Anodic Synthesis Research Articles

Anodically Grown Pt(II) Oxide Microelectrode/Nanoelectrode pH Sensor

Operando measurements of local pH at the nanoscale can significantly improve the understanding of the complex microenvironments that exist in electrochemical systems. However, attempts to easily fabricate a nano-sized pH electrode that can operate under a wide range of pH conditions and have fast temporal responses have been difficult. Here, we show that an anodic-grown Pt/Pt(II) oxide pH sensor manufactured in alkaline conditions (1 M NaOH) shows a near-Nernstian response (−60 mV/pH) from pH 0 to pH 14, is insensitive to dissolved oxygen, cation, and anion identities, and responds correctly in solution with different ionic strengths. This is in contrast to Pt/Pt(II) oxide films grown in acidic media, which do not demonstrate a Nernstian relationship due to cation interference other than H+. We observed a response time of 2.25 s, corresponding to 90% of the final measured pH, for an approximately twelve-fold pH step change when growing the Pt(II) oxide layer on a platinum nanoelectrode. Our findings emphasize the influence of solution pH used for anodization synthesis on the anodic Pt(II) oxide pH sensing properties. The direct oxidation approach for fabricating Pt/Pt(II) oxide microelectrode/nanoelectrode pH sensors can simplify the manufacture of real-time pH sensors for complex aqueous environments.

Anodic Synthesis of Highly Ordered TiO2 Nanotube Arrays: Role of Electrolyte Composition on the Structural, Morphological, Optical, and Photo-electrochemical Properties

The fluoride species present in two different anodizing electrolytes were used to produce TiO2 nanotube arrays (TiO2 NTAs) by simultaneous anodic reaction and chemical dissolution. In this investigation, two different electrolytes were used for the preparation; [Eth-TiO2 NAs: 95 ml ethylene glycol+0.5% NH4F+5 ml DI water] and [Gly-TiO2 NAs: 75 ml glycerine+0.5% NH4F+25 ml DI water]. The effects of the prepared electrolytes used in the synthesis of TiO2 nanotube arrays on structural element composition, morphology, and optical properties are the focus of this study and are characterized by X-ray diffraction (XRD), scanning electron microscopy field emission (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and UV-vis diffusion reflection spectroscopy (DRS), respectively. The photoelectrochemical properties of TiO2 NTAs prepared in different electrolytes were investigated. The photoelectrochemical performance of TiO2 NTAs in Na2SO3 (0.1 M) and Na2S (0.1) was examined under the light of 100 mW/cm2 from a xenon lamp. Comparing the photoelectrochemical (PEC) results of both electrolytes, we find that Eth-TiO2 NTAs contribute a wide surface area resulting in an enhanced PEC response. TiO2 NTs, which were prepared with Eth-TiO2 NTAs, exhibited the highest photocurrent density, 0.326 mA cm–2, and photoconversion efficiency (0.22%).

Unveiling graphite anodic expansion: Insights from electrochemical techniques, mass spectrometry, and kinetic modelling

Anodic expansion of graphite at different pH has been studied by coupling a mass spectrometer to an electrochemical cell. The mass spectrometry technique permits to follow the electrochemical gasification of graphite as well as the reaction products formed from the electrolyte. The current and mass spectrometry signals suggest that the neutral medium is the least aggressive for expansion. In addition, chronoamperometric expansion of graphite at different potentials has been carried out using the neutral medium. This experimental approach permits to get detailed information about the reaction mechanism that produces graphene-oxide based materials. The effect of potential and electrolyte concentration have been studied, and it has been observed that the degree of oxidation of the graphene oxide material obtained can be controlled. In addition, a kinetic model based on a phase-moving boundary has been used to describe the chronoamperometric experiments. Two types of graphene oxide materials have been obtained with the anodic synthesis and have been classified as few-layer graphene oxides (FLGOs) and graphene oxide quantum dots (GOQDs). The physicochemical and electrochemical properties of both products have been studied.

Structural, morphological, and optical properties of CuO nanoblade-decorated TiO2 nanotubular photoelectrodes

Titania (TiO2) nanotubular photoelectrodes are a competitive component of titania-based photoelectrochemical water splitting systems. However, TiO2 actively absorbs light in the UV region, which limits its usefulness in solar water splitting, a fast-growing clean energy alternative. In this study, the structural, morphological and optical properties of CuO/TiO2 nanostructures on conductive transparent F-doped SnO2 (FTO) coated glass substrates are engineered for potential application in solar water splitting. The efficacy of a three-step anodization synthesis process to develop free-standing high-fidelity nanotubular TiO2 thin films (∼8μm) is demonstrated. CuO nanoblades were deposited on TiO2/FTO by a successive ionic layer adsorption reaction (SILAR). An increase in the precursor concentration and number of immersion cycles influenced the adsorption of CuO and the resultant red shift in the absorption range. SEM and TEM analyses confirm the formation of a heterostructure, with evidence of CuO nanostructures within the TiO2 nanotubular arrays and on the top of the tubes.

