H2O2 In Alkaline Medium Research Articles

RGO-Modified paper supported Globe Thistles-Like NiCo2S4 flexible electrodes enhancing H2O2 sensing

The Globe Thistles-Like (GTL) NiCo2S4 nanostructures were supported on reduced graphene oxide modified filter paper (FP). The prepared GTL NiCo2S4/rGO/FP is investigated as a disposable and flexible electrode for the electrochemical detection of H2O2 in alkaline media. Owing to the rich redox active sites, the synergistic effect between Co3+ and Ni2+, and the rapid electron transportation of substituting sulfur (S) for oxygen (O) in NiCo2O4, the GTL NiCo2S4/rGO/FP exhibits considerable enzyme-free H2O2 sensing performance with wide linear H2O2 ranging from 38.8 to 37306.8 μM, high sensitivity of 2.4326 mA mM−1 cm−2, and low detection limit of 0.08 μM. The GTL NiCo2S4/rGO/FP electrode has stable sensing performance and is highly selective toward analyte for physiological interfering species. The excellent electrochemical performance of GTL NiCo2S4/rGO/FP composite is attributed to the GTL structure of NiCo2S4. By studying the hydrothermal reaction time, electrochemical active surface area, and hydrophilic-hydrophobic surfaces of GTL NiCo2S4/rGO/FP composite, the relationship between the microstructure and sensing performance of the composite was elucidated. Surely this study opens up new possibilities for the application of low-cost, biodegradable flexible electrode materials in wearable sensors in the near future.

In-situ monitoring of hydrogen peroxide production at nickel single-atom electrocatalyst

Electrochemical oxygen reduction reaction (ORR) to hydrogen peroxide (H2O2) is a common method to address the growing demands of H2O2. To map a clear understanding of structure–activity relationship of electrocatalyst for H2O2 production, it is necessary to real-time quantitative monitor of H2O2 in the initial production process. However, we found that the common off-line methods such as spectrophotometry, titration, etc., are not reliably during in-situ ORR process. Here, a simple and real-time simultaneous electrochemical production and determination of H2O2 system is constructed by using a dual-functional nickel (Ni) single-atom electrocatalyst. The electro-production part is conducted with a DC power supply, air pump, and dual-electrode system, while the electro-detection part consists of a three-electrode system. Compared with traditional off-line H2O2 measure methods, the present on-line determination of H2O2 protocol provides more reliable results in the quantitative monitoring of H2O2, and with a wide detection concentration range from 20 pM to 22.2 mM and a low detection limit of 6.87 pM. NiOOH on single Ni site is an important intermediate for efficient detection of H2O2 in alkaline medium. The Ni-SAC sensor also shows well anti-interferential and selective ability, high reproducibility and stability of H2O2 sensing up to 12 days. This simple-to-operate method offers a new window to record a reliable structure–activity relationship on electrocatalyst engineering in electrochemistry.

Charge-Polarized Selenium Vacancy in Nickel Diselenide Enabling Efficient and Stable Electrocatalytic Conversion of Oxygen to Hydrogen Peroxide.

Vacancy engineering is deemed as one of the powerful protocols to tune the catalytic activity of electrocatalysts. Herein, Se-vacancy with charge polarization is created in the NiSe2 structure (NiSe2 -VSe ) via a sequential phase conversion strategy. By a combined analysis of the Rietveld method, transient photovoltage spectra (TPV), in situ Raman and density functional theory (DFT) calculation, it is unequivocally discovered that the presence of charge-polarized Se-vacancy is beneficial for stabilizing the structure, decreasing the electron transfer kinetics, as well as optimizing the free adsorption energy of reaction intermediate during two-electron oxygen reduction reaction (2e- ORR). Benefiting from these merits, the as-prepared NiSe2 -VSe delivered the highest selectivity of 96% toward H2 O2 in alkaline media, together with a selectivity higher than 90% over the wide potential range from 0.25 to 0.55V, ranking it in the top level among the previously reported transition metal-based electrocatalysts. Most notably, it also displayed admirable stability with only a slight selectivity decay after 5000 cycles of accelerated degradation test (ADT).

