H2O2 In Acid Solution Research Articles

Heterostructure and interface engineering of Ni0.85Se-MoSe2@PEI for enhancing electrocatalytic acidic oxygen reduction to hydrogen peroxide

Two-electron oxygen reduction reaction (2e− ORR) for hydrogen peroxide (H2O2) production in acidic solution is becoming a promising synthetic method due to its mild and green process. However, it is still hindered by sluggish kinetics and low selectivity. Given that heterostructure can enhance electron transfer and provide abundant active sites, interface modification can optimize O2 adsorption configurations and the adsorption energy of the reaction intermediates to improve ORR activity and selectivity. Here, we coupled heterostructures of Ni0.85Se-MoSe2 and polyethyleneimine (PEI) functionalization to enhance the activity and selectivity of the 2e− ORR for the efficient production of H2O2 in acidic solutions. The as-fabricated Ni0.85Se-MoSe2@PEI performed 91.7 % selectivity of H2O2 in the rotating ring-disk electrode test, while the H2O2 yield rate was up to 3.57 mol gcat.−1h−1 and the Faraday efficiency was 95.5 % in the H-type cell. In addition, Ni0.85Se-MoSe2@PEI maintains excellent stability in long-term operation, verifying the practicability of the catalyst. The combination of heterostructure and interface engineering provides research ideas for the electrochemical synthesis of H2O2.

O2-Generating Metal-Organic Framework-Based Hydrophobic Photosensitizer Delivery System for Enhanced Photodynamic Therapy.

Photodynamic therapy (PDT) has been introduced as a photochemical process for treatment by causing cancer cell death and necrosis, with higher accuracy and few side effects. However, the hydrophobicity of most photosensitizers and hypoxia at the tumor sites are two crucial problems to be solved to achieve a successful PDT. Herein, we designed and constructed a novel metal-organic framework-based drug delivery system (BSA-MnO2/Ce6@ZIF-8) with tumor microenvironment controllability. In our system, the hydrophobic photosensitizer chlorin e6 (Ce6) was one-pot incorporated into the matrix of zeolitic imidazolate framework 8 (ZIF-8) to form the Ce6@ZIF-8 compound, which can efficiently keep the Ce6 molecules isolated and avoid them self-aggregate, and the loading rate of Ce6 was high up to 28.3 wt %. The bovine serum albumin (BSA)-MnO2 nanoparticles (NPs) with catalase-like activity were loaded onto the surface of ZIF-8, having the capacity for self-sufficiency of O2 under the circumstance of H2O2 in acid solution, relieving hypoxia in cancer cells and thereby improving the PDT efficiency greatly when irradiated by low power density (230 mW/cm2) 650 nm light. Moreover, the MnO2 NPs react with H2O2 in acid solution to produce Mn2+, granting the system the qualification of a contrast agent for magnetic resonance imaging. Therefore, our nanoplatform would further contribute to the treatment of hypoxic tumors in clinical practice.

High-Concentration Single Atomic Pt Sites on Hollow CuSx for Selective O2 Reduction to H2O2 in Acid Solution

Summary The electrochemical direct synthesis of hydrogen peroxide (H2O2) is significant but still challenging because of the lack of highly selective and active catalysts. Here, we report the synthesis of hollow nanospheres constructed by atomically dispersing platinum in amorphous CuSx support (h-Pt1-CuSx) with a high concentration of single atomic Pt sites (24.8 at%), and this catalyst can consistently reduce O2 into H2O2 with selectivity of 92%–96% over a wide potential range of 0.05–0.7 V versus RHE in HClO4 electrolyte. Scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy confirmed the atomically isolated form of Pt with a low valance of +0.75. An electrochemical device that can synthesize H2O2 directly from H2 and O2 is fabricated with H2O2 productivity as high as 546 ± 30 mol kgcat−1 h−1. The well-defined and high-concentration single atomic Pt sites result in ultrahigh productivity of H2O2.

Low overpotential water oxidation at neutral pH catalyzed by a copper(ii) porphyrin.

