and regular nanochannels. 2D COFs provide a 1D nanochannel to form the proton transport channels. The abovementioned features afford a powerful potential platform for designing materials as proton transportation carriers. Herein, the authors incorporate sulfonic acid groups on the pore walls as proton sources for enhancing proton transport conductivity in the 1D channel. Interestingly, the sulfonic acid COFs (S-COFs) electrolytes being binder free exhibit excellent proton conductivity of ≈1.5 × 10−2 S cm−1 at 25 ℃ and 95% relative humidity (RH), which rank the excellent performance in standard proton-conducting electrolytes. The S-COFs electrolytes keep the high proton conduction over the 24 h. The activation energy is estimated to be as low as 0.17 eV, which is much lower than most reported COFs. This research opens a new window to evolve great potential of structural design for COFs as the high proton-conducting electrolytes.

Electrocatalytic ammonia oxidation reaction (AOR) was executed on the copper oxide layer, electrochemically deposited on a glassy carbon electrode (GCE) surface. The XPS analysis revealed that the oxide film contains 80% Cu(I) and 20% Cu(II) species. The EIS analysis suggests that the resultant surface can catalyze ammonia oxidation reactions efficiently. The as prepared GCE-Cu2O.CuO favored the neutral medium for executing AOR with a degradation rate of 3.76 × 10−4 mol min−1 cm−2. Kinetic investigation shows that ammonia oxidation involves a three electron transfer first-order reaction. Tafel analysis of current–potential polarization curves indicates that species such as NH3 or NHads and NH2ads intermediates do not influence the reaction rate, which made the electrode unique for carrying out AOR. The formal potential value of AOR was evaluated to be ~0.7 V vs Ag/AgCl (sat.KCl) having standard rate constant (k°) of 5.52 × 10−6 cm/s.

Christmas-tree-shaped Pd nanostructures were synthesized using a simple one-step electrodeposition method with no additives on a glassy carbon electrode (GCE) surface. Growth of the hierarchical nanostructures was optimized through the applied potential, deposition time, and precursor concentration. Comprehensive characterization techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and cyclic voltammetry (CV) were used to characterize structural features of the Christmas-tree-shaped Pd nanostructures. Our Christmas-tree-shaped Pd nanostructures showed excellent catalytic activity for ascorbic acid (AA) electro-oxidation in the alkaline condition. The modified electrode exhibited current density of 4.5 mA cm−2: much higher than that of unmodified GCE (0.6 mA cm−2). This simple electrodeposition technique with well-defined hierarchical Pd nanostructures is expected to offer new perspectives using Pd-based nanostructured surfaces in different research areas.

<p>Two-dimensional covalent organic frameworks (2D COFs) have attracted much attentions in proton conduction, owing to their regular pore channels and easy functionalization. However, most of COFs required the loading of...</p>

Proton-exchange membrane fuel cells (PEMFCs) are a highly promising green and environmentally friendly way to serve the sustainable development of human civilization. However, high-cost synthesis and pollution problems of perfluorinated sulfonic acid membranes are still not resolved. In this research, we designed and constructed porous organic polymers (POPs) with high porosity and excellent stability via the Friedel-Crafts acylation reaction using commercial products as building blocks and low-cost FeCl3 as a catalyst through a simple operation. POP-BP-1 was successfully synthesized using 1,4-bis(chloromethyl)benzene as a cross-linking agent and reactant. POP-BP-TPOT was prepared using 2,4,6-Triphenoxy-1,3,5-Triazine (TPOT) as a building unit into the skeleton of POP-BP-1. Sulfonated POPs (S-POPs) were densely decorated with sulfonic acid groups by postsulfonation. POP-BP-TPOT with abundant triazine units and sulfonic acid groups showed high water uptake. The sulfonated triazine-based polymer showed excellent proton conductivity up to 10-2 S cm-1 at 95% relative humidity (RH) under 25 °C and low activation energy of 0.19 eV. Fuel-cell test was also demonstrated using the polymer. This research suggests that the construction of S-POPs opens a suitable method to design high proton-conducting materials.

Along with the rapid development of economic integration and regional economization worldwide, the growth of green and sustainable resources has posed a major concern. Proton-exchange membrane fuel cells (PEMFCs) are examples of green, resource-conserving, and environmentally protective energy resources. Porous organic polymers (POPs), a new class of porous materials with high porosity, permanent pores, excellent stability, and easily modified functional units, can offer a good platform as proton-conducting electrolytes for fuel cells. However, a simple and general design to construct POPs with high proton conductivity presents a challenging project. For this study, we used simple benzene and aromatic benzene as building units through a facile and cost-effective process to create a series of POPs. We further prepared sulfonated POPs (S-POPs) with high-density sulfonic acid groups via post-sulphonation. The S-POPs displayed excellent proton conductivity up to 10-2 S cm-1 at 25 °C and 95% relative humidity (RH), and high conductivity up to 10-1 S cm-1 at 80 °C and 95% RH, which ranked top among the most proton-conducting POPs. These results suggest that construction of S-POPs offers a simple and universal way to evolve structural designs for high proton-conductive materials. This journal is

