Direct Peroxide Research Articles

Direct Hydrogen Peroxide Synthesis on a Sn-doped CuWO4/Sn Anode and an Air-Breathing Cathode

Direct Hydrogen Peroxide Synthesis on a Sn-doped CuWO₄/Sn Anode and an Air-Breathing Cathode

Development of bifunctional vaginal suppositories by joint use terconazole and probiotic for treatment and prophylaxis of vulvovaginal candidiasis

Objective The objective of this article is the creation and investigation of bifunctional suppositories that are endowed with antifungal and probiotic properties intended for the treatment of vulvovaginal candidiasis (VVC) and colonization of the vaginal cavity by powerful lactobacilli. Materials and methods Freeze-dried Lactobacillus delbrueckii MH10 was used as a probiotic, which is an active producer of H2O2 isolated from a healthy woman’s vagina. Hydrophilic PEG 4000/400, amphiphilic Suppocire AP, and lipophilic Novata ABPH bases were used for the preparation of vaginal suppositories and each included 80 mg terconazole and 25 mg (∼109 CFU) lactobacilli. The release kinetic of active agents from suppositories was studied using the British Pharmacopeia’s basket dissolution method, and the physicochemical properties were studied using known methods. Bioadhesion of suppositories was evaluated by flow rate from polyacrylamide substrate inclined at 60°. Antagonism of lactobacillus against fungi was studied using the disk diffusion method and joint cultivation in simulated vaginal fluid. Results The release rate of active ingredients from the suppositories was PEG 4000/400 > Suppocire AP > Novata ABPH in decreasing order. Suppositories made of Suppocire AP possessed higher adhesion ability to artificial mucosa and longer shelf life. It was revealed that during joint cultivation L. delbrueckii MH10 kills more than 90% of C. albicans population. Conclusions Due to its physicochemical, biopharmaceutical, and bioadhesive properties, the base Suppocire AP is preferable for manufacturing vaginal bifunctional suppositories. Lactobacilli kill C. albicans by coaggregating and direct releasing hydrogen peroxide onto target cells.

Synergistic Hybrid Support Comprising TiO2–Carbon and Ordered PdNi Alloy for Direct Hydrogen Peroxide Synthesis

Synergistic Hybrid Support Comprising TiO₂–Carbon and Ordered PdNi Alloy for Direct Hydrogen Peroxide Synthesis

A Career in Catalysis: Graham J. Hutchings

This Account is to commemorate the 70th birthday of Graham Hutchings and his diverse and distinguished career in catalysis, working in industry and academia. The scope of his work is wide ranging, and he has contributed to many areas of catalysis and has been a pioneer in several of them. Notable contributions to the discipline include novel methods of catalyst preparation for both metal oxides and supported nanoparticles, selective oxidation, acetylene hydrochlorination, and direct hydrogen peroxide synthesis, and he has played a central role in the discovery, application, and understanding of gold-based catalysts. The aim of this article is to provide an outline of his career and highlight some of the contributions he has made to the field of catalysis. Successfully supervising over 190 Ph.D. students, working directly with more than 90 postdoctoral researchers, and collaborating widely nationally and internationally, his work has influenced many in the discipline of heterogeneous catalysis.

Hydrogen sulfide (H2S) signaling in plant development and stress responses.

Hydrogen sulfide (H2S) was initially recognized as a toxic gas and its biological functions in mammalian cells have been gradually discovered during the past decades. In the latest decade, numerous studies have revealed that H2S has versatile functions in plants as well. In this review, we summarize H2S-mediated sulfur metabolic pathways, as well as the progress in the recognition of its biological functions in plant growth and development, particularly its physiological functions in biotic and abiotic stress responses. Besides direct chemical reactions, nitric oxide (NO) and hydrogen peroxide (H2O2) have complex relationships with H2S in plant signaling, both of which mediate protein post-translational modification (PTM) to attack the cysteine residues. We also discuss recent progress in the research on the three types of PTMs and their biological functions in plants. Finally, we propose the relevant issues that need to be addressed in the future research.Graphic abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s42994-021-00035-4.

