Anodic Pretreatment Research Articles

Electrochemical determination of ibuprofen by batch‐injection analysis using a BORON‐doped ultrananocrystalline diamond electrode

AbstractIn this paper, the evaluation of a boron‐doped ultrananocrystalline diamond (BD‐UNCD) electrode for the determination of ibuprofen (IBU) in pharmaceutical formulations using batch‐injection analysis with amperometric detection (BIA‐AD) is presented. The BD‐UNCD electrode was characterized by Raman spectroscopy and the electrochemical measurements were carried out before and after anodic pretreatment. An improved electrochemical response for IBU oxidation was observed using BD‐UNCD as compared to commercial boron‐doped diamond electrode. The optimized method based on the BIA‐AD system was carried out by using 2.0 V as the detection potential, a dispensing rate of 211.9 μL s−1, and an injection volume of 40 μL in an electrochemical cell containing 30.0 mL of 1.0 mol L−1 HClO4 as the supporting electrolyte. The proposed method provided an analytical curve within a linear dynamic range from 1.84 to 20.0 μmol L−1 (R2=0.9967) and a limit of detection of 0.55 μmol L−1. The intra‐day (n=10) and inter‐day (n=2) precisions for IBU concentrations of 5.0 and 10.0 μmol L−1 assessed as relative standard deviation (%RSD) ranged from 2.65 to 5.84 %. The accuracy of the method was assessed through the determination of IBU in pharmaceutical samples (tablets and solutions), yielding results that were consistent with those obtained through the comparative method (HPLC‐DAD).

Insight into the effective electrocatalytic sulfide removal from aqueous solutions using surface oxidized stainless-steel anode and its desulfurization mechanism

The electrochemical oxidation of hydrogen sulfide (H2S) has shown its potential for the real application of H2S emission control in wastewater treatment. In this study, a surface corrosion treatment of stainless steel (SS) was optimized by regulate Ni content in the oxide film on the SS AISI 304 surface for sulfide removal. The X-ray photoelectron spectroscopy and linear sweeping voltammetry results indicated a higher Ni content in the oxide film of surface-oxidized stainless steel (SOSS) attributed to a higher sulfide removal potential. Sulfide removal experiment results showed that SS-150 (with 150 s anodic pretreatment) anodes achieved the highest Ni content of 69% with the best sulfide removal efficiency, i.e., 97% within 48 h, which increased by 20% compared to the untreated SS. This study also demonstrated a strategy for in situ removal of deposited sulfur on the anodes by cathodic treatment at −0.38 V vs. RHE to alleviate the common issue of sulfur passivation. Density functional theory (DFT) calculation revealed that NiOOH was the major active species in SS-150 oxide film for a faster sulfide removal rate. The study developed a SS surface modification process for Ni content regulation that contributed to better sulfide removal efficiency.

Electrochemical Behavior of Quinones Classically Used for Bioenergetical Applications: Considerations and Insights about the Anodic Side

AbstractQuinones are electrochemical probes which are used for a large range of applications including bioenergetics. One electrochemical feature of quinones is their possible slow electron transfer kinetics. In this article we compared several quinones towards electron transfer kinetics and the ability of anodic pretreatment to increase electron transfer rate constant. Rotating disk electrode and chronoamperometry measurements were used to revisit their electrochemical behavior. Additionally, the number of electrons exchanged as a function of the characteristic time was used as a proxy to investigate kinetic limitations. A model was suggested to rationalize our results. Beyond a classification of quinones regarding the kinetic and thermodynamic ability of the hydroquinone form to be re‐oxidized, some intrinsic physicochemical properties were identified from our model (such as a time dependency of the exchanged number of electrons) to characterize such important redox mediators.

