Anodic Oxidation Research Articles

Non-Innocent Role of Sacrificial Anodes in Electrochemical Nickel-Catalyzed C(sp2)-C(sp3) Cross-Electrophile Coupling.

Sacrificial anodes composed of inexpensive metals such as Zn, Fe, and Mg are widely used to support electrochemical nickel-catalyzed cross-electrophile coupling (XEC) reactions, in addition to other reductive electrochemical transformations. Such anodes are appealing because they provide a stable counter-electrode potential and typically avoid interference with the reductive chemistry. The present study outlines the development of an electrochemical Ni-catalyzed XEC reaction that streamlines access to a key pharmaceutical intermediate. Metal ions derived from sacrificial anode oxidation, however, directly contribute to homocoupling and proto-dehalogenation side products that are commonly formed in chemical and electrochemical Ni-catalyzed XEC reactions. Use of a divided cell limits interference by the anode-derived metal ions and supports a high product yield with negligible side product formation, introducing a strategy to overcome one of the main limitations of Ni-catalyzed XEC.

Self-sacrificing and self-supporting biomass carbon anode–assisted water electrolysis for low-cost hydrogen production

Electrooxidation of renewable and CO2-neutral biomass for low-cost hydrogen production is a promising and green technology. Various biomass platform molecules (BPMs) oxidation assisted hydrogen production technologies have obtained noticeable progress. However, BPMs anodic oxidation is highly dependent on electrocatalysts, and the oxidation mechanism is ambiguous. Meanwhile, the complexity and insolubility of natural biomass severely constrain the efficient utilization of biomass resources. Here, we develop a self-sacrificing and self-supporting carbon anode (SSCA) using waste corncobs. The combined results from multiple characterizations reveal that the structure-property-activity relationship of SSCA in carbon oxidation reaction (COR). Theoretical calculations demonstrate that carbon atoms with a high spin density play a pivotal role in reducing the adsorption energy of the reactive oxygen intermediate (*OH) during the transition from OH- to *OH, thereby promoting COR. Additionally, the HER||COR system allows driving a current density of 400 [Formula: see text] at 1.24 V at 80 °C, with a hydrogen production electric consumption of 2.96 kWh Nm-3 (H2). The strategy provides a ground-breaking perspective on the large-scale utilization of biomass and low-energy water electrolysis for hydrogen production.

Hydrogen Production at a Low Voltage of 0.46 V @ 0.4 A/cm2 at 850 °C in SOECs Enhanced by Anode Oxidation of Methane

Hydrogen Production at a Low Voltage of 0.46 V @ 0.4 A/cm² at 850 °C in SOECs Enhanced by Anode Oxidation of Methane

Enhancing the Stability of Cu‐Based Electrocatalyst via Fe Alloy in Electrocatalytic Formaldehyde Oxidation with Long Durability

AbstractElectrocatalytic formaldehyde oxidation with metal Cu electrocatalyst has attracted significant interest since it can produce H2 at the anode and make it possible to construct a bipolar hydrogen production cell with low voltage. However, the activity of the Cu electrocatalyst will be greatly weakened after oxidizing it to Cu+ or Cu2+. Here, a CuFe bimetallic catalyst is developed to efficiently catalyze the electro‐oxidation process of HCHO to produce H2 at a potential of 0.10 VRHE with a current density of 100 mA cm−2. It is confirmed that introducing Fe in a CuFe catalyst can regulate the electron configuration to prevent Cu0 oxidation and improve the stability of the catalysts. The introduction of Fe can reduce the energy barrier of the reaction process, and make the C─H bond more easily split on CuFe. A bipolar hydrogen production device is constructed by combining the anodic oxidation of HCHO with the cathodic hydrogen evolution. The current density of 500 mA cm−2 is achieved at a cell voltage of 0.6 V. The faradaic efficiency is ≈100% and the device is stable for ≈50 h. The research provides a promising path toward the secure, effective, and expandable generation of high‐purity H2 at both anodic and cathodic electrodes.

