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Photoelectrochemical water splitting has attracted significant attention as an environment-friendly method to generate H2 and O2. Electrodes composed of powders exhibit a large surface area and are favorable for surface reactions; however, their high resistance prevents charge transportation. In contrast, photoelectrodes composed of a dense film exhibit high conductivity; however, they constitute a small surface area. Therefore, a combination of these two films can lead to higher photoelectrochemical activities. Herein, a particulate/dense TiO2 hybrid electrode exhibited eightfold and twofold higher activities for water oxidation at sufficiently positive potentials as compared to those of the single particulate and dense film electrodes, respectively. Electrochemical impedance measurements and the light intensity dependence of the photocurrent suggest that the activity enhancement is responsible for the synergistic effects of effective charge separation in the highly conductive dense TiO2 film and effective hole-consuming reaction at the particulate TiO2 layer. However, the activity rather decreased near the onset potential of water oxidation (<0.3 V) under the illumination of light near the bandgap energy (375 nm). Such an activity decrease was not observed for the 340 nm illumination; hence, the recombination of charge carriers generated in dense and particulate layers is responsible: the charge transfer resistance at the particulate/dense interface prevents the effective charge separation. These results demonstrate that the combination of particulate matter and dense films can produce a synergistic effect; however, the resistance at the junction remains a significant bottleneck, rendering resistance reduction necessary to maximize the advantages of hybrid electrodes, especially under the illumination of longer wavelength light. [ABSTRACT FROM AUTHOR]

Direct formic acid fuel cells (DFAFCs) are one of the most promising power sources due to its high conversion efficiency; relatively low carbon emissions, toxicity, and flammability; convenience; and low-cost storage and transportation. However, the key challenge to large-scale commercial applications is its poor power performance and the catalyst's high preparation cost. In this study, a new sandwich-structured Pd/polypyrrole-graphene/Pd (Pd/PPy-Gns/Pd)-modified glassy carbon electrode (GCE) was prepared using a simple constant potential (CP) electrodeposition technique. On the basis of the unique synthetic procedure and structural advantages, the Pd/PPy-Gns/Pd shows a fast charge/mass transport rate, high electrocatalytic activity, and great stability for formic acid electro-oxidation (FAO). The mass activity of Pd/PPy-Gns/Pd electrode reaches 917 mA·mg−1Pd. The excellent catalytic activity is mainly due to the uniform embedding of Pd nanoparticles on the polypyrrole-graphene (PPy-Gns) support, which exposes more active sites, and prevents the shedding and inactivation of Pd nanoparticles. At the same time, the introduction of graphene (Gns) in the PPy further improved the conductivity of the catalyst and accelerated the transfer of electrons. [ABSTRACT FROM AUTHOR]

The many pollutants detected in water represent a global environmental issue. Emerging and persistent organic pollutants are particularly difficult to remove using traditional treatment methods. Electro-oxidation and sulfate-radical-based advanced oxidation processes are innovative removal methods for these contaminants. These approaches rely on the generation of hydroxyl and sulfate radicals during electro-oxidation and sulfate activation, respectively. In addition, hybrid activation, in which these methods are combined, is interesting because of the synergistic effect of hydroxyl and sulfate radicals. Hybrid activation effectiveness in pollutant removal can be influenced by various factors, particularly the materials used for the anode. This review focuses on various organic pollutants. However, it focuses more on pharmaceutical pollutants, particularly paracetamol, as this is the most frequently detected emerging pollutant. It then discusses electro-oxidation, photocatalysis and sulfate radicals, highlighting their unique advantages and their performance for water treatment. It focuses on perovskite oxides as an anode material, with a particular interest in calcium copper titanate (CCTO), due to its unique properties. The review describes different CCTO synthesis techniques, modifications, and applications for water remediation. [ABSTRACT FROM AUTHOR]

A novel approach to surface modification was developed to improve the corrosion performance of biodegradable magnesium alloys. Additively manufactured magnesium samples and Mg-Mn-based magnesium alloys were used in this study. This method involves the combination of plasma electrolytic oxidation to create a porous ceramic-like matrix, followed by treatment with protective biocompatible agents. The most efficient method for the PEO-layer impregnation using sodium oleate and polycaprolactone was selected and optimized. The correlation between the structure, composition, and protective properties of the hybrid coatings was established. The composition of the formed polymer-containing layers was established using XPS and Raman microspectroscopy. The presence of sodium oleate and its distribution across the coating surface was confirmed at the microscale. The corrosion-protection level of the hybrid layers was assessed using potentiodynamic polarization measurements, electrochemical impedance spectroscopy, hydrogen evolution testing, and gravimetry (mass-loss tests) in vitro. The oleate-containing polycaprolactone layers (HC-SO 0.1–2) demonstrated stable corrosion behavior even after 7 days of immersion in Hank's balanced salt solution. The corrosion-current density and impedance modulus measured at a frequency of 0.1 Hz for the samples with hybrid coating after 7 days of exposure were equal to 5.68 × 10−8 A∙cm−2 and 2.03 × 106 Ω∙cm2, respectively. The developed method of surface modification demonstrates the coating's self-healing properties. The effectiveness of employing hybrid anticorrosive bioactive PEO coatings for biomedical products made from magnesium and its alloys was demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual oxidation by H 2 O 2 and Ce4+ induces lattice disordering in Prussian blue analogue. • More catalytically active high-valence species can be generated during dual oxidation. • Lattice disordering leads to enriched reactive sites for the pre-oxidation. • Remarkable OER activity with low overpotential, high current density, excellent intrinsic activity and ultrastable performance. Electro-oxidation reactions (EORs) are important half reactions in overall and assisted water electrolysis, which are crucial in achieving economic and sustainable hydrogen production and realizing simultaneous wastewater treatment. Current studies indicate that the high-valence metal ions that are locally enriched in the catalysts or generated in situ during the anodic preoxidation process are active species for EORs. Hence, designing (pre)catalysts with enriched local active sites and boosted preoxidation is of great importance. In this work, with a focus on improving the EOR performance toward the oxygen evolution reaction (OER) and the urea oxidation reaction (UOR), we fabricated a lattice-disordered high-entropy FeCuCoNiZn hydroxide nanoarray catalyst that exhibits robust bifunctional OER and UOR behavior. The high-entropy feature could bring in a unique catalytic ensemble effect and remarkably improve the intrinsic OER/UOR activity. The lattice-disordered structure could not only enrich the local high-valence metal ions as active sites but also provide abundant reactive surface sites to accelerate the preoxidation process, thus leading to enriched active sites for the OER and UOR. Benefitting from the structural merits, the lattice-disordered high-entropy catalyst exhibits excellent OER and UOR activity with low overpotential, large current density and enhanced intrinsic activity, and no performance degradation but dramatic 35.3% and 88.7% enhancement in activity can be achieved during the long-term OER and UOR tests, respectively. The robust OER and UOR performance makes the lattice-disordered high-entropy catalyst a promising candidate for overall and urea-assisted water electrolysis from industrial, agricultural and sanitary wastewater. [ABSTRACT FROM AUTHOR]