Anode surface pretreatment to optimize electrochemical performance of aqueous zinc-ion batteries

The aqueous zinc-ion batteries (AZIBs) exhibit promising potential as a viable solution for large energy storage. Solving dendrite growth the surface of zinc metal anode in AZIBs is of great significance for its application in energy storage field. Among the many strategies for solving the zinc anode problem, the influence of zinc anode pretreatment is often ignored. The effect of sandpaper physical polishing on the performance of zinc anode was studied in this paper. The striated grooves formed on the surface of the zinc anode after sandpaper treatment make the zinc anode have a large specific surface area and a high zinc plating/stripping kinetics. It was found that sandpaper with larger mesh count (the finer the sandpaper) could reduce roughness and had the higher the electrochemical performance of zinc anodes. Consequently, the cycle life of 2000 M-Zn symmetric battery can reach 900 h under the current density of 0.5 mA cm−2. In the application of energy storage, the full battery composed of 2000 M-Zn and sodium doped V2O5 cathode (NVO) still has a specific capacity of 148.6 mAh g−1 after 500 cycles, and has a stable rate performance. The pretreatment strategy of zinc anode holds significant importance in the applications of AZIBs.

Beyond conventional: unveiling the impact of Zn anode pretreatment in aqueous zinc-ion batteries

Chemically etched Zn shows superior cycling stability in Zn-ion batteries, achieving 5000 cycles with 71% retention. In situ TXM, AFM, and EBSD reveal a unique 3D structure and Zn deposition along the (002) plane, reducing dendrite formation.

The enhancement of hydrogen evolution reaction on nanoplatelet-shaped MoS2 via anodic pretreatment

This work presents the effect of anodic pretreatment of 2D-MoS2 nanoplatelet-shaped films hydrothermally synthesized on the anodized Ti substrate for electrocatalytic H2 evolution from water. Structural and compositional changes in MoS2 species assembly were studied by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The electrochemical performance of designed catalysts was studied in 0.5 mol L−1 H2SO4 solution by cyclic voltammetry and chronopotentiometry for 12 h. The growing hydrogen evolution reaction efficiency upon anodic pretreatment was ascribed to increased sulfur content in the MoS2 nanoplatelet edges in the form of more active bridging S22− and apical S2− groups.

Boron-doped {113}, {115} and {118}-oriented single-crystal diamond electrodes: Effect of surface pre-treatment

In this study, the effect of vicinal crystal orientation ({113}, {115}, and {118}), boron doping level, and surface termination induced by various pre-treatments on electrical and electrochemical properties of single crystal boron-doped diamond (SC-BDD) electrodes was carefully investigated. van de Pauw measurements confirmed Hall concentration to increase with increasing vicinal angle, {118} < {115} < {113}. As-deposited H-terminated surfaces were converted to predominantly O-terminated surfaces (confirmed by X-ray photoelectron spectroscopy) using hot acid, ozone and anodic pre-treatments, or by spontaneous oxidation in air. This conversion was recognized by inhibited heterogeneous electron transfer kinetics of inner-sphere redox markers ([Fe(CN)6]3−/4− and dopamine), by an increase in double layer capacitance and charge transfer resistance values. The most pronounced surface oxidation was recognized for electrodes with the lowest boron content as a result of blocked boron atoms by oxygen functionalities and loss of superficial hydrogen on the surface. Reverse conversion from oxidized to H-terminated surfaces using cathodic pre-treatment led mainly to restoration of electrochemical parameters. Moreover, spontaneous oxidation of electrode surfaces in ambient atmosphere was confirmed, with the fastest being within the first five days. The results show the key role of boron content, and hence the crystal orientation and superficial hydrogen in affecting conductivity and performance of SC-BDD electrodes, which is demonstrated by changes in heterogenous electron transfer kinetics of surface sensitive redox systems.