One-Step Synthesis of Aminobenzoic Acid Functionalized Graphene Oxide by Electrochemical Exfoliation of Graphite for Oxygen Reduction to Hydrogen Peroxide and Supercapacitors.

Graphene-based materials have attracted considerable attention as promising electrocatalysts for the oxygen reduction reaction (ORR) and as electrode materials for supercapacitors. In this work, electrochemical exfoliation of graphite in the presence of 4-aminebenzoic acid (4-ABA) is used as a one-step method to prepare graphene oxide materials (EGO) functionalized with aminobenzoic acid (EGO-ABA). The EGO and EGO-ABAs materials were characterized by FT-IR spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and scanning electron microscopy. It was found that the EGO-ABA materials have smaller flake size and higher density of oxygenated functional groups compared to bare EGO. The electrochemical studies showed that the EGO-ABA catalysts have higher activity for the ORR to H2O2 in alkaline medium compared to EGO due to their higher density of oxygenated functional groups. However, bare EGO has a higher selectivity for the 2-electron process (81%) compared to the EGO-ABA (between 64 and 72%) which was related to a lower content of carbonyl groups. The specific capacitance of the EGO-ABA materials was higher than that of EGO, with an increase by a factor of 3 for the materials prepared from exfoliation in 5 mM 4-ABA/0.1 M H2SO4. This electrode material also showed a remarkable cycling capability with a loss of only 19.4% after 5000 cycles at 50 mVs-1.

High-performance H2O2 paper fuel cell boosted via electrolyte toning and radical generation

Cellulose paper has been employed to develop pumpless microfluidic fuel cells. Meanwhile, hydrogen peroxide as both the fuel and oxidant has attracted attention since it is eco-friendly for producing only water. However, low open-circuit voltage (OCV) and power density of reported H2O2 fuel cells due to the mixed potentials (simultaneous oxidation and reduction at the same electrode) preclude its applications. In this study, a H2O2 paper fuel cell with a gel-aided dual-electrolyte configuration has been proposed for the first time to solve this problem. An ion-conductive hydrogel has been sandwiched between the independent catholyte and anolyte flows to serve as part of the electrolyte. Its OCV has been elevated to 1 V and a high peak power density of 10.2 mW cm−2 has been achieved by toning the electrolytes, which exceeds most reported H2O2 fuel cells. The results demonstrate that alkaline anolyte benefits the cell performance more significantly than acidic catholyte does. The reaction mechanism at each electrode was further studied to provide insights for future development of H2O2 fuel cells: the reduction at the cathode follows the Fenton reaction; as for the oxidation at the anode, it was first revealed that H2O2 oxidation was facilitated by free radicals generated from H2O2 in alkaline media. Besides, the radicals also help to maintain a large voltage difference between the electrodes. Furthermore, this fuel cell shows great durability and can be instantly re-activated upon refueling. This gel-aided dual-electrolyte fuel cell design can pave a way for practical applications of direct H2O2 fuel cells.

Vertical graphene array for efficient electrocatalytic reduction of oxygen to hydrogen peroxide

Hydrogen peroxide (H2O2) is a green chemical oxidant that finds widespread use in the chemical industry. The electrocatalytic oxygen reduction reaction (ORR) is presently attracting a lot of attention as an environmentally friendly synthetic route towards H2O2. However, the efficient reduction of O2 to produce H2O2 at high current densities (> 100 mA cm−2), thereby achieving viable H2O2 yields, remains a challenge. Herein, we demonstrate that vertical graphene arrays grown on carbon paper (denoted herein as VG array) via plasma-enhanced chemical vapor deposition show outstanding activity for ORR to H2O2 in alkaline media at high current densities. The VG array electrode delivered a Faradaic efficiency of 94% and a H2O2 production rate of 61.3 mg h−1 cm−2 at 100 mA cm−2, and similarly impressive performance at 200 mA cm−2 (81% and 102.8 mg cm−2 h−1, respectively), outperforming most catalysts reported to date for electrochemical H2O2 synthesis. The remarkable performance of the VG array electrode is ascribed to the interconnected network of graphene nanosheets which ensures a high availability of graphene edge active sites (thus a high H2O2 selectivity) and fast electron transfer during ORR. Further, gas-liquid-solid three-phase interfaces formed between the graphene nanosheets facilitate a steady supply of O2 from the gas phase when the electrode was applied in a flow cell. Results encourage the application array electrodes in electrochemical H2O2 synthesis, whilst also offering a roadmap to future industrial H2O2 production.