In this work, the synergism between the nano nickel particles and its carbon xerogel support, CX, together with their graphite substrate, G, leads to an efficient Nickel/CX/G electrode for electrocatalysis of ethanol oxidation reaction, EOR. The preparation conditions are optimized. The optimum electrode is made of 6 % weight of Ni doped in CX matrix and drop‐casted on a graphite surface, Ni‐6/CX/G. The catalyst structure and morphology are investigated using XRD, SEM, TEM and FTIR techniques. The electrochemical activity towards EOR is tested in 1 M NaOH+1 M Ethanol solutions by cyclic voltammetry combined with a rotating ring disk electrode. The optimum electrode shows an oxidation peak current density value of 5925 A.gNi-1 ${{\rm A}.{{\rm g}}_{{\rm N}{\rm i}}^{-1}}$ and considerable stability. This electrode may serve as a good candidate for the anode in the Direct Alkaline Ethanol Fuel Cell, DAEFC. [ABSTRACT FROM AUTHOR]

The preparation and characterization of oxide coatings made by plasma electrolytic oxidation (PEO) process on aluminum in two different electrolyte solutions of opposite pH values with addition of Ce-enriched ZSM-5 zeolite are investigated in this paper. The first selected electrolyte solution is highly acidic pH < 3, prepared with tungstosilicic acid (H4O40SiW12), while the second one is made with sodium tungstate (Na2WO4) creating highly alkaline PEO environment with pH > 12. Phase structure, chemical composition, morphology, photoluminescent properties, and photocatalytic activity of deposited oxide coatings are discussed. Properties of PEO coatings are analyzed against processing time revealing dynamics of PEO under defined conditions. Both sets of oxide coatings have similar chemical composition and morphology, but the photocatalytic activity is considerably higher for oxide coatings made in alkaline environment. [ABSTRACT FROM AUTHOR]

Currently, great importance has been assigned to designing cutting-edge materials for oxygen and hydrogen generation from hybrid water electrolysis as an ideal fuel alternative in energy-conversion devices. This work reports on the electrochemical organic molecule oxidation in alkaline media, intending to promote water electrolysis at early onset potential with more current densities using Sn-Cu oxidized heterostructures. The electrocatalysts were easily and rapidly synthesized by the microwave-heated synthesis process in the presence of a small quantity of ethylene glycol. The X-ray diffraction and Field Emission Scanning Electron Microscopy analyses confirm the presence of CuO and SnO2 phases, which significantly improves the electrochemical activity of the composite toward the Oxygen Evolution Reaction (OER) in alkaline media in the presence of 1.0 mol L−1 ethanol, yielding 8.0 mA cm−2 at 1.6 V. The charge transfer resistance (Rct) was determined using electrochemical impedance spectroscopy, and the result shows that the Rct of SnO2/CuO drastically decreased. The findings in this work highlight that the designed oxidized heterostructures with non-noble metals are promising candidates for energy conversion devices and sensors. Furthermore, this work confirms the advantages of using an assisted microwave heating process to develop an advanced SnO2/CuO composite with the potential to be used in electro-oxidation processes. [ABSTRACT FROM AUTHOR]

The effect of various cleaning methods on coating morphology and their effectiveness in removing organic contaminants has been studied in this research. Bioactive coatings containing titanium oxides and hydroxyapatite (HAP) were obtained through plasma electrolytic oxidation in aqueous electrolytes and molten salts. The cleaning procedure for the coated surface was performed using autoclave (A), ultraviolet light (UV), radio frequency (RF), air plasma (P), and UV-ozone cleaner (O). The samples were characterized using scanning electron microscopy (SEM) with an EDS detector, X-ray photoelectron spectroscopy (XPS), X-ray phase analysis (XRD), and contact angle (CA) measurements. The conducted studies revealed that the samples obtained from molten salt exhibited a finer crystalline structure morphology (275 nm) compared to those obtained from aqueous electrolytes (350 nm). After applying surface cleaning methods, the carbon content decreased from 5.21 at.% to 0.11 at.% (XPS), which directly corresponds to a reduction in organic contaminations and a decrease in the contact angle as follows: A > UV > P > O. This holds true for both coatings obtained in molten salt (25.3° > 19.5° > 10.5° > 7.5°) and coatings obtained in aqueous electrolytes (35.2° > 28.3° > 26.1° > 16.6°). The most effective and moderate cleaning method is ozone treatment. [ABSTRACT FROM AUTHOR]

Transition metal oxide (TMO) binary compounds have shown good performance in energy devices. Therefore, the present study investigates the performance of hydrothermally synthesized cobalt molybdate (CoMoO4) with a flower-like morphology for electrodes in supercapacitors and methanol oxidation reaction (MOR). The morphology and microstructure were examined using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy-dispersive spectroscope (EDS) mapping. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) were analyzed to examine the potential of nanocomposites for supercapacitor electrodes. The results showed the specific capacitance of 243 F/g in a 6 M KOH solution with a stability of 82% after 2000 cycles. The MOR investigation of the synthesized electrode suggested a suitable trend for methanol oxidation at the optimal scan rate and concentration. As a result, CoMoO4 can be a relatively cost-effective option for use in supercapacitor electrodes and an attractive and inexpensive catalyst for methanol oxidation. [ABSTRACT FROM AUTHOR]

The plasma electrolytic oxidation method was used with AZ31 magnesium alloy plates for improving the corrosion resistance of the alloy. Process parameters for the plasma electrolytic oxidation setup were optimized by studying the effects of KOH concentration, operating voltage, and pulse properties on the obtained coating. These conditions were then used to produce plasma electrolytic oxidation coated AZ31 sample and were tested by immersion in 3 % NaCl solution for 1 week. Three types of modifiers were used in the electrolyte and concentrations of the modifiers were varied to study the effect of concentration on the performance of coating obtained. The extent of corrosion was visually examined, and it was found that an electrolyte recipe with all three modifiers produced the best results. [ABSTRACT FROM AUTHOR]

Purpose: A novel semiconducting macromolecule-polyperylene tetraamide (PPTI) was first synthesized with a simple method using 3, 4, 9, 10-perylene tetracarboxylic acid (PTCA) and hydrazine hydrate (N2H4). Design/methodology/approach: The Ag nanoparticle was doped on the surface or inside of the PPTI film to obtain a highly sensitive hydrazine sensor-Ag/PPTI, which was synthesized within one step. The structure of Ag/PPTI was characterized through various techniques such as Fourier transform infrared (FT-IR), thermogravimetric analyzer (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy measurements (XPS) and scanning electronic microscopy (SEM). Findings: According to cyclic voltammetry results, Ag/PPTI/GCE indicated good electrocatalytic activity toward the oxidation of hydrazine. The amperometric detection of hydrazine was then applied on Ag/PPTI/GCE. It exhibited a wide linear range from 0.05 to 50 µM, a low detection limit (S/N = 3) of 0.05 µM and high sensitivity of 0.45 µA/(µM•cm2). Originality/value: In authors' perception, this approach emerges as an effective technique for developing efficient chemical sensors for environmental pollutants. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDH) frameworks have shown significant enhancement in stability and reusability, and their tailorable architecture brings new insight into the development of the next generation of hybrid materials, which attracted considerable attention in many fields over the years. One of the factors contributing to the widespread applicability of layered double hydroxides is their adaptable composition, which can accommodate a wide spectrum of potential anionic guests. This exceptional property makes the LDH system simple to adjust for various applications. However, most LDH systems are synthesized in situ in an autoclave at high temperatures and pressures that severely restrict the industrial use of such coating systems. In this study, LDH was directly synthesized on a magnesium alloy that had undergone plasma electrolytic oxidation (PEO) treatment in the presence of ethylenediaminetetraacetic acid, thereby avoiding the use of hydrothermal autoclave conditions. This LDH system was compared with a hybrid architecture consisting of organic-inorganic self-assembly. An organic layer was fabricated on top of the LDH film using 4-Aminophenol (Aph) compound, resulting in a smart hierarchical structure that can provide a robust Aph@LDH film with excellent anti-corrosion performance. At the molecular level, the conjugation characteristics and adsorption mechanism of Aph molecule were studied using two levels of theory as follows. First, Localized orbit locator (LOL)-π isosurface, electrostatic potential (ESP) distribution, and average local ionization energy (ALIE) on the molecular surface were used to highlight localization region, reveal the favorable electrophilic and nucleophilic attacks, and clearly explore the type of interactions that occurred around interesting regions. Second, first-principles based on density functional theory (DFT) was applied to study the hybrid mechanism of Aph on LDH system and elucidate their mutual interactions. The experimental and computational analyses suggest that the high π-electron density and delocalization characteristics of the functional groups and benzene ring in the Aph molecule played a leading role in the synergistic effects arising from the combination of organic and inorganic coatings. This work provides a promising approach to design advanced hybrid materials with exceptional electrochemical performance. [ABSTRACT FROM AUTHOR]

