Showing papers on "Hydrogen peroxide published in 2020"

Hydrophobic zeolite modification for in situ peroxide formation in methane oxidation to methanol

Abstract: Selective partial oxidation of methane to methanol suffers from low efficiency. Here, we report a heterogeneous catalyst system for enhanced methanol productivity in methane oxidation by in situ generated hydrogen peroxide at mild temperature (70°C). The catalyst was synthesized by fixation of AuPd alloy nanoparticles within aluminosilicate zeolite crystals, followed by modification of the external surface of the zeolite with organosilanes. The silanes appear to allow diffusion of hydrogen, oxygen, and methane to the catalyst active sites, while confining the generated peroxide there to enhance its reaction probability. At 17.3% conversion of methane, methanol selectivity reached 92%, corresponding to methanol productivity up to 91.6 millimoles per gram of AuPd per hour.

Simultaneously tuning charge separation and oxygen reduction pathway on graphitic carbon nitride by polyethylenimine for boosted photocatalytic hydrogen peroxide production

Abstract: The synthesis of hydrogen peroxide (H2O2) from H2O and O2 by metal-free photocatalysts (e.g., graphitic carbon nitride, C3N4) is a potentially promising approach to generate H2O2. However, the phot...

A Review on Challenges and Successes in Atomic-Scale Design of Catalysts for Electrochemical Synthesis of Hydrogen Peroxide

Abstract: Hydrogen peroxide is a valuable chemical oxidant with a wide range of applications in a variety of industrial processes, especially in water sanitization. Electrochemical synthesis of hydrogen pero...

Bioinspired Copper Single-Atom Catalysts for Tumor Parallel Catalytic Therapy

Abstract: The oxidation of intracellular biomolecules by reactive oxygen species (ROS) forms the basis for ROS-based tumor therapy. However, the current therapeutic modalities cannot catalyze H2 O2 and O2 concurrently for ROS generation, thereby leading to unsatisfactory therapeutic efficacy. Herein, it is reported a bioinspired hollow N-doped carbon sphere doped with a single-atom copper species (Cu-HNCS) that can directly catalyze the decomposition of both oxygen and hydrogen peroxide to ROS, namely superoxide ion (O2 •- ) and the hydroxyl radical (•OH), respectively, in an acidic tumor microenvironment for the oxidation of intracellular biomolecules without external energy input, thus resulting in an enhanced tumor growth inhibitory effect. Notably, the Fenton reaction turnover frequency of Cu species in Cu-HNCS is ≈5000 times higher than that of Fe in commercial Fe3 O4 nanoparticles. Experimental results and density functional theory calculations reveal that the high catalytic activity of Cu-HNCS originates from the single-atom copper, and the calculation predicts a next-generation Fenton catalyst. This work provides an effective paradigm of tumor parallel catalytic therapy for considerably enhanced therapeutic efficacy.

Direct insights into the role of epoxy groups on cobalt sites for acidic H2O2 production

Abstract: Hydrogen peroxide produced by electrochemical oxygen reduction reaction provides a potentially cost effective and energy efficient alternative to the industrial anthraquinone process. In this study, we demonstrate that by modulating the oxygen functional groups near the atomically dispersed cobalt sites with proper electrochemical/chemical treatments, a highly active and selective oxygen reduction process for hydrogen peroxide production can be obtained in acidic electrolyte, showing a negligible amount of onset overpotential and nearly 100% selectivity within a wide range of applied potentials. Combined spectroscopic results reveal that the exceptionally enhanced performance of hydrogen peroxide generation originates from the presence of epoxy groups near the Co–N4 centers, which has resulted in the modification of the electronic structure of the cobalt atoms. Computational modeling demonstrates these electronically modified cobalt atoms will enhance the hydrogen peroxide productivity during oxygen reduction reaction in acid, providing insights into the design of electroactive materials for effective peroxide production. The production of hydrogen peroxide by electrochemical oxygen reduction is an attractive alternative to the industrial process, but catalysts should be optimized. Here, the authors enhance hydrogen peroxide production in acidic media with epoxy groups near cobalt centers on carbon nanotubes.

