Promoting Piezocatalytic H2O2 Production in Pure Water by Loading Metal-Organic Cage-Modified Gold Nanoparticles on Graphitic Carbon Nitride

Piezocatalytic hydrogen peroxide (H₂O₂) production is a green synthesis method, but the rapid complexation of charge carriers in piezocatalysts and the difficulty of adsorbing substrates limit its performance. Here, metal-organic cage-coated gold nanoparticles are anchored on graphitic carbon nitride (MOC-AuNP/g-C₃N₄) via hydrogen bond to serve as the multifunctional sites for efficient H₂O₂ production. Experiments and theoretical calculations prove that MOC-AuNP/g-C₃N₄ simultaneously optimize three key parts of piezocatalytic H₂O₂ production: i) the MOC component enhances substrate (O₂) and product (H₂O₂) adsorption via host–guest interaction and hinders the rapid decomposition of H₂O₂ on MOC-AuNP/g-C₃N₄, ii) the AuNP component affords a strong interfacial electric field that significantly promotes the migration of electrons from g-C₃N₄ for O₂ reduction reaction (ORR), iii) holes are used for H₂O oxidation reaction (WOR) to produce O₂ and H⁺ to further promote ORR. Thus, MOC-AuNP/g-C₃N₄ can be used as an efficient piezocatalyst to generate H₂O₂ at rates up to 120.21 μmol g⁻¹ h⁻¹ in air and pure water without using sacrificial agents. This work proposes a new strategy for efficient piezocatalytic H₂O₂ synthesis by constructing multiple active sites in semiconductor catalysts via hydrogen bonding, by enhancing substrate adsorption, rapid separation of electron-hole pairs and preventing rapid decomposition of H₂O₂.     

Application of Si‐doped graphene as a metal‐free catalyst for decomposition of formic acid: A theoretical study

Using density functional theory calculations, the adsorption and catalytic decomposition of formic acid (HCOOH) over Si‐doped graphene are investigated. For the stable adsorption geometries of HCOOH over Si‐doped graphene, the electronic structure properties are analyzed by adsorption energy, density of states, and charge density difference. A comparison of the reaction pathways reveals that both dehydration and dehydrogenation of HCOOH can occur over Si‐doped graphene. The estimated reaction energies and the activation barriers suggest that for the dehydration of HCOOH on the Si‐doped graphene, the rate‐controlling step is H + OH → H₂O reaction. For the dehydrogenation of HCOOH, the rate‐determining step is the breaking of the C? H bond of the HCOO group to form the CO₂ molecule and the atomic H. Our results reveal that the low cost Si‐doped graphene can be used as an efficient nonmetal catalyst for O? H bond cleavage of HCOOH. © 2015 Wiley Periodicals, Inc.     

Catalytic decomposition of hydrogen peroxide on fine particle ferrites and cobaltites

The kinetics of heterogeneous decomposition of hydrogen peroxide on fine particle ferrites, MFe₂O₄ and cobaltites, MCo₂O₄, where M=Mn, Fe, Co, Ni, Zn and Mg, have been investigated. The decomposition of H₂O₂ was found to be first order at low concentration (0·3%) and zero order at high concentration (30%) of H₂O₂. The catalytic activity of cobaltites on the decomposition of H₂O₂ is found to be better than ferrites. The observed catalytic behaviour of ferrites and cobaltites has been attributed to their fine particle nature, large surface area and electronic structure.     

H2O和OH在UO(100)表面吸附的密度泛函研究

运用密度泛函理论中的广义梯度近似(GCA)的PW91方法结合周期性平板模型,研究了H2O分子和OH在UO(100)表面上的吸附.通过对不同吸附位的吸附能和几何结构参数的计算和比较发现:水分子在UO(100)表面的吸附为化学吸附,水分子平面与UO(100)表面夹角为15°的吸附构型最稳定,吸附能最大,近89 kJ·mol-1.对H2O吸附前后的态密度分析可知,H2O通过其O原子的P轨道与底物U原子的d轨道作用.本文还进一步探讨H2O在UO(100)表面的解离机理.     

