H2O2 Oxidation Research Articles

Nonheme iron catalyst mimics heme-dependent haloperoxidase for efficient bromination and oxidation.

The [Fe]/H2O2 oxidation system has found wide applications in chemistry and biology. Halogenation with this [Fe]/H2O2 oxidation protocol and halide (X-) in the biological system is well established with the identification of heme-iron-dependent haloperoxidases. However, mimicking such halogenation process is rarely explored for practical use in organic synthesis. Here, we report the development of a nonheme iron catalyst that mimics the heme-iron-dependent haloperoxidases to catalyze the generation of HOBr from H2O2/Br- with high efficiency. We discovered that a tridentate terpyridine (TPY) ligand designed for Fenton chemistry was optimal for FeBr3 to form a stable nonheme iron catalyst [Fe(TPY)Br3], which catalyzed arene bromination, Hunsdiecker-type decarboxylative bromination, bromolactonization, and oxidation of sulfides and thiols. Mechanistic studies revealed that Fenton chemistry ([Fe]/H2O2) might operate to generate hydroxyl radical (HO•), which oxidize bromide ion [Br-] into reactive HOBr. This nonheme iron catalyst represents a biomimetic model for heme-iron-dependent haloperoxidases with potential applications in organic synthesis, drug discovery, and biology.

Selective photooxidation of methane to C1 oxygenates by constructing heterojunction photocatalyst with mild oxidation ability

Selective photocatalytic aerobic oxidation of methane to value-added chemicals offers a promising pathway for sustainable chemical industry, yet remains a huge challenge owing to the consecutive overoxidation of primary products. Here, a type II heterojunction were constructed in Ag-AgBr/ZnO to reduce the oxidation potential of stimulated holes and prevent the undesirable CH4 overoxidation side reactions. For photocatalytic oxidation of methane under ambient temperature, the products yield of 1499.6 μmol gcat−1 h−1 with a primary products selectivity of 77.9% was achieved over Ag-AgBr/ZnO, which demonstrate remarkable improvement compared to Ag/ZnO (1089.9 μmol gcat−1 h−1, 40.1%). The superior activity and selectivity result from the promoted charge separation and the redox potential matching with methane activation after introducing AgBr species. Mechanism investigation elucidated that the photo-generated holes transferred from the valence band of ZnO to that of AgBr, which prevent H2O oxidation and enhance the selective generation of •OOH radical.

Cu Anchored Carbon Nitride (Cu/CN) Catalyzes Selective Oxidation of Thiol by Controlling Reactive Oxygen Species Generation.

Production of H2O2 using heterogeneous semiconductor photocatalysts has emerged as an ecofriendly and practical approach across various applications, ranging from environmental detoxification to fuel cells and chemical synthesis. Extensive efforts have been devoted to engineering semiconductors to enhance their catalytic capabilities for H2O2 production. However, in chemical synthesis, the utilization of the potent oxidant H2O2 can present challenges in selectively oxidizing organic compounds. In this study, we introduce copper atoms into carbon nitride (Cu/CN), facilitating the generation of hydroperoxyl radicals (·OOH) as primary reactive oxidants and offering reaction conditions entirely devoid of H2O2 via the Fenton reaction. Cu/CN demonstrates selective oxidation of thiols to disulfides, in contrast to other current heterogeneous photocatalysts that yield undesired overoxidized side products, such as thiosulfinate and thiosulfonate. Cu/CN's controllable capacity for specific ROS generation, broad substrate scopes, and recyclability empower greener and highly selective photooxidation of organic compounds.

Modulating the electronic structure of Mn promotes singlet oxygen generation from electrochemical oxidation of H2O via O-O coupling

Selectively catalytic conversion H2O into singlet oxygen (1O2) without additional oxidants is considered as an economic-efficient method for organic pollutants degradation. However, H2O are more consistent with the spin state of 1O2 than common oxygen (O2), retarding the kinetics of spin transition-induced reaction between O2 and 1O2. Herein, we report an unprecedented 1O2 mediated electrocatalytic oxidation process, which allows O–O coupling for 1O2 evolution from H2O over CrMn@C anode. The electron occupancy (eg) of CrMn@C (0.89) is very close to the optimal eg (0.95) of manganese-based materials reported in the literature, which facilitates the activation of H2O on surface. Mn(Mn0.193Cr1.808)O4-Mn in CrMn@C electrode significantly promotes the activation of H2O to produce *O, followed by coupling of *O at adjacent sites to produce *OO, which further spontaneously forms 1O2. And H218O isotope experiments provide direct evidence for the production of 1O2 directly from H2O. Consequently, the production of 1O2 is enhanced with the yield of 785.6 μmol·L−1. Such 1O2-dominated electrocatalytic oxidation system can achieve efficient removal of electron-rich pollutant (bisphenol A) and improve the biodegradability of pharmaceutical wastewater (from 0.17 to 0.39).