A Generic “Engraving in Aprotic Medium” Strategy toward Stabilized Zn Anodes

AbstractZn foil pretreatment is a direct route to alleviating Zn anode instability and maintaining high energy performance in Zn metal batteries. Unfortunately, prevailing methods for achieving an ideal Zn surface texture do not enable durable operation under a large depth of discharge, thus impairing the Zn utilization ratio. Zn etching is a more feasible way to control the surface texture, but this approach remains relatively unexplored. In this study, a general strategy is reported for Zn foil engraving in aprotic media to realize efficient anode pretreatment in terms of stability. These tests are performed using high‐valence metal ions (especially Mo5+) in an aprotic environment as the key etchant to render a homogenously‐distributed, 3D porous architecture on the Zn foil surface. Comprehensive experimental results and theoretical simulations revealed enhanced Zn nucleation and growth. This specially designed electrode exhibited a long lifespan with a large depth of discharge of 88% in symmetric cells. When assembled with a ZnxV2O5 cathode, the constructed cell demonstrated nearly full capacity retention even under stringent conditions (e.g., an N/P capacity ratio of 5.5). This study demonstrates the potential of a Zn etching pretreatment to address the prototypical instability issues of Zn anodes.

Investigation of the electrochemical properties of vinblastine on boron-doped diamond electrode treated with anodic pre-treatment in anionic surfactant medium

Investigation of the electrochemical properties of vinblastine on boron-doped diamond electrode treated with anodic pre-treatment in anionic surfactant medium

Improved procedure for square-wave voltammetric sensing of fenhexamid residues on blueberries peel surface at the anodically pretreated boron-doped diamond electrode

BackgroundFungicide fenhexamid (FH) has a high residual concentration on fruits and vegetables, thus, it is of high importance to monitor the level of FH residues on foodstuff samples. So far, the assay of FH residues in selected foodstuff samples has been conducted by electroanalytical methods on sp2 carbon-based electrodes that are well-known to be susceptible to severe fouling of the electrodes surfaces during electrochemical measurements. As an alternative, sp3 carbon-based electrode such as boron-doped diamond (BDD) can be used in the analysis of FH residues retained on the peel surface of foodstuff (blueberries) sample. ResultsIn situ anodic pretreatment of the BDDE surface was found to be the most successful strategy to remediate the passivated BDDE surface by FH oxidation (by)products, and the best validation parameters, i.e., the widest linear range (3.0–100.0 μmol L−1), the highest sensitivity (0.0265 μA L μmol−1) and the lowest limit of detection (0.821 μmol L−1), were achieved on the anodically pretreated BDDE (APT–BDDE) in a Britton-Robinson buffer, pH 2.0, using square-wave voltammetry (SWV). The assay of FH residues retained on blueberries peel surface was performed on the APT–BDDE using SWV, and the obtained concentration of FH residues of 6.152 μmol L−1 (1.859 mg kg−1) was found to be below the maximum residue value fixed for blueberries by the European Union regulations (20 mg kg−1). Significance and noveltyIn this work, a protocol based on a very easy and fast foodstuff sample preparation procedure combined with the straightforward pretreatment approach of the BDDE surface was elaborated for the first time for the monitoring of the level of FH residues retained on the peel surface of blueberries samples. The presented reliable, cost-effective, and easy-to-use protocol could find its application as a rapid screening method for the control of food safety.

Controlling the thickness and composition of stainless steel surface oxide film for anodic sulfide removal

Hydrogen sulfide is hazardous and toxic, and is present at many waste streams of industry processes. Anodic sulfide oxidation is a potentially effective approach to remove sulfide in aqueous media. This study therefore prepared and optimized surface oxide film on AISI 304 stainless steel (SS) as active and stable anode for sulfide removal. Among stainless steel samples of different anodization pretreatment duration, the anode with 15 min pretreatment (SS-15) resulted in the best sulfide removal at the same testing conditions, and achieved 48% and 18% improvement in terms of sulfide removal efficiency compared with the untreated SS and graphite, respectively. ANOVA-based tests (overall and for pairwise comparisons) also suggest the data are indeed valid. When anode potential was set no more than 1.62 V vs. reversible hydrogen electrode (RHE), direct sulfide oxidation dominated; and further increase in anode potential would initiate oxygen evolution reaction (OER) which contributed to indirect sulfide oxidation. Surface characterization found that the varying corrosion pretreatment duration led to oxide films of different thickness and chemical composition. The pretreatment duration from 15 min to 90 min increased the oxide film thickness from 178 nm to 264 nm and decreased the composition of FeOOH and NiOOH, which were most likely the catalytic active species for sulfide oxidation revealed by high-resolution XPS. Electrochemical analysis confirmed that the smaller thickness and enriched FeOOH/NiOOH composition in SS-15 led to a lower charge transfer resistance, a lower mass transfer resistance, and meanwhile a greater material stability. Depth profiling via high-resolution XPS identified metallic Fe inside oxide films and its presence may also promote the conductivity of the oxide film. This study demonstrated that anodization pretreatment of stainless steel was able to prepare effective and stable anode for electrochemical sulfide removal by controlling the thickness and composition of oxide films.