Effect of hydrogen gas impurities on the hydrogen dissociation on iron surface

A small addition of oxygen to hydrogen gas is known to mitigate the hydrogen embrittlement (HE) of steels. As atomic hydrogen dissolution in steels is responsible for embrittlement, catalysis of molecular hydrogen dissociation by the steel surface is an essential step in the embrittlement process. The most probable role of oxygen in mitigating HE is to inhibit the reactions between molecular hydrogen and the steel surface. To elucidate the mechanism of such surface reaction of hydrogen with the steel in the presence of oxygen, hydrogen, and oxygen adsorption, dissociation, and coadsorption on the Fe(100) surface were investigated using density functional theory. The results show that traces of O₂ would successfully compete with H₂ for surface adsorption sites due to the grater attractive force acting on the O₂ molecule compared to H₂. The H₂ dissociation would be hindered on iron surfaces with predissociated oxygen. Prompted by the notable results for H₂ + O₂, other practical systems were considered, that is, H₂ + CO and CH₄. Calculations were performed for the CO chemisorption and H₂ dissociation on iron surface with predissociated CO, as well as, CH₄ surface dissociation. The results indicate that CO inhibition of H₂ dissociation proceeds via similar mechanism to O₂ induced inhibition, whereas CH₄ traces in the H₂ gas have no effect on H₂ dissociation. © 2014 Wiley Periodicals, Inc.     

A Facile Preparation of H2O2 Sensors Using Layer‐by‐Layer Deposited Thin Films Composed of Poly(ethyleneimine) and Carboxymethyl Cellulose as Matrices for Immobilizing Hemin

A layer‐by‐layer (LbL) thin film composed of poly(ethyleneimine) (PEI) and carboxymethyl cellulose (CMC) was prepared on the surface of a gold (Au) disk electrode and the LbL layer was impregnated with hemin to fabricate amperometric hydrogen peroxide (H₂O₂) sensors. Hemin can be easily immobilized in the LbL layer by immersing the LbL film‐coated electrode in the hemin solution. The hemin‐modified electrode thus prepared exhibited an amperometric response to H₂O₂ on the basis of the electrochemical reduction catalyzed by hemin. The output current of the hemin‐modified electrode depended on the concentration of H₂O₂ over the range of 0.005–1.0 mM. Thus, the LbL film composed of PEI and CMC was found to be an excellent material for the facile preparation of hemin‐based H₂O₂ sensors.     

Molecular Level Modulation of Anthraquinone-containing Resorcinol-formaldehyde Resin Photocatalysts for H2O2 Production with Exceeding 1.2 % Efficiency

Designing polymeric photocatalysts at the molecular level to modulate the photogenerated charge behavior is a promising and challenging strategy for efficient hydrogen peroxide (H₂O₂) photosynthesis. Here, we introduce electron-deficient 1,4-dihydroxyanthraquinone (DHAQ) into the framework of resorcinol-formaldehyde (RF) resin, which modulates the donor/acceptor ratio from the perspective of molecular design for promoting the charge separation. Interestingly, H₂O₂ can be produced via oxygen reduction and water oxidation pathways, verified by isotopic labeling and in situ characterization techniques. Density functional theory (DFT) calculations elucidate that DHAQ can reduce the energy barrier for H₂O₂ production. RF-DHAQ exhibits excellent overall photosynthesis of H₂O₂ with a solar-to-chemical conversion (SCC) efficiency exceeding 1.2 %. This work opens a new avenue to design polymeric photocatalysts at the molecular level for high-efficiency artificial photosynthesis.     