Synthesis of coordination polymers of cobalt meso-pyridylporphyrins and its oxygen reduction properties

The present work sheds light on the role of coordinating side groups on the porphine ring in deciding the extent of the metalation reaction as well as the formation of coordination polymers of porphyrin. Electrocatalytic activity of coordination polymers of isomers of pyridylporphyrins has been investigated after pyrolysing them at different temperatures. The pyrolysed materials were characterized by XRD, XPS, SEM, TEM and BET techniques. The electrocatalytic behaviour of the sample were investigated by modifying the glassy carbon electrode with the sample (in both normal and pyrolysed form). The electrode modified using the pyrolysed sample of polymerized pyridylporphyrin at 800 °C acted as a good electrocatalyst for the reduction of dioxygen. The studies on kinetics of oxygen reduction using rotating disk electrode shows the reduction through 2-electron pathway forming H2O2 in alkaline medium.

A digital capture movie-based robotized Flow-batch luminometer for in-line magnetic nanoparticle solid phase extraction and chemiluminescent measurement

The advantages of chemiluminescence, digitally captured movies, magnetic solid-phase extraction (MSPE) and a robotized Flow-batch system were united to develop a new automated luminometer. This digital movie-based robotized Flow-batch luminometer was successfully applied for in-line MSPE, and sensitive, selective determination of Cu2+ in Cachaça (a distilled spirit made from fermented sugarcane juice). Magnetic Fe3O4@Al2O3 nanoparticles immobilized with 1-(2-pyridylazo)-2-naphthol and sodium dodecyl sulfate were employed as magnetic adsorbents. The catalytic effect of Cu2+ on luminol oxidation using H2O2 in alkaline medium was employed to generate the chemiluminescent signals, which were measured via digital movies. The method presented satisfactory analytical features when compared with previous studies, yielding: LOD = 7 μg L−1, recovery rates = 94.8–106.5%, RSD < 1.7% (n = 3) and sample throughput = 11 h − 1. The proposed luminometer provides a synergistic union of MSPE, chemiluminescence, digital movies, and robotized Flow-batch system, and envisions further applications in determining various analytes in diverse complex samples.

Removal of chromium from wastewater by swine hair residues applied as a putative biofilter.

Swine production chain generates residues with potential application in environmental processes. This study aimed at the use of swine hair as a potential biofilter for hexavalent chromium (Cr(VI)) removal from wastewater of tannery industry. The hair was pretreated using H2O2 in alkaline medium, and statistical analysis was carried out to evaluate the hair degradation, as well the Cr(VI) removal by the potential pretreated biofilter. The results showed 99% of Cr(VI) removal in 105 min of treatment in large pH range (1-10). Treated and untreated effluents were submitted to cytotoxicity study using vegetable and animal cells, demonstrating a significant reduction on toxicity to both cells. Therefore, swine hair demonstrated to be a promising residue for heavy metal removal on the perspective of an environmentally friendly technique.

Copper(II) complexes with spherical morphology generated in one step by amphiphilic ligands: in situ view of the self-assembling, characterization, catalytic activity

Cyclotri- and tetrasiloxanes having a methyl group and a carboxylic acid coupled through thioether bridge at each silicon atom were used to coordinate copper(II). The amphiphilic character conferred by the co-existence of the two moieties with opposite behaviour on the silicon atom gives the molecule the ability to form aggregates in solution. When copper salt is added, the metal is quickly coordinated by carboxyl groups within these aggregates, as in situ taken microscopy images and video reveal, forming blue spheres. This morphology was confirmed by scanning and transmission electron microscopy, while the coordinating structures and their compositions were estimated by IR spectroscopy and UV–Vis diffuse reflectance spectroscopy, wide angle X-ray diffraction and energy-dispersive X-ray analysis. The wetting tests and moisture sorption analysis indicate hydrophobic materials, while thermal analysis shows a thermal stability of at least up to 180 °C. The compounds catalyze the decomposition of H2O2 in alkaline medium, the values found for the rate constant being between 0.8 and 3.8 × 10−3s-1.