In this work, plasma electrolytic oxidation (PEO) coatings were produced on magnesium alloy AZ31 in aluminate, silicate and phosphate- based electrolytes, and followed by hydrothermal treatments in order to synthesis layered double hydroxides (LDHs) based nanocontainers. LDHs synthesis was done in three different growth solutions (deionized water, sodium nitrate and aluminum nitrate containing solution). In frame of this work it was shown, that it was difficult to form LDHs on Si-based PEO coating, due to more stable silicate phases in comparison with aluminate and phosphate phases in respective PEO coatings. The obtained hybrid LDH/PEO coatings were characterized using SEM, EDS and GDOES, and then the corrosion protection was further investigated by EIS. Based on the obtained results, it was confirmed that, the hydrothermal treatments in Al3+ containing solution played an important role on overall corrosion resistance for phosphate and silicate-based PEO coatings, but not for Al-based PEO coatings. [ABSTRACT FROM AUTHOR]

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When aluminum alloys are coupled with dissimilar materials, they often act as corrosion anodes and are suscepted to accelerated corrosion. Therefore, deepening our knowledge of such corrosion phenomena, related mechanisms, and elaborating new prediction model is of great theoretical and practical significance. In this paper, such mechanisms are explained from both macroscopic and microscopic points of view by considering several aspects such as the second phase particle type, grain size, and environmental ions. More specifically, different perspectives on such a problem are elaborated, which take into account: the properties of the coupling pair materials, geometrical characteristics, environmental media characteristics, the corrosion regularity of different types of aluminum alloys, the influence of area ratio on anode corrosion current density, the interference of the solution primary ions represented by Cl- and the accompanying ions represented by Al3+. A review is also conducted of the standard test methods used in the study of aluminum alloys galvanic corrosion and of research methods such as the Wire Beam Electrodes Technology (WBE), the Scanning Kelvin Probe Force Microscopy (SKPFM) technology. Finally, three kinds of inhibition technologies are discussed, including the anodic oxidation treatment, the corrosion inhibitor treatment and the coating protection method. [ABSTRACT FROM AUTHOR]

In this work, we investigated the possible incorporation of YAG (yttrium aluminum garnet)-Ce particles into plasma electrolytic oxidation (PEO) coatings on 1050AA (aluminum alloy) in order to endow the surface with photoluminescent properties. Different treatment times and current modes (direct or pulsed) were tested as PEO process parameters using as electrolyte a silicates-containing solution. The microstructure of the samples was characterized by SEM and XRD measurements, the corrosion properties were determined by EIS tests, whereas the photoluminescence was evaluated with a proper spectrometer. The concentration of the YAG-Ce particles incorporated in the PEO coating was strongly influenced by the current mode, and in particular, it was higher with pulsed current mode. A higher content of YAG-Ce particles results in a better corrosion resistance and photoluminescent effect. PEO process in pulsed unipolar mode using an electrolyte containing YAG-Ce particles resulted an effective way to produce samples of 1050AA with a surface characterized by photoluminescent properties. [ABSTRACT FROM AUTHOR]

The addition of Cr nanoparticles to a plasma electrolytic oxidation (PEO) electrolyte offers the possibility of producing layers with a broader range of coating compositions and improved properties. In this study, the effects of nanoparticles and various voltages on coating formation, microscopic morphology, and phase composition were investigated with in situ incorporation of Cr nanoparticles into PEO-coated Mg alloy. The results show that the corrosion performance of the coating was significantly improved when the final voltage was set to 460 V and the concentration of Cr nanoparticles was 1 g/L. Compared to the particle-free coating, the corrosion current density of the coating with the addition of 1 g/L Cr nanoparticles was reduced by two orders of magnitude. The impedance at the low frequency (0.01 Hz) increased by more than one order of magnitude after one hour of immersion, indicating a considerable improvement in corrosion resistance. Due to the high temperature during the coating-formation process, the Cr nanoparticles were oxidized, resulting in the formation of Cr2O3. The existence of Cr2O3 slightly increased the growth rate of the coating and sealed the open pores of the coating. [ABSTRACT FROM AUTHOR]

Plasma electrolytic oxidation (PEO), as a cost effective and environmentally friendly technology, has been applied on magnesium and its alloys to improve wear and corrosion resistance. Additionally, combining with particles addition in the electrolyte and/or various post-treatments could diminish the intrinsic structural defects of the PEO coatings and provide multifunctionalities, including wear resistance, corrosion resistance, self-lubrication, and self-healing. This paper reviews recent progress on PEO composite coatings prepared by in situ incorporation of functional particles and/or post-treatments on magnesium and its alloys. The focus is given to the microstructural and functional changes of the PEO coatings, particularly on the wear and corrosion behaviors. [ABSTRACT FROM AUTHOR]

Materials composed of various constituents with distinct physical or chemical features are named composites. Merging components in the composite structure leads to new properties creation or the intrinsic properties magnification of the components, or synergetic effects. Here, the ternary nanocomposite of copper, nickel, and iron oxides was electrodeposited on the glassy carbon electrode (GCE) surface to facilitate the ethanol electro-oxidation reaction (EOR) and overcome the electrode fouling problem while prolonging its efficiency. The GCEs were modified by three different procedures and activated by CV cycling in an alkaline solution, and their electro-catalytic activity was tested toward EOR. The ternary electrocatalysts prepared by two-steps electrodeposition of their components (Ni,Fe 2 O 3 /Cu and Cu/Ni,Fe 2 O 3) demonstrated higher peak current and more negative peak potential (E pa = 476 mV, I pa = 492 μA, and E pa = 510 mV, I pa = 644 μA, respectively) than the binary electrocatalyst of Ni,Fe 2 O 3 toward EOR. The best electro-catalytic efficiency was acquired for the simultaneous electrodeposition of nano Cu, Ni, and Fe 2 O 3 on the GCE surface (Cu,Ni,Fe 2 O 3 , E pa = 530 mV, I pa = 3179 μA). The physicochemical and electro-catalytic characterizations of the fabricated electrocatalysts were evaluated by various techniques. The fast and facile engineered design of the GCE modification with the ternary Cu,Ni,Fe 2 O 3 components led to a high current density of about 101 mA/cm2 with increased tolerance against poisoning intermediates resulting in longtime stability for EOR in alkaline media. The synergistic effect between nano Ni, Cu, and Fe oxides provided promising properties for the EOR pursuing the construction of a powerful device with commercialization potential. • On-step electrodeposition of Cu,Ni,Fe 2 O 3 ternary nano-composite • Improvement of the electron transfer kinetic of EOR • High tolerance against poisoning intermediates and longtime stability for EOR • Promising electro-catalytic performance of Cu,Ni,Fe 2 O 3 /GCE for EOR • Achievement of a high current density of ∼101 mA/cm2 for EOR [ABSTRACT FROM AUTHOR]

