Diffusion-controlled Kinetics Research Articles

Selective recovery of noble metals from electronic waste leachates via coral-like adsorbents

Coral-like adsorbents (BCTC@PEI) with polyethyleneimine backbones and a crosslinked network are engineered to selectively recover gold, palladium, and platinum, from synthetic E-waste leachates. These adsorbents exhibit high maximum adsorption capacities (qmax) according to the Langmuir isotherm: 2405, 1084, and 1153 mg/g for Au, Pd, and Pt, respectively (at 25 °C). The adsorption processes fit well with the pseudo-second-order kinetics (R2 > 0.99), with rapid equilibrium (te) achieved within 5 and 10 min for Au and Pd, respectively. The coral-like morphologies and macroporous structure facilitate intraparticle diffusion, resulting in a bulk diffusion-controlled kinetics. By combining experimental design and systematic characterizations, the adsorption mechanism is confirmed to involve synergetic forces, including electrostatic, chelation, and redox interactions (excluding redox interactions for Pd recovery). Furthermore, a significant separation factor (103-106) is realized among noble metals and competing metals, with effective adsorption (>89 % recovery) maintained over eight regeneration/reuse cycles. Over 90 % of Au recovery is also realized with real E-waste leachates. With their high adsorption capacity, rapid kinetics, high selectivity, and robust stability, these coral-like adsorbents hold great potential for selectively recovering noble metals from E-waste leachates.

Silver Nanoparticle-Embedded Hydrogels for Electrochemical Sensing of Sulfamethoxazole Residues in Meat.

A disposable electrochemical sensor based on silver nanoparticle-embedded cellulose hydrogel composites was developed for sensitive detection of sulfamethoxazole residues in meat samples. Scanning electron microscopy confirmed the porous structure of the cellulose matrix anchored with 20-50 nm silver nanoparticles (AgNPs). Fourier transform infrared spectroscopy and X-ray diffraction verified that the metallic AgNPs coordinated with the amorphous cellulose chains. At an optimum 0.5% loading, the nanocomposite sensor showed a peak-to-peak separation of 150 mV, diffusion-controlled charge transfer kinetics, and an electron transfer coefficient of 0.6 using a ferro/ferricyanide redox probe. Square-wave voltammetry was applied for sensing sulfamethoxazole based on its two-electron oxidation peak at 0.72 V vs. Ag/AgCl in Britton-Robinson buffer of pH 7.0. A linear detection range of 0.1-100 μM sulfamethoxazole was obtained with a sensitivity of 0.752 μA/μM and limit of detection of 0.04 μM. Successful recovery between 86 and 92% and less than 6% RSD was achieved from spiked meat samples. The key benefits of the proposed disposable sensor include facile fabrication, an antifouling surface, and a reliable quantification ability, meeting regulatory limits. This research demonstrates the potential of novel cellulose-silver nanocomposite materials towards developing rapid, low-cost electroanalytical devices for decentralized on-site screening of veterinary drug residues to ensure food safety.

Supercritical CO2 mediated construction of aluminium waste recovered γ-Al2O3 impregnated Dracaena trifasciata biomass-derived carbon composite: A robust electrocatalyst for mutagenic pollutant detection

Inspired by the waste-to-wealth concept, we have recovered the gamma phase aluminium oxide nanoparticles (γ-Al2O3 NPs) from waste aluminium (Al) foils and fabricated a composite with Dracaena trifasciata biomass-derived activated carbon matrix (DT-AC) using supercritical carbon-di-oxide (SC-CO2) pathway. The prepared samples are characterized altogether by various micro- and spectroscopic analyses. Based on the results, the recovered γ-Al2O3 NPs are well impregnated in the DT-AC surface by the action of the microbubble effect from the SC-CO2. The higher D-band and ID/IG value of 1.07 in the Al2O3/DT-AC nanocomposite indicate increased defects and the amorphous nature of the carbon materials. The effect of scan rate (ν) demonstrated greater linearity in ν1/2 vs peak current in the electrochemical detection study of the mutagenic pollutant 4-(methylamino) phenol hemi sulfate, showing a quasi-reversible electron transfer process undergoing diffusion-controlled kinetics. Furthermore, the limit of detection is determined to be 3.2 nM L–1 with an extensive linear range, spanning from 0.05 to 618.25 µM/L. The incredible sensitivity of 2.117 μA μM−1 cm−2, along with excellent selectivity, repeatability, and stability, is observed. Further, the respectable recovery percentage of 98.61 % in the environmental water sample is perceived. The observed outcomes suggest that the prepared Al2O3/DT-AC composite performs as an excellent electrocatalyst material, and the processing techniques used are thought to be sustainable in nature.