Low overpotential water oxidation under mild conditions is required for new energy conversion technologies with potential application prospects. Extensive studies on molecular catalysis have been performed to gain fundamental knowledge for the rational designing of cheap, efficient and robust catalysts. We herein report a water-soluble CuII complex of tetrakis(4-N-methylpyridyl)porphyrin (1), which catalyzes the oxygen evolution reaction (OER) in neutral aqueous solutions with small overpotentials: the onset potential of the catalytic water oxidation wave measured at current density j = 0.10 mA cm-2 is 1.13 V versus a normal hydrogen electrode (NHE), which corresponds to an onset overpotential of 310 mV. Constant potential electrolysis of 1 at neutral pH and at 1.30 V versus NHE displayed a substantial and stable current for O2 evolution with a faradaic efficiency of >93%. More importantly, in addition to the 4e water oxidation to O2 at neutral pH, 1 can catalyze the 2e water oxidation to H2O2 in acidic solutions. The produced H2O2 is detected by rotating ring-disk electrode measurements and by the sodium iodide method after bulk electrolysis at pH 3.0. This work presents an efficient and robust Cu-based catalyst for water oxidation in both neutral and acidic solutions. The observation of H2O2 during water oxidation catalysis is rare and will provide new insights into the water oxidation mechanism.

Honeycomb-Satellite Structured pH/H2O2-Responsive Degradable Nanoplatform for Efficient Photodynamic Therapy and Multimodal Imaging.

The oxygen-deprived environment of a solid tumor is still great restriction in achieving an efficient photodynamic therapy (PDT). In this work, we developed a smart pH-controllable and H2O2-responsive nanoplatform with degradable property, which was based on honeycomb manganese oxide (hMnO2) nanospheres loaded with Ce6-sensitized core-shell-shell structured up-conversion nanoparticles (NaGdF4:Yb/Er,Tm@NaGdF4:Yb@NaNdF4:Yb) (abbreviated as hMUC). In the system, the speedy breakup of the as-prepared hMnO2 nanostructures results in release of loaded Ce6-sensitized UCNPs under the condition of H2O2 in acid solution. When exposed to tissue-penetrable 808 nm laser, up-conversion nanoparticles (UCNPs) emit higher-energy visible photons which would be absorbed by Ce6 to yield cytotoxic reactive oxygen species (ROS), thus triggering PDT treatment naturally. Moreover, the in vitro and in vivo experiments demonstrate that hMUC sample with the honeycomb-satellite structure can serve as multimodal bioimaging contrast agent for self-enhanced upconversion luminescence (UCL), magnetic resonance imaging (MRI) and computed tomography (CT) imaging, indicating that the as-prepared hMUC could be used in imaging-guided diagnosis and treatment, which has a potential application in the PDT treatment of tumor.

Effect of Surface Preparation on the Residual Oxide Thickness and Material Loss of InGaAs Layer

Indium gallium arsenide (InGaAs) can be introduced as a new channel material for improving device performance due to its high electron mobility. Surface preparation of InGaAs in wet chemical processes should be controlled because InGaAs is not as robust as Si against the wet chemistries. In this work, oxidation and etching behavior on InGaAs surface were investigated for acidic and basic treatments. It was observed that the oxidation states decreased after HCl treatment as compared to as-received InGaAs surface, while they increased after NH4OH treatment. The oxidation states increased after addition of H2O2 in both acidic and basic solutions. It is suggested that dissolution of the oxidized InGaAs layer is dominant in acidic solution, while it is a rate limiting step in the basic solution. Therefore, the concentration of oxidant such as H2O2 in acidic solution is important factor to determine residual oxidation and overall etching rate of InGaAs layer.

An Unusual O-O Bond Formation Route Results in Low Overpotential Water Oxidation at Neutral pH by a Cu <sup>II</sup> Catalyst

Low overpotential water oxidation under mild conditions is required for new energy conversion technologies with potential application prospects. Extensive studies on molecular catalysis have been performed to gain fundamental knowledge for rational design of cheap, efficient and robust catalysts. We herein report a CuII complex of tetrakis(4-N-methylpyridyl)porphyrin (1), which catalyzes the oxygen evolution reaction (OER) in neutral aqueous solution with a small onset overpotential of 290 mV. An unusual coupling of two [Por• −CuII−OH] units is proposed. Experimental and theoretical studies verified that such new O−O bond formation strategy accounts for the observed low overpotential water oxidation. In addition to the 4e water oxidation to O2 at neutral pH, 1 catalyzes the 2e water oxidation to H2O2 in acidic solutions. This work presents an efficient and robust Cu-based catalyst for water oxidation in both neutral and acidic solutions. The proposed O−O bond formation mechanism will enrich the knowledge of molecular catalysis.