Dextran modified magnetic nanoparticles based solid phase extraction coupled with linear sweep voltammetry for the speciation of Cr(VI) and Cr(III) in tea, coffee, and mineral water samples

A simple and fast solid phase microextraction method using magnetic dextran (Sephadex G-150) as a sorbent was developed for the extraction, separation and speciation analysis of chromium ions. The retained Cr(VI) ions on the magnetic dextran sorbents were eluted and detected by linear sweep voltammetry at the gold nanoparticles modified screen- printed carbon electrode. The linear range, detection limit, quantification limit, and preconcentration factor of the established method for Cr(VI) and Cr(III) were calculated to be 0.5–10 μM, 0.01 μM, 0.1 μM, and 40, respectively. Chromium(III) concentration was determined after conversion of Cr(III) to Cr(VI) by H2O2 in alkaline media (NH4OH). The method was successfully applied to the speciation and determination of Cr(VI) and Cr(III) in artificial water and food samples using the standard addition method. The applicability of the method was confirmed by analysis of real food samples yielding good recovery values (92% and 102%).

Hierarchical oxygen-implanted MoS2 nanoparticle decorated graphene for the non-enzymatic electrochemical sensing of hydrogen peroxide in alkaline media

Owing to the extensive applications of hydrogen peroxide (H2O2) in biological, environmental and chemical engineering, it is of great importance to investigate sensitive and selective sensing platform towards the detection of H2O2. Herein, oxygen-implanted MoS2 nanoparticles decorated graphene nanocomposite is synthesized via a facile one-pot solvothermal method for the sensitive detection of H2O2 in alkaline media. The structure and morphology of the MoS2/graphene nanocomposites were systematically characterized, showing that Mo-O bonds are formed and oxygen is implanted into the crystal structure in the nanocomposite. As a result, the MoS2/graphene composite exhibited enhanced electron transfer kinetics and excellent electro-reduction performance towards H2O2 in alkaline media. Under optimum conditions, the fabricated sensor demonstrated a wide linear response towards H2O2 in the range of 0.25–16mM with a low detection limit of 0.12μM and high sensitivity of 269.7μAmM−1cm−2. Besides, the constructed sensor presented a good selectivity to H2O2 with the presence of other interfering species. Therefore, the proposed sensor was successfully applied for the detection and determination of H2O2 in real sample, indicating great potential for the practical applications.

Non-enzymatic hydrogen peroxide detection at NiO nanoporous thin film- electrodes prepared by physical vapor deposition at oblique angles

In this work we report a non-enzymatic sensor for hydrogen peroxide (H2O2) detection based on nanostructured nickel thin films prepared by physical vapor deposition at oblique angles. Porous thin films deposited on ITO substrates were characterized by X-ray diffraction analysis, scanning electron microcopy (SEMs), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques such as Cyclic Voltammetry (CV) and Constant Potential Amperometry (CPA). The microstructure of the thin films consisted of inclined and separated Ni nanocolumns forming a porous thin layer of about 500nm thickness. Prior to their use, the films surface was electrochemically modified and the chemical state studied by CV and XPS analysis. These techniques also showed that Ni2+/Ni3+ species were involved in the electrochemical oxidation and detection of H2O2 in alkaline medium. Main analytical parameters such as sensitivity (807mAM−1cm−2), limit of detection (3.22μM) and linear range (0.011–2.4mM) were obtained under optimal operation conditions. Sensors depicted an outstanding selectivity and a high stability and they were successfully used to determine H2O2 concentration in commercial antiseptic solutions.