Porous organic polymers (POPs) are excellent adsorbent candidates owing to their high porosity, permanent pore, and well-designed structure. Ionic porous organic polymers (i-POPs) are a special type of POPs, which can greatly improve the capacity of guest molecules through electrostatic interactions. However, most reported i-POPs have shortcomings such as low porosity and high-cost synthesis procedure. With these considerations in mind, several ionic porous organic polymers (i-POP-BP-BPTMs) have been successfully designed and synthesized by using the commercial and simple-synthesized building units via a simple and cost-effective process. i-POP-BP-BPTMs indicated excellent porosity including the highest BET surface area (1491–1753 m2 g−1) and the best pore volume (2.19–2.94 cm3 g−1) among most reported ionic POPs. Interestingly, i-POP-BP-BPTM was found to be highly effective in iodine vapor capture up to 415 wt%, which is higher than the value of all reported ionic POPs. These results offer a new way to design and construct functional ionic POPs.

Well-defined silver dendrite nanostructures with primary and secondary branches on a glassy carbon electrode (GCE) surface are first demonstrated using a simple wet chemical electroless deposition method without any aid of a surfactant. The properties of dendrite structures were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Results of XPS and XRD indicated that most of the silver particles were not oxidized. The obtained silver dendrite GCE (Ag/GCE) showed high electrochemical activity toward catalytic oxidation for ascorbic acid (AA). The oxidation process followed a stepwise mechanism at slower scan rates (υ < 0.15 V s-1) and a concerted mechanism at faster scan rates (υ > 0.15 V s-1). The silver nanostructures are stable on the GCE surface and could be employed as an anode for an AA fuel cell.

A glassy carbon electrode (GCE) surface was modified with gold nanoparticles (Au NPs) via electroless deposition method. It was observed that a pristine GCE surface does not deposit Au NPs through an electroless process. However, while a GCE surface is electrochemically pretreated then sites having negative charges are generated which enables Au (III) particles to be deposited on its surface. The X-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the electrode surface. It was found that Au NPs are deposited on the GCE surface (Au-GCE) having flower like shapes. The resultant surface was employed to execute electrocatalytic oxygen reduction reactions (ORR). By analyzing hydrodynamic voltammograms, it was confirmed that ORR undergoes a 2e−transfer pathway and H2O2 is generated on the Au-GCE surface having a standard rate constant (ko) of 5.48 × 10−9 cm s−1 at +0.05 V vs. Ag/AgCl (sat. KCl) in 0.1 M H2SO4. The in-situ generated H2O2 can degrade methylene blue (MB) via Electro-Fenton process. The MB degradation was found to match well with the 1st order kinetic model with a homogeneous rate constant of 4.36 ×10−3 min-1.

Kinetics of electrocatalytic oxidation of arsenite ions has been investigated at a Pt disk electrode using cyclic voltammetry, convolution potential sweep voltammetry and electrochemical impedance spectroscopy. A complimentary environment pertaining to oxidation reactions of arsenite ions is attained in the acidic medium compared to a neutral or basic medium. It is suggested that in the neutral and basic media, direct electron transfer from the solution to electrode instigate the oxidation process without any pre adsorption. Meanwhile, in the acidic medium, prior to oxidation, arsenite ions are adsorbed on the Pt surface and a stepwise reaction mechanism is involved. Using impedance analysis, it is suggested that different forms of surface oxides at various pH values control the oxidation kinetics.

H-ZSM-5 zeolite is an inorganic material with large surface area and well-defined internal structure with porous uniform cages, cavities or channels. In this study, H-ZSM-5 was synthesised by calcination of the NH4-form at 500 °C for 3 h in air flow. This protonated H-ZSM-5 has been characterized in detail, which includes its optical, structural, morphological, and elemental properties by various conventional methods. For probable chemical sensor development, H-ZSM-5 was deposited on a silver electrode (AgE, surface area, 0.0216 cm2) to fabricate a sensor with a fast response towards selective 4-amino phenol (4-AMP) in the liquid phase. The sensor exhibited good sensitivity and long-term stability and enhanced electrochemical responses. The calibration plot was linear (r2 = 0.9979) over the 0.1 nM to 1.0 mM 4-AMP concentration ranges. The sensitivity was ∼2.085 μA cm-2 nM-1 and the detection limit was 0.02 nM (at a signal-to-noise ratio (SNR) of 3). By employing CV and EIS techniques, it was unveiled that the sensor is not well-operative in the absence of air. This shows a promising future for sensitive sensor development using mesoporous H-ZSM-5 by I-V methods for applications in the detection of hazardous and carcinogenic phenolic compounds in environmental and health care fields.