Synergistic effect of Cu-doped NiO for enhancing urea electrooxidation: Comparative electrochemical and DFT studies

Cobalt-nickel composite nano-grass as an excellent electrode for urea oxidation

Urea-contaminated wastewater requires extensive energy for proper treatment before safe discharge to the surroundings. Direct urea fuel cells (DUFCs) could be utilized efficiently to treat urea-polluted water and generate electricity. The precious/expensive catalyst utilized at the electrodes is one of the main significant challenges to DUFC commercialization. In this study, a non-precious standalone electrode cobalt-nickel composites directly formed using a facile hydrothermal method on a highly porous conductive nickel foam (NF) surface. The developed electrode has an excellent nano-grass morphology and demonstrates outstanding activity towards urea electro-oxidation. Using a 0.33 M urea, the current density @ 0.5 V (vs. Ag/AgCl) in the case of the cobalt-nickel composite with the nano-grass electrode (Co/NF) is significantly higher than that obtained using the bare NF electrode. At the same conditions, the Co/NF electrode is successfully operated for a long term (24 h) with a slight degradation in the performance, with no effect on the surface morphology. The steady-state current generated after 24 hours of cell operation is twenty times that obtained using the bare NF. The perfect performance of the modified electrode is related to the synergetic effect between Ni and Co, excellent nano-grass morphology, and ease of charge transfer. The prepared materials on the surface of the NF have a high electrochemically active surface area of 44 cm2 that is significantly higher than that of bare NF.

Current progress in layered double hydroxide-based electrocatalysts for urea oxidation: insights into strategies and mechanisms

The urea oxidation reaction (UOR) presents a more favorable alternative to the conventional oxygen evolution reaction (OER) for hydrogen production due to its lower thermodynamic potential. This method offers advantages over traditional hydrogen production approaches due to favorable operating conditions and potentially lower costs. However, the complex 6-electron transfer process in UOR limits its performance. Researchers are tackling this challenge by designing advanced electrocatalysts with optimized properties, such as porosity, heterostructures, controlled defects, surface functionalization, and fine-tuned electronic structures. This significant progress in UOR catalyst design holds promise for the future of clean energy technologies. In view of this, layered double hydroxides (LDHs) are attracting significant interest for their potential role in urea electrolysis due to the synergistic cooperation of metals, flexible configuration, tunable electronic composition and unique layered structure. This review examines the recent significant advancements in the design and synthesis of LDH-based UOR catalysts. Beyond highlighting recent breakthroughs in UOR catalysts, this review critically stresses the design strategies and challenges in urea electrolysis towards energy conversion. Moreover, this comprehensive approach provides a valuable forward-looking perspective on future research directions.

Tailored Ni(OH)2/CuCo/Ni(OH)2 Composite Interfaces for Efficient and Durable Urea Oxidation Reaction

Electrocatalytic urea oxidation reaction is a promising alternative to water oxidation for more efficient hydrogen production due to its significantly lower thermodynamic potential. However, achieving efficient electrochemical urea oxidation remains a formidable challenge, and development of an improved electrocatalyst with an optimal physicochemical and electronic structure toward urea oxidation is desired. This can be accomplished by designing a tailored two-dimensional composite with an abundance of active sites in a favorable electronic environment. In this study, we demonstrate the fabrication of a self-supported, electrochemically grown metal/mixed metal hydroxide composite interface via a two-step electrodeposition method. Specifically, Ni(OH)2 was electrodeposited on the top of the CuCo layer (Ni(OH)2/CuCo/Ni(OH)2), and the resultant 2D composite structure required 1.333 ± 0.006 V to oxidize urea electrochemically to achieve a current density of 10 mA cm-2, which outperformed the potential required for individual components, Ni(OH)2 and CuCo. The high density of Ni3+ active sites in the composite structure facilitated high electrocatalyst activity and stability. Ni(OH)2/CuCo/Ni(OH)2 was stable for at least 50 h without any noticeable degradation in the activity or alteration of the morphology. As a bifunctional electrocatalyst, the material also exhibited excellent performance for water oxidation with 260 mV overpotential and 50 h stability. In a two-electrode configuration coupled with a NiMo cathode catalyst, the electrolyzer required 1.42 V cell voltage for overall urea splitting. Overall, the engineered Ni(OH)2/CuCo/Ni(OH)2 composite demonstrated exceptional potential as an efficient and stable electrocatalyst for both urea and water oxidation reactions, paving the way for more effective hydrogen production technologies.