Designing Pt-based electrocatalysts with high catalytic activity and CO tolerance is challenging but extremely desirable for alkaline hydrogen oxidation reaction. Herein we report the design of a series of single-atom lanthanide (La, Ce, Pr, Nd, and Lu)-embedded ultrasmall Pt nanoclusters for efficient alkaline hydrogen electro-oxidation catalysis based on vapor filling and spatially confined reduction/growth of metal species. Mechanism studies reveal that oxophilic single-atom lanthanide species in Pt nanoclusters can serve as the Lewis acid site for selective OH- adsorption and regulate the binding strength of intermediates on Pt sites, which promotes the kinetics of hydrogen oxidation and CO oxidation by accelerating the combination of OH− and *H/*CO in kinetics and thermodynamics, endowing the electrocatalyst with up to 14.3-times higher mass activity than commercial Pt/C and enhanced CO tolerance. This work may shed light on the design of metal nanocluster-based electrocatalysts for energy conversion. Exploring enhanced catalysts for alkaline hydrogen oxidation with high catalytic activity and CO tolerance is highly desired yet challenging. Here, the authors report single-atom lanthanide embedded Pt nanoclusters with high activities and durability. [ABSTRACT FROM AUTHOR]

The synthesis of Pt−Rh alloy nanowires (NWs) using straightforward methodologies remains a challenge. Here, carbon‐supported Pt and Pt−Rh nanowire catalysts were synthesised by chemical reduction at room temperature, without using surfactants or templates. The method of synthesis used yielded Pt/C NWs and a mixture of nanowires with some nanoparticles for the Pt−Rh/C catalysts (characterised using XRD, TEM, EDX, XPS, and XAS). The nanoparticles form due to differences in the surface energy and atomic radius between Pt and Rh. The binary NWs are found to be more active towards ethanol oxidation than the commercial Pt/C reference catalyst. Additionally, the Pt−Rh/C NW catalyst displays a specific activity 2.5‐fold higher than the Pt/C NWs and Pt/C reference catalysts after 15 min of chronoamperometric tests (at 0.5 V vs RHE). Thus, the synthesised carbon‐supported Pt NWs and Pt−Rh nanowires‐nanoparticles are promising alternatives for direct ethanol fuel cell anodes. [ABSTRACT FROM AUTHOR]

The plasma electrolytic oxidation (PEO) coatings have different applications, and their modifications or developments are generally with a specific application target. Therefore, the PEO coating assessments often envisage that particular application without considering other possibilities or infeasibilities of developed PEO coatings from a different perspective. Electrochemical impedance spectroscopy (EIS), a powerful technique for PEO coating assessment, is manifold because it can assess almost every structural, morphological, chemical, and electrochemical feature of PEO coatings. Therefore, a review paper describing an all-purpose EIS behavior of PEO coatings is essential for researchers and engineers for a complete PEO coating assessment beyond their target application. Herein, the relevant PEO coating literature reports sufficient to understand the PEO coating assessment fundamentals are included in this review for researchers and engineers from all perspectives without compiling all literature reports on EIS studies of PEO coatings. [ABSTRACT FROM AUTHOR]

Electrooxidation of 5‐hydroxymethylfurfural (HMF) into 2,5‐furandicarboxylic acid (FDCA) is a highly promising approach for producing value‐added chemicals from biomass. However, developing highly efficient electrocatalysts for HMF oxidation (HMFOR) with high current density in large‐scale productions remains a challenge. Herein, it is demonstrated that the Mn‐doped NiS nanosheet electrocatalysts grown directly on 3D graphite felt (GF) substrates can efficiently perform electrooxidation of HMF into FDCA at industrial‐level current density (500 mA cm−2) in the H‐cell. The Mn0.2NiS/GF exhibits excellent HMFOR performance with high selectivity (98.3%), yield (97.6%), faradaic efficiency (94.2%), and robust stability (10 cycles). Especially, FDCA production rate up to 4.56 g h−1 can be achieved, superior to those reported in HMFOR literatures. Furthermore, by scaling up the Mn0.2NiS/GF electrode area and assembling it in a continuous‐flow electrolyzer, high FDCA production rate of 44.32 g h−1 is achieved. The high activity of Mn0.2NiS/GF for HMFOR can be attributed to incorporation of Mn into NiS material, theoretical calculation results indicate that the Mn and Ni as both the adsorption sites for HMF oxidation, thereby effectively facilitate the HMF electro‐oxidation performance. This work provides a strategy for developing potential industrial‐grade electrocatalysts at a large current density. [ABSTRACT FROM AUTHOR]

Numerous studies have been reported to improve the selectivity of uric acid (UA) by eliminating the interference from other electroactive species that coexist in biological fluids. However, two main challenges associated with the nonenzymatic electrochemical detection of UA need to be overcome to achieve practical applications in biological samples. Those are the chemical fouling of electrodes caused by the oxidation product of UA and biofouling due to the non-specific absorption of biological macromolecules. It was found that the residual oxo-functional groups and defects on graphene played a crucial part in both electrocatalysis and anti-biofouling. Here, graphene oxide (GO) was tuned by electro-oxidation and electro-reduction and was investigated in antifouling and electrocatalytic performances for the electrochemical sensing of UA by using pristine GO, BSA bound GO, electro-reduction-treated GO and electro-oxidation-treated GO. The electro-oxidation-treated GO was explored in electrochemical sensing for the first time and exhibited the highest sensitivity and low fouling properties. Holey GO might be formed on the electrode surface by the electrochemical oxidation method in a mild and green solution without the use of an acid. The different electrode interfaces as well as the interaction with BSA were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy, contact angle measurements, scanning electron microscopy, electrochemistry, and electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Vanadium-based carbides have been applied as Pt-free counter electrodes (CEs) electro-catalysts for dye-sensitized solar cells (DSSCs) due to the advantages of earth-abundant reserves, diverse composition, ease modification, and low cost. Herein, the polyoxovanadate (NH 4) 2 V 6 O 16 as V source assisted by dicyandiamide (C 2 H 4 N 4) as C source via simply physical mixing by ball-milling to assemble VC@C precursors. And then, five different VC@C composites derived from precursors with mass ratios of dicyandiamide to polyoxovanadate of 5:1, 10:1, 15:1, 20:1 and 25:1 at 900 °C, and further achieved power conversion efficiencies (PCEs) of 5.4%, 5.6%, 6.6%, 6.2% and 5.1% as CEs for regenerate traditional I 3 −/I− couple in the encapsulated DSSCs, respectively. The effects of different mass ratio of dicyandiamide on the catalytic performances of VC@C composite CEs were also assessed using cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization experiments. The photocurrent-photovoltage (J - V) results indicated that VC@C composites CEs had high conductivity and rich number of active sites, which indicated that VC@C composites could be a cost-effective and high-performance alternative Pt-based CEs catalyst for DSSCs. • The pyrolysis of polyoxovanadates assisted by C 2 H 4 N 4 to derive VC@C composites. • VC@C composites were designed as counter electrode by the mass ratio optimized. • The obtained VC@C-3 has high conductivity and rich active sites. • The DSSCs with VC@C-3 composites CEs had the highest PCE of 6.6%. [ABSTRACT FROM AUTHOR]