Biomass-derived SiOx/C nanocomposite anode synthesis by induction heating for lithium ion battery

Biomass-derived SiOx/C nanocomposite anode synthesis by induction heating for lithium ion battery

Impact of calcination temperature on optimized NiO anode synthesis for batteries

Impact of calcination temperature on optimized NiO anode synthesis for batteries

Simultaneous ammonia and organics degradation from municipal landfill leachate by electrochemical oxidation

ABSTRACT The two primary issues for wide implementation of the electrochemical oxidation of wastewater are the significant cost of electrode and high energy consumption. On the other side, conventional biological processes and membrane technology have several drawbacks for recalcitrant landfill leachate (LL) treatment. To address these issues, graphite/PbO2 anode was used to treat medium to mature age (biodegradability index, 5-day biochemical oxygen demand/chemical oxygen demand: 0.25) LL. To reduce the cost of the oxidation process and maximize the efficiency, operating conditions were optimized. The optimum parameter values were obtained as 24.7 mA cm−2, 180 ± 3 rpm, and 1.9 cm of current density, stirring rate, and electrode gap, respectively. Dissolved organic carbon (DOC), chemical oxygen demand (COD), and ammonia-N removal efficiencies of 55 ± 1.4%, 81 ± 1.9%, and 56 ± 3% were obtained after 8 h of degradation at optimum conditions. The decrease in aromatic substances and ultraviolet (UV) quenching materials were evaluated by UV-Visible spectroscopy and Specific UV absorbance. The conversion of aromatic compounds into simpler molecule compounds was also verified by Fourier-transform infrared spectroscopy analysis. The lab-scale anode synthesis cost was evaluated as 0.42 USD.

High mechanical strength Si anode synthesis with interlayer bonded expanded graphite structure for lithium-ion batteries

Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries, their widespread commercial adoption is still hindered by significant volume expansion during cycling, especially at high active mass loadings crucial for practical use. The root of these challenges lies in the mechanical instability of the material, which subsequently leads to the structural failure of the electrode. Here, we present a novel synthesis of a composite combining expanded graphite and silicon nanoparticles. This composite features a unique interlayer-bonded graphite structure, achieved through the application of a modified spark plasma sintering method. Notably, this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength (Vickers hardness: up to 658 MPa, Young’s modulus: 11.6 GPa). This strength effectively accommodates silicon expansion, resulting in an impressive areal capacity of 2.9 mA h cm−2 (736 mA h g−1) and a steady cycle life (93% after 100 cycles). Such outstanding performance is paired with features appropriate for large-scale industrial production of silicon batteries, such as active mass loading of at least 3.9 mg cm−2, a high-tap density electrode material of 1.68 g cm−3 (secondary clusters: 1.12 g cm−3), and a production yield of up to 1 kg per day.

Sodium Dodecyl Sulfate-Adjusted Phase Composition of Hydrated Tungsten Oxides as Stable Self-Supporting Electrodes for Supercapacitors with High Volumetric Specific Capacitance.

High pseudocapacitive activity of hydrated tungsten oxides (WO3·xH2O, x = 1 or 2) makes them promising materials for supercapacitors (SCs). During their synthesis, additives such as complexing agents and surfactants generally can only affect the morphology and/or size of the products. Here, we demonstrate that not only morphology and size of WO3·xH2O were affected, its phase composition could also change from WO3·2H2O to WO3·H2O simply by increasing the amount of sodium dodecyl sulfate (SDS) during its anodization synthesis. To the best of our knowledge, such a phenomenon has not been reported before. In addition, SDS introduced a special structure to the products, i.e., WO3·xH2O nanoplatelets constructed from nanoparticle multilayers with abundant nanogaps between the multilayers, which further arranged into nanoflowers with increased amounts of SDS. Benefiting from such a structure, low internal resistance, enhanced stability, and fast redox kinetics, the as-obtained WO3·xH2O/W-3 self-supporting electrode showed a high volumetric specific capacitance of 1402.92 F cm-3 and good cycling stability (a capacity retention of 106% after 10 000 cycles). In addition, an all-solid-state asymmetric SC device based on WO3·xH2O/W-3 delivered high a volumetric energy density of 44.0 mW h cm-3 at 0.5 W cm-3. Our method demonstrates a potential way to fabricate excellent self-supporting electrodes for SCs.