C3N4–Mn/CNT composite as a heterogeneous catalyst in the electro-peroxone process for promoting the reaction between O3and H2O2in acid solution

The C3N4–Mn/CNT catalyst promotes the reaction between O3and H2O2in acid solution, and enhances the degradation efficiency of the electro-peroxone process.

A promising ozone-based advanced oxidation process for effective generation of hydroxyl radicals in acidic solution

The oxidative efficiency of H2O2/O3 in the presence or absence of titanium silicalite of TS-1 was investigated at pH value of 3.0, in which acetic acid was selected as the target organic compound owing to its inert to ozone. The removal rate of acetic acid by H2O2/O3 was negligible (5.6% in 30min) because of the impossible deprotonation reaction of H2O2 in acidic solution. However, addition of titanium silicalite of TS-1 could greatly improve the oxidative efficiency of H2O2/O3 (29% in 30min). The results of effects of different parameters such as concentration of H2O2, concentration of TS-1, rate of ozone input, and pH value, on the oxidative efficiency of TS-1/H2O2/O3 showed that the degradation of HAc by TS-1/H2O2/O3 was controlled by the transfers of reactants (including ozone and HAc) to the surface of TS-1. The tests of addition of tert-butyl alcohol and dimethyl sulfoxide (DMSO) both confirmed generation of hydroxyl radicals in this process. The rate of generation of hydroxyl radicals could be controlled by adjusting the concentration of H2O2. The mechanism for generation of hydroxyl radicals might be the reaction of some reactive oxygen species (including Ti(IV)-superoxide and Ti(IV)-hydroperoxide/peroxide), which resulted from the interaction of TS-1 with H2O2, with dissolved ozone. The results are of significance for the effective pretreatment of acidic wastewater containing refractory ozone-inert organic matter.

Direct electron transfer of glucose oxidase and dual hydrogen peroxide and glucose detection based on water-dispersible carbon nanotubes derivative

A water-dispersible multi-walled carbon nanotubes (MWCNTs) derivative, MWCNTs-1-one-dihydroxypyridine (MWCNTs-Py) was synthesis via Friedel–Crafts chemical acylation. Raman spectra demonstrated the conjugated level of MWCNTs-Py was retained after this chemical modification. MWCNTs-Py showed dual hydrogen peroxide (H2O2) and glucose detections without mutual interference by adjusting pH value. It was sensitive to H2O2 in acidic solution and displayed the high performances of sensitivity, linear range, response time and stability; meanwhile it did not respond to H2O2 in neutral solution. In addition, this positively charged MWCNTs-Py could adsorb glucose oxidase (GOD) by electrostatic attraction. MWCNTs-Py-GOD/GC electrode showed the direct electron transfer (DET) of GOD with a pair of well-defined redox peaks, attesting the bioactivity of GOD was retained due to the non-destroyed immobilization. The high surface coverage of active GOD (3.5×10−9molcm−2) resulted in exhibiting a good electrocatalytic activity toward glucose. This glucose sensor showed high sensitivity (68.1μAmM−1cm−2) in a linear range from 3μM to 7mM in neutral buffer solution. The proposed sensor could distinguish H2O2 and glucose, thus owning high selectivity and reliability.