Hydroxyl and sulfate radicals-based electrochemical advanced oxidation process for treating dye-bearing wastewater – a review

ABSTRACT Dye-bearing wastewater presents a substantial ecological risk. Consequently, there is a critical requirement for efficient treatment strategies. Electrochemical advanced oxidation processes (EAOPs) utilizing hydroxyl and sulfate radicals emerge as viable alternatives to degrade dye pollutants effectively. This review article emphasizes the implementation of EAOPs in the treatment of both synthetic and actual dye-bearing wastewater. The fundamentals, chemistry, and recent developments concerning hydroxyl radicals-based EAOP, including anodic oxidation, electro-Fenton, and sulfate radicals-based EAOP, have been thoroughly reviewed. Furthermore, the article explores the comparative effectiveness of the individual hydroxyl and sulfate radical systems as well as the integrated hydroxyl and sulfate radical systems within a singular electrochemical cell. It has been established that sulfate radicals demonstrate a higher oxidation potential, greater pH adaptability, and a longer half-life in comparison to hydroxyl radicals, making them efficient for dye degradation when assessed against anodic oxidation and electro-Fenton processes. Thus, EAOPs represent a promising technological approach for the remediation of dye-bearing wastewater.

Simple and fast self-polymerization of benzidine using anodic exfloated graphene oxide nanosheet

Simple and fast self-polymerization of benzidine using anodic exfloated graphene oxide nanosheet

Orthogonal Nano‐Engineering (ONE): Modulating Nanotopography and Surface Chemistry of Aluminum Oxide for Superior Antibiofouling and Enhanced Chemical Stability

AbstractDecoupling certain material surface properties can be key to attaining critical property‐activity relationships that underpin their antibiofouling performance. Here, orthogonal nano‐engineering (ONE) is employed to decouple the influences of nanotopography and surface chemistry on surface antibiofouling. Nanotopography and surface chemistry are systematically varied with a two‐step process. Controlled nanotopography is obtained by electrochemical anodization of aluminum, which generated anodic aluminum oxide (AAO) surfaces with cylindrical nanopores (diameters: 15, 25, and 100 nm). To modify surface chemistry while preserving nanotopography, an ultrathin (≈5 nm) yet stable zwitterionic coating of poly(divinylbenzene‐4‐vinylpyridyl sulfobetaine) is deposited on these surfaces using initiated chemical vapor deposition (iCVD). Antibiofouling performance is assessed by quantifying 48‐h biomass formed by gram positive and negative bacteria. The ONE surfaces demonstrated enhanced antibiofouling performance, with small‐pore nanotopography and zwitterionic chemistry each lowered biomass accumulation by tested species, with potential additive effects. The most effective chemistry‐topography combination (ZW‐AAO15) enabled an overall reduction of 91% for Escherichia coli, 76% for Staphylococcus epidermidis, 69% for Listeria monocytogenes, and 67% for Staphylococcus aureus, relative to the uncoated nanosmooth control. Additionally, the composite ZW coating exhibited encouraging anticorrosion properties under both static and turbulent cleaning conditions, vital to antibiofouling applications in healthcare and food industries.

Aluminium surface work hardening enables multi-scale 3D lithography.

Multi-scale structures are ubiquitous in biological systems. However, manufacturing man-made structures with controllable features spanning multiple length scales, particularly down to nanoscale features, is very challenging, which seriously impacts their collective properties. Here we introduce an aluminium-based three-dimensional lithography that combines sequential nano-micro-macro-imprinting and anodization of multi-scale anodic aluminium oxide templates to manufacture well-defined multi-scale structures, using various materials. The high-fidelity nano-patterns and micro-patterns were facilitated by the surface work hardening phenomenon, where the nano-patterns can be further fine-tailored by anodization to have high-aspect-ratio and tunable nano-holes. Based on the aluminium-based three-dimensional lithography, multi-scale materials across length scales of at least 107 orders of magnitude were precisely fabricated, including carbon, semiconductors and metals. We integrated pressure sensors and biosensors with superior and customizable performances by tailoring the multi-scale carbon networks on different length scales from nanofibres and micropyramids to macrodome arrays. This work provides a versatile technique for prototyping on-demand multi-scale structures and materials to explore desirable mechanical and physical properties.