Diffusion-controlled annealing kinetics of interstitial H in SnO2

SnO2 is a prototypical transparent conducting oxide that finds widespread applications as transparent electrodes, gas sensors, and transparent thin-film devices. Hydrogen impurities in SnO2 give rise to unintentional n-type behavior and unexpected changes to conductivity. Interstitial H (Hi) and H at an oxygen vacancy (HO) are both shallow donors in SnO2. An O–H vibrational line at 3155 cm−1, that can be produced by a thermal anneal at 500 °C followed by a rapid quench, has been assigned to the Hi center and is unstable at room temperature on a timescale of weeks. An IR absorption study of the decay kinetics of the 3155 cm−1 O–H line has been performed. The disappearance of Hi upon annealing has been found to follow second-order kinetics. Measurements of the decay rate for a range of temperatures have determined an activation energy for the diffusion of interstitial H in SnO2. These results provide fundamental information about how unintentional hydrogen impurities and their reactions can change the conductivity of SnO2 device materials in processes as simple as thermal annealing in an inert ambient.

Boosted zn-ion storage in high crystalline VS4 anode by enhanced diffusion-controlled kinetics

Rechargeable aqueous zinc ion energy storage devices based on Zn metal anode are highly promising for grid-scale energy storage due to their abundant reserves, low cost and remarkable safety; however, they also suffer from the uncontrollable Zn dendrites issue, self-corrosion, surface passivation and poor Zn metal utilization (<5%). In this work, a VS4 anode was regulated by graphene oxide (GO) with an increased crystallinity to form a three-dimensional VS4/reduced GO (3D-VG) anode for advanced zinc-ion batteries and zinc-ion hybrid supercapacitors (ZIBs and ZHCs). The optimized VS4 phase in 3D-VG facilitated a rapid diffusion-controlled dominated electrochemical kinetics. Meanwhile, benefiting from a conductive 3D hierarchical graphene framework anchoring well-distributed VS4 nanoflakes, the 3D-VG hybrid delivered a high reversible capacity of 468 mAh/g after 100 cycles at 1 A/g and kept a stable capacity of 177 mAh/g after 2000 cycles at 5A/g based on a synergetic energy storage mechanism with intercalation and conversion. Based on 3D-VG anode, both of the assembled ZIB and ZHC devices exhibited excellent stability and ultralong lifespans which demonstrated that 3D-VG is a promising anode for zinc ion energy storage devices.

Interface Engineering Regulation by Improving Self‐Decomposition of Lithium Salt‐Type Additive using Ultrasound

AbstractLithium salt‐type additives have triggered widespread concern because of their excellent film‐forming properties to construct a solid electrolyte interphase (SEI) with high stability and low impedance. However, little attention has been paid to enhancing the utilization efficiency of the expensive lithium salt‐type additives. Herein, the main factor limiting the decomposition of lithium difluoro bis(oxalate) phosphate (LiDFBOP) during the initial SEI formation is clarified. Combining the electrochemical analysis results and quantum chemistry calculations, it is inferred that LiDFBOP preferentially decomposes and generates soluble products accumulating on the graphite surface due to diffusion control kinetics. The excessive aggregation of these products on the electrode inhibits the subsequent continuous decomposition of LiDFBOP. An ultrasound auxiliary method is developed to accelerate the soluble product diffusion and promote the reduction decomposition of LiDFBOP increasing the inorganics content of Li2C2O4 and LiF in the formed SEI. Accordingly, the cell performance is greatly improved compared with that without ultrasound: Li/graphite cells with ultrasound can retain 60.60% of initial capacity after 500 cycles at 1C. This work not only pioneers the study of improving the utilization efficiency of additives contributing to reducing the electrolytes cost but also has direct guiding significance in the targeted regulation of interface properties.