Single-Atom Co-N4 Electrocatalyst Enabling Four-Electron Oxygen Reduction with Enhanced Hydrogen Peroxide Tolerance for Selective Sensing.

Abstract: Electrocatalysis of four-electron oxygen reduction reaction (ORR) provides a promising approach for energy transfer, storage and oxygen monitoring. However, it is always accompanied by the reductio...

Z‐scheme photocatalytic production of hydrogen peroxide over Bi4O5Br2/g-C3N4 heterostructure under visible light

Abstract: Photocatalytic production of hydrogen peroxide from water and oxygen is a promising technique due to the green and sustainable solar-to-chemical energy conversion. However, in the absence of organic sacrificial agents as electron donors, the relatively low photocatalytic H2O2 productivity is still far from satisfactory. Herein, we present a Z‐scheme photocatalytic production of hydrogen peroxide over Bi4O5Br2/g-C3N4 heterostructure under visible light without additive organics. The obtained Bi4O5Br2/g-C3N4 heterostructure exhibited a highest H2O2 production of 124 μM in 60 min by a Z-scheme photocatalytic mechanism. The photoinduced electrons of Bi4O5Br2 combine with the holes of g-C3N4 at the contact interface, and the e− and h+ of the heterostructure are mainly derived from the conduction band of g-C3N4 and valence band of Bi4O5Br2, respectively. As such, more e− and h+ of Bi4O5Br2/g-C3N4 heterostructure are available to reduce oxygen and oxidize water, respectively, with more ·O2− and ·OH generated and thus more H2O2 produced.

Endogenous Labile Iron Pool-Mediated Free Radical Generation for Cancer Chemodynamic Therapy.

Abstract: Current chemodynamic therapy (CDT) primarily relies on the delivery of transition metal ions with Fenton activity to trigger hydroxyl radical production from hydrogen peroxide. However, administrat...

Catalyst Design for Electrochemical Oxygen Reduction toward Hydrogen Peroxide

Abstract: Precise electrochemical synthesis under ambient conditions has provided emerging opportunities for renewable energy utilization. Among many promising systems, the production of hydrogen peroxide (H2O2) from the cathodic oxygen reduction reaction (ORR) has attracted considerable interest in past decades due to the increasing market demands and the vital role of ORR in the electrocatalysis field. This work describes recent advances in cathodic materials for H2O2 synthesis from 2eORR. By using Pt as a stereotype, the tuning knobs are overviewed, including the intrinsic binding strength of oxygenated species, the intermediate diffusion path and the isolation of Pt–Pt ensembles that enable 2eORR pathway from 4etotal reduction. This knowledge is successfully applied to other transition metal systems and leads to the discovery of more efficient alloy catalysts with balanced improvement on both activity and selectivity. In addition, mesostructure engineering and heteroatoms doping strategies on carbon-based materials, which significantly boost the H2O2 production efficiency as compared to intact carbon sites, are also reviewed. Finally, future directions and challenges of transferring developed catalysts from lab scale tests to pilot plant operations are briefly outlooked.

Near-Complete Suppression of Oxygen Evolution for Photoelectrochemical H2O Oxidative H2O2 Synthesis

Abstract: Solar energy-assisted water oxidative hydrogen peroxide (H2O2) production on an anode combined with H2 production on a cathode increases the value of solar water splitting, but the challenge of the...

Exogenous salicylic acid and hydrogen peroxide attenuate drought stress in rice.

Abstract: Hydrogen peroxide (H2O2) and salicylic acid (SA) exhibit protective effects against a wide array of stresses. In this study, we investigated the relative efficacy of exogenous H2O2 and SA in conferring drought tolerance in rice (Oryza sativa L.). The experiment was repeated two times, firstly in a hydroponic system and secondly in soil. The results revealed that drought hampered germination indices, seedling growth, photosynthetic pigments, and water content, whereas increased proline content. It also triggered higher H2O2 production and consequently elevated lipid peroxidation, which is a particular indication of oxidative damage. However, exogenous H2O2 or SA treatment effectively alleviated oxidative damage in rice seedlings both in hydroponic and soil systems via upregulating antioxidant enzymes. Nevertheless, regulation of proline level and augmentation of plant-water status were crucial to confer drought tolerance. Exogenous H2O2 or SA also protected photosynthetic pigments from oxidative damage that might help to maintain normal photosynthesis under drought. Besides, 5 mmol/L H2O2 and 0.5 or 1 mmol/L SA showed similar effectiveness on mitigating drought stress. Finally, our findings suggest that exogenous H2O2 or SA could evenly be effectual in the amending growth of rice seedlings under drought conditions.