Theoretical studies of adsorption property on Ir_4/MgO and Ir_4/γ-Al_2O_3

The adsorption properties of atomic and molecular species on Ir4/MgO and Ir4/γ-Al2O3 have been systematically studied by means of planewave density functional theory(DFT)calculations using the periodic boundary conditions.The binding energies of these species were ordered as follows:H2O相似文献   

Heterogeneous Uptake of Hydrogen Peroxide on Mineral Oxides

The interaction of mineral oxides (α-Al₂O₃, MgO, Fe₂O₃, and SiO₂) with hydrogen peroxide was investigated using the Knudsen cell reactor. The initial reactive uptake coefficients for the commercially available powders are measured as (1.00±0.11)×10^-4 for α-Al₂O₃, (1.66±0.23)×10^-4 for MgO, (9.70±1.95)×10^-5 for Fe₂O₃, and (5.22±0.9)×10^-5 for SiO₂. These metal oxide powders exhibit some catalytic behavior toward the decomposition of hydrogen peroxide excluding SiO₂. H₂O₂ can be destroyed on Fe₂O₃ surface and O₂ is formed. The experimental results suggest that the heterogeneous loss on mineral surface can represent an important sink of hydrogen peroxide.     

Photo-Driven Quasi-Topological Transformation Exposing Highly Active Nitrogen Cation Sites for Enhanced Photocatalytic H2O2 Production

Herein, the exposure of highly-active nitrogen cation sites has been accomplished by photo-driven quasi-topological transformation of a 1,10-phenanthroline-5,6-dione-based covalent organic framework (COF), which contributes to hydrogen peroxide (H₂O₂) synthesis during the 2-electron O₂ photoreduction. The exposed nitrogen cation sites with photo-enhanced Lewis acidity not only act as the electron-transfer motor to adjust the inherent charge distribution, powering continuous and stable charge separation, and broadening visible-light adsorption, but also providing a large number of active sites for O₂ adsorption. The optimal catalyst shows a high H₂O₂ production rate of 11965 μmol g⁻¹ h⁻¹ under visible light irradiation and a remarkable apparent quantum yield of 12.9 % at 400 nm, better than most of the previously reported COF photocatalysts. This work provides new insights for designing photo-switchable nitrogen cation sites as catalytic centers toward efficient solar to chemical energy conversion.     

Surface interaction of H2O and H2S onto Ca12O12 nanocluster: Quantum‐chemical analyses

To find the selectivity of H₂S, we explicate the adsorption properties of water (H₂O) and hydrogen sulfide (H₂S) molecules on the external surfaces of free Ca₁₂O₁₂ nanocages using the density functional theory method. More specifically, binding energies, natural bond orbital charge transfer, dipole moment, molecular electrostatic potential, frontier molecular orbitals, density of states, and global indices of activities are calculated to deeply understand the impacts of the aforementioned molecules on the electronic and chemical properties of Ca₁₂O₁₂ nanocages. Our theoretical findings indicate that although H₂O seems to be adsorbed in molecular form, the H₂S molecule is fully dissociated during the adsorption process because of the weak bond between sulfur and hydrogen atoms of the molecule. Interestingly, the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap of the nanocage is decreased by 1.87 eV upon H₂S adsorption, indicating that the electrical conductivity of the nanocage is strongly increased by the dissociation process. In addition, the values of softness and electrophilicity for the H₂S‐Ca₁₂O₁₂ complex are higher than those for the free nanocage. Our results suggest that Ca₁₂O₁₂ nanoclusters show promise in the adsorption/dissociation of H₂S molecules, which can be used further for designing its selective sensor.     

Effect of the chemical and structural modification of CMK-3 mesoporous carbon molecular sieve on hydrogen adsorption

The effect of the conditions of postsynthetic modification of CMK-3 carbon mesoporous molecular sieves on their structural and adsorption properties was studied. The specific surface, volume, pore size, and hydrogen adsorption are markedly enhanced upon activation of CMK-3 by thermal, steam, and chemical treatment using H₂, CO₂, H₂O₂, and HNO₃. Analysis of the occupancy density of the mesopore surface indicated increased hydrogen adsorption capacity of the hydrogen-activated carbon surface of CMK-3. Hydrogen adsorption is increased from 1.20 to 2.23 mass % at 1 atm and 77 K by steam treatment. This effect may be employed to create efficient carbon MMS adsorbents, including composite adsorbents, for the accumulation and storage of hydrogen at high pressure (adsorption >6 mass %).     