Anodic Synthesis of Peptides in Biphasic Electrolytic Solutions

Peptide synthesis requires a large amount of condensing reagents, and once the condensation is complete, all of the reagents become waste. Based on the recognition of these issues, we decided to investigate the possibility of linking the condensing agent function to electrode electron transfer. Using this reaction system, all the elongation reaction steps were carried out by the electrolytic method. The electrolytic peptide synthesis method has been confirmed to efficiently proceed with the condensation of all amino acids, and the products and by-products can be easily separated. It is expected to be applied as a material production method that significantly reduces the use of energy and materials.

Ligand-Oxidation-Based Anodic Synthesis of Oriented Films of Conductive M-Catecholate Metal-Organic Frameworks with Controllable Thickness.

Effective control over the crystallization of metal-organic framework (MOF) films is of great importance not only for the performance study and optimization in related applications but also for the fundamental understanding of the involved reticular chemistry. Featuring many technological advantages, electrochemical synthesis has been extensively reported for many MOF materials but is still challenged by the production of dense oriented films with a large-range tuning of thickness. Here, we report a ligand-oxidation-based anodic strategy capable of synthesizing oriented films of two-dimensional (2D) and three-dimensional (3D) conductive M-catecholate MOFs (2D Cu3(HHTP)2, 2D Zn3(HHTP)2, 2D Co3(HHTP)2, 3D YbHHTP, and 2D Cu2TBA) with tunable thicknesses up to tens of micrometers on commonly used electrodes. This anodic strategy relies on the oxidation of redox-active catechol ligands and follows a stepwise electrochemical-chemical reaction mechanism to achieve effective control over crystallizing M-catecholate MOFs into films oriented in the [001] direction. Benefiting from the electrically conductive nature, Cu3(HHTP)2 films could be thickened at a steady rate (17.4 nm·min-1) from ∼90 nm to 10.7 μm via a growth mechanism differing from those adopted in previous electrochemical synthesis of dense MOF films with limited thickness due to the self-inhibition effect. This anodic synthesis could be further combined with a templating strategy to fabricate not only films with well-defined 2D features in sizes from micrometers to millimeters but also high aspect ratio mesostructures, such as nanorods, of Cu3(HHTP)2.

Role of the Coordination of Metal Ions by Ammonia for the Anodic Electrosynthesis of MOF Films

Metal-organic frameworks (MOFs), consisting of inorganic nodes coordinated by organic ligands, have received tremendous attention in the past decades due to their high surface area, high porosity, designable pore-aperture shape/size, and tunable building units (including metal centers and functional ligands). For most of their applications, such as separation, catalysis, sensors, and energy storage/conversion devices, MOFs in the form of films/membranes are desired. Anodic electrodeposition is a promising and cost-effective method to in-situ prepare metal-organic framework (MOF) films on metal substrates. However, the anodic synthesis of continuous zeolitic imidazolate framework (ZIF) films, an important subclass of MOF materials, has been proved challenging. Here, we report a facile anodic deposition method that enables the ultra-fast preparation of uniform and continuous ZIF-8 films with tunable thickness from the aqueous solution at room temperature by using the ammonia hydroxide-assisted deprotonation strategy (AHADS). The growth rate of the MOF films is flexibly controlled by the applied current densities, the concentration of the linkers, and the amount of added ammonia hydroxide. The roll-to-roll deposition of the ZIF-8 films on the zinc foils shows the possibility of this method for large-scale industrial synthesis. The control experiments and theoretical calculations reveal that the formation of Zn(NH3)4 2+ complex by adding excessive ammonia hydroxide is crucial to promote the coordination of 2-Methylimidazole (Hmim) with Zn2+. Afterward, the Zn2+ cation attracts electrons of Hmim and thus weakens the N-H bond, which decreases the free energy for the deprotonation of Hmim. As a result, the ZIF-8 films can be aqueously deposited at low pH under room temperature. Various pure ZIF films (ZIF-4, ZIF-7, and ZIF-67) with different metal nodes or organic linkers were successfully deposited via this strategy. In addition, ZIF-8 films deposited on the zinc foil show ability to decrease the overpotential for the zinc plating and stripping, suggesting its possibility for use in reversible zinc metal batteries. This work broadens the applicability of anodic deposition and indicates the potential applications of metal-supported MOF films in energy storage and conversion fields

Construction of the Fast Potassiation Path in Sbx Bi1-x @NC Anode with Ultrahigh Cycling Stability for Potassium-Ion Batteries.