Optimization Strategies of Hybrid Lithium Titanate Oxide/Carbon Anodes for Lithium-Ion Batteries

Lithium-ion batteries, due to their high energy density, compact size, long lifetime, and low environmental impact, have achieved a dominant position in everyday life. These attributes have made them the preferred choice for powering portable devices such as laptops and smartphones, power tools, and electric vehicles. As technology advances rapidly, the demand for even more efficient energy storage devices continues to rise. In lithium-ion batteries, anodes play a crucial role, with lithium titanate oxide standing out as a highly promising material. This anode is favored for its exceptional cycle stability, safety features, and fast charging capabilities. The impressive cycle stability of lithium titanate oxide is largely due to its zero-strain nature, meaning it undergoes minimal volume changes during lithium-ion insertion and extraction. This stability enhances the anode’s durability, leading to longer battery life. In addition, the lithium titanate oxide anode operates at a voltage of approximately 1.55 V vs. Li+/Li, significantly reducing the risk of dendrite formation, a major safety concern that can cause short circuits and fires. The material’s spinel structure, with its large active surface area, further allows fast electron transfer and ion diffusion, facilitating fast charging. This review explores the characteristics of lithium titanate oxide, the various synthesis methods employed, and its integration with carbon materials to enhance cycle stability, coulombic efficiency, and safety. It also proposes strategies for optimizing lithium titanate oxide properties to create sustainable anodes with reduced environmental impact using eco-friendly routes.

Continuously tunable negative pressure for engineering high-symmetry nanocrystalline phases

In this work, the phenomenon of strain induced by a mismatch in thermal expansion coefficients between a thin film and its substrate is harnessed in a new context, replacing the canonical planar support with a three-dimensional (3-D), nanoconfining scaffold in which we embed a material of interest. In this manner, we demonstrate a general approach to exert a continuously tunable, triaxial, tensile strain, defying the Poisson ratio of the embedded material and achieving the exotic condition of "negative pressure." This approach is hypothetically generalizable to materials of low modulus and high thermal expansion coefficient, and we use it here to achieve negative pressure in perovskite-phase CsPbI3 embedded within the cylindrical pores of anodic aluminum oxide membranes. Through controlled thermal hysteresis, the perovskite crystal structure can be continuously tuned toward higher symmetry when confined in a scaffold with pore size <40 nm, in contrast with the symmetry-reducing action of any other mechanical perturbation. We use this effect to control the octahedral rotation angle that is critical to the remarkable photovoltaic attributes of halide perovskites. Under hundreds of megapascals of apparent negative pressure, the bandgap tunability is observed to follow the same quantitative trend observed for hydrostatic positive pressure, exploring the negative pressure region and demonstrating the relative dominance of bond stretching effects over average octahedral rotation angle on electronic structure. This study reveals and quantifies the structural and electronic consequences of 3D tensile strain present by design and provides a framework for understanding adventitious strain present in all nanocomposite materials.

Quantitative Examination and Mechanistic Insights of Polymer Chain Conformation Confined in Nanopores by Time-Resolved Fluorescence Resonance Energy Transfer.

The conformational studies of polymers confined at the nanoscale remain challenging and controversial due to the limitations of characterization techniques. In this study, we utilized the high sensitivity of time-resolved fluorescence resonance energy transfer (trFRET) and a site-specific dye-labeling strategy to characterize the conformation of polymer chains confined in anodic aluminum oxide (AAO) nanopores. This strategy introduced a fluorescent donor (carbazole) and acceptor (anthracene) at the center of poly(butyl methacrylate) (PBMA) chains grown by atom transfer radical polymerization (ATRP). By quantitatively analyzing fluorescence decay through the Förster mechanism and the Drake-Klafter-Levitz (DKL) formalism, we can determine both the energy transfer efficiency and the spatial distribution of the dyes. This analysis revealed that the PBMA chains, with a molecular weight of 40 kDa, maintained their bulk-like conformation even when confined within nanopores as small as 10 nm in diameter. This study is the first to demonstrate the use of trFRET for investigating chain conformation in confined polymer systems, which can be generalized to other polymer types and polymer topologies in different confined geometries.

Synthesis of a Hard Anodic Oxide Coating with a Structure Allowing for Its Modification by Nanoparticles

A hard anodic oxide coating’s characteristic porous structure allows for its modification by the incorporation of nanoparticles. However, achieving an appropriate microstructure requires an optimal pore arrangement and shape, which is influenced by the electrolyte composition, current densities, temperature, and processing time. To achieve pores with a diameter of about 50 nm and the most regular structure, a range of these parameters were tested. Using a two-stage manufacturing process had a beneficial effect on increasing the microporosity of the coating. The addition of phthalic acid at 0 °C did not increase the pore diameter, but allowed for the process to be carried out at higher temperatures. However, the coating produced at 20 °C had a larger pore diameter, but numerous defects. The coating obtained from the three-component solution had the most regular structure, but the smallest pore diameter.