Evolution of the Lignin Chemical Structure during the Bioethanol Production Process and Its Inhibition to Enzymatic Hydrolysis

Abstract: To illuminate the lignin evolution after hydrogen peroxide presoaking prior to ammonia fiber expansion pretreatment (H-AFEX) pretreatment and enzymatic hydrolysis, ball-milled wood lignins were sep...

Stable and selective electrosynthesis of hydrogen peroxide and the electro-Fenton process on CoSe2 polymorph catalysts

Abstract: Electrochemical synthesis of hydrogen peroxide (H2O2) in acidic solution can enable the electro-Fenton process for decentralized environmental remediation, but robust and inexpensive electrocatalysts for the selective two-electron oxygen reduction reaction (2e− ORR) are lacking. Here, we present a joint computational/experimental study that shows both structural polymorphs of earth-abundant cobalt diselenide (orthorhombic o-CoSe2 and cubic c-CoSe2) are stable against surface oxidation and catalyst leaching due to the weak O* binding to Se sites, are highly active and selective for the 2e− ORR, and deliver higher kinetic current densities for H2O2 production than the state-of-the-art noble metal or single-atom catalysts in acidic solution. o-CoSe2 nanowires directly grown on carbon paper electrodes allow for the steady bulk electrosynthesis of H2O2 in 0.05 M H2SO4 with a practically useful accumulated concentration of 547 ppm, the highest among the reported 2e− ORR catalysts in acidic solution. Such efficient and stable H2O2 electrogeneration further enables the effective electro-Fenton process for model organic pollutant degradation.

A Highly Selective and Sensitive Chemiluminescent Probe for Real‐Time Monitoring of Hydrogen Peroxide in Cells and Animals

Abstract: Selective and sensitive molecular probes for hydrogen peroxide (H2 O2 ), which plays diverse roles in oxidative stress and redox signaling, are urgently needed to investigate the physiological and pathological effects of H2 O2 . A lack of reliable tools for in vivo imaging has hampered the development of H2 O2 mediated therapeutics. By combining a specific tandem Payne/Dakin reaction with a chemiluminescent scaffold, H2 O2 -CL-510 was developed as a highly selective and sensitive probe for detection of H2 O2 both in vitro and in vivo. A rapid 430-fold enhancement of chemiluminescence was triggered directly by H2 O2 without any laser excitation. Arsenic trioxide induced oxidative damage in leukemia was successfully detected. In particular, cerebral ischemia-reperfusion injury-induced H2 O2 fluxes were visualized in rat brains using H2 O2 -CL-510, providing a new chemical tool for real-time monitoring of H2 O2 dynamics in living animals.

Mesoporous Carbon Hollow Spheres as Efficient Electrocatalystsfor Oxygen Reduction to Hydrogen Peroxide in Neutral Electrolytes

Abstract: Hydrogen peroxide is a widely used and important chemical in industry. A two-electron electrochemical oxygen reduction reaction (2e– ORR) is a clean and on-site method for H2O2 production. Here, we...

Silicon Foliar Application Mitigates Salt Stress in Sweet Pepper Plants by Enhancing Water Status, Photosynthesis, Antioxidant Enzyme Activity and Fruit Yield.

Abstract: Silicon is one of the most significant elements in plants under abiotic stress, so we investigated the role of silicon in alleviation of the detrimental effects of salinity at two concentrations (1500 and 3000 ppm sodium chloride) in sweet pepper plants in two seasons (2018 and 2019). Our results indicated that relative water content, concentrations of chlorophyll a and b, nitrogen, phosphorus and potassium contents, number of fruits plant−1, fruit fresh weight plant−1 (g) and fruit yield (ton hectare−1) significantly decreased in salt-stressed sweet pepper plants as compared to control plants. In addition, electrolyte leakage, proline, lipid peroxidation, superoxide (O2−) and hydrogen peroxide (H2O2) levels, soluble sugars, sucrose, and starch content as well as sodium content significantly increased under salinity conditions. Conversely, foliar application of silicon led to improvements in concentrations of chlorophyll a and b and mineral nutrients, water status, and fruit yield of sweet pepper plants. Furthermore, lipid peroxidation, electrolyte leakage, levels of superoxide, and hydrogen peroxide were decreased with silicon treatments.