Due to the scarce of lithium resources, potassium-ion batteries (PIBs) have attracted extensive attention due to their similar electrochemical properties to lithium-ion batteries (LIBs) and more abundant potassium resources. Even though there is considerable progress in SbBi alloy anode for LIBs and PIBs, most studies are focused on the morphology/structure tuning, while the inherent physical features of alloy composition's effect on the electrochemical performance are rarely investigated. Herein, combined the nanonization, carbon compounding, and alloying with composition regulation, the anode of nitrogen-doped carbon-coated Sbx Bi1-x (Sbx Bi1-x @NC) with a series of tuned chemical compositions is designed as an ideal model. The density functional theory (DFT) calculation and experimental investigation results show that the K+ diffusion barrier is lower and the path is easier to carry out when element Bi dominates the potassiation reaction, which is also the reason for better circulation. The optimized Sb0.25 Bi0.75 @NC shows an excellent cycling performance with a reversible specific capacity of 301.9mAhg-1 after 500 cycles at 0.1Ag-1 . Meanwhile, the charge-discharge mechanism is intuitively invetigated and analyzed by in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) in detail. Such an alloy-type anode synthesis approach and in situ observation method provide an adjustable strategy for the designing and investigating of PIB anodes.

Preparation of anode by MOF pyrolysis enabled long-life rechargeable zinc nickel batteries

Water-induced parasitic reaction and zinc dendrite growth caused by uneven electric field distribution on the surface of the zinc anode are the most controversial problems in the practical application of zinc-nickel rechargeable batteries in large-scale energy storage. Herein, Bi2O3/In2O3 doped ZnO@C synthesized by MOF pyrolysis with good cycle stability. The ability to inhibit hydrogen evolution and achieve uniform deposition of zinc is characterized by CV, Tafel, and scanning electron microscopy (SEM). Benefiting from the high hydrogen evolution overpotential and high electrical conductivity, Bi2O3 doped ZnO@C (BCZ) and In2O3 doped ZnO@C (ICZ) electrodes deliver high capacity of 640 mA h g−1 and 580 mA h g−1 at 10 C after 1200 and 3400 cycles, respectively, and reveals long-term cyclic stability with capacity retention over 90%. This work provides new ideas for the anode synthesis of aqueous rechargeable zinc metal batteries and other batteries.

Effect of concentration of Fe-dopant on the photoelectrochemical properties of Titania nanotube arrays

TiO 2 nanotubes have attracted great attention because of their photoelectrochemical activity. Metallic doping using a simple and rapid synthesizing approach can be a way to enhance this application. This paper describes a novel one-step anodization synthesis of Fe-doped TiO 2 nanotubes with various concentrations of iron doping. FESEM, XRD, and EDX were used to analyze the effect of doping concentration on the morphology, structure, and composition of the prepared samples respectively, and the results showed the formation of the anatase phase of TiO 2 nanotube arrays with Fe incorporation in the TiO 2 lattice. Although the Fe insertion in the TiO 2 lattice leads to better crystallinity, the non-uniformity in the morphology of doped samples suggests that adequate doping is required to maintain uniformity in the morphology. The absorption spectra of all the Fe-doped TiO 2 samples showed a red shift in their absorption edges compared to pristine TiO 2 . This shift was observed more in the samples with higher doping concentrations. The photocurrent density of Fe-doped samples was observed to be significantly higher than that of the pristine TiO2 sample. This improvement was found to be concentration-dependent, with the best results being obtained from a sample doped at a level of 0.5%. The samples also showed high photostability, which, together with the increased photocurrent density, points to Fe-doped TiO 2 as a promising photoanode material.

Water lily seed-inspired silicon/carbon composite anode synthesis for high-performance Li-ion battery

Water lily seed-inspired silicon/carbon composite anode synthesis for high-performance Li-ion battery

Quantitative manipulation of covalent bonds to obtain ultra-stable half/full Li-ion batteries via gel encapsulation-post annealing route

To ensure a satisfactory stability and conductivity, excess carbonaceous component has to be introduced in anode materials at most cases, which sacrifices the energy density of the half/full cell. Herein, a new strategy is proposed that metal-heteroatom bonds are quantitatively introduced to enhance the interaction between each component in electrode. This strategy is successfully applied in fabricating Mo-based (MoO2-X@N– C) electrode materials with active materials content as high as 65.00%. The realization of quantitative control mainly results from the usage of gelatin that can anchor each active component together for the abundant functional groups. As a result, long-life cycle capacity (400 mAh/g at 1 A/g for 2700 cycles) is achieved. Moreover, the full cell of the LiFePO4//MoO2-2@N–C exhibits 124 mAh/g after 100-cycle and maintains the high energy density of 166.7 Wh/kg. This work gives light on anode synthesis that can be large scale-produced with a time-saving strategy for ultra-stable energy storage devices.