Electrochemical Synthesis of Alkenylsulfonates from Alkynes, NaHSO3 and Alcohols

Comprehensive SummaryAlkenylsulfonates are commonly encountered in medicinal chemistry, polymer chemistry, and organic synthesis. In this research, an electrochemical reaction involving alkynes, NaHSO3, and alcohols has been developed. This method yields functionalized alkenylsulfonates in good yields with broad functional group tolerance. Mechanism studies indicate that anodic oxidation of inorganic sulfite, radical insertion process, and HAT process are involved in this transformation.

ENHANCING SURFACE CHARACTERISTICS OF AA2024-T3 AIRCRAFT ALLOY THROUGH SYNERGISTIC ANODIZATION AND CERIUM CONVERSION COATING. PART I: PERFORMANCE IN MODEL CORROSIVE MEDIUM

The present study is devoted to the monitoring of the performance of AA2024-T3 specimens, after the formation of Anodic Aluminum Oxide (AAO) layer and/or deposition of a Ceruim Conversion Coating (CeCC), obtained at 20°C and 50°C, respectively. Although both methods are well described in the literature, there is no sufficient information regarding the effect of their combination on their behaviour in corrosive media. The performance of the respective specimens was elucidated after 24 h of exposure to 3.5 % NaCl model corrosive medium (MCM) by means of Electrochemical Impedance Spectroscopy (EIS) and acquisition of Potentiodynamic Scanning (PDS) curves. Since the combined AAO/CeCC coating primers revealed superior barrier properties, the respective specimens weresubjected to long-term corrosion tests of up to 672 h of exposure to the MCM to evaluate their durability. The results revealed the synergistic effect of the combination of the surface treatment procedures on effective corrosion mitigation.

Electrochemical Degradation of Methylene Blue using Aluminum Doped Copper Oxide Electrode: Modeling and Optimization

An electrochemical oxidation process with an aluminum-doped copper oxide (Al@CuO) anode was modeled and optimized for the degradation of methylene blue (MB). The Al@CuO anode material was prepared by the thermal decomposition method. X-ray fluorescence (XRF) analysis confirmed the successful deposition of CuO on the aluminum substrate. The influence of current density, electrolysis time, and MB concentration on the performance of the electrochemical degradation of MB was modeled using Box-Behnken design (BBD). The accuracy of the proposed quadratic model by BBD was confirmed with a p-value &lt; 0.0001 and adj-R2 &gt; 0.9. The optimum MB degradation efficiency of 53.23 % was obtained at 80 mg MB concentration, 40 min electrolysis time, and 3.75 V applied current. The kinetics on the MB electrochemical degradation process using Al@CuO followed pseudo first-order kinetics model. These studies revealed that the Al@CuO anode electrode is not a promising anode for the electrochemical degradation of methylene blue.

Membrane-free Electrolysis Production of Hydrogen Peroxide on Low-Cost Metal-Free Electrocatalysts for Dye Degradation.

The efficient production of hydrogen peroxide (H2O2) solution was achieved by combining cathodic two-electron oxygen reduction (2e- ORR) and anodic two-electron water oxidation (2e- WOR) in two half-reaction cells. h-BN loaded on carbon fibers (h-BN@C) is prepared and employed as an anode material to catalyze 2e- WOR, while sulfonated commercial BP-2000 carbons (BP-2000-SO3H) were prepared as the cathode materials for 2e- ORR. In a 2 M KHCO3 solution, an overall Faradaic efficiency of 97% and a total H2O2 production rate of 1872 mmol g-1 h-1 over metal-free electrodes were accomplished in a membrane-free flow cell. The dilute H2O2 solution could be directly used to degrade cationic Rhodamine B or methyl orange and anionic methylene blue dyes in water. This work proved low-cost production of dilute H2O2 solution in simple membrane-free flow cells with single electrolyte and on-site utilization for efficient dye degradation.

A Fe3+-Doped TiO2 Superhydrophilic Coating with Transparent and Long-Lasting Antifogging Properties Constructed Based on Nanostructured Antireflective and Capillary Anchoring Effects.