Phenolic acid-containing compounds enhanced Fe3+/peroxides processes for efficient removal of sulfamethoxazole in surface waters

Sulfamethoxazole (SMX) in surface waters has raised widespread concerns due to its potential environmental and biological hazards. In this study, the performance, mechanism, and environmental application of phenolic acid-containing compounds (PACCs) enhanced Fe3+/peroxides processes for SMX degradation were investigated. PACCs with two Ar-OH groups exhibited the lowest toxicity and the best enhancement performance (65%–66% of PDS, 47%–58% of PMS and 61%–63% of H2O2), which were attributed to the excellent chelating and reducing ability towards Fe3+. Free radicals played the predominant role in PDS (37% of SO4−·, 34% of ·OH), PMS (37% of SO4−·, 35% of ·OH) and H2O2 (61% of ·OH) oxidation processes. FeIVO2+ play a non-negligible role in PDS and PMS processes (ŋ[PMSO2] = 52%–80% and ŋ[PMSO2] = 59%–72%). PDS and PMS processes were suitable for a pH range of 3.0–9.0, while the H2O2 process was 3.0–10.0. PDS and PMS processes exhibited stronger resistance to the common anions in surface waters. PMS process exhibited higher adaptability to surface waters quality (92%–98%). This study provides a novel approach for enhancing the degradation of SMX in natural surface waters.

Disruptions of rpiAB Genes Encoding Ribose-5-Phosphate Isomerases in E. coli Increases Sensitivity of Bacteria to Antibiotics.

In Escherichia coli cells, the main enzymes involved in pentose interconversion are ribose-5-phosphate isomerases RpiA and RpiB and ribulose-5-phosphate epimerase Rpe. The inactivation of rpiAB limits ribose-5-phosphate (R5P) synthesis via the oxidative branch of the pentose phosphate pathway (PPP) and unexpectedly results in antibiotic supersensitivity. This type of metabolism is accompanied by significant changes in the level of reducing equivalents of NADPH and glutathione, as well as a sharp drop in the ATP pool. However, this redox and energy imbalance does not lead to the activation of the soxRS oxidative stress defense system but the increased sensitivity to oxidants paraquat and H2O2. The deletion of rpiAB leads to a significant increase in the activity of transketalase (Tkt), a key enzyme of the nonoxidative branch of the PPP and increased sensitivity to ribose added in the growth medium. The phenotype of supersensitivity of rpiAB to antibiotics and ribose can be suppressed by activating the utilization of sedoheptulose-7-phosphate, which originates from R5P, to LPS synthesis or limitation of nucleoside catabolism by the inactivation of the DeoB enzyme, responsible for conversion of ribose-1-phospate to R5P. Our results indicate that the induction of unidirectional synthesis of R5P is the cause of supersensitivity to antibiotics in rpiAB mutant.

Anticorrosive and Antibacterial Evaluation of ZnO Nanoscale Sheets Electrosynthesized onto Ti6Al4V and Nitinol Alloys Previously Modified by Chemical Oxidation in H2O2

Anticorrosive and Antibacterial Evaluation of ZnO Nanoscale Sheets Electrosynthesized onto Ti6Al4V and Nitinol Alloys Previously Modified by Chemical Oxidation in H2O2

Dual‐Site NiO/Bi3O4Br Heterojunction Catalyst for High‐Efficiency CO2‐to‐CH4 Conversion

AbstractSolar light‐driven conversion of CO2 into chemicals with high calorific value is regarded as an upcoming carbon utilization technology for alleviating the energy crisis. This technique faces the challenge of low CO2 conversion and product yield due to charge recombination in the catalyst. In this paper, a dual‐reaction site heterojunction catalyst was designed and fabricated by combining NiO with Bi3O4Br nanosheets, for the separation of CO2 reduction and H2O oxidation semireactions, which effectively promoted electrons and holes separation. The resulting catalyst exhibited a high CH4 production rate (8.12 µmol/g) and selectivity (94.69%). Electron distribution and band structure were investigated to explain the satisfactory catalytic performance. In addition, combining the in‐situ DRIFTS results, a formic acid‐intermediated CO2‐to‐CH4 reaction pathway was proposed. This work aims to pave the way for CH4 production via CO2 photoreduction with high efficiency and selectivity.