Carbon nanotube-graphene supported bimetallic electrocatalyst for direct borohydride hydrogen peroxide fuel cells

At present study, carbon nanotube-graphene (CNT-G) supported PtAu, Au and Pt catalysts were prepared by microwave-assisted synthesis method to investigate the direct liquid-fed sodium borohydride/hydrogen peroxide (NaBH4/H2O2) fuel cell performance. Prepared catalysts were characterized by TGA, XRD, TEM, ICP-OES, cyclic voltammetry and rotating disc electrode (RDE) voltammetry. The catalysts were tested in a single NaBH4/H2O2 fuel cell with 25 cm2 active area to evaluate fuel cell performance. The effects of temperature and fuel concentration on fuel cell performance were examined to observed best operating conditions. As a result of direct NaBH4/H2O2 fuel cell experiments, maximum power densities of 139 mW/cm2, 125 mW/cm2 and 113 mW/cm2 were obtained for PtAu/CNT-G, Au/CNT-G and Pt/CNT-G catalysts, respectively. PtAu/CNT-G catalyst showed the enhanced NaBH4/H2O2 fuel cell performance, which was higher than the Pt/CNT-G catalyst and Au/CNT-G catalyst at 50 °C. The enhanced NaBH4/H2O2 performance can be attributed to synergistic effects between Pt and Au particles on CNT-G support providing a better catalyst utilization and interaction. These results suggest that the prepared PtAu/CNT-G catalyst is a promising anode catalyst for NaBH4/H2O2 fuel cell application.

Promotional effect of surface plasmon resonance on direct formation of hydrogen peroxide from H2 and O2 over Pd/Graphene-Au nanorod catalytic system

A promotional effect of surface plasmon resonance (SPR) on direct hydrogen peroxide (H2O2) formation from H2 and O2 over a structure-controlled Pd-Au catalytic system is reported herein. Pd NPs supported on reduced graphene oxide (rGO) layer-coated Au nanorod (NR) nanocomposite catalysts were synthesized, and the structure was confirmed by multiple characterization techniques. H2O2 production is highly enhanced under visible light irradiation in the direct H2O2 formation from H2 and O2. The H2O2 decomposition test and the H2-D2 exchange reaction reveal that the SPR of Au NRs facilitates H2 activation on the Pd NP surface, leading to efficient H2O2 production. Furthermore, the rGO layer not only functions as an electron mediator in the catalytic reaction, but also contributes to the control of Pd NP sizes in the catalyst synthesis.

Isolated Pd Sites as Selective Catalysts for Electrochemical and Direct Hydrogen Peroxide Synthesis

Palladium nanoparticles have been studied extensively as catalysts for the direct synthesis of hydrogen peroxide, where selectivity remains a key challenge. Alloying Pd with other metals and using acid and halide promoters are commonly employed to increase H2O2 selectivity; however, the sites that can selectively produce H2O2 have not been identified and the role of these additives remains unclear. Here, we report the synthesis of atomically dispersed PdClx/C as a model catalyst for H2O2 production without the presence of extended Pd surfaces. We show that these isolated cationic Pd sites can form H2O2 with significantly higher selectivity than metallic Pd nanoparticles in both the reaction of H2 and O2 and the electrochemical oxygen reduction reaction. These results demonstrate that catalysts containing high populations of isolated Pd sites are selective catalysts for this two-electron reduction reaction and that the performance of materials in the direct synthesis reaction and electrocatalytic oxygen reduction reaction has many similarities.

Safe direct synthesis of H2O2 within the explosion limit of H2 enabled by low-temperature stable bcc-PdCu alloy membrane

Pd based membrane provides an inherently safer way to handle flammable mixture of hydrogen and oxygen, as it could selectively isolate hydrogen from other gases. However, due to their susceptibility to hydrogen embrittlement, pure Pd membranes are not suitable for processes at low temperature. To solve this problem, body-centered cubic (bcc)-PdCu alloy membranes were prepared by the combination of electroplating and electroless plating. The hydrogen permeation rate (JH2), N2 leak rate (JN2) and H2/N2 selectivity (αH2/N2) remained stable through 200 h continuous operation in H2 at 298 K and ΔPH2 = 100 kPa. The excellent low-temperature tolerance of bcc-PdCu membranes rendered them ideal materials for the capture and activation of hydrogen during the direct hydrogen peroxide synthesis from hydrogen and oxygen. The reaction could be performed safely within the explosive limit of hydrogen/oxygen by feeding the gases separately from the opposite sides of the membrane with no direct contact. 60 mmol m−2 h−1 formation rate, 40% H2O2 selectivity, and a nearly 100% hydrogen conversion was reached at 298 K, 500 kPa.