Simplified kinetics model for hydrogen gas generation from metallic aluminum in municipal solid waste incineration bottom ash

The reaction of metallic aluminum in the incineration bottom ash (IBA) with an alkaline medium generates hydrogen (H2) gas. The generated H2 has caused severe cracking when IBA is used as construction material. Studies have then explored applications of IBA in aerated concretes where H2 from metallic aluminum can be utilized advantageously and found that the kinetics of H2 generation influence the cellular structure and mechanical properties. However, no kinetics model is available to understand the reaction kinetics of H2 gas generation from IBA. This study presents a simplified kinetics model employing the shrinking core model for H2 generation from metallic aluminum in IBA. The uniform distribution of metallic aluminum in IBA particles and average particle size were considered to make the model simplified for practical applications. The model was calibrated by the hydrogen gas generation from IBA and a known alkaline solution (NaOH). The temperature dependency of the reaction rate was implemented using the Arrhenius equation. The study showed that the hydrogen gas generation in IBA demonstrated reaction control kinetics at higher temperatures (≥ 60 °C) and diffusion control kinetics at lower temperatures (≈ 25 °C). The yield of hydrogen gas generation also decreased with the reduction in reaction temperature. The kinetics model was successfully validated against the experimental data for the local IBA. The presented model is expected to improve the understanding of dynamic H2 gas generation from metallic aluminum in IBA and guide the development of aerated composites with target properties where IBA is used as an aerating agent.

A sensitive, selective non-enzymatic electrochemical detection and kinetic study of glucose over Pt nanoparticles/SWCNTs/NiO ternary nanocomposite

BackgroundThe coupling of inorganic metal nanoparticles, semiconductor-based metal oxide nanostructures, and carbon nanomaterials is a promising strategy to fabricate efficient electrochemical sensors. Herein, we successfully designed a sensitive and selective electrochemical glucose sensor using Pt nanoparticles (PtNPs) decorated single-wall carbon nanotubes (SWCNTs) and nickel oxide (NiO) nanostructure-based composite materials. MethodsThe nanocomposite was synthesized without applying any dispersant or stabilizer using simple ultrasonication and photo-reduction techniques. Significant findingsThe morphology of nanocomposite reveals a homogenous dispersion of CNTs and PtNPs over the NiO nanostructure. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that the ternary nanocomposite-modified glassy carbon electrode (Pt@CNTs/NiO/GCE) displayed enhanced catalytic activity compared to CNTs/NiO/GCE, NiO/GCE or bare GGE electrodes. Kinetics studies indicated that the glucose electrooxidation using Pt@CNTs/NiO modified GCE followed irreversible diffusion-controlled kinetics with a transfer co-efficient value (α) ≈ 0.50. Amperometric sensing investigation revealed excellent sensitivity (149.36 µA mM−1 cm−2) and a lower limit of detection value (2.16 µM). The currently fabricated sensor electrode showed appropriate selectivity in the presence of various organic and inorganic species with outstanding repeatability, reproducibility, and sensor stability. The newly fabricated nanocomposite can represent a promising electro-catalyst for the efficient sensing of glucose and other biomolecules by the electrochemical approach.

Analysis of catechol as an environmental pollutant based on electropolymerised methyl orange modified carbon paste sensor

ABSTRACT The present research work outlines a low-cost and green electrochemical approach for the assay of ecological toxin catechol (CT) based on electro-polymerised methyl orange (MO)-activated carbon paste electrode (CPE) as a responsive, simple and low-priced electrocatalyst. The CT electrochemical response was premeditated on the surface of poly methyl orange-activated carbon paste electrode (Poly(MO)ACPE) using different voltammetric methods such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) which recommends that the Poly(MO)ACPE shows good electrocatalytic nature for the electrochemical redox reaction of CT with high peak current response as associated to the bare carbon paste electrode (BCPE). The CT molecules expose electrochemical quasi-reversible reactions (oxidation and reduction nature) at Poly(MO)ACPE, which was done by a diffusion-controlled reaction kinetics. The practicability of this sensor was verified using the DPV method; here the CT peak current was improved with the varied concentration of CT in the range from 1.0 µM to 36.0 µM, and the corresponding limit of detection (LOD) and limit of quantification (LOQ) were 0.880 × 10−8 M and 2.935 × 10−8 M, respectively. The prepared sensor was efficiently tested with different interferents using the DPV method. Here, the sensor shows a lesser interference effect for the CT redox reaction nature. Finally, this sensor was applied for the analysis of CT in water and green tea samples, and the outcomes noticed a good CT recoveries.