In this study, white thermal control coatings were produced on a 6061 Al alloy using plasma electrolytic oxidation (PEO). The coatings were mainly formed by incorporating K2ZrF6. The phase composition, microstructure, thickness, and roughness of the coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), a surface roughness tester, and an eddy current thickness meter, respectively. The solar absorbance and infrared emissivity of the PEO coatings were measured using a UV–Vis–NIR spectrophotometer and FTIR spectrometer, respectively. The addition of K2ZrF6 to the trisodium phosphate electrolyte was found to significantly enhance the thickness of the white PEO coating on the Al alloy, with the coating thickness increasing in proportion to the concentration of K2ZrF6. Meanwhile, the surface roughness was observed to stabilize at a certain level as the K2ZrF6 concentration increased. At the same time, the addition of K2ZrF6 altered the growth mechanism of the coating. In the absence of K2ZrF6 in the electrolyte, the PEO coating on the Al alloy surface predominantly developed outwards. However, with the introduction of K2ZrF6, the coating's growth mode transitioned to a combination of outward and inward growth, with the proportion of inward growth progressively increasing in proportion to the concentration of K2ZrF6. The addition of K2ZrF6 substantially enhanced the adhesion of the coating to the substrate and endowed it with exceptional thermal shock resistance, as the inward growth of the coating was facilitated by the presence of K2ZrF6. In addition, the phase composition of the aluminum alloy PEO coating in the electrolyte containing K2ZrF6 was dominated by tetragonal zirconia (t-ZrO2) and monoclinic zirconia (m-ZrO2). With the increase in K2ZrF6 concentration, the L* value of the coating increased from 71.69 to 90.53. Moreover, the coating absorbance α decreased, while the emissivity ε increased. Notably, at a K2ZrF6 concentration of 15 g/L, the coating exhibited the lowest absorbance (0.16) and the highest emissivity (0.72), which are attributed to the enhanced roughness resulting from the substantial increase in coating thickness caused by the addition of K2ZrF6, as well as the presence of ZrO2 with higher emissivity within the coating. [ABSTRACT FROM AUTHOR]

Coatings with a thickness from ~40 to ~50 µm on Ti6Al4V titanium alloys were formed by plasma electrolytic oxidation (PEO) in a silicate-hypophosphite electrolyte with the addition of graphene oxide. The PEO treatment was carried out in the anode–cathode mode (50 Hz) at a ratio of anode and cathode currents of 1:1; their sum density was 20 A/dm2, and the treatment's duration was 30 min. The effect of the graphene oxide's concentration in the electrolyte on the thickness, roughness, hardness, surface morphology, structure, composition, and tribological characteristics of the PEO coatings was studied. Wear experiments, under dry conditions, were carried out in a ball-on-disk tribotester with an applied load of 5 N, a sliding speed of 0.1 m·s−1, and a sliding distance of 1000 m. According to the obtained results, the addition of graphene oxide (GO) into the base silicate-hypophosphite electrolyte leads to a slight decrease in the coefficient of friction (from 0.73 to 0.69) and a reduction in the wear rate by more than 1.5 times (from 8.04 to 5.2 mm3/N·m), with an increase in the GO's concentration from 0 to 0.5 kg/m3, respectively. This occurs due to the formation of a GO-containing lubricating tribolayer upon contact with the coating of the counter-body in the friction pair. Delamination of the coatings during wear occurs due to contact fatigue; with an increase in the concentration of GO in the electrolyte from 0 to 0.5 kg/m3, this process slows down by more than four times. [ABSTRACT FROM AUTHOR]

A versatile multifunctional laboratory-based near ambient pressure x-ray photoelectron spectroscopy (XPS) instrument is presented. The entire device is highly customized regarding geometry, exchangeable manipulators and sample stages for liquid- and solid-state electrochemistry, cryochemistry, and heterogeneous catalysis. It therefore delivers novel and unique access to a variety of experimental approaches toward a broad choice of functional materials and their specific surface processes. The high-temperature (electro)catalysis manipulator is designed for probing solid state/gas phase interactions for heterogeneous catalysts including solid electrolyzer/fuel cell electrocatalysts at pressures up to 15 mbar and temperatures from room temperature to 1000 °C. The liquid electrochemistry manipulator is specifically designed for in situ spectroscopic investigations of polarized solid/liquid interfaces using aqueous electrolytes and the third one for experiments for ice and ice-like materials at cryogenic temperatures to approximately −190 °C. The flexible and modular combination of these setups provides the opportunity to address a broad spectrum of in situ and operando XPS experiments on a laboratory-based system, circumventing the limited accessibility of experiments at synchrotron facilities. [ABSTRACT FROM AUTHOR]

The initial discharge process of plasma electrolytic oxidation (PEO) on the 60 vol. % SiCP/2009 aluminum matrix composite in silicate solution was in situ monitored by sound and vibration measurement techniques. The underwater sound, airborne sound, and sample vibration signals were detected in the initial 120 s of the PEO process, and their generation mechanism was discussed. In terms of waveforms and spectrograms of the sound and vibration signals, the initial PEO process can be divided into five stages: conventional anodizing stage (I), glow discharge stage (Ⅱ), tiny spark discharge stage (Ⅲ), large spark discharge stage (Ⅳ), and strong spark discharge stage (Ⅴ). The sound and vibration signals during the PEO process are attributed to the evolution of bubbles, which are from the plasma discharge, electrochemical reactions, and vaporization of electrolyte under Joule heat. In stage I, these signals completely come from the bubbles produced by the evaporative electrolyte and electrochemical reactions. In stages Ⅱ–Ⅴ, the bubbles from the plasma discharge gradually become the main source of these signals with increasing discharge intensity. In addition, the spike peaks on the waveforms of these signals at stage Ⅴ are related to the strong discharge sparks. These results demonstrate that sound and vibration measurement techniques can effectively monitor the PEO discharge process. [ABSTRACT FROM AUTHOR]