Fabrication, and Direct Current and cryogenic analysis of SF6-treated AlGaN/GaN Schottky barrier diodes

Schottky contacts on fluorine implanted AlGaN/GaN heterostructures with the ideality factor close to unity and low on-voltage threshold are presented in this paper. An SF6 plasma anode pretreatment followed by a specific low-temperature annealing is also compared to a nonannealed sample. In addition, physical-model parameters are extracted by means of cryogenic temperature measurements to understand the conduction mechanisms involved in annealed diodes, showing better DC performances than their nonannealed counterparts. Furthermore, annealing induces a decrease of the ideality factor, which sets the field-enhanced thermionic emission as the main conduction mechanism, and reduces the tunneling reverse current leakage. This effect is attributed to the recovery of the plasma-induced damages.

Simple Portable Voltammetric Sensor Using Anodized Screen-Printed Graphene Electrode for the Quantitative Analysis of p-Hydroxybenzoic Acid in Cosmetics.

Screen-printed graphene electrodes (SPGEs) have become a potential option in electrochemical applications because of their outstanding properties and disposable approach to miniaturize the electrodes for onsite analysis. Herein, the detection of para-hydroxybenzoic acid (PHBA) in cosmetics using the anodized SPGE has been pioneered and reported. The simple anodization of the SPGE surface was operated by anodic pretreatment at a constant potential on SPGE. The surface morphologies and electrochemical behaviors of anodized SPGEs in different anodization electrolytes were examined. Using anodized SPGE in a phosphate-buffered solution, a nontoxic solution, the sensitivity of PHBA detection was significantly improved compared with pristine SPGE owing to the increase of the polar oxygen-containing functional group during the anodization. The anodized SPGE could detect a PHBA down to 0.073 μmol/L. Finally, the developed anodized SPGE presented high ability and feasibility for PHBA detection in cosmetics. Furthermore, a facile electrode preparation step with a nontoxic solution can present high reproducibility and compatibility with a portable potentiostat for onsite PHBA detection during manufacturing.

Anodically Pretreated Electrodes Using a Nontoxic Reagent: A New Voltammetric Sensing for Selective and Simultaneous Determination of Synthetic Dyes

A novel voltammetric electrode based on a screen-printed graphene electrode pretreated by the anodically pretreated process using a nontoxic reagent was first developed. A phosphate buffer solution (0.1 M) at pH 7 was used as a supporting electrolyte for the anodic pretreatment process. After the oxidizing process, the pretreated electrode was used to investigate the electrochemical properties of sunset yellow (SY) and tartrazine (TAR). The well-defined oxidation peaks of SY and TAR were clearly observed at +0.45 and +0.70 V (vs Ag/AgCl), respectively. Under the selected experimental variables, the calibration curves of SY and TAR were obtained in the ranges of 0.01–5.0 μM and 0.1–10.0 μM, with the LOD values being experimentally obtained (S/N = 3) and found to be 10 and 100 nM for SY and TAR, respectively. The developed electrode was successfully applied to the simultaneous determination of SY and TAR in nonalcoholic beverages, with the recovery values being in the range of 97.96%–102.76% and % relative errors are 1.5%–6.99%, which can be accepted. This new finding offers a simple, environmentally friendly process and cost-effectiveness for electrode fabrication. Moreover, this procedure can be considered as an alternative method for the routine analysis of food colorants.