Determination of catechol in water based on gold nanoclusters-catalyzed chemiluminescence

In this paper, a novel chemiluminescence (CL) system is introduced based on the reaction of fluorescein and H2O2 in alkaline medium. Gold nanoclusters (Au NCs) were synthesized using a facile BSA-stabilized method and were then applied to the fluorescein-H2O2 system for the first time, which effectively enhanced the intensity of the CL system. The addition of trace level of catechol into the CL system caused significant quenching of luminescence intensity. At optimal experimental conditions, the decreased CL intensity exhibited a favorable linear relation with catechol concentration. Based on this inhibitory phenomenon, a flow injection CL method with good selectivity was developed for determining catechol. A possible reaction mechanism was also proposed according to results of the kinetic curves of Au NCs in fluorescein-H2O2 CL system, radical scavengers and the spectra of CL, fluorescent and UV-visible. Finally, this method has been successfully used for the analysis of catechol in environmental water samples.

Hydrothermal synthesis of cobalt oxide porous nanoribbons anchored with reduced graphene oxide for hydrogen peroxide detection

A new Co3O4-reduced graphene oxide (Co3O4–rGO) nanostructure was successfully prepared by hydrothermal-synthesized Co3O4 porous nanoribbons with an approximate length of 6–17 μm, a width of 21–737 nm, and a thickness of 33–80 nm hybridizing with reduced graphene oxide. The electrochemical properties of the Co3O4–rGO-modified electrode were investigated by the cyclic voltammograms and amperometric current–time method. The modified electrode shows high electrochemical activity for the catalytic reduction and detection of H2O2 in alkaline medium. The nonenzymatic hydrogen peroxide sensor exhibits wide linear range of 1–18.5 mM (R = 0.99439), high adsorption amount about 3.24 × 10−6 mol/cm2, and a low detection limit of 5.35 × 10−7 M (S/N = 3). In addition, the sensor has a fast response (<5 s), good long-term stability, excellent repeatability (3.22 % relative standard deviation), and high selectivity. These outstanding properties of the sensor derive from their particular hybrid structure and synergistic effects between rGO and Co3O4.

Oxygen reduction to hydrogen peroxide on Fe3O4 nanoparticles supported on Printex carbon and Graphene

Fe3O4 nanoparticles supported on graphene (Fe3O4/graphene) and Printex carbon (Fe3O4/Printex) are reported as promising catalysts for oxygen reduction reaction (ORR) to H2O2 in alkaline medium. The catalysts were synthesized by a simple precipitation method using NaBH4 as reducing agent to favor the formation of the magnetite phase. The structure and morphology of the catalysts was evaluated by x-ray diffraction, transmission electron microscopy and small angle electron diffraction. The electrocatalytic activity towards ORR was investigated by means of cyclic and linear voltammetries in 1molL−1 KOH. The linear polarization curves highlighted the synergetic effect between the oxide and the carbon supports. Analysis of the polarization curves showed that electro-catalytic activity of the materials towards oxygen reduction expressed by the current density at −0.3V vs SCE increases from Printex (0.29mAcm−2)<Fe3O4/Printex (0.38mAcm−2)<graphene (0.85mAcm−2)<Fe3O4/graphene (1.12mAcm−2). The number of exchanged electrons was close to 2.7 for both catalysts, and the % H2O2 electro-generated above 60% in the −0.2 to −0.7V (vs SCE) potential range. Furthermore, both Fe3O4/graphene and Fe3O4/Printex catalysts show excellent durability.

Use of a vanadium nanostructured material for hydrogen peroxide electrogeneration

This paper reports the use of different proportions of vanadium nanostructured electrocatalysts for H2O2 electrogeneration. A comparative study using different mass proportions of vanadium (1%, 6%, 12%, 15% and 20%) was performed to produce H2O2. The V/C materials were prepared by a modified polymeric precursor method (PPM) and characterized by X-ray diffraction and transmission electron microscopy (TEM) analysis. XRD results identified different phases comprising V2O5 and VO2 while TEM micrographs show the vanadium nanoparticles in the range of 1–3nm. The rotating ring–disk electrode (RRDE) technique was used to evaluate the kinetics of the oxygen reduction reaction (ORR). The results showed that the 12% V/C prepared by the PPM was the best composite among those investigated for the production of H2O2 in a 1molL−1 NaOH electrolyte solution because this electrocatalyst exhibited a H2O2 conversion efficiency of 68%. The ring current obtained with 12% V/C was greater than the obtained with Vulcan carbon, which was used as a reference material for H2O2 production and exhibited an efficiency of 31%. After the study with the RRDE, gas-diffusion electrodes (GDEs) containing the catalyst were used to evaluate the amount of H2O2 produced during exhaustive electrolysis. On the basis of these results, the 12% V/C GDE produced 620mgL−1 of H2O2 in alkaline media, whereas the Vulcan carbon GDE produced only 369mgL−1 at the same potential. In acidic media, the 12% V/C GDE produced 107mgL−1 of H2O2, whereas Vulcan carbon produced only 72mgL−1 at the same potential, indicating the better activity of V/C for H2O2 electrogeneration. The 12% V/C is composed primarily of the V2O5 phase, which shows acidic character that can increase the acidity of the surface, providing greater hydrophilicity and, consequently, greater activity toward the ORR via two-electron transference.