Critical Review of Transport Properties of HCl, KOH, and NaOH in High Temperature Water and Correlations for Transport Properties of H3O+ and OH−

High-temperature tracer diffusion coefficients for H3O+ and OH− are important parameters in the modeling of diffusion-controlled reaction kinetics and mass transport processes under hydrothermal conditions, and these tracer diffusion coefficients are directly related to the ionic electrical conductivities in the limit of infinite dilution through the Nernst–Einstein relationship. The limiting conductivity of H3O+ and OH− in water is controlled by two separate mechanisms of ionic movement: (i) the bulk ionic diffusion and (ii) proton hopping, also known as “Grotthuss” mechanism and/or “prototropic transfer.” This work reports a critical assessment of the limiting electrical conductivity data (Λ°) for aqueous HCl, KOH, and NaOH measured above room temperature. The initial assessed dataset included temperatures from 273.15 K up to 873.15 K and water densities from 1000 kg m−3 down to 270 kg m−3 and was reduced down to a final critically evaluated dataset spanning temperatures between 273.15 and 678.15 K and densities between 346 and 1006 kg m−3. The results were used to derive values for the excess conductivity due to prototropic transfer, λE°, of H3O+ and OH− using correlations previously reported for aqueous KCl. Simple empirical correlations of water viscosity and density were derived for Λ°(HCl), Λ°(KOH), Λ°(NaOH), λE°(H3O+), and λE°(OH−). Tests using the λE°(OH−) correlation and a previously reported function for Λ°(NaCl) show that the NaOH data can be accurately reproduced to within the estimated uncertainties. The reported correlations provide a means to model more accurately the tracer diffusion coefficients for H3O+ and OH− to supercritical conditions.

Solid state synthesis of barium zirconate and its kinetic analysis

In this study, barium zirconate was synthesized by solid-state reaction using barium carbonate and zirconium dioxide. The reaction process and optimum heat treatment condition were determined by the techniques of X-ray diffraction, scanning electron microscopy & energy dispersive spectroscopy, and thermogravimetric & differential scanning calorimetry, etc. The results showed that the solid-state reaction starts at 1000 °C, and the optimum synthesis temperature was determined as 1200 °C. The reaction kinetic parameters were calculated using the Kissinger method, Ozawa's method, and Coats-Redfern method, the reaction activation energies of the first two were 251.42 kJ·mol−1 and 261.35 kJ·mol−1, respectively. The reaction mechanism was determined by the Coats-Redfern method based on different kinetic models, it follows the diffusion-controlled kinetics, and belongs to 1-D diffusion reaction. The reaction activation energy decreased from 342.56 kJ·mol−1 to 272.32 kJ·mol−1 as the heating rate increased from 5 K·min−1 to 20 K·min−1.

Resolving the kinetics of transcription factor recognition of the target DNA site via advanced single-molecule FRET spectroscopy.

Transcription factors function by specifically binding to target DNA sites to initiate gene expression. Such DNA recognition process usually involves an interplay between high-affinity binding to the cognate sequence and low-affinity binding to any other DNA. The latter enables scanning of the DNA via a 1D diffusive process, which combined with 3D diffusion-collision kinetics, facilitates target location. 1D diffusion has been observed using single-molecule fluorescence tracking on many DNA binding proteins (DPBs). Powerful experimental methods are also available to determine the sequence logo recognized by any given DBP. However, there are no approaches available that resolve the kinetics of locking into the target site, which is essential to elucidate the mechanisms of cognate DNA recognition. Here we introduce such an approach, by using single-molecule FRET spectroscopy and maximum likelihood analysis of photon arrival times. We apply it to determine the rates of lock-into and release-from the target site of the Engrailed homeodomain (EnHD). To resolve between non-specific and cognate DNA binding we exploit the recent discovery that EnHD changes conformation upon cognate binding, resulting in a large shift in transfer efficiency between a donor-acceptor pair placed at the protein ends. Our experiments on a 21-bp dsDNA containing the EnHD cognate sequence reveal that EnHD finds its target in few milliseconds. Remarkably, the on-rate at the C50 is mostly invariant over orders of magnitude differences in ionic strength and DNA concentration. This is because the changes in affinity caused by ionic strength are mostly recapitulated on the off-rate, which is the exact opposite to diffusion-control kinetics. We hence conclude that EnHD's lock-into target kinetics are controlled by its conformational dynamics, which makes the response time for controlling transcription only dependent on site occupancy levels.

High temperature corrosion resistance of FeCr(Ni, Al) alloys as bulk/overlay weld coatings in the presence of KCl at 600 °C

The long-term high temperature corrosion behavior of FeCr(Ni, Al) alloys, both in bulk form and as overlay welds, was investigated in a new experimental setup, in the presence of KCl at 600 °C. All the alloys experienced breakaway oxidation, with the bulk materials exhibiting better corrosion resistance than the overlay weld coatings with similar compositions. All results indicate diffusion-controlled kinetics, and the analysis revealed an improved corrosion behavior connected to an increased Cr content in the inward-growing scale.