6-thioguanine (6-TG) is an anticancer drug with narrow safe dose range and intense toxic reactions, so it is urgently necessary to evaluate its clinical usage. Therefore, from the point of view of human health control, the 6-TG determination in biological matrices is of great significance. The current attempt was made to produce magnetic core–shell Fe3O4@SiO2/MWCNT nanocomposite (MCFSMW) to construct a novel selective and sensitive electrochemical 6-TG sensor. The characteristics of synthesized nanocomposite were determined by X-ray Diffraction, Fourier Transform Infrared Spectrometry, Scanning Electron Microscopy and Energy-Dispersive X-ray. The sensor fabrication was based on the surface modification of screen-printed electrode (SPE) with MCFSMW (MCFSMW/SPE). The MCFSMW/SPE possessed an appropriate response and an appreciable electrooxidation behaviors toward the 6-TG detection. There was a significant enhancement in the 6-TG electro-oxidation signal on the MCFSMW/SPE surface compared to the bare SPE. The proposed protocol was explored by chronoamperometry, cyclic voltammetry, and differential pulse voltammetry (DPV). The DPV findings clarified a broad linear relationship between the 6-TG concentrations and the peak height ranged from 0.01 to 280.0 µM with a limit of detection as narrow as 1.0 nM. The practical potency of MCFSMW/SPE was confirmed by sensing of 6-TG in the biological matrices. [ABSTRACT FROM AUTHOR]

Bimetallic Pt3Eu/C, Pt3La/C, and Pt3Ce/C electrocatalysts have been prepared, characterized, and tested for ethanol electro-oxidation (EEO). The materials were synthesized by chemical reduction with NaBH4, rendering nanosized particles with actual compositions close to the nominals and no alloy formation. X-ray photoelectron spectroscopy (XPS) confirmed that the auxiliary rare-earth metals were present on the surface in oxide form. The electrochemical analyses in acid and alkaline EEO evidenced that, compared to Pt/C, the addition of rare earth metals in the form of oxides reduced the onset potential, increased the current density, and enhanced the stability. The results were fully confirmed in the DEFC single-cell measurements. Finally, the presence of rare earth metals in the oxidized form increased the percentage of acetic acid as the final product, making the electrocatalysts more selective and efficient than Pt/C, where acetaldehyde was the main product. [ABSTRACT FROM AUTHOR]

We design and prepare porous N-doped carbon sub-microspheres (Por-N–C-SS) using the phenolic resin sub-microspheres as precursor and potassium hydroxide as pore forming agent by polymerization-carbonization strategy. Pt and Cu ions are impregnated on surface of Por-N–C-SS, and then PtCu/Por-N–C-SS are obtained by a facile reduction process. The as-fabricated Por-N–C-SS exhibits the spherical structure with the diameter size of 200–500 nm. And Por-N–C-SS also possesses high specific surface area of 2222 m2 g−1 and large pore volume of 1.02 cm3 g−1. Benefiting from alloy effect of highly dispersed PtCu and N-doped porous carbon architecture, PtCu/Por-N–C-SS shows excellent electrocatalytic performance toward methanol oxidation reaction with high peak current density (4661 mA cm−2 mg−1 Pt) and large Jf/Jb value (1.18), exceeding commercial Pt/C catalyst in acid media. Furthermore, PtCu/Por-N–C-SS also reveals an outstanding catalytic stability, promoting its practical application in fuel cells. [ABSTRACT FROM AUTHOR]

AZ31 alloy is a widely used material in biomedical applications. It is an alternative alloy for temporary implantation due to its low weight and superior biocompatibility. However, surface properties such as wear and corrosion are quite weak compared to other metallic biomaterials. It is extremely important to improve the surface properties, as these two mechanisms cause very serious material damage on Mg alloys separately or synergistically. In this context, oxidation processes are carried out with the plasma electrolytic oxidation (PEO) method, which provides very successful adhesion in alloys such as AZ31. In this study, the tribocorrosion performance of the films produced by doping Cu, B and Zn elements using PEO was investigated. The simultaneous effects of corrosion and wear mechanisms on surfaces were investigated with experiments carried out in artificial body fluid (SBF). It was concluded that the porous oxide films undergo morphological changes with the effect of additive elements, this change in morphology has a barrier effect, especially against corrosion attacks, and the improved corrosion resistance also improves the wear performance. According to the OCP measurements made under wear, the surface that showed the most noble behavior was Zn-doped (−0.71 V). A similar behavior can be mentioned for the wear test carried out together with the potentiodynamic polarization test. It minimized the Zn current density value in the structure (2.3 × 10−6 A/cm2). [ABSTRACT FROM AUTHOR]

In the present study, the distribution of Ag in the coating formed on Mg-Ag alloy by plasma electrolytic oxidation (PEO) and its ionic release kinetics when exposed to a 0.9 wt.% NaCl solution at 37 °C have been investigated. Both metallic Ag and Ag oxide particles with ∼5 to ∼40 nm in diameters were observed in the PEO coating. Further, an Ag-enriched layer of ∼20 nm in thickness at the substrate/coating interface was also observed. The PEO coating on the Mg-Ag alloy not only increases its corrosion resistance with the corrosion current density decreasing by up to 3 orders of magnitude from 8.04 × 10−3 to 4.03 × 10−6 A/cm2, but also controls the release of Ag+ to the level that is sufficient for anti-infective efficacy without causing cytotoxicity to mammal cells. [ABSTRACT FROM AUTHOR]

Antibiotic pollution has posed a serious threat to water environments. To cope with this issue, layered double hydroxides (LDHs) have been employed and exhibited effective removability. However, most of LDHs adsorb antibiotics for water decontamination, which is difficult to degrade the pollutants and usually takes a quite long treatment time. In this work, Mn doped NiAl‐LDHs electrode was synthesized for antibiotic degradation with target pollutant tetracycline (TC). The removal efficiency of TC was then investigated by conducting electro‐oxidation with Mn doped NiAl‐LDHs anode. Specifically, some Mn doped NiAl‐LDHs nanoflowers were shed from NF substrate during the oxidation process, thus forming a 3D‐like electrode device and facilitating TC removal. Meanwhile, due to particle electrode‐like architecture and electro‐oxidation of the composite electrode, high concentration of TC can be removed quickly in a short time, and the removal efficiency can reach 92.6% in 5 min. [ABSTRACT FROM AUTHOR]

In this paper, for the first time, a CoNi2O4 nanocatalyst coated on the surface of activated carbon wheat husk (ACWH) was synthesized in the form of CoNi2O4/ACWH through a hydrothermal process. The electrocatalytic activity of this catalyst was evaluated using methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) processes for use in anodes of alcohol fuel cells. Adding ACWH, as a cheap carbon biomass with an excellent active surface area, improves the performance of the catalyst in the oxidation of alcohols. The current density of CoNi2O4/ACWH in the MOR process is 160 mA/cm2 at an optimal methanol concentration of 2 M; this oxidation current density in the EOR process and at a concentration of 1.5 M ethanol is 150 mA/cm2. The stability of CoNi2O4/ACWH in MOR and EOR processes, after 1000 consecutive CV cycles, is 98.6% and 94.6%, respectively. [ABSTRACT FROM AUTHOR]