Spontaneous redox synthesis of Prussian blue/graphene nanocomposite as a non-precious metal catalyst for efficient four-electron oxygen reduction in acidic medium

A Prussian blue/graphene (PB/GE) nanocomposite is synthesized as a non-precious metal catalyst by a spontaneous redox reaction in acidic solution with Fe powder, K3[Fe(CN)6], and graphene oxide as precursors. The resulting PB/GE nanocomposite is characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The PB/GE nanocomposite-modified glassy carbon electrode (PB/GE–GCE) exhibits good electrocatalytic activity and long-term stability toward the oxygen reduction reaction (ORR). The reduced form of PB, Prussian white, has favorable electrocatalytic activity for the reduction of O2 and H2O2 in acidic solutions. Rotating ring-disk voltammetric measurements clearly show that the dominant product of ORR at the PB–GCE is water produced by the 4e− reduction of O2 at all potentials. ORR at the PB/GE–GCE occurs mainly inside the PB lattice through the 4e− reduction pathway at E > −0.5 V and on GE nanosheets through the “2 + 2” mechanism involving H2O2 as the intermediate product at E < −0.5 V. The PB/GE nanocomposite is a potentially efficient and cost-effective catalyst for fuel cells.

A 195Pt NMR study of the oxidation of [PtCl4]2− with chlorate, bromate, and hydrogen peroxide in acidic aqueous solution

195Pt NMR has been used to investigate the distribution of Pt(IV) products after oxidation of [PtCl4]2− with sodium chlorate (NaClO3), sodium bromate (NaBrO3), and H2O2 in acidic solutions and, for comparison, with H2O2 in water. The relative rates of oxidation of [PtCl4]2− with NaClO3 and H2O2 in 1 mol L−1 HClO4 at 50°C are comparable, while that with NaBrO3 is significantly higher. Our 195Pt NMR results confirm previous work on the oxidation of [PtCl4]2− with H2O2 in water, which results in mainly trans-[PtCl4(OH)2]2− as product. By contrast oxidation of [PtCl4]2− with NaClO3 and NaBrO3 in acidic solutions results in the distribution of several [PtCl n (H2O)6− n ]4− n (n = 2–6) and [PtCl n Br m (H2O)6− n − m ]4− n − m (n, m = 2–6) species; notably the distribution of product species is dominated by cis-[PtCl4(H2O)2] in solution. This species can be unambiguously identified by the 35Cl/37Cl-isotope-induced effects on the 195Pt NMR resonance shape in solution. trans-[PtCl4(OH)2]2− was co-crystallized with 18-crown-6 to form trans-K2[PtCl4(OH)2](18-cr-6)2 · 2H2O and the single crystal X-ray structure is reported. Oxidation of [PtCl4]2− with H2O2 in various acidic solutions gives qualitatively similar Pt(IV) species distributions as found for NaClO3, and the implications of these results are discussed in the context of Pt(II)→Pt(IV) oxidation reactions by these oxidants in aqueous solutions.

Electrosynthesis of hydrogen peroxide in acidic solutions by mediated oxygen reduction in a three-phase (aqueous/organic/gaseous) system Part I: Emulsion structure, electrode kinetics and batch electrolysis

The mediated electrosynthesis of H2O2 in acidic solutions (pH 0.9–3.0) was investigated in a three-phase, aqueous/organic/gaseous system using 2-ethyl-9,10-anthraquinone (EtAQ) as mediator (redox catalyst). The main hydrogen peroxide producing route is the in situ mediating cycle: EtAQ electroreduction–homogeneous oxidation of anthrahydroquinone (EtAQH2). The organic phase was composed of tributylphosphate solvent (TBP) with 0.2 M tetrabutylammonium perchlorate (TBAP) supporting electrolyte, 0.06 M tricaprylmethylammonium chloride (A336) surface active agent, and 0.1–0.2 M EtAQ mediator. Part I of this two part work deals with the physico-chemical characteristics of the emulsion electrolyte (e.g., ionic conductivity, emulsion type, H2O2 partition between the aqueous and organic phases), and kinetic aspects (both electrode and homogenous) of the mediation cycle. Furthermore, batch electrosynthesis experiments are presented employing reticulated vitreous carbon cathodes (specific surface area 1800 m2 m−3) operated at superficial current densities of 500–800 A m−2. During 10 h batch electrolysis involving the emulsion mediated system with O2 purge at 0.1 MPa pressure, H2O2 concentrations in the range 0.53–0.61 M were obtained in 0.1 M H2SO4 (pH 0.9) and 2 M Na2SO4(acidified to pH3). The corresponding apparent current efficiencies were from 46 to 68%. Part II of the present work describes investigations using flow-by fixed-bed electrochemical cells with co-current upward three-phase flow.