Facile Synthesis of Triazoles using Electrospray-Deposited Copper Nanomaterials to Catalyze Azide-Alkyne Cycloaddition (AAC) Click Reactions.

Electrospray deposition of copper salt-containing microdroplets onto the liquid surface of an electrically grounded reaction mixture leads to the formation of Cu nanoclusters, which then catalyze the azide-alkyne cycloaddition (AAC) reaction to form triazoles. This method of in situ nanocatalyst preparation provided 17 times higher catalytic activity compared to that in the conventional catalytic reaction. The gentle landing of the Cu-containing droplets onto the liquid surface forms a thin film of catalyst which promotes the heterogeneous AAC reaction while showing diffusion-controlled kinetics. UV-vis spectral characterization confirms that the catalyst is comprised of Cu nanoclusters. This unique catalytic strategy was validated using several substrates and the corresponding products were confirmed by tandem mass spectrometry (MS/MS) analysis.

Creation of an extrinsic pseudocapacitive material presenting extraordinary cycling-life with the battery-type material Co(OH)2 by S2− doping for application in supercapacitors

Some battery-type materials show the potential for storing high density energy in supercapacitors because of their high theoretical capacity. So far, the very unsatisfied electrochemical performance is still the label of these battery-type materials, which is attributed to their diffusion-controlled kinetics of energy storage. Some efforts try to transform their electrochemical behavior to extrinsic pseudocapacitive behavior through nanostructuring. However, the extrinsic pseudocapacitive materials are rare due to the restriction of no phase transformation. In this work, we propose an alternative strategy to create an extrinsic pseudocapacitive material from the typical battery-type material Co(OH)2 by S2− doping. The doped S2− ions further increase energybarrierfor the intercalation of OH− ions into the interlayer space of Co(OH)2, thus suppressing its bulk phase transformation. Also, the decreased OH− ions-Co(OH)2 interaction plus the surface reaction feature induced by S2− doping results in the pseudocapacitive behavior. Thus, the S2− doped Co(OH)2 presents the comprehensive electrochemical signatures of pseudocapacitive materials and an extraordinary cycling life of 200,000 charge-discharge cycles. This work initiates a new way for acquiring electrode materials with high electrochemical performance for application in supercapacitors.

Mechanistic Insight into Ultrafast Kinetics of Sodium Cointercalation in Few-Layer Graphitic Carbon.

Fast-charging sodium ion batteries remain deeply challenged by the lack of suitable carbonaceous anodes that exhibit intercalation plateau with fast kinetics. Here we develop a few-layer graphitic carbon with nanoscale architecture, which enables shortened Na+ ion diffusion path and fast formation of fully intercalated phase at the same time. Combined in situ Raman and electrochemical test reveal that this graphitic carbon with highly crystalline few layers follows surface-controlled intercalation rather than typical diffusion-controlled kinetics observed in natural graphite. As a result, a few-layer graphitic carbon anode maintains the reversible capacity of 106 mAh g-1 at 10 A g-1 and achieves 87% capacity retention even after 10 000 cycles at 1 A g-1. This work provides new insight on the Na storage mechanism in fast-charging graphitic carbon as well as the design of carbon anodes for high-rate sodium ion batteries.

Highly sensitive and selective electrochemical sensor for detecting imidacloprid pesticide using novel silver nanoparticles/mesoporous carbon/hematite ore ternary nanocomposite

The increasing use of neonicotinoid class of pesticides in agriculture is a major concern for environmental pollution and water resource and can cause adverse health effects. Herein, we report a novel electrochemical sensor for sensitive and selective determination of Imidacloprid (IMC) pesticide using Ag nanoparticles deposited on mesoporous carbon and naturally extracted hematite ore (Ag@Meso-C/Hematite Ore) nanocomposite. The morphology and surface structure of undoped hematite ore disclosed the combination of Fe2O3 and Fe3O4 phases with a nanorod shape, whereas the ternary nanocomposite showed homogenously dispersed carbon nanomaterials and AgNPs with an average diameter 6.65 nm over the naturally extracted ore. The electrocatalytic investigation demonstrated irreversible diffusion-controlled kinetics with four-electron and four-proton exchanged electro-reduction. Detection of IMC by linear sweep voltammetry (LSV) depicts a wide linear detection range (63 – 870 μM) with a sensitivity 0.1955 μAμM-1cm-2 and a detection limit 1.06 μM. Additionally, excellent sensitivity (0.8113 μAμM-1cm-2) and a detection limit (0.257 μM) was ensured within a wide range of 10.80–195.50 µM using the amperometic technique. The excellent sensing performance is likely related to the combination of merits of the three different components of the ternary nanocomposite. Moreover, during the IMC detection, the Ag@Meso-C/Hematite Ore based sensor electrode exhibited a unique selectivity behavior and excellent reproducibility, repeatability, and storage stability. Finally, the current developed sensory system based on naturally occurring hematite ore can provide a good alternative as a sensitive approach for the detection of various target analytes in chemical sensing studies.