Accurate and rapid determination of cholesterol levels in bio-fluids is important because it is an important index for the bio-medical diagnosis of several lethal diseases. Accordingly, electrochemical non-enzymatic bio-sensors offer accurate and rapid detection and exhibit unique features, such as simple handling, affordability, and a very low detection limit with a wider linear range. In this study, a simple, low-cost galvanic deposition technique was employed to develop a thin layer of nanoflakes WO3 on hexagonal ZnO nanoplate using Zn foil as an oxidizable anode, and the composite film (ZnO/WO3) was explored for the electrochemical non-enzymatic detection of cholesterol. The film offers excellent sensitivity (176.6 μA cm−2 mM−1) with a very low detection limit (5.5 nM) at the electrode interfacial surface. During the electro-oxidation of cholesterol, the electrode utilized operational potential (+0.43 V vs. Ag/AgCl) to convert to oxysterol with higher selectivity using hydroxyl radicals (˙OH) as intermediates. The production of ˙OH radicals was confirmed by the effect of terephthalic acid (TPA) on the analyte using photoluminescence spectroscopy. Selectivity in the presence of other interfering agents, long-term stability, repeatability and reproducibility of the biosensor was also ensured for practical application in clinical diagnosis in a real blood sample. [ABSTRACT FROM AUTHOR]

By adopting the strategy of generating chelating agents during plasma electrolytic oxidation (PEO), PEO coatings were prepared in acidic eletrolytic solution by constant current mode. The effect of NaF concentration on the coating and the growth and regulation mechanism of fluoride in acidic eletrolytic solution by constant current mode were explored. The composition, structure, corrosion resistance, and formation mechanism of the coating were investigated. The results showed that the addition of NaF into the acidic electrolyte solution caused the pore diameter decreased, while the coating thickness and compactness were increased. The increase of NaF concentration in the acid electrolyte increases the MgF2 content and affects the adhesion of the coating to the substrate, which was attributed to the changes in the spark discharge characteristics. Subsequently, the self-sealing of the coating and the amount of MgF2 composition in the coating will affect the corrosion resistance of the coating. The PEO coating fabricated in the acidic electrolyte solution containing 7 g/L NaF displayed small pore size, stronger bonding, and thicker coating, which resulted in superior corrosion resistance, the lowest corrosion tendency and enhance the polarization resistance. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of Sm 2 O 3 incorporated palladium based electrocatalyst, supported over reduced graphene oxide (rGO). Pd x Sm y nanoparticles (20 wt %) are distributed over rGO surface by using sodium borohydride reduction technique. Different physicochemical analyses are used to characterize the Pd x Sm y /rGO electro-catalysts (x = 2,4,6 and y = 8,6,4). The synthesized materials (Pd x Sm y /rGOs) are investigated for their catalytic capabilities toward electro-oxidation of formic acid. The results show that adding Sm 2 O 3 to the Pd/rGO electrocatalyst boosts electrochemical activities of the materials toward formic acid oxidation. The optimized catalyst (Pd 6 Sm 4 /rGO) shows excellent activity towards formic acid oxidation with current density of 46.70 mA/cm2 compared to reference catalysts i.e., Pd/rGO (28.78 mA/cm2) and Pd/C (22.22 mA/cm2). The optimized catalyst also demonstrates high CO tolerance and great stability during formic acid oxidation reaction. The enhanced activity and stability are attributed to the synergistic interaction between Sm 2 O 3, and palladium nanoparticles supported over reduced graphene oxide. [Display omitted] • Sm 2 O 3 incorporated Pd electrocatalysts (Pd x Sm y /rGO) are synthesized. • Pd x Sm y /rGO electrocatalysts are investigated for formic acid oxidation reaction. • Adding Sm 2 O 3 to the Pd/rGO electrocatalyst boosts the electrochemical activity. • Pd 6 Sm 4 /rGO shows current density of 46.70 A/cm2 compared to the Pd/rGO (28.78 Acm2). • Pd 6 Sm 4 /rGO demonstrates high CO tolerance and great stability. [ABSTRACT FROM AUTHOR]

Electrolysis of water is a sustainable route to produce clean hydrogen. Full water‐splitting requires a high applied potential, in part because of the pH‐dependency of the H2 and O2 evolution reactions (HER and OER), which are proton‐coupled electron transfer (PCET) reactions. Therefore, the minimum required potential will not change at different pHs. TEMPO [(2,2,6,6‐tetramethyl‐1‐piperidin‐1‐yl)oxyl], a stable free‐radical that undergoes fast electro‐oxidation by a single‐electron transfer (ET) process, is pH‐independent. Here, we show that the combination of PCET and ET processes enables hydrogen production from water at low cell potentials below the theoretical value for full water‐splitting by simple pH adjustment. As a case study, we combined the HER with the oxidation of benzylamine by anodically oxidized TEMPO. The pH‐independent electrocatalytic oxidation of TEMPO permits the operation of a hybrid water‐splitting cell that shows promise to perform at a low cell potential (≈1 V) and neutral pH conditions. [ABSTRACT FROM AUTHOR]

Herein we show that Pt(111) and Pt(100) can produce the ketone through the oxidation of the secondary carbon of the polyols. After the Bi modification, the selectivity for the ketone formation increases. On the other hand, we observe that pure and Bi‐modified Pt(110) only produced the C3 molecules oxidized in the primary carbon, and it is the only facet that shows an enhancement in the activity due to the modification. In line with these findings, small Pt nanoparticles are not selective for ketone formation. Finally, based on data obtained through DFT calculations, we suggest that positively charged Bi adatoms interact with the OH‐ groups of the enediol‐like intermediate (believed to be the precursor for the ketone/aldehyde production), facilitating the oxidation of the secondary carbon to produce DHA. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to develop a sol-gel-based coating to provide a long-lasting corrosion protection on AZ31 Mg alloy. Silane-based sol-gel coatings have been successfully applied to Mg alloys for corrosion protection. However, the micro or nano defects formed during condensation and solidification will cause the coating failure during a long-lasting immersion in a saline solution. More durable corrosion-protective sol-gel coatings are needed. Design/methodology/approach: A sol-gel-based coating was modified on AZ31 Mg alloy by levodopa (DOPA). The long-lasting corrosion protection mechanism was studied by multiple electrochemical testing methods and surface characterization techniques. Findings: Long-term testing by electrochemical impedance spectroscopy in aqueous 0.1 M NaCl indicated that the modified DOPA@sol-gel coating exhibited significant corrosion protection performance (>14 days). In comparison, the DOPA-free sol-gel coating failed only after three days of testing. The improved corrosion protection is attributed to the self-polymerized DOPA filling to the micro or nano defects in the glassy cross-linked networks of the sol-gel coating, which greatly improves the compactness of the coating. Originality/value: The method of this study is simple and easy to process, the raw materials are green and the protective effect is excellent, which is of significance for the study of magnesium alloy corrosion protection. [ABSTRACT FROM AUTHOR]

This paper is devoted to the study of the current density distribution effect on plasma electrolytic oxidation process and resultant coatings on a Zr-1Nb alloy. The influence of the distance between the plates simultaneously placed into an electrolyzer was evaluated to assess the throwing power of the PEO process. The current density on the facing surfaces of the plates decreases when the distance between them shrinks. This current density has a notable impact on the resultant PEO coating in terms of the surface morphology parameters and electrochemically evaluated corrosion resistance. The influence of this effect is low on the stages of anodizing and spark discharges (60–120 s of the PEO), and significantly increases on the stage of microarc discharges (120–360 s of the PEO). The coating obtained with a smaller distance between the plates, while having the same coating thickness as the others, exhibits higher wear resistance. New correlations between the current density, diffusion coefficient, time constant of nucleation and the coating thickness in the middle of the facing samples were established; in addition, a correlation of the coating morphology in this area with the roughness parameters RPc, RSm was shown. This study contributes to the development of optimized PEO processes for the simultaneously coated several devices of complex shape, e.g., orthopedic implants. [ABSTRACT FROM AUTHOR]