Adsorption and decomposition of diacylic peroxides on the surfaces of dispersed oxides

The adsorption of oligo(sebacoyl peroxide) on Aerosil and MgO and benzoyl peroxide on Fe₂O₃, Cr₂O₃, and V₂O₅ has been studied. It has been established that peroxide adsorption on the considered adsorbents is described by the Langmuir equation. Benzoyl-peroxide adsorption increases in the series Fe₂O₃ < Cr₂O₃ < V₂O₅. The process of thermal decomposition of peroxides in the presence of the listed adsorbents has been studied. The overall reaction of peroxide decomposition comprises two components, i.e., the decomposition processes occurring in a solution and on an adsorbent surface. Kinetic and activation parameters of the thermal-decomposition reactions in the solutions and on the surfaces have been determined.     

New data on the mechanism of hydrogen peroxide decomposition in acetic acid in the presence of vanadyl and cobalt (II) acetylacetonates

The process of catalytic hydrogen peroxide decomposition in acetic acid in the presence of vanadyl and cobalt (II) acetylacetonates was studied using modern spectroscopic and kinetic techniques. The formation of intermediates during the catalytic decomposition of hydrogen peroxide in the presence of VO(acac)₂ was observed using UV—Vis and ESR spectroscopy. The decomposition of H₂O₂ occurs both catalytically and via the radical route.     

Parameters of Li2O2 · H2O crystallization from the LiOH-H2O2-H2O ternary system

The decomposition kinetics of peroxide products contained in the liquid phase of the LiOH-H₂O₂-H₂O ternary system were studied, and the applicability of the solubility method to studying this system was demonstrated for hydrogen peroxide concentrations in the liquid phase from 2 to 6 wt % and temperatures of 21–33°C. The stabilizing influence of solid Li₂O₂ · H₂O on hydrogen peroxide decomposition was demonstrated. The temperature and concentration boundaries of existence were determined for the Li₂O₂ · H₂O phase, whose identity was verified by chemical analysis and qualitative X-ray powder diffraction analysis.     

Kinetics and mechanisms of decomposition reaction of hydrogen peroxide in presence of metal complexes

Hydrogen peroxide was discovered in 1818 and has been used in bleaching for over a century [ 1 ]. H₂O₂ on its own is a relatively weak oxidant under mild conditions: It can achieve some oxidations unaided, but for the majority of applications it requires activation in one way or another. Some activation methods, e.g., Fenton's reagent, are almost as old [ 2 ]. However, by far the bulk of useful chemistry has been discovered in the last 50 years, and many catalytic methods are much more recent. Although the decomposition of hydrogen peroxide is often employed as a standard reaction to determine the catalytic activity of metal complexes and metal oxides [ 3 , 4 ], it has recently been extensively used in intrinsically clean processes and in end‐of‐pipe treatment of effluent of chemical industries [ 5 , 6 ]. Furthermore, the adoption of H₂O₂ as an alternative of current industrial oxidation processes offer environmental advantages, some of which are (1) replacement of stoichiometric metal oxidants, (2) replacement of halogens, (3) replacement or reduction of solvent usage, and (4) avoidance of salt by‐products. On the other hand, wasteful decomposition of hydrogen peroxide due to trace transition metals in wash water in the fabric bleach industry, was also recognized [ 7 ]. The low intrinsic reactivity of H₂O₂ is actually an advantage, in that a method can be chosen which selectively activates it to perform a given oxidation. There are three main active oxidants derived from hydrogen peroxide, depending on the nature of the activator; they are (1) inorganic oxidant systems, (2) active oxygen species, and (3) per oxygen intermediates. Two general types of mechanisms have been postulated for the decomposition of hydrogen peroxide in the presence of transition metal complexes. The first is the radical mechanism (outer sphere), which was proposed by Haber and Weiss for the Fe(III)‐H₂O₂ system [ 8 ]. The key features of this mechanism were the discrete formation of hydroxyl and hydroperoxy radicals, which can form a redox cycle with the Fe(II)/Fe(III) couple. The second is the peroxide complex mechanism, which was proposed by Kremer and Stein [ 9 ]. The significant difference in the peroxide complex mechanism is the two‐electron oxidation of Fe(III) to Fe(V) with the resulting breaking of the peroxide oxygen‐oxygen bond. It is our intention in this article to briefly summarize the kinetics as well as the mechanisms of the decomposition of hydrogen peroxide, homogeneously and heterogeneously, in the presence of transition metal complexes. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 643–666, 2000     