Electroanalytical determination of Allura Red in beverage samples using an anodically pretreated graphite electrode

ABSTRACT In this study, an anodically pretreated pencil graphite electrode (Ptre/PGE) which has oxygen-containing groups was used for the electrochemical determination of Allura Red (AR) by differential pulse voltammetry (DPV) method for the first time in the literature. In order to be more selective and sensitive the pencil graphite electrode, the anodic pretreatment process was performed by applying a constant +1.8 V potential for 250 s in pH 9 phosphate buffer solution using chronoamperometry method. The characterisation studies of the sensor were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) methods. Interference effects of sunset yellow, tartrazine, amaranth, aspartame, glucose, gelatin, and ascorbic acid on AR determination with Ptre/PGE were investigated. The limit of detection and quantitation values was found as 75 and 251 nmol L−1, respectively. The Ptre/PGE has been used for the determination of AR in cherry juice and energy drink samples, where it provides recovery ranging from 98.40% to 100.8%.

Enhanced bioenergy recovery and nutrient removal from swine wastewater using an airlift-type photosynthetic microbial fuel cell

Swine wastewater (SW) was used herein as the substrate in an airlift-type photosynthetic microbial fuel cell (APMFC) for power generation, and also, after anode pre-treatment, as a medium for Chlorella vulgaris cultivation in the cathode compartment accompanied with CO2 biofixation. Compared to heterotrophic cultivation, APMFC under mixotrophic cultivation showed a better performance in biomass yield, lipid accumulation and power generation. The highest chemical oxygen demand (COD) removal (96.3%), total organic carbon (TOC) removal (95.1%), NH4+-N removal (99.1%), and total phosphorus (TP) removal (98.9%) were achieved using 2-fold diluted SW. In APMFC (SW of 2-fold dilution), the highest CO2 biofixation rate and lipid productivity reached 1149 mg L−1 d−1 and 164 mg L−1 d−1, respectively. Ammonium migration from the anodic compartment to the cathodic compartment gradually increased as the ammonium concentration increased in the anolyte. The energy balance analysis suggested that the highest net energy output reached 1.92 kWh m−3 in APMFC fed with 2-fold diluted SW, which showed a superiority in clean energy production. Microbial community analysis indicated that the electrogenic microorganisms were further enriched in the anodic biofilm, which could enhance the power generation. This study provided a promising way for simultaneous SW treatment, CO2 biofixation and bioenergy generation.

Next-Generation Diamond Electrodes for Neurochemical Sensing: Challenges and Opportunities.

Carbon-based electrodes combined with fast-scan cyclic voltammetry (FSCV) enable neurochemical sensing with high spatiotemporal resolution and sensitivity. While their attractive electrochemical and conductive properties have established a long history of use in the detection of neurotransmitters both in vitro and in vivo, carbon fiber microelectrodes (CFMEs) also have limitations in their fabrication, flexibility, and chronic stability. Diamond is a form of carbon with a more rigid bonding structure (sp3-hybridized) which can become conductive when boron-doped. Boron-doped diamond (BDD) is characterized by an extremely wide potential window, low background current, and good biocompatibility. Additionally, methods for processing and patterning diamond allow for high-throughput batch fabrication and customization of electrode arrays with unique architectures. While tradeoffs in sensitivity can undermine the advantages of BDD as a neurochemical sensor, there are numerous untapped opportunities to further improve performance, including anodic pretreatment, or optimization of the FSCV waveform, instrumentation, sp2/sp3 character, doping, surface characteristics, and signal processing. Here, we review the state-of-the-art in diamond electrodes for neurochemical sensing and discuss potential opportunities for future advancements of the technology. We highlight our team’s progress with the development of an all-diamond fiber ultramicroelectrode as a novel approach to advance the performance and applications of diamond-based neurochemical sensors.