Enabling Direct H2O2 Production in Acidic Media through Rational Design of Transition Metal Single Atom Catalyst

Summary The electrochemical oxygen reduction reaction in acidic media offers an attractive route for direct hydrogen peroxide (H2O2) generation and on-site applications. Unfortunately there is still a lack of cost-effective electrocatalysts with high catalytic performance. Here, we theoretically designed and experimentally demonstrated that a cobalt single-atom catalyst (Co SAC) anchored in nitrogen-doped graphene, with optimized adsorption energy of the *OOH intermediate, exhibited a high H2O2 production rate, which even slightly outperformed the state-of-the-art noble-metal-based electrocatalysts. The kinetic current of H2O2 production over Co SAC could reach 1 mA / cm disk 2 at 0.6 V versus reversible hydrogen electrode in 0.1 M HClO4 with H2O2 faraday efficiency > 90%, and these performance measures could be sustained for 10 h without decay. Further kinetic analysis and operando X-ray absorption study combined with density functional theory (DFT) calculation demonstrated that the nitrogen-coordinated single Co atom was the active site and the reaction was rate-limited by the first electron transfer step.

High-performance direct hydrogen peroxide fuel cells (DHPFCs) with silver nanowire-graphene hybrid aerogel as highly-conductive mesoporous electrodes

Direct hydrogen peroxide fuel cells have inspired the benign interests for air-independent submarine and underwater unmanned electronic applications. Yet, the process of H2O2 reduction reaction is significantly hindered by the sluggish electron transfer kinetics and poor mass transport efficiency. Herein, a three-dimensional monolithic silver nanowire aerogel assisted by the graphene monolayers is prepared, and validated as a promising H2O2 reduction catalyst. The interconnected, continuous aerogels and the substrate-free features allow the electron rapid flow and mass transport. Attributed to above advantages, the composites exhibit a high effectiveness and a low impedance during the catalysis. The direct hydrogen peroxide fuel cell equipped with these hybrid aerogels delivers a maximum power density of 1.4 W g−1 and 11.25 W g−1 $−1 based on the electrode weight and capital cost, which are substantially higher than previous values. The concept of building three-dimensional aerogels as self-standing electrodes provides a method for designing and manufacturing next-generation direct hydrogen peroxide fuel cells to bring the technology much closer to commercialization.

Catalytic consequences of the identity of surface reactive intermediates during direct hydrogen peroxide formation on Pd particles

H2O2 formation directly from H2 and O2 on Pd particles in water has proven to proceed via two different kinetic regimes defined by the operating H2/O2 ratios using kinetics, isotopic experiments and variation of particle sizes under conditions of kinetic control. These kinetic regimes exhibit different rate equations, kinetic isotope effects and structure sensitivity, while a transition among regimes occurs as the surface reactive intermediates changing from nearly uncovered to saturated with chemisorbed hydrogen (H*) with the increasing of H2/O2 ratio. On nearly bare Pd surfaces, irreversible H2 dissociation limits the rates of H2O2 formation and H2 conversion, thus, rates increase proportionally with H2 pressure but independent of O2 pressure. On H* saturated Pd surfaces, H2 dissociation approaches to chemical equilibrium and the H* mediated HOOH* formation step becomes the sole kinetically relevant step, therefore, rates become insensitive to H2 pressure but are linearly proportional to O2 pressure. The first-order rate coefficients for H2O2 formation become a single-valued function of the operating H2/O2 ratio.

Reduced graphene oxide foam supported CoNi nanosheets as an efficient anode catalyst for direct borohydride hydrogen peroxide fuel cell

Abstract Catalytic performance and NaBH4 utilization are two crucial concerns in the electrooxidation of NaBH4. To improve the inherent properties of regular performance and low fuel utilization of the transition metal Co and Ni, an efficient anode catalyst of ultra-thin CoNi nanosheets modified novel 3D self-supported reduced graphene oxide foam is prepared in this work. The alkaline condition borohydride oxidation reaction on the prepared catalyst is investigated in a typical three-electrode system. The prepared catalyst shows a high performance due to the large electrochemical active surface area, low activation energy (8.29 kJ·mol−1), and the small electrochemical impedance it embraced. Linear scan voltammetry recorded in a low concentration of NaBH4 suggests that borohydride oxidation is a first-order reaction on the prepared catalyst. Based on the unique structure of the catalyst, which is useful to capture the hydrogen and perform further oxidation of hydrogen, higher utilization of NaBH4 achieved on the catalyst. Besides, the prepared anode catalyst applied to a direct borohydride-hydrogen peroxide fuel cell (DBHPFC). The results of polarization curve and power density curves, as well as stability research, all indicate that the as-prepared catalyst is a highly efficient anode material for application in DBHPFC.

Does SpNox directly produce hydrogen peroxide?