Expeditious Electrochemical Synthesis of Mesoporous Chalcogenide Flakes: Mesoporous Cu2Se as a Potential High‐Rate Anode for Sodium‐Ion Battery

Nanostructured copper selenide (Cu2 Se) attracts much interest as it shows outstanding performance as thermoelectric, photo-thermal, and optical material. The mesoporous structure is also a promising morphology to obtain better performance for electrochemical and catalytic applications, thanks to its high surface area. A simple one-step electrochemical method is proposed for mesoporous chalcogenides synthesis. The synthesized Cu2 Se material has two types of mesopores (9 and 18 nm in diameter), which are uniformly distributed inside the flakes. These materials are also implemented for sodium (Na) ion battery (NIB) anode as a proof of concept. The electrode employing the mesoporous Cu2 Se exhibits superior and more stable specific capacity as a NIB anode compared to the non-porous samples. The electrode also exhibits excellent rate tolerance at each current density, from 100 to 1000mA g-1 . It is suggested that the mesoporous structure is advantageous for the insertion of Na ions inside the flakes. Electrochemical analysis indicates that the mesoporous electrode possesses more prominent diffusion-controlled kinetics during the sodiation-desodiation process, which contributes to the improvement of Na-ion storage performance.

Pseudo-capacitive and kinetic enhancement of metal oxides and pillared graphite composite for stabilizing battery anodes

Nanostructured TiO2 and SnO2 possess reciprocal energy storage properties, but challenges remain in fully exploiting their complementary merits. Here, this study reports a strategy of chemically suturing metal oxides in a cushioning graphite network (SnO2[O]rTiO2-PGN) in order to construct an advanced and reliable energy storage material with a unique configuration for energy storage processes. The suggested SnO2[O]rTiO2-PGN configuration provides sturdy interconnections between phases and chemically wraps the SnO2 nanoparticles around disordered TiO2 (SnO2[O]rTiO2) into a cushioning plier-linked graphite network (PGN) system with nanometer interlayer distance (~ 1.2 nm). Subsequently, the SnO2[O]rTiO2-PGN reveals superior lithium-ion storage performance compared to all 16 of the control group samples and commercial graphite anode (keeps around 600 mAh g−1 at 100 mA g−1 after 250 cycles). This work clarifies the enhanced pseudo-capacitive contribution and the major diffusion-controlled energy storage kinetics. The validity of preventing volume expansion is demonstrated through the visualized image evidence of electrode integrity.

Electrocatalytic oxidation of ascorbic acid in the basic medium over electrochemically functionalized glassy carbon surface

In a mild acidic medium (0.10 M H2SO4), a pristine glassy carbon electrode (GCE) has been electrochemically activated via electrochemical oxidation which has been used for efficient ascorbic acid (AA) direct oxidation. An oxidized GCE exhibits a well-defined redox pair in 0.10 M H2SO4 due to development of functional groups (C=O) on the surface of the GCE during the electrochemical oxidation process. Electrochemical and X-ray photoelectron spectroscopy (XPS) have been employed to characterize the GCE surface before and after functionalization. The resultant electrode surface was employed to execute electrochemical oxidation of ascorbic acid molecules in an alkaline medium. The voltametric measurements of AA oxidation at the oxidized GCE showed that the oxidized GCE exhibited better electrochemical performance in 0.10 M NaOH compared to the pristine GCE. It was observed that oxidation of AA followed 1st order and diffusion-controlled kinetics on the oxidized GCE surface. The hydrodynamic voltammogram analysis confirmed that oxidation of AA proceeds via a 2e− transfer pathway and followed a stepwise mechanism. It was found that, for the oxidation of AA, the standard rate constant (ko) has a value 4.47 × 10−3 cm s−1 with a Eo value of −0.29 V vs Ag/AgCl (sat. KCl). The proposed oxidized GCE successfully decreases AA oxidation overpotentials, which enhances the possibility of using it as an anode in ascorbic acid (AA) fuel cells.