Progress of Electrochemical Hydrogen Peroxide Synthesisover Single Atom Catalysts

Abstract: The electrochemical oxygen reduction reaction (ORR) via the two-electron pathway provides a promising approach for the direct synthesis of hydrogen peroxide (H2O2) and its on-site utilizations. The...

Engineering Three-Dimensional (3D) Out-of-Plane Graphene Edge Sites for Highly-Selective Two-Electron Oxygen Reduction Electrocatalysis

Abstract: Selective two-electron oxygen reduction reaction (ORR) offers a promising route for hydrogen peroxide synthesis, and defective sp2-carbon-based materials are attractive, low-cost electrocatalysts f...

Scalable neutral H2O2 electrosynthesis by platinum diphosphide nanocrystals by regulating oxygen reduction reaction pathways.

Abstract: Despite progress in small scale electrocatalytic production of hydrogen peroxide (H2O2) using a rotating ring-disk electrode, further work is needed to develop a non-toxic, selective, and stable O2-to-H2O2 electrocatalyst for realizing continuous on-site production of neutral hydrogen peroxide. We report ultrasmall and monodisperse colloidal PtP2 nanocrystals that achieve H2O2 production at near zero-overpotential with near unity H2O2 selectivity at 0.27 V vs. RHE. Density functional theory calculations indicate that P promotes hydrogenation of OOH* to H2O2 by weakening the Pt-OOH* bond and suppressing the dissociative OOH* to O* pathway. Atomic layer deposition of Al2O3 prevents NC aggregation and enables application in a polymer electrolyte membrane fuel cell (PEMFC) with a maximum r(H2O2) of 2.26 mmol h−1 cm−2 and a current efficiency of 78.8% even at a high current density of 150 mA cm−2. Catalyst stability enables an accumulated neutral H2O2 concentration in 600 mL of 3.0 wt% (pH = 6.6). The synthesis of high concentration H2O2 from water and oxygen at moderate conditions could provide an on-site H2O2 source for medical and water purification applications. Here, authors show Al2O3-stabilized PtP2 nanocrystals to enable selective, stable and efficient neutral pH H2O2 production.

High-Efficiency Electrocatalysis of Molecular Oxygen toward Hydroxyl Radicals Enabled by an Atomically Dispersed Iron Catalyst

Abstract: Fenton catalysis represents the promising technology to produce super-active ·OH for tackling severe water environment pollution issues, whereas it suffers from low atomic efficiency, poor pH adapt...

Reaction-Based Luminescent Probes for Reactive Sulfur, Oxygen, and Nitrogen Species: Analytical Techniques and Recent Progress.

Abstract: Gasotransmitters and related reactive sulfur, oxygen, and nitrogen species such as nitric oxide (NO), hydrogen sul-fide (H2S), carbon monoxide (CO), hydrogen peroxide (H2O2) and downstream products like peroxynitrite (ONOO–), polysulfides (HSnH), hydroxyl radical (HO•), and azanone (nitroxyl, HNO) are produced under physiological condi-tions and impact cellular signaling and stress. Evolution-ary pressures have driven life to develop sophisticated mechanisms to control the formation and response to this complex reactive species interactome, making it a critical fulcrum that balances health and disease in human physiol-ogy. Driven by a need to understand and measure these types of reactive species, the last decade has witnessed ex-tensive research activity in developing reaction-based probes for optical detection and imaging of reactive sulfur, oxygen, and nitrogen species in living systems. – The cen-tral advantage of this approach is that it is compatible with living cells and animals, thereby enabling t...

Oxygen-Vacancy-Enhanced Peroxidase-like Activity of Reduced Co3O4 Nanocomposites for the Colorimetric Detection of H2O2 and Glucose.