In recent years, nanoparticles are increasingly used in scientific research and have attracted the attention of many scholars. In this paper, ceramic coatings were prepared on the surface of magnesium and its alloys using the plasma electrolytic oxidation (PEO) technique. We investigated different nanoparticles added to the electrolyte and explored the mechanism of nanoparticle effects on the formation and protection mechanism, morphology and structure, thickness and roughness, and electrochemical corrosion behavior of the coatings. The results show that the coating morphology changes significantly and the surface is more uniform and dense due to the addition of nanoparticles in the electrolyte. The addition of nanoparticles increases the thickness of the coating to some extent, but as its addition to the electrolyte increases, the coating thickness decreases. Since the prepared coatings inevitably produce micropores and microcracks, which may have an impact on the corrosion resistance of the coatings, how to improve the corrosion resistance of the coatings has become a common concern. Nanoparticles can participate in the growth of the coating and will enter the micropores under discharge conditions. On the one hand, they can play a role in closing the porous layer, and on the other hand, they will form some special structures on the surface, thus improving the corrosion resistance of the coating. Finally, we outlook the problems and challenges of the PEO technique in practical applications. [ABSTRACT FROM AUTHOR]

A novel process and method for treating ciprofloxacin (CIP) antibiotic wastewater using pulsed electrooxidation at boron-doped diamond (BDD) electrodes have been developed to address the issues of low efficiency and high energy consumption associated with traditional electrochemical oxidation methods. The effects of pulsed direct current (PDC), pulsed alternating current (PAC), and direct current (DC) on chemical oxygen demand (COD) removal were studied. It was found that complete degradation of CIP could be achieved within 45 min using PAC. COD removal reached 92.4% after 90 min of PAC electrooxidation for 90 mg·dm−3 CIP wastewater under optimized conditions of current density (j) = 30 mA·cm−2, initial pH (pH 0) = 3, sodium sulfate concentration (c (Na 2 SO 4)) = 50 mmol·dm−3, and frequency (f) = 100 Hz. The electrical energy consumption (EEC) was found to be 35 W·h·dm−3. The CIP degradation followed a quasi-first order kinetic law. The degradation pathway was found to involve hydroxylation of the quinolone moiety, cleavage of the piperazine ring, and fluorine substitution (OH/F substitution). The results showed that PAC electrochemical oxidation at all-BDD electrodes exhibited the highest removal efficiency and lowest EEC for CIP removal. This study provides a novel and effective approach for the efficient treatment of CIP antibiotic wastewater using bidirectional pulse current at all-BDD electrodes. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a clean energy source that can either be directly used as fuel or a hydrogen carrier due to its high energy density and high hydrogen content. The NH3 electro-oxidation reaction (AOR) is the main reaction in both direct NH3 fuel cells and NH3 electrolysis. The AOR is thermodynamically favorable; however, the sluggish kinetics of the reaction can result in issues such as high overpotential, slow reaction rate, deactivation, etc. To overcome this, multiple strategies have been discussed to develop electrocatalysts that maintain a robust reaction rate in low overpotential regions. In this review, the fundamentals of AOR, including thermodynamics, kinetics, and experimental techniques, are studied. This review also focused on recent progress for catalyst modifications and their effects, with a particular focus on Pt- or Ni-based electrocatalysts. Additionally, vacant rooms needed to be developed was pointed, and a way to overcome the limitations was suggested. The fundamentals and efforts to prepare catalysts reviewed in this work will be effective in proposing and designing new robust electrocatalysts leading to advance AOR in practice. [ABSTRACT FROM AUTHOR]

Corrosion of metals can occur under coatings making early visual detection almost impossible which enables corrosion to progress undetected. Nondestructive evaluation can be used to inspect parts during their life. Thermography uses the difference in thermal properties between defective and sound areas to locate defects by applying a short pulse of heat and monitoring the surface temperature of the sample with an infrared camera. However, currently, inspection is reliant on highly trained operators to analyze images for defects and in the case of corrosion, judge its growth. The aim of this research was to develop and test a novel algorithm to identify and quantify the onset of corrosion under coatings and monitor the growth. Using this algorithm, the corrosion was autonomously detected in a variety of mild steel samples exposed to three different corrosive environments. The method successfully detected, quantified, and monitored the growth of corrosion under coatings accurately and robustly using thermal images gathered by a microbolometer infrared camera. The extent of corrosion was reported with an accuracy of 3% absolute error when compared to the true extent. [ABSTRACT FROM AUTHOR]

In the present study, investigation of the applicability and efficiency of electrochemical oxidation (EO) processes for slaughterhouse wastewater (SWW) was targeted by evaluating the treatment efficiency and energy consumption values. The effects of operating parameters, such as the type of supporting electrolyte (SE) (Na2SO4, NaNO3, NaCl, and KCI), supporting electrolyte concentration (SE concentration) (0.1–0.4 M), initial wastewater pH (3–11), and current density (CD) (4.06–12.18 mA/cm2) on the removal of chemical oxygen demand (COD), suspended solids (SS), turbidity, and color were investigated. The most effective electrolyte type was observed to be NaCl. The experiment with 0.2 M SE type and 4.06 mA/cm2 current density, at a stirring speed of 400 rpm was accepted as optimum. For these conditions, it was observed that the COD, color, turbidity, and suspended solids (SS) removals were 80.05, 98.64, 99.18, and 98.47%, and energy consumption of 210.7 kWh/m3, respectively. It has been observed that the electro-oxidation process provides substantial efficiency in undesirable parameters in wastewater after 3 h of operation. Additional processes can be added to this process so that the SWW can be reused after treatment, and the recovery and further treatment of the wastewater can be achieved. [ABSTRACT FROM AUTHOR]

• A combined method was created for the formation of composite coatings on magnesium. • The low SFE and hierarchical structure determined superhydrophobic properties. • Superhydrophobic properties are preserved in a wide range of temperature. • The high surface hydrophobicity is maintained during accelerated climatic tests. A novel combined method for the formation of composite coatings on the Mg-Mn-Ce alloy is developed. Ceramic like matrix was formed on the Mg alloy surface by the plasma electrolytic oxidation. Then the samples were subsequently processed by dip-coating in an alcohol suspension of superdispersed polytetrafluoroethylene and spraying with the tetrafluoroethylene telomers solution. SEM, OSP, and SPM was used to study structure of formed surfaces. It was established by measurements of CA and CAH, as well as surface free energy calculations that formed coatings demonstrate superhydrophobic properties due to the presence of an irregular hierarchical surface structure and low surface free energy of fluoropolymers. The coating preserves its hydrophobic properties after exposure to high and low temperatures, for a long time as well as being in corrosive environments. EDS and XRD data analysis confirmed the presence of organofluorine compounds in the composite layers, including in the form of crystalline polytetrafluoroethylene. Using potentiodynamic polarization test and EIS, it was found that the resulting coatings significantly increase the corrosion resistance of Mg material. These data are also confirmed by salt spray tests for 40 days. Incorporation of fluoropolymers additionally decrease coatings coefficient of friction. [ABSTRACT FROM AUTHOR]