NADPH oxidases (NOXs) are a family of transmembrane enzymes that generate reactive oxygen species (ROS), which in humans acts both as a cytotoxic agent in autoimmunity and as a signaling molecule in many physiological processes. Human NOXes can produce different ROS species; for example, NOX2 isoform generates superoxide whereas NOX4 isoform produces mainly hydrogen peroxide. The ROS species produced affects downstream signaling, and misregulation produces disease states. A recently discovered prokaryotic NOX, SpNOX, provides an ideal model system to investigate controls on ROS product. SpNOX was previously shown to produce superoxide. Because superoxide spontaneously dismutes at a fast rate, assays that detect hydrogen peroxide cannot be used to assess direct hydrogen peroxide formation. Instead, as in the case of xanthine oxidase, we estimate total electron flux and also superoxide production; we assume that any difference between these values reflects direct hydrogen peroxide production by the enzyme. We estimate electron flux using three assays: i/ monitoring NADPH consumption using absorbance (340 nm); ii/ monitoring NADPH consumption using fluorescence (ex 345/em 454); iii/ monitoring cytochrome c reduction by the FAD of a dehydrogenase‐domain only construct of SpNOX. Superoxide generation from full‐length SpNOX is estimated by the superoxide‐dismutase‐inhibitable portion of cytochrome c reduction, monitored by absorbance at 550 nm. Here we present our findings regarding relative production of superoxide and hydrogen peroxide by SpNOX, as a first step toward manipulating ROS product in this model system.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A nanocomposite consisting of gold nanobipyramids and multiwalled carbon nanotubes for amperometric nonenzymatic sensing of glucose and hydrogen peroxide.

Gold nanobipyramids were synthesized by a seed-mediated growth method and then supported by multi-walled carbon nanotubes (denoted as AuNBP/MWCNTs). The electrocatalytic activity of the AuNBP/MWCNTs on a glassy carbon electrode (GCE) towards direct glucose oxidation and hydrogen peroxide reduction was superior to that of AuNBPs and MWCNTs. The modified GCE, operated at a typical working voltage of +0.15V (vs. SCE) and in 0.1M NaOH solution, exhibits a linear response in the 10μM to 36.7mM glucose concentration range with a 3.0μM detection limit (at S/N = 3) and a sensitivity of 101.2μAmM-1cm-2. It also demonstrates good sensitivity towards hydrogen peroxide in atpH7solution at a working potential of -0.50V (vs. SCE), with a linear responserange from 5.0μM to 47.3mM, a sensitivity of 170.6μAmM-1cm-2 and a detection limit of 1.5μM. Graphical abstract A electrochemical sensing platform based on the use ofgold nanobipyramidsandmulti-walled carbon nanotubes nanocomposites (AuNBP/MWCNTs) is described for the determination of glucose and hydrogen peroxide.

Structure, Activity, and Faradaic Efficiency of Nitrogen-Doped Porous Carbon Catalysts for Direct Electrochemical Hydrogen Peroxide Production.

Carbon materials doped with nitrogen are active catalysts for the electrochemical two-electron oxygen reduction reaction (ORR) to hydrogen peroxide. Insights into the individual role of the various chemical nitrogen functionalities in the H2 O2 production, however, have remained scarce. Here, we explore a catalytically very active family of nitrogen-doped porous carbon materials, prepared by direct pyrolysis of ordered mesoporous carbon (CMK-3) with polyethylenimine (PEI). Voltammetric rotating ring-disk analysis in combination with chronoamperometric bulk electrolysis measurements in electrolysis cells demonstrate a pronounced effect of the applied potentials, current densities, and electrolyte pH on the H2 O2 selectivity and absolute production rates. H2 O2 selectivity up to 95.3 % was achieved in acidic environment, whereas the largest H2 O2 production rate of 570.1 mmol g-1 catalyst h-1 was observed in neutral solution. X-ray photoemission spectroscopy (XPS) analysis suggests a key mechanistic role of pyridinic-N in the catalytic process in acid, whereas graphitic-N groups appear to be catalytically active moieties in neutral and alkaline conditions. Our results contribute to the understanding and aid the rational design of efficient carbon-based H2 O2 production catalysts.

Porous Nanocrystalline Silicon Supported Bimetallic Pd-Au Catalysts: Preparation, Characterization, and Direct Hydrogen Peroxide Synthesis.