Wet oxidative removal of low-valent sulfur by addition of H2O2 to Bayer fluid

ABSTRACT The presence of sulfur in sodium aluminate solution can disrupt the Bayer process in alumina production. H2O2 is used as an oxidant to convert low-valent sulfur (S2−) into high-valent sulfur (i.e. S2O3 2−, SO3 2−, and SO4 2−). This paper combines thermodynamic calculations and experimentation to propose the mechanism of the oxidation reaction between H2O2 and different valences of sulfur (i.e. S2O3 2−, SO3 2−, and SO4 2−) in sodium aluminate solution with the oxidation effect of S2− being the most obvious. By studying the oxidation effect of H2O2 dosage, oxidation time, and oxidation temperature on different valences of sulfur in sodium aluminate solution, it was found that the removal rate of S2− reached 91.85% with 9% H2O2 dosage, 260 °C oxidation temperature, and 60 min oxidation time. The experimental results were consistent with the thermodynamic calculations. Finally, the reaction between H2O2 and different valences of sulfur in sodium aluminate solution was described in detail, providing theoretical support for the desulfurisation of high-sulfur bauxite in the production of alumina through the Bayer process.

Prolonging Charge Carrier Lifetime via Intraband Defect Levels in S-Scheme Heterojunctions for Artificial Photosynthesis.

S-scheme heterostructure photocatalysts, distinguished by unique charge-transfer pathways and exceptional catalytic redox capabilities, have found widespread applications in addressing challenging chemical processes, including the photocatalytic reduction of CO2 with a high reaction barrier. Nevertheless, the influence of intraband defect levels within S-scheme heterojunctions on charge separation, carrier lifetime, and surface catalytic reactions has, for the most part, been overlooked. Herein, we develop a tunable defect-level-assisted strategy to construct an electron reservoir, effectively prolonging the lifetime of charge carriers through the rapid capture and gradual release of photoelectrons within WO3-x/In2S3 S-scheme heterojunctions, as authenticated by femtosecond transient absorption spectroscopy and theoretical simulations. The surface photoredox mechanism, unraveled by Gibbs free energy calculations, demonstrates that oxygen-vacancy-induced defect states in WO3-x/In2S3 heterojunctions unlock the rate-determining H2O oxidation into free oxygen molecules by forming metastable oxygen intermediates, contributing to the facilitation of H2O photooxidation. This distinct role, combined with the extended carrier lifetime, results in boosted CO2 photoreduction with nearly 100 % CO selectivity in the absence of any photosensitizer or scavenger. Our work sheds light on the role of controllable defect levels in governing charge transfer dynamics within S-scheme heterojunctions, thereby inspiring the development of more advanced photocatalysts for artificial photosynthesis.

Polydopamine-coated hollow carbon nitride as a full-spectral response photocatalyst for efficient H2O2 production via redox dual pathways

Achieving rapid and highly selective photocatalytic production of H2O2 from H2O and O2 over carbon nitride (CN) continues to pose a significant challenge. Here, a polydopamine (PDA) cover-layer modified hollow carbon nitride (HCP) is prepared to address this issue. Incorporating PDA not only introduces active site for O2 reduction, but also optimizes the Gibbs free energy for the formation of *OH intermediate during H2O oxidation. Additionally, the excellent light absorption and electronic mobility properties of PDA also contribute to the optimized features of HCP-24, resulting in a broad response across the spectrum and efficiently facilitates the generation of H2O2 through both O2 reduction and H2O oxidation pathways. Notably, HCP-24 demonstrates a significantly enhanced H2O2 evolution rate, achieving 5.5 times higher production (116.25 μmol g−1 h−1) compared to pristine CN (20.95 μmol g−1 h−1). This research provides valuable insights for the advancement of efficient catalysts for the photocatalytic generation of H2O2.

Simultaneous Photocatalytic CO2 Reduction and H2O Oxidation Under Non-Sacrificial Ambient Conditions.

The utilization of CO2, H2O, and solar energy is regarded as a sustainable route for converting CO2 into chemical feedstocks, paving the way for carbon neutrality and reclamation. However, the simultaneous photocatalytic CO2 reduction and H2O oxidation under non-sacrificial ambient conditions is still a significant challenge. Researchers have carried out extensive exploration and achieved dramatic developments in this area. In this review, we first primarily elucidate the principles of two half-reactions in the photocatalytic conversion of CO2 with H2O, i. e., CO2 reduction by the photo-generated electrons and protons, and H2O oxidation by the photo-generated holes without sacrificial agents. Subsequently, the strategies to promote two half-reactions are summarized, including the vacancy/facet/morphology design, adjacent redox site construction, and Z-scheme heterojunction development. Finally, we present the advanced in situ characterizations and future perspectives in this field. This review aims to provide fresh insights into effectively simultaneous photocatalytic CO2 reduction and H2O oxidation under non-sacrificial ambient conditions.