Effects of pre-anodizing and phosphates on energy consumption and corrosion performance of PEO coatings on AA6082

A significant reduction in the energy consumption of Plasma Electrolytic Oxidation (PEO) coatings on AA6082 alloy was obtained using strategies based on electrolyte selection and a precursor anodic film. PEO coatings were developed on AA6082 in silicate-based electrolytes with different phosphate species without and with a precursor oxide layer. The electrical response and, therefore, the specific energy consumption depended on the phosphate species and most notably on the applied pretreatment. The best result was obtained after anodic pretreatment and PEO in silicate-polyphosphate electrolyte with a reduction up to ⁓66% in comparison with the most conventional treatment (direct PEO in orthophosphate electrolyte). The corrosion response is not affected significantly by the pre-anodizing treatment either for short or prolonged immersion times revealing that coatings synthesised under high-energy efficient conditions have comparable corrosion performance under aggressive corrosive environments compared to conventional PEO processes.

The opportunity of 6-monoacetylmorphine to selectively detect heroin at preanodized screen printed electrodes

The illicit consumption of heroin is an increasing concern in our society. For this reason, rapid analytical methods to seize heroin samples in the field are of paramount importance to hinder drug trafficking, and thus prevent the availability of heroin in the drug market. The present work reports on the enriched electrochemical fingerprint of heroin, allowing its selective detection in street samples, based on the use of electrochemical pretreated screen printed electrodes (p-SPE). The voltammetric identification is built on two oxidation peaks of both heroin and its degradation product 6-monoacetylmorphine (6-MAM), generated in alkaline conditions. Interestingly, an anodic pretreatment of the screen printed electrodes (SPE) shifts the peak potential of paracetamol (the most encountered cutting agent in heroin seizures), allowing the detection of 6-MAM peak, overlapping with the paracetamol signal in the case of untreated SPE. Subsequently, the characterization of the p-SPE with scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, Raman and Fourier transform infrared (FTIR) spectroscopy is provided to demonstrate local changes on the surface of the electrode. From an analytical perspective, p-SPE provide higher sensitivity (0.019 μA μM−1), excellent reproducibility (6-MAM, RSD = 2.85%, and heroin RSD = 0.91%, n = 5) and lower limits of detection (LOD) (5.2 μM) in comparison to untreated SPE. The proposed protocol which integrates a tailor-made script is interrogated against common cutting agents, and finally, validated with the screening of 14 street samples, also analyzed by standard methods. Besides, a comparison with portable spectroscopic techniques on the confiscated samples shows the better performance of the electrochemical strategy. Overall, this sensing approach offers promising results for the rapid on-site profiling of suspicious heroin samples, also in the presence of paracetamol.

The effect of CTAB, a cationic surfactant, on the adsorption ability of the boron-doped diamond electrode: Application for voltammetric sensing of Bisphenol A and Hydroquinone in water samples

The present study introduces for the first time the effect of the cationic surfactant, cetyltrimethylammonium bromide (CTAB) on the adsorption capability of the boron-doped diamond (BDD) electrode for the sensing of environmental pollutants bisphenol A (BPA) and hydroquinone (HQ). Cathodic pretreatment of the electrode surface after an anodic pretreatment exhibited a best electrochemical response for these two phenolic compounds. The electrochemical characteristics of BPA and HQ were first sufficiently documented by cyclic voltammetry in aqueous solutions without the addition of surfactant over a shorter and longer potential range. Square-wave voltammetry was employed for a detailed study depending on the operational conditions (e.g., pH and nature of supporting electrolyte, concentration of CTAB, accumulation variables, instrumental parameters, etc.). The sensitivity of the voltammetric measurements for BPA and HQ was increased when CTAB was present in strong acidic media (more effective for BPA) due to its interaction with the neutral forms of the selected compounds on the hydrophobic surface of BDD electrode. Besides, a significant increase in the detecting sensitivity of BPA in CTAB-containing solutions could be obtained after applying an accumulation process. Using square-wave stripping mode (after 30 s accumulation at open-circuit condition) in 0.1 M H2SO4 containing 1 × 10−4 M CTAB, the limits of detection were found to be 0.05 μg/mL (2.19 × 10-7 M), and 0.23 μg/mL (2.09 × 10-6 M) for the simultaneous determination of BPA and HQ, respectively. In this way, modification-free BDD electrode could introduce an alternative to chemically modified electrodes for the analysis of environmental samples.