Bimetallic Pd-Au catalysts were prepared on the porous nanocrystalline silicon (PSi) for the first time. The catalysts were tested in the reaction of direct hydrogen peroxide synthesis and characterized by standard structural and chemical techniques. It was shown that the Pd-Au/PSi catalyst prepared from conventional H2[PdCl4] and H[AuCl4] precursors contains monometallic Pd and a range of different Pd-Au alloy nanoparticles over the oxidized PSi surface. The PdAu2/PSi catalyst prepared from the [Pd(NH3)4][AuCl4]2 double complex salt (DCS) single-source precursor predominantly contains bimetallic Pd-Au alloy nanoparticles. For both catalysts the surface of bimetallic nanoparticles is Pd-enriched and contains palladium in Pd0 and Pd2+ states. Among the catalysts studied, the PdAu2/PSi catalyst was the most active and selective in the direct H2O2 synthesis with H2O2 productivity of 0.5 at selectivity of 50% and H2O2 concentration of 0.023 M in 0.03 M H2SO4-methanol solution after 5 h on stream at −10°C and atmospheric pressure. This performance is due to high activity in the H2O2 synthesis reaction and low activities in the undesirable H2O2 decomposition and hydrogenation reactions. Good performance of the PdAu2/PSi catalyst was associated with the major part of Pd in the catalyst being in the form of the bimetallic Pd-Au nanoparticles. Porous silicon was concluded to be a promising catalytic support for direct hydrogen peroxide synthesis due to its inertness with respect to undesirable side reactions, high thermal stability, and conductivity, possibility of safe operation at high temperatures and pressures and a well-established manufacturing process.

Progress Towards Direct Hydrogen Peroxide Fuel Cells (DHPFCs) as an Energy Storage Concept

This review introduces the concept of direct H2O2 fuel cells and discusses the merits of these systems in comparison with other ‘clean-energy’ fuels. Through electrochemical methods, H2O2 fuel can be generated from environmentally benign energy sources such as wind and solar. It also produces only water and oxygen when it is utilised in a direct H2O2 fuel cell, making it a fully reversible system. The electrochemical methods for H2O2 production are discussed here as well as the recent research aimed at increasing the efficiency and power of direct H2O2 fuel cells.

3D ordered macroporous SmCoO3 perovskite for highly active and selective hydrogen peroxide detection

We reported the direct electrochemical hydrogen peroxide detection on three-dimensionally ordered macroporous SmCoO3 (3DOM-SmCoO3) perovskite oxide electrode synthesized via a poly (methyl methacrylate) (PMMA) colloidal crystal templating route. The low-cost and simple 3DOM-SmCoO3 sensor not only overcome the various disadvantages of enzyme- and noble metal-based sensors but also display a superior sensing performance for H2O2 detection. More importantly, using 800 nm PMMA microspheres, a hexagonally ordered macroporous crystalline structure can be created, which features large surface area (20.14 m2 g−1) and large, open, interconnected channels for facile reactants and ions diffusions. The resultant 3DOM-SmCoO3 synthesized using 800 nm PMMA microspheres template (3D-SC-800) displayed higher sensitivity (715 and 460 μA mM−1 cm−2), lower limit of detection (0.004 μM), larger detection linear range (0.1–10,000 μM), and higher selectivity in the presence of interfering species (i.e., glucose, ascorbic acid, dopamine, and uric acid), for H2O2 detection, relative to SmCoO3 (SC) and SmCoO3 synthesized using 200 nm PMMA template (3D-SC-200). Our comprehensive electrochemical characterization attributes the superior H2O2 electrooxidation performance of 3D-SC-800 to its fast electron transfer kinetics and diffusion rate. What we demonstrated here bolsters the future opportunity to harness ordered macroporous perovskite oxide-based materials for highly active and selective non-enzymatic H2O2 detection.

Direct unassisted hydrogen peroxide generation from oxygen and water on plasmonic Ag-graphene-Cu nanosandwitch

A nanosandwich made from Ag nanoparticles (Ag NPs) arrays, the two-dimension single-layer graphene (SG) and metallic Cu contact was constructed for the hydrogen peroxide (H2O2) generation utilizing solar energy without an external bias. The shifting of binding energy towards lower energy in Ag core-level electronic spectrum is an evidence of strong coupling between Ag and graphene, which can efficiently transfer hot-holes from Ag to Cu by a built-in electric field so that the hot-electrons on Ag NPs are directly utilized to initiate the H2O2 generation. This Ag-graphene-Cu nanosandwitch can provide a stable photocurrent of −15.8μAcm−2, a stable photovoltaic voltage of 17.5mVcm−2, and a H2O2 yield of 229.33μM after 6h. To understand the mechanism of oxygen reduction reaction (ORR) in Ag-graphene-Cu systems, the electron transfer number for photocatalytic ORR and the surface facet of Ag NPs were studied. The Ag NPs in Ag-graphene-Cu systems with the deposition time of 180s clearly shows that an amount of 〈200〉 facets are distributed on Ag nanoparticle surface, which can catalyze ORR by 2-electron pathway to generate H2O2 efficiently. This novel Ag-graphene-Cu nanosandwitch offers a new transfer path for hot-electrons and potentially provides a new concept for driving efficient solar energy to chemical energy.