Superhydrophilic surfaces have attracted great interest in antifogging applications. However, balancing long-lasting superhydrophilicity and high transparency on antifogging surfaces remains a serious problem to be solved. The objective of this work is to prepare superhydrophilic coatings with transparent and long-lasting antifogging properties. In the design, a three-step method was used to obtain the target coatings: (1) magnetron sputtering deposition of a TiN film to provide high intensity, (2) anodic oxidation of the TiN film to obtain TiO2 nanoparticles intended for nanostructured antireflective and capillary structures, and (3) the sol-gel method for the preparation of Fe3+-doped TiO2 coatings using spin-coating in order to achieve superhydrophilicity. The nanostructures, due to their subwavelength dimensions, not only provide high transparency but also recoverable superhydrophilicity owing to the presence of a capillary anchoring effect that prevents the coating from dissolving and peeling off after soaking. The doping of Fe3+ broadened the photoresponse range and maintained the long-lasting superhydrophilicity. Tests showed that the 2 mol % Fe3+-doped TiO2 coating with nanostructures exhibited the highest transparency, longest-lasting superhydrophilicity, and antifogging properties. Furthermore, the coating provided excellent self-cleaning properties, as well as mechanical and chemical stability.

Recycling the Spent Lithium-ion Battery into Nanocubes Cobalt Oxide Supercapacitor Electrode

Background:: Cobalt oxide nanocubes have garnered significant attention as potential supercapacitor electrodes due to their unique structural and electrochemical properties. The spent lithium-ion batteries (LiBs) are considered as zero-cost source for cobalt oxide production. Objective:: The aim of this work is to recover cobalt oxide from spent LiBs and study its electrochemical performance as a supercapacitor electrode material. Method:: This study uses an electrodeposition method to obtain cobalt oxide honeycomb-like anodes coated on Ni foam substrates from spent Li-ion batteries for supercapacitors applications. The effect of annealing temperature on the cobalt oxide anode has been carefully investigated; 450 ºC annealing temperature results in nanocubes on the surface of the cobalt oxide electrode. X-ray diffraction confirmed the formation of the Co3O4-NiO electrode. Results:: The Co3O4-NiO nanocubes electrode has shown a high specific capacitance of 1400 F g-1 at 1 A g-1 and high capacitance retention of ~96 % after 2250 cycles at a constant current density of 10 A g-1 compared to 900 F g-1 at 1 A g-1 as for prepared Co3O4 honeycomb. Conclusion:: This strategy proves that the paramount importance of Co3O4-NiO nanocubes, meticulously synthesized at elevated temperatures, as a supremely effective active material upon deposition onto transition metal foam current collectors, establishing their indispensability for supercapacitor applications.

Linear Paired Electrolysis Enables Redox-Neutral (3 + 2) Annulation of Benzofuran with Vinyldiazo Compounds.

Electrosynthesis has emerged as a versatile and sustainable tool in organic chemistry, offering an efficient pathway for the construction of complex molecular architectures under mild and environmentally benign conditions. Traditional electrochemical approaches, however, predominantly rely on either anodic oxidation or cathodic reduction, limiting their capacity to achieve redox-neutral transformations using a single electrode. In this work, we introduce a linear paired electrolysis strategy that circumvents these limitations, enabling a redox-neutral (3 + 2) annulation of benzofuran with vinyldiazo compounds. This method facilitates the formation of benzofuran-fused tricyclic scaffolds, which are valuable in synthetic chemistry and medicinal applications. The transformation proceeds through sequential anodic oxidation and cathodic reduction, leveraging a radical cation pathway to deliver polycyclic compounds with high selectivity. The efficiency and mechanism of this process are thoroughly validated using cyclic voltammetry and in situ electrochemical mass spectrometry (EC-MS) and supported by theoretical calculations, shedding light on the potential of redox-neutral electrochemical transformations.

Electrokinetics-Driven Anodic Oxide Pore Formation: Linear and Weakly Nonlinear Analysis

Abstract Anodization of aluminium in an acidic medium facilitates the formation of well-ordered nanoporous anodic oxide films. The mechanism of pore formation is investigated as a morphological instability using a simplified model. The model accounts for the high field conduction law and field-assisted reactions (oxide formation/dissolution) only at the oxide-solution interface. The role of Butler–Volmer electrokinetics, electrolyte pH, anodic efficiency, and interface curvature on reaction kinetics are taken into account. Linear stability analysis suggests that the oxide film is unstable to well-defined wavelengths in specific ranges of parameters such as anodizing efficiency, applied voltage and electrolyte pH. Subsequently, a weakly nonlinear analysis is carried out to determine the nature of bifurcation beyond the stability threshold. Our findings indicate that the instability exhibits a subcritical nature, well in agreement with experimental observations.