Si1–xGex anode synthesis on plastic films for flexible rechargeable batteries

SiGe is a promising anode material for replacing graphite in next generation thin-film batteries owing to its high theoretical charge/discharge capacity. Metal-induced layer exchange (LE) is a unique technique used for the low-temperature synthesis of SiGe layers on arbitrary substrates. Here, we demonstrate the synthesis of Si1−xGex (x = 0–1) layers on plastic films using Al-induced LE. The resulting SiGe layers exhibited high electrical conductivity (up to 1200 S cm−1), reflecting the self-organized doping effect of LE. Moreover, the Si1−xGex layer synthesized by the same process was adopted as the anode for the lithium-ion battery. All Si1−xGex anodes showed clear charge/discharge operation and high coulombic efficiency (≥ 97%) after 100 cycles. While the discharge capacities almost reflected the theoretical values at each x at 0.1 C, the capacity degradation with increasing current rate strongly depended on x. Si-rich samples exhibited high initial capacity and low capacity retention, while Ge-rich samples showed contrasting characteristics. In particular, the Si1−xGex layers with x ≥ 0.8 showed excellent current rate performance owing to their high electrical conductivity and low volume expansion, maintaining a high capacity (> 500 mAh g–1) even at a high current rate (10 C). Thus, we revealed the relationship between SiGe composition and anode characteristics for the SiGe layers formed by LE at low temperatures. These results will pave the way for the next generation of flexible batteries based on SiGe anodes.

Preliminary Study of pH Sensor for Engine Oil Deterioration Detection Using Anodized Ta2O5 Nanotubular

pH sensor is one of the sensing principles that can be employed in detection of engine oil deterioration. To avoid unnecessary changing of engine oil while maintaining the oil quality consumed by car’s engine, engine oil deterioration sensor is required to continuously monitor the oil condition. In this work, we fabricated pH sensor sensing layer made up of tantalum thin film. Ta2O5nanotubular was constructed as the medium of interaction to measure the quality of engine oil. Anodization synthesis method was used to fabricate the sensing layer by varying the anodization time. Two samples anodized at 30 min and 60 min were tested in pH buffer solution at pH ranging from 2, 4, 7, 10 and 12. Further characterization using field emission scanning electron microscope (FESEM) was conducted to investigate the surface morphology properties, while X-ray diffraction (XRD) was conducted to obtain crystal properties of Ta2O5nanotubular. A homogeneous Ta2O5nanostructures with cubic crystal structure and pore diameter ranging between 15 to 20 nm was obtained. 30 min sample tested in pH buffer solution has better adsorption of H+ions with linear pH sensitivity of 31.616 mV/pH and good stability. Therefore, anodization method can be an alternative to fabricate pH sensor for oil deterioration detection system.Additionally, other study on chemical sensor for the detection of engine oil deterioration level wasalsodiscussed in this paper.

Electrochemical fabrication of Ru[bpy]32+@Cu-MOF(-SH)/Au photo/electrochemical coupling interface and its DNA-based biosensing performance

An electrochemical fabrication method of Ru[bpy]32+@Cu-MOF(-SH)/Au (MOF = metal–organic framework) was developed with a photo/electrochemical information characterization and a DNA-based biosensing validation for the proposed interface. Applying an anodic synthesis method, a modification layer of Ru[bpy]32+ encapsulated with MOF was formed on the Au electrode surface to fabricate an interface with photo/electrochemical dual-signal response. Combining the scanning electrochemical microscopy (SECM) imaging technology with electrochemical and electrochemiluminescence (ECL) detection, the information about the interfacial photo/electrochemical bi-functional properties was explored from three aspects of the parameter variable, intensity variable, and morphology variable. The results show that the effect of parameter variables on the interfacial response follows an “interference effect” mechanism. Under the optimized conditions, the background and the saturation ECL intensities are 610.0 and 24.0 with a quenching efficiency of 96.1% and a detection limit of 30 fM. The saturation current is 48.8 µA with a detection limit of 330.0 nM. Both ECL and electrochemical imaging methods can corroborate each other, validating the logical correlation between the interface fabrication and the response performance in the regional interfacial distribution and laying a methodological foundation for evaluating the interface fabrication quality based on imaging morphology qualitatively. The proposed interface can construct photo/electrochemical dual-signal DNA-based biosensors.