Promoting Solar-driven Hydrogen Peroxide Production over Thiazole-based Conjugated Polymers via Generating and Converting Singlet Oxygen

Solar-driven synthesis of hydrogen peroxide (H₂O₂) from water and air provides a low-cost and eco-friendly alternative route to the traditional anthraquinone method. Herein, four thiazole-based conjugated polymers (Tz-CPs: TTz , BTz , TBTz and BBTz ) are synthesized via aldimine condensation. BBTz exhibits the highest H₂O₂ production rate of 7274 μmol g⁻¹ h⁻¹ in pure water. Further, the reaction path is analyzed by electron paramagnetic resonance (EPR), in situ diffuse reflectance infrared Fourier transform (DRIFT) and theoretical calculation, highlighting the prominent role of singlet oxygen (¹O₂). The generation of ¹O₂ occurs through the oxidation of superoxide radical (⋅O₂⁻) and subsequent conversion into endoperoxides via [4+2] cycloaddition over BBTz , which promotes charge separation and reduces the barrier for H₂O₂ production. This work provides new insight into the mechanism of photocatalytic O₂ reduction and the molecular design of superior single-polymer photocatalysts.     

A Theoretical Study of the Interaction of Hydrogen and Oxygen with Palladium or Gold Adsorbed on Pyridine‐Like Nitrogen‐Doped Graphene

The interaction of H₂ and O₂ molecules in the presence of nitrogen‐doped graphene decorated with either a palladium or gold atom was investigated by using density functional theory. It was found that two hydrogen molecules were adsorbed on the palladium atom. The interaction of these adsorbed hydrogen molecules with two oxygen molecules generates two hydrogen peroxide molecules first through a Eley–Rideal mechanism and then through a Langmuir–Hinshelwood mechanism. The barrier energies for this reaction were small; therefore, we expect that this process may occur spontaneously at room temperature. In the case of gold, a single hydrogen molecule is adsorbed and dissociated on the metal atom. The interaction of the dissociated hydrogen molecule on the surface with one oxygen molecule generates a water molecule. The competitive adsorption between oxygen and hydrogen molecules slightly favors oxygen adsorption.     

Pd(111), Pd(100)及Pd(110)表面H2和O2直接合成H2O2的密度泛函理论研究

采用周期性密度泛函理论研究了H₂和O₂在Pd(111),Pd(100)及Pd(110)表面上直接合成H₂O₂的反应机理,对反应的主要基元步骤进行了计算和分析.结果表明,Pd(111)表面对H₂O₂直接合成的催化选择性最好,表面原子密度较低的Pd(100)表面和Pd(110)表面上含有O-O键的表面物种解离严重,不利于H₂O₂的生成.H₂O₂的选择性与含有O-O键表面物种的O-O键能和表面物种的结合能有关.含有O-O键的表面物种在表面的结合能越大,越容易发生解离,不利于形成H₂O₂.     

Differential scanning calorimetry of hydrogen peroxide and hydrogen peroxide-treated lignocellulose. I. Ambient pressure conditions

The decomposition reaction of aqueous solutions of hydrogen peroxide was examined by DSC at ambient pressure, and the heat of evaporation of H₂O₂ was determined. The reaction parameters for the oxidation reaction of lignocellulose (wood powder) with hydrogen peroxide were also examined. The pans made from gold and alodined (pyrophosphate /fluoride treated) aluminum were unsuitable for the work due to surface catalysis, in contrast to pure aluminum which proved to be acceptable within the temperature range examined. In pans made from pure aluminum, the reaction between lignocellulose and hydrogen peroxide takes place after the latter evaporates, i.e. it represents a gas—solid reaction.