Stenosing Crohn’s disease patients display gut autophagy/oxidative stress imbalance

In this pilot study, we assessed the role of autophagy in Crohn’s Disease (CD), particularly in patients with a stenosing phenotype. Through the analysis of biopsied specimens from 36 patients, including 11 controls and 25 CD patients, categorized into inflammatory and stenosing groups, we identified a significant reduction in the autophagosomal marker Lc3b-II in patients with active inflammation and stenosis. This was paralleled by an increase in oxidative stress markers, including sNOX2-dp and H2O2, and a decrease in the antioxidant capacity measured by HBA, suggesting an imbalance in autophagy and oxidative stress mechanisms. Additionally, our findings show a correlation between autophagy markers and oxidative stress levels, indicating that autophagy dysfunction may play a pivotal role in CD and in the progression of a stenosing disease phenotype, by failing to eliminate detrimental molecules and pathogenic bacteria, thereby promoting fibrosis. This study is the first to demonstrate in vivo autophagy inhibition in stenosing CD patients and suggests that stimulating autophagic processes could offer a new avenue for the prevention and treatment of intestinal fibrosis in CD. Our results highlight the importance of exploring the interactions between autophagy, the fibrotic process, and the inflammatory cascade, opening avenues for potential therapeutic interventions in CD management.

Pairing Oxygen Reduction and Water Oxidation for Dual‐Pathway H2O2 Production

AbstractHydrogen peroxide (H2O2) is a crucial chemical applied in various industry sectors. However, the current industrial anthraquinone process for H2O2 synthesis is carbon‐intensive. With sunlight and renewable electricity as energy inputs, photocatalysis and electrocatalysis have great potential for green H2O2 production from oxygen (O2) and water (H2O). Herein, we review the advances in pairing two‐electron O2 reduction and two‐electron H2O oxidation reactions for dual‐pathway H2O2 synthesis. The basic principles, paired redox reactions, and catalytic device configurations are introduced initially. Aligning with the energy input, the latest photocatalysts, electrocatalysts, and photo‐electrocatalysts for dual‐pathway H2O2 production are discussed afterward. Finally, we outlook the research opportunities in the future. This minireview aims to provide insights and guidelines for the broad community who are interested in catalyst design and innovative technology for on‐site H2O2 synthesis.

Pairing Oxygen Reduction and Water Oxidation for Dual-Pathway H2O2 Production.

Hydrogen peroxide (H2O2) is a crucial chemical applied in various industry sectors. However, the current industrial anthraquinone process for H2O2 synthesis is carbon-intensive. With sunlight and renewable electricity as energy inputs, photocatalysis and electrocatalysis have great potential for green H2O2 production from oxygen (O2) and water (H2O). Herein, we review the advances in pairing two-electron O2 reduction and two-electron H2O oxidation reactions for dual-pathway H2O2 synthesis. The basic principles, paired redox reactions, and catalytic device configurations are introduced initially. Aligning with the energy input, the latest photocatalysts, electrocatalysts, and photo-electrocatalysts for dual-pathway H2O2 production are discussed afterward. Finally, we outlook the research opportunities in the future. This minireview aims to provide insights and guidelines for the broad community who are interested in catalyst design and innovative technology for on-site H2O2 synthesis.

High-efficiency treatment of oily wastewater by photocatalytic in-situ Fenton oxidation under visible light

Oily wastewater poses a significant threat to environmental safety, and complex water environments have caused numerous disturbances in oil pollution treatment. Therefore, constructing composite systems is expected to improve oil pollution treatment efficiency. This study developed an efficient photocatalytic in-situ Fenton oxidation system, HTCC@ZnFe2O4/Ag3PO4 (HZFA), loaded onto polypropylene spheres (PP) for treating oily wastewater (diesel oil) in complex environments. The built-in electric field of HZFA promotes photogenerated carrier separation, enhancing photocatalytic effect. At a diesel concentration of 3.2 g/L, performance of HZFA degraded diesel in deionized water and artificial seawater (ASW) were 60.80 % and 52.62 %, respectively, much higher than a pure photocatalytic system (13.84 %). The dual system compensated for single system defects like instability and narrow application range, achieving 8 effective cycles in ASW. Experimental and computational results showed that high oxidation and reduction potentials in the dual system promoted hydrocarbon oxidative degradation and H2O2 production/activation. The amount of OH, O2−, and h+ produced in different environments is fundamental for the stabilization of catalytic degradation by HZFA. GC–MS and DFT analysis revealed potential oxidative chain-breaking processes for diesel components like alkanes, aromatics, alcohols, acids, aldehydes, and esters. This study offers a new method for green and efficient oily wastewater treatment, overcoming inherent defects of traditional Fenton, with broad application prospects.

Hydroxylated SiO2-modified {0 0 1}