Abstract: Colorimetric assays have drawn increasing research interest with respect to the quantitative detection of hydrogen peroxide (H2O2) based on artificial enzymes because of their advantages with respe...

Phosphorus-doped porous carbon nitride for efficient sole production of hydrogen peroxide via photocatalytic water splitting with a two-channel pathway

Abstract: The production of hydrogen peroxide (H2O2) by photocatalytic water splitting has attracted much attention due to the wide application of H2O2 as a multi-functional chemical. Most of the present photocatalysts require sacrificial agents and/or noble metal cocatalysts. Herein, we report that phosphorus-doped porous carbon nitride (CPN), as a metal-free photocatalyst, achieves the photocatalytic water splitting via a two-channel pathway (water oxidation reaction and oxygen reduction reaction) with high H2O2 yield of 1968 μmol g−1 h−1 (highest yield in current records without sacrificial agent) under room temperature and normal pressure without sacrificial agent and cocatalyst. The quantum efficiency of the sole production of H2O2 was measured to be 1.57% under wavelength λ = 420 nm and the solar energy conversion efficiency was determined to be 0.43%. In the present reaction system, the concentration of H2O2 can be up to 0.171% (wt%) in a one-batch reaction using 80 mg CPN catalyst (in 15 mL oxygen saturated H2O) after 36 h under visible light illumination. H2O2 obtained by this metal-free catalyst without adding a sacrificial agent is more conducive to subsequent purification in industrial production.

Graphene-Supported Single Nickel Atom Catalyst for Highly Selective and Efficient Hydrogen Peroxide Production.

Abstract: Hydrogen peroxide (H2O2) production by electrocatalytic two-electron oxygen reduction shows promise as a replacement for energy-intensive anthraquinone oxidation or H2/O2 direct synthesis. Here, we report on graphene-supported Ni single-atom (SA) electrocatalysts, which are synthesized by a simple surfactant-free reduction process with enhanced electrocatalytic activity and stability. Unlike conventional Ni nanoparticles or alloy catalysts, the well-dispersed Ni-SA sites lack adjacent Ni atoms. This structure promotes H2O2 production by a two-electron oxygen reduction pathway under an alkaline condition (pH = 13). This catalyst exhibited enhanced H2O2 selectivity (>94%) with a considerable mass activity (2.11 A mgNi-1 at 0.60 V vs reversible hydrogen electrode), owing to the presence of oxygen functional groups and isolated Ni sites. Density functional theory calculations provide insights into the role of this catalyst in optimizing the two-electron oxygen reduction reaction pathway with high H2O2 selectivity. This work suggests a new method for controlling reaction pathways in atomically dispersed non-noble catalysts.

pH-Independent Production of Hydroxyl Radical from Atomic H*-Mediated Electrocatalytic H2O2 Reduction: A Green Fenton Process without Byproducts.

Abstract: Hydroxyl radical (•OH) can hydroxylate or dehydrogenate organics without forming extra products and is thereby expediently applied in extensive domains. Although it can be efficiently produced through single-electron transfer from transition-metal-containing activators to hydrogen peroxide (H2O2), narrow applicable pH range, strict activator/H2O2 ratio requirement, and byproducts that are formed in the mixture with the background matrix necessitate the need for additional energy-intensive up/downstream treatments. Here, we show a green Fenton process in an electrochemical cell, where the electro-generated atomic H* on a Pd/graphite cathode enables the efficient conversion of H2O2 into •OH and subsequent degradation of organic pollutants (80% efficiency). Operando liquid time-of-fight secondary ion mass spectrometry verified that H2O2 activation takes place through a transition state of the Pd-H*-H2O2 adduct with a low reaction energy barrier of 0.92 eV, whereby the lone electron in atomic H* can readily cleave the peroxide bridge, with •OH and H2O as products (ΔGr = -1.344 eV). Using H+ or H2O as the resource, we demonstrate that the well-directed output of H* determines the pH-independent production of •OH for stable conversion of organic contaminants in wider pH ranges (3-12). The research pioneers a novel path for eliminating the restrictions that are historically challenging in the traditional Fenton process.