Electrosynthesis of hydrogen peroxide in acidic solutions by mediated oxygen reduction in a three-phase (aqueous/organic/gaseous) system. Part II: Experiments in flow-by fixed-bed electrochemical cells with three-phase flow

The second part of the work concerned with mediated electrosynthesis of H2O2 in acidic solutions (pH 3) deals with investigations using divided flow-by fixed bed electrochemical cells operated with co-current three-phase flow (aqueous/organic emulsion and O2 gas at 0.1 MPa). Graphite felt (GF) and reticulated vitreous carbon (RVC) were evaluated as cathodes at superficial current densities up to 3000 A m−2. Typically, at current densities above 600 A m−2 graphite felt yielded higher peroxide concentrations per pass and current efficiencies, most likely due to the almost an order of magnitude higher organic liquid to solid mass transfer capacity for 2-ethyl-9,10-anthraquinone (EtAQ) mediator, that is, 0.13 s−1 in the case of GF vs 0.015 s−1 for RVC with 39 ppc (pores per cm). Factorial experiments revealed a positive interaction effect between superficial current density and emulsion load with respect to the current efficiency for H2O2 electrosynthesis. Thus, at the highest investigated superficial current density of 3000 A m−2, the current efficiency was 84% when the emulsion load was at the highest explored level of 11.7 kg m−2 s−1, whilest for the lowest level of emulsion load, 2.8 kg m−2 s−1, the current efficiency for H2O2 was 18%. Furthermore, the presence of 1 mM cationic surfactant, tricaprylmethylammonium chloride (CH3(C8H17)3N+Cl−, A336), had a positive main effect of about 12% on H2O2 current efficiency and there was also a positive synergistic effect between surfactant and emulsion load, estimated at about 7%. The aqueous to organic phase volume ratio, in the range of 0.9/1 and 3/1, had a statistically insignificant effect on the current efficiency for H2O2 generation. A decrease of the aqueous to organic phase volume ratio from 3 to 0.9 increased the cell voltage from about 6.5 to 7.3 V.

On the mechanism of the γ-radiolysis of deoxygenated aqueous solutions of hydrazine

A reaction mechanism has been devised by trial and error that accounts for most of the data that have been obtained from γ-radiolysis studies under deaerated conditions and which hitherto have not been satisfactorily explained. The major features of the proposed mechanism are the following. (a) Hydrazyl radicals N2H4•+ and •N2H3 react by disproportionation to form N2H2 and hydrazine, and by combination either as the free radicals or with one of them complexed with a hydrazine molecule, N2H5+ or N2H4, to produce N2 + 2NH3. This accounts for the observed strong dependence of the radiolytic decomposition yields (G-values) on [N2H5+]. (b) Hydrogen atoms (hydrated electrons) are proposed to react with N2H5+ (N2H4) by a split path to form H2 + N2H4•+ (•N2H3) and •NH2 + NH4+ (NH3), which helps to account for the observed values of G(H2); reduction of N2H2 by H• to •N2H3 is also required to explain fully the values of G(H2). (c) In alkaline solution the decrease in decomposition yields is explained in terms of the dissociation of H2O2 to HO2−, which is more readily oxidised to O2•−. This, together with the much longer lifetime of O2•− at high pH, results in the reduction by O2•− of •N2H3 back to N2H4. The effect of added H2O2 in acidic solution can be explained if it forms a complex with N2H4•+ followed by reaction with another N2H4•+ to form N2 + 2H2O.

The preparation and characterization of iron trihydroxide, Fe(OH)3

Iron trihydroxide has been prepared by the oxidation of FeSO4 with [Co(III)(en)(dien)]2O2[ClO4]4, [Co(III)(tetraen)]2O2[ClO4]4, and H2O2 in acid solution. These materials have been characterized by DTA, magnetic susceptibility, Mössbauer spectroscopy. X-ray powder diffraction, and electron microscopy. Particle sizes are found to be ~80 Å in diameter, but in the case of the (tetraen) preparation we find needle-like crystallites ~1200 Å × 400 Å × 50 Å in size. The magnitudes of the hyperfine fields follow the particle size variation. These materials have quite a different behaviour from the Fe(OH)3 gels prepared from basic solution.