A quantitative colorimetric assay of H2O2 and glucose using silver nanoparticles induced by H2O2 and UV

Abstract A simple spectrophotometric assay of H2O2 and glucose using Ag nanoparticles has been carried out. Relying on the synergistic effect of H2O2 reduction and ultraviolet (UV) irradiation, Ag nanoparticles with enhanced absorption signals were synthesized. H2O2 served as a reducing agent in the Ag nanoparticles formation in which Ag+ was reduced to Ag0 by O2− generated via the decomposition of H2O2 in alkaline media. On the other hand, photoreduction of Ag+ to Ag0 under UV irradiations also contributed to the nanoparticles formation. The synthesized nanoparticles were characterized by TEM, XPS, and XRD. The proposed method could determine H2O2 with concentrations ranging from 5.0 × 10−7 to 6.0 × 10−5 mol/L. The detection limit was estimated to be 2.0 × 10−7 mol/L. Since the conversion of glucose to gluconic acid catalyzed by glucose oxidase was companied with the formation of H2O2, the sensing protocol has been successfully utilized for the determination of glucose in human blood samples. The results were in good agreement with those determined by a local hospital. This colorimetric sensor thus holds great promises in clinical applications.

Automated Sequential‐injection Chemiluminescence Determination of Glucosamine Sulphate via Luminol‐Hydrogen Peroxide System

AbstractA highly sensitive automated sequential‐injection chemiluminescence (SIA‐CL) method for determination of glucosamine sulphate (GLS) was developed. The goal of the present work is the evaluation of the enhancement effect of the investigated drug glucosamine sulphate on the chemiluminescence reaction between luminol and H2O2 in alkaline medium of 1.0 × 10−2 mol L−1 sodium hydroxide at pH 11. The experimental conditions affecting the CL reaction such as the sequence of the reagents, concentrations, flow rate and aspirated volumes of reactants were systematically investigated and optimized. Under optimum conditions 50 μL of 1.0 × 10−3 mol L−1 luminol, 30 μL of a GLS test solution and 50 μL of 1.0 × 10−2 mol L−1 H2O2 were used and the luminescing zone was pushed into the detector at a flow rate 100 μL s−1. The proposed method recorded high sensitivity, accuracy and simplicity that could be clarified as linear concentration range 1.0‐2000 ng mL−1 with rectilinear part (r = 0.9992, n = 9) and limit of detection 0.3 ng mL−1, along with relative standard deviation 1.3%. It was found that the developed method can be used directly to determine the investigated drug GLS in its pharmaceutical dosage forms and in spiked serum and urine by diluting the samples for a 1000 fold. The obtained results were statistically analyzed and compared with those obtained by the reported method.

Electrocatalytic performance of silica nanoparticles on graphene oxide sheets for hydrogen peroxide sensing

Graphene oxide–silica nanoparticles composite was successfully synthesized for the nonenzymatic detection of H2O2. Characterization was performed by FT-IR, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The composite consisting of graphene oxide and silica nanoparticles exhibited good electrochemical activity for the detection of H2O2 in alkaline medium. Low detection limit (2.6μM), good reproducibility (R2=0.997) and a wide linear range (5.22μM–10.43mM) were obtained based on amperometric study. These results suggest that the catalytic property of silica nanoparticles towards H2O2 could be enhanced with graphene oxide, making these composites promising novel materials for the development of nonenzymatic sensors.