Synthesis of nickel-sphere coated Ni-Mn layer for efficient electrochemical detection of urea

Using a trustworthy electrochemical sensor in the detection of urea in real blood samples received a great attention these days. A thin layer of nickel-coated nickel-manganese (Ni@NiMn) is electrodeposited on a glassy carbon electrode (GC) (Ni@NiMn/GC) surface and used to construct the electrochemical sensor for urea detection. Whereas, electrodeposition is considered as strong technique for the controllable synthesis of nanoparticles. Thus, X-ray diffraction (XRD), atomic force microscope (AFM), and scanning electron microscope (SEM) techniques were used to characterize the produced electrode. AFM and SEM pictures revealed additional details about the surface morphology, which revealed a homogenous and smooth coating. Furthermore, electrochemical research was carried out in alkaline medium utilizing various electrochemical methods, including cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The electrochemical investigations showed that the electrode had good performance, high stability and effective charge transfer capabilities. The structural, morphological, and electrochemical characteristics of Ni@NiMn/GC electrodes were well understood using the analytical and electrochemical techniques. The electrode showed a limit of detection (LOD) equal to 0.0187 µM and a linear range of detection of 1.0-10 mM of urea. Furthermore, real blood samples were used to examine the efficiency of the prepared sensor. Otherwise, the anti-interfering ability of the modified catalyst was examined toward various interfering species.

The Enhanced Performance of NiCuOOH/NiCu(OH)2 Electrode Using Pre-Conversion Treatment for the Electrochemical Oxidation of Ammonia

Electrochemical oxidation of ammonia is an attractive process for wastewater treatment, hydrogen production, and ammonia fuel cells. However, the sluggish kinetics of the anode reaction has limited its applications, leading to a high demand for novel electrocatalysts. Herein, the electrode with the in situ growth of NiCu(OH)2 was partially transformed into the NiCuOOH phase by a pre-treatment using highly oxidative solutions. As revealed by SEM, XPS, and electrochemical analysis, such a strategy maintained the 3D structure, while inducing more active sites before the in situ generation of oxyhydroxide sites during the electrochemical reaction. The optimized NiCuOOH-1 sample exhibited the current density of 6.06 mA cm-2 at 0.5 V, which is 1.67 times higher than that of NiCu(OH)2 (3.63 mA cm-2). Moreover, the sample with a higher crystalline degree of the NiCuOOH phase exhibited lower performance, demonstrating the importance of a moderate treatment condition. In addition, the NiCuOOH-1 sample presented low selectivity (<20%) towards NO2- and stable activity during the long-term operation. The findings of this study would provide valuable insights into the development of transition metal electrocatalysts for ammonia oxidation.

Engineering advanced noble-metal-free electrocatalysts for energy-saving hydrogen production from alkaline water via urea electrolysis

When the anodic oxygen evolution reaction (OER) of water splitting is replaced by the urea oxidation reaction (UOR), the electrolyzer can fulfill hydrogen generation in an energy-economic manner for urea electrolysis as well as sewage purification. However, owing to the sluggish kinetics from a six-electron process for UOR, it is in great demand to design and fabricate high-performance and affordable electrocatalysts. Over the past years, numerous non-precious materials (especially nickel-involved samples) have offered huge potential as catalysts for urea electrolysis under alkaline conditions, even in comparison with frequently used noble-metal ones. In this review, recent efforts and progress in these high-efficiency noble-metal-free electrocatalysts are comprehensively summarized. The fundamentals and principles of UOR are first described, followed by highlighting UOR mechanism progress, and then some discussion about density functional theory (DFT) calculations and operando investigations is given to disclose the real reaction mechanism. Afterward, aiming to improve or optimize UOR electrocatalytic properties, various noble-metal-free catalytic materials are introduced in detail and classified into different classes, highlighting the underlying activity-structure relationships. Furthermore, new design trends are also discussed, including targetedly designing nanostructured materials, manipulating anodic products, combining theory and in situ experiments, and constructing bifunctional catalysts. Ultimately, we point out the outlook and explore the possible future opportunities by analyzing the remaining challenges in this booming field.

Urea catalytic oxidation for energy and environmental applications

Urea is one of the most essential reactive nitrogen species in the nitrogen cycle and plays an indispensable role in the water-energy-food nexus. However, untreated urea or urine wastewater causes severe environmental pollution and threatens human health. Electrocatalytic and photo(electro)catalytic urea oxidation technologies under mild conditions have become promising methods for energy recovery and environmental remediation. An in-depth understanding of the reaction mechanisms of the urea oxidation reaction (UOR) is important to design efficient electrocatalysts/photo(electro)catalysts for these technologies. This review provides a critical appraisal of the recent advances in the UOR by means of both electrocatalysis and photo(electro)catalysis, aiming to comprehensively assess this emerging field from fundamentals and materials, to practical applications. The emphasis of this review is on the design and development strategies for electrocatalysts/photo(electro)catalysts based on reaction pathways. Meanwhile, the UOR in natural urine is discussed, focusing on the influence of impurity ions. A particular emphasis is placed on the application of the UOR in energy and environmental fields, such as hydrogen production by urea electrolysis, urea fuel cells, and urea/urine wastewater remediation. Finally, future directions, prospects, and remaining challenges are discussed for this emerging research field. This critical review significantly increases the understanding of current progress in urea conversion and the development of a sustainable nitrogen economy.

Synergetic effect of essential oils and calcium phosphate nanoparticles for enhancement the corrosion resistance of titanium dental implant

Calcium phosphate (CaPO4) coating is one of various methods that is used to modify the topography and the chemistry of Ti dental implant surface to solve sever oral problems that result from diseases, accidents, or even caries due to its biocompatibility. In this work, anodized (Ti-bare) was coated by CaPO4 prepared from amorphous calcium phosphate nanoparticles (ACP-NPs) and confirmed the structure by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) techniques. Ti-bare was coated by prepared CaPO4 through the casting process, and the morphology of Ti/CaPO4 was characterized by scanning electron microscope (SEM) where the nano-flakes shape of CaPO4 and measured to be 60 ~ 80 nm was confirmed. The stability of Ti-bare and coated Ti/CaPO4 was studied in a simulated saliva solution using electrochemical impedance spectroscopy (EIS) and linear polarization techniques to deduce their corrosion resistance. Furthermore, three essential oils (EO), Cumin, Thyme, and Coriander, were used to stimulate their synergistic effect with the CaPO4 coat to enhance the corrosion resistance of Ti implant in an oral environment. The fitting EIS parameters based on Rs [RctC]W circuit proved that the charge transfer resistance (Rct) of Ti/CaPO4 increased by 264.4, 88.2, and 437.5% for Cumin, Thyme, and Coriander, respectively, at 2% concentration.

FeNi supported on carbon sponge for efficient urea oxidation in direct urea fuel cell

The direct urea fuel cell (DUFC) is a power generation equipment with urea-rich wastewater or urine as fuel source. It has the unique ability to purify sewage while simultaneously generating electricity, making it a highly efficient and environmentally friendly option. In this paper, pomegranate seed-like Ni nano-blocks and Fe nanosheets were synthesized by electrodeposition and chemical reduction and attached to the carbonized melamine sponge matrix. The N-doped carbon sponge (NCS) provided a large number of polyhedral holes, which allowed for efficient gas escape through channels. The combination of Fe reduces the initial urea oxidation potential, reaction activation energy and reaction resistance. The synthesized FeNi supported on N-doped carbon sponge composite (FeNi@NCS) has a catalytic current density of 625 mA cm-2 and a Tafel slope of 42.51 mV dec-1 for urea electrooxidation reaction (UOR). Assembling the direct urine-hydrogen peroxide fuel cell (DUrHPFC) resulted in the highest performance output. The open circuit voltage (OCV) was 0.98 V, and the peak power density reached 9.61 mW cm-2. The results show that the prepared catalyst provides an opportunity to solve the problems that hinder the development of urea green cycle at present.

High-performance spinel NiMn2O4 supported carbon felt for effective electrochemical conversion of ethylene glycol and hydrogen evolution applications

One of the most effective electrocatalysts for electrochemical oxidation reactions is NiMn2O4 spinel oxide. Here, a 3-D porous substrate with good conductivity called carbon felt (CF) is utilized. The composite of NiMn2O4-supported carbon felt was prepared using the facile hydrothermal method. The prepared electrode was characterized by various surface and bulk analyses like powder X-ray diffraction, X-ray photon spectroscopy (XPS), Scanning and transmitted electron microscopy, thermal analysis (DTA), energy dispersive X-ray (EDX), and Brunauer-Emmett-Teller (BET). The activity of NiMn2O4 toward the electrochemical conversion of ethylene glycol at a wide range of concentrations was investigated. The electrode showed a current density of 24 mA cm-2 at a potential of 0.5 V (vs. Ag/AgCl). Furthermore, the ability of the electrode toward hydrogen evaluation in an alkaline medium was performed. Thus, the electrode achieved a current density equal 10 mA cm-2 at an overpotential of 210 mV (vs. RHE), and the provided Tafel slope was 98 mV dec-1.

Green synthesis of Ag nanoparticle supported on graphene oxide for efficient nitrite sensing in a water sample

Water is essential for conserving biodiversity, ecology, and human health, but because of population growth and declining clean water supplies, wastewater must be treated to meet demand. Nitrite is one of the contaminants in wastewater that is well-known. It is crucial to identify nitrite since it can be fatal to humans in excessive doses. Utilizing a straightforward and effective electrochemical sensor, nitrite in actual water samples may be determined electrochemically. The sensor is created by coating the surface of a GC electrode with a thin layer of graphene oxide (GO), followed by a coating of silver nanoparticles. The modified electrode reached a linear detection range of 1-400 µM. thus, the activity of the electrode was investigated at different pH values ranging from 4 to 10 to cover acidic to highly basic environments. However, the electrode recorded limit of detection (LOD) is equal to 0.084, 0.090, and 0.055 µM for pH 4, 7, and 10, respectively. Additionally, the electrode activity was utilized in tap water and wastewater that the LOD reported as 0.16 and 0.157 µM for tape water and wastewater, respectively.

Modulation Strategies for the Preparation of High-Performance Catalysts for Urea Oxidation Reaction and Their Applications

Compared with the traditional electrolysis of water to produce hydrogen, urea-assisted electrolysis of water to produce hydrogen has significant advantages and has received extensive attention from researchers. Unfortunately, urea oxidation reaction (UOR) involves a complex six-electron transfer process leading to high overpotential, which forces researchers to develop high-performance UOR catalysts to drive the development of urea-assisted water splitting. Based on the UOR mechanism and extensive literature research, this review summarizes the strategies for preparing highly efficient UOR catalysts. First, the UOR mechanism is introduced and the characteristics of excellent UOR catalysts are pointed out. Aiming at this, the following modulation strategies are proposed to improve the catalytic performance based on summarizing various literature: 1) Accelerating the active phase formation to reduce initial potential; 2) Creating double active sites to trigger a new UOR mechanism; 3) Accelerating urea adsorption and promoting C─N bond cleavage to ensure the effective conduct of UOR; 4) Promoting the desorption of CO2 to improve stability and prevent catalyst poisoning; 5) Promoting electron transfer to overcome the inherent slow dynamics of UOR; 6) Increasing active sites or active surface area. Then, the application of UOR in electrochemical devices is summarized. Finally, the current deficiencies and future directions are discussed.

Synthesis and characterization of lead-based metal-organic framework nano-needles for effective water splitting application

Metal organic frameworks (MOFs) are a class of porous materials characterized by robust linkages between organic ligands and metal ions. Metal-organic frameworks (MOFs) exhibit significant characteristics such as high porosity, extensive surface area, and exceptional chemical stability, provided the constituent components are meticulously selected. A metal-organic framework (MOF) containing lead and ligands derived from 4-aminobenzoic acid and 2-carboxybenzaldehyde has been synthesized using the sonochemical methodology. The crystals produced were subjected to various analytical techniques such as Fourier-transform infrared spectroscopy (FT-IR), Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET), and thermal analysis. The BET analysis yielded results indicating a surface area was found to be 1304.27 m2 g-1. The total pore volume was estimated as 2.13 cm3 g-1 with an average pore size of 4.61 nm., rendering them highly advantageous for a diverse range of practical applications. The activity of the modified Pb-MOF electrode was employed toward water-splitting applications. The electrode reached the current density of 50 mA cm-2 at an overpotential of - 0.6 V (vs. RHE) for hydrogen evolution, and 50 mA cm-2 at an overpotential of 1.7 V (vs. RHE) for oxygen evolution.

Chitosan Supports Boosting NiCo2O4 for Catalyzed Urea Electrochemical Removal Application

Currently, wastewater containing high urea levels poses a significant risk to human health. Else, electrocatalytic methodologies have the potential to transform urea present in urea-rich wastewater into hydrogen, thereby contributing towards environmental conservation and facilitating the production of sustainable energy. The characterization of the NiCo2O4@chitosan catalyst was performed by various analytical techniques, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, the activity of electrodes toward urea removal was investigated by several electrochemical techniques. As a function of current density, the performance of the modified NiCo2O4@chitosan surface was employed to remove urea using electrochemical oxidation. Consequently, the current density measurement was 43 mA cm-2 in a solution of 1.0 M urea and 1.0 M KOH. Different kinetic characteristics were investigated, including charge transfer coefficient (α), Tafel slope (29 mV dec-1), diffusion coefficient (1.87 × 10-5 cm2 s-1), and surface coverage 4.29 × 10-9 mol cm-2. The electrode showed high stability whereas it lost 10.4% of its initial current after 5 h of urea oxidation.

Construction, Characterization, DFT Computational Study, and Evaluation the Performance of Some New N-Amino Pyridinone Schiff Base Catalyzed with Ceric(IV) Ammonium Nitrate (CAN) as Corrosion Inhibitors in Some Petroleum Applications

In this paper, two novel organic inhibitors, TAP-TPP and TAP-CEQ, were prepared via Schiff base condensation as a green chemistry methodology using an eco-friendly catalyst, ceric ammonium nitrate, with a high yield (87% and 91%), and characterized via elemental analysis, FTIR, 1H, and 13C NMR spectroscopic analysis tools. Weight loss assessment was utilized as a chemical testing method, and the maximum inhibition efficiency of TAP-TPP and TAP-CEQ is 89.4% and 91.8%, respectively. PDP and EIS were electrochemical measures to determine the efficacy of both inhibitors as anticorrosion for carbon steel alloys in 2 M HCl aggressive media. The collected electrochemical results demonstrated that both inhibitors behaved as excellent anticorrosion agents for metallic constructions. According to the potentiodynamic polarization (PDP) analysis, these organic inhibitors worked as mixed-type inhibitors. The adsorption isotherm revealed that undertaken compounds obeyed Langmuir adsorption isotherm with the free energies of adsorption of ranged from ΔG = − 34.29 to − 34.63 kJ Mol−1. Also, electrochemical impedance spectroscopy (EIS) data confirmed that the values charge transfer resistance (Rct) was increased by increasing the concentration of the injected inhibitor molecules. In contrast, the electrochemical double layer (Cdl) was dramatically decreased. The work was supported by two-surface analysis methods such as SEM and EDX. For more details, the values of percentage inhibition efficiency can be ordered as follows: TAP-CEQ > TAP-TPP. Finally, a suitable inhibition mechanism and theoretical studies including EHOMO, ELUMO, diploe moment (µ), and electrophilicity index (ω) were assumed and discussed in detailed.

High-performance IN738 superalloy derived from turbine blade waste for efficient ethanol, ethylene glycol, and urea electrooxidation

In this work, IN738 superalloy used previously in gas turbines was recycled and used as a working electrode for the electrooxidation of different fuels, namely ethylene glycol, ethanol, and urea. The electrocatalytic efficiency of the electrode was studied by cyclic voltammetry, chronoamperometry, and electrochemical impedance. Several kinetics parameters like diffusion coefficient, Tafel slope, rate constant, and activation energy were calculated. The modified electrode was characterized as received using XRD, SEM, and EDAX to elucidate the crystal structure and surface morphology before and after electrochemical oxidation. The anodic current densities of electrochemical oxidation of ethanol, ethylene glycol, and urea were 29, 17, and 12 mA.cm−2, respectively, in an alkaline solution at a potential of 0.6 V (vs. Ag/AgCl). The kinetic parameters like diffusion coefficients for ethanol, ethylene glycol, and urea were found to be 1.5 $$\times$$ × 10–6, 1.038 $$\times$$ × 10–6, and 0.64 $$\times$$ × 10–6 cm2 s−1, respectively. The charge transfer resistances were estimated for electrooxidation of different fuels by electrochemical impedance spectroscopy (EIS).

Graphical Abstract

Nafee S, Alamro FS, Pashameah RA, Ahmed HA, Medany SS. Zinc Nanocomposite Supported Chitosan for Nitrite Sensing and Hydrogen Evolution Applications

Nanoparticles of ZnO-Chitosan (Zn-Chit) composite were prepared using precipitation methods. Several analytical techniques, such as scanning electron microscope (SEM), transmitted electron microscope (TEM), powder X-ray diffraction (XRD), infrared spectroscopy (IR), and thermal analysis, were used to characterize the prepared composite. The activity of the modified composite was investigated for nitrite sensing and hydrogen production applications using various electrochemical techniques. A comparative study was performed for pristine ZnO and ZnO loaded on chitosan. The modified Zn-Chit has a linear range of detection 1–150 µM and a limit of detection (LOD) = 0.402 µM (response time ~3 s). The activity of the modified electrode was investigated in a real sample (milk). Furthermore, the anti-interference capability of the surface was utilized in the presence of several inorganic salts and organic additives. Additionally, Zn-Chit composite was employed as an efficient catalyst for hydrogen production in an acidic medium. Thus, the electrode showed long-term stability toward fuel production and enhanced energy security. The electrode reached a current density of 50 mA cm−2 at an overpotential equal to −0.31 and −0.2 V (vs. RHE) for GC/ZnO and GC/Zn-Chit, respectively. Electrode durability was studied for long-time constant potential chronoamperometry for 5 h. The electrodes lost 8% and 9% of the initial current for GC/ZnO and GC/Zn-Chit, respectively.

Nafee S, Alamro FS, Pashameah RA, Ahmed HA, Medany SS. Zinc Nanocomposite Supported Chitosan for Nitrite Sensing and Hydrogen Evolution Applications

Nanoparticles of ZnO-Chitosan (Zn-Chit) composite were prepared using precipitation methods. Several analytical techniques, such as scanning electron microscope (SEM), transmitted electron microscope (TEM), powder X-ray diffraction (XRD), infrared spectroscopy (IR), and thermal analysis, were used to characterize the prepared composite. The activity of the modified composite was investigated for nitrite sensing and hydrogen production applications using various electrochemical techniques. A comparative study was performed for pristine ZnO and ZnO loaded on chitosan. The modified Zn-Chit has a linear range of detection 1-150 µM and a limit of detection (LOD) = 0.402 µM (response time ~3 s). The activity of the modified electrode was investigated in a real sample (milk). Furthermore, the anti-interference capability of the surface was utilized in the presence of several inorganic salts and organic additives. Additionally, Zn-Chit composite was employed as an efficient catalyst for hydrogen production in an acidic medium. Thus, the electrode showed long-term stability toward fuel production and enhanced energy security. The electrode reached a current density of 50 mA cm-2 at an overpotential equal to -0.31 and -0.2 V (vs. RHE) for GC/ZnO and GC/Zn-Chit, respectively. Electrode durability was studied for long-time constant potential chronoamperometry for 5 h. The electrodes lost 8% and 9% of the initial current for GC/ZnO and GC/Zn-Chit, respectively.

Polyaniline-Supported Nickel Oxide Flower for Efficient Nitrite Electrochemical Detection in Water

A modified electrode with conducting polymer (Polyaniline) and NiO nanoflowers was prepared to detect nitrite ions in drinking water. A simple method was used to prepare the NiO nanoflower (NiOnF). Several techniques characterized the as-prepared NiOnF to determine the chemical structure and surface morphology of the NiO, such as XRD, XPS, FT-IR, and TGA. The activity of the electrode toward nitrite sensing was investigated over a wide range of pH (i.e., 2 to 10). The amperometry method was used to determine the linear detection range and limit. Accordingly, the modified electrode GC/PANI/NiOnf showed a linear range of detection at 0.1-1 µM and 1-500 µM. At the same time, the limit of detection (LOD) was 9.7 and 64 nM for low and high concentrations, respectively. Furthermore, the kinetic characteristics of nitrite, such as diffusion and transport coefficients, were investigated in various media. Moreover, the charge transfer resistance was utilized for nitrite electrooxidation in different pH values by the electrochemical impedance technique (EIS). The anti-interfering criteria of the modified surfaces were utilized in the existence of many interfering cations in water (e.g., K+, Na+, Cu2+, Zn2+, Ba2+, Ca2+, Cr2+, Cd2+, Pd2+). A real sample of the Nile River was spiked with nitrite to study the activity of the electrode in a real case sample (response time ~4 s). The interaction between nitrite ions and NiO{100} surface was studied using DFT calculations as a function of adsorption energy.

Sputtered Cu-doped NiO thin films as an efficient electrocatalyst for methanol oxidation

The efficient electrocatalysts for direct methanol oxidation play an essential role in the electrochemical energy conversion systems for their application in a wide range of portable applications. Consequently, Cu-doped NiO thin films on fluorine-doped tin oxide (FTO) were successfully prepared by the co-sputtering deposition technique, using various deposition times (300, 600, 900, and 1200 seconds), and producing films of different thicknesses (30, 55, 90, and 120 nm, respectively). X-ray diffraction (XRD) revealed the ideal crystallinity of the structure of the prepared films and was used to observe the effect of the thickness of the films on the crystal size. Energy-dispersive X-ray spectroscopy (EDS) confirmed the purity of the deposited film without any contamination. Field emission scanning electron microscopy (FESEM) images confirmed the film thickness increase with increasing deposition time. The surface roughness value of the Cu-NiO 1200 film was found to be 3.2 nm based on the atomic force microscopy (AFM) measurements. The deposited thin films of different thicknesses have been used as electrocatalysts for methanol oxidation at various concentrations of methanol (0, 0.5, 1, and 2 M), and displayed the highest electrocatalytic performance in 1 M methanol. Cu-doped NiO thin films have the advantage as electrocatalysts where they can be used directly without adding any binder or conducting agents, this is because Cu-doped NiO is deposited with high adhesion and strong electrical contact to the FTO substrate. A clear impact on the catalytic activity with increasing film thickness and a correlation between the film thickness and its catalytic activity was observed. The current density increased by about 60% for the Cu-NiO 1200 sample compared to Cu-NiO 300 sample, with the lowest onset potential of 0.4 V vs. Ag/AgCl. All deposited thin films of different thicknesses exhibited high stability at 0.6 V in 1 M methanol. This will open the window toward using physical deposition techniques for optimizing the electrocatalytic activity of different catalysts for electrocatalytic applications.

Experimental and theoretical studies for corrosion of molybdenum electrode using streptomycin drug in phosphoric acid medium

Corrosion inhibition of molybdenum electrode in H3PO4 acid medium of different concentrations (3.0 to 13 M) has been investigated utilizing different electrochemical techniques. It was observed that the most corrosive concentration is 3.0 M orthophosphoric acid concentration. The effect of adding Cl- to 3.0 M orthophosphoric acid in the concentration range of 0.1 to 1.0 M was also studied. This study showed that the most corrosive medium is 3.0 M containing 1.0 M chloride ion with the greatest rate of hydrogen production. In 3.0 M H3PO4 acid with 1.0 M of NaCl, the tested electrode's corrosion and hydrogen production may be successfully suppressed by adding Streptomycin of 10 mM concentration leading to high inhibition efficiency. The outcomes of the studies were confirmed by scanning electron microscopic examination. Additionally, a computational chemistry approach was used to investigate how streptomycin adsorbs and inhibits corrosion at the interface of metal surfaces, and the outcomes of the computational studies are in excellent accord with the experimental findings.

High-Density NiCu Bimetallic Phosphide Nanosheet Clusters Constructed by Cu-Induced Effect Boost Total Urea Hydrolysis for Hydrogen Production

The development of urea electrolysis technologies toward energy-saving hydrogen production can alleviate the environmental issues caused by urea-rich wastewater. In the current practices, the development of high-performance electrocatalysts in urea electrolysis remains critical. In this work, the NiCu-P/NF catalyst is prepared by anchoring Ni/Cu bimetallic phosphide nanosheets onto Ni foam (NF). In the experiments, the micron-sized elemental Cu polyhedron is first anchored on the surface of the NF substrate to provide more space for the growth of bimetallic nanosheets. Meanwhile, the Cu element adjusted the electron distribution within the composite and formed Ni/P orbital vacancies, which in turn accelerated the kinetic process. As a result, the optimal NiCu-P/NF sample exhibits excellent catalytic activity and cycling stability in a hybrid electrolysis system for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Further, the alkaline urea-containing electrolyzer is assembled with NiCu-P/NF as two electrodes reached a current density of 50 mA cm^-2 with a low driving potential of 1.422 V, which outperforms the typical commercial noble metal electrolyzer (RuO₂||Pt/C). Those findings suggest the feasibility of the substrate regulation strategy to increase the growth density of active species in preparation of an efficient bifunctional electrocatalyst for cracking the urea-containing wastewater.

Methanol and Ethanol Electrooxidation on ZrO2/NiO/rGO

Recently, transition metal oxides have been considered for various applications due to their unique properties. We present the synthesis of a three-component catalyst consisting of zirconium oxide (ZrO₂), nickel oxide (NiO), and reduced graphene oxide (rGO) in the form of ZrO₂/NiO/rGO by a simple one-step hydrothermal method. X-ray powder diffraction (XRD), scanning electron microscope (SEM), and bright-field transmission electron microscopy (BF-TEM) analyses were performed to accurately characterize the catalysts. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) analyses were also carried out to investigate the methanol and ethanol alcohol electrooxidation ability of the synthesized nanocatalysts. Inspired by the good potential of metal oxides in the field of catalysts, especially in fuel-cell anodes, we investigated the capability of this catalyst in the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). After proving the successful synthesis and examining the surface morphology of these materials, detailed electrochemical tests were performed to show the outstanding capability of this new nanocatalyst for use in the anode of alcohol fuel cells. ZrO₂/NiO/rGO indicated a current density of 26.6 mA/cm² at a peak potential of 0.52 V and 99.5% cyclic stability in the MOR and a current density of 17.3 mA/cm² at a peak potential of 0.52 V and 98.5% cyclic stability in the EOR (at optimal concentration/scan rate 20 mV/s), representing an attractive option for use in the anode of alcoholic fuel cells.

Cu-induced NiCu-P and NiCu-Pi with multilayered nanostructures as highly efficient electrodes for hydrogen production via urea electrolysis

Since urea is commonly present in domestic sewage and industrial wastewater, its use in hydrogen production by electrolysis can simultaneously help in water decontamination. To achieve this goal, the development of highly active and inexpensive urea electrolysis catalysts is necessary. This study deals with the preparation of multilayered nickel and copper phosphides/phosphates (NiCu-P/NF and NiCu-Pi/NF) supported on Ni foam (NF) and their application as new electrocatalyst types for the electrolysis of urea-containing wastewaters. In these materials, Cu atoms induce the formation of multilayer nanostructures and modulate electron distribution, allowing for the exposure of additional active sites and acceleration of the process kinetics. NiCu-P/NF is used as a cathode and NiCu-Pi/NF as an anode in an electrolysis cell and exhibits significant catalytic activity and stability in the urea oxidation reaction (UOR) and the hydrogen evolution reaction (HER). The NiCu-Pi/NF||NiCu-P/NF electrolysis cell, operating with an alkaline urea-containing aqueous electrolyte, achieves a current density of 10 mA cm^- at a potential of 1.41 V, which is less than required by the RuO₂||Pt/C cell utilizing commercial noble metal-based electrodes. The study provides a novel strategy for designing efficient catalysts to produce hydrogen by urea electrolysis.

Fabrication of a Tubular CuO/NiO Biomimetic Nanozyme with Synergistically Promoted Peroxidase-like Performance for Isoniazid Sensing

Isoniazid is an antibiotic primarily used in clinical treatment of tuberculosis, but excessive usage can lead to serious consequences such as hepatotoxicity, neurotoxicity, and even coma and death. Therefore, it is critical to exploit a quick, facile, and acute way for isoniazid analysis. In this work, we have demonstrated an efficient electrospinning-carbonation-wet chemistry reaction-calcination process to fabricate CuO/NiO nanotubes (NTs) as a promising nanozyme for peroxidase (POD) mimicking. In virtue of the distinct tubular structure and synergy between CuO and NiO from the mechanisms of both electron transfer and hydroxyl radical generation, a remarkably improved catalytic activity is realized for the CuO/NiO NTs compared with bare CuO and NiO samples. According to the admirable POD-like property, a rapid colorimetric detection for isoniazid is accomplished with a detection limit of 0.4 μM (S/N = 3) and favorable selectivity. In addition, the sensing capability of isoniazid in a real sample is also investigated with satisfactory results. This work offers a novel tactic to fabricate high-performance nanozymes with efficient isoniazid sensing capabilities to address challenges in disease treatment efficacy and public safety monitoring.

In situ construction of Fe3O4@FeOOH for efficient electrocatalytic urea oxidation

Substituting water oxidation half of water splitting with anodic oxidation of urea can reduce the cost of H₂ production and provide an avenue for treating urea-rich wastewater. However, developing an efficient and stable electrocatalyst is necessary to overcome the indolent kinetics of the urea oxidation reaction (UOR). Accordingly, we have used the Schikorr reaction to deposit Fe₃O₄ particles on the nickel foam (Fe₃O₄/NF). Results from the various analysis indicated that under the operational conditions, Fe₃O₄ underwent surface reconstruction to produce a heterolayered structure wherein a catalytically active FeOOH layer encased a conducting Fe₃O₄. Fe₃O₄/NF outperformed RuO₂ as a UOR catalyst and delivered a current density of 10 50 and 100 mA cm^-2 at low applied potentials of 1.38 1.42 and 1.46 V, respectively, with a Tafel slope of 28 mV dec^-1. At the applied potential of 1.4 V, Fe₃O₄/NF demonstrated a turnover frequency (TOF) of 2.8 × 10^-3 s^-1, highlighting its superior intrinsic activity. In addition, a symmetrical urea electrolyzer constructed using Fe₃O₄/NF produced the current density of 10 mA cm^-2 at a cell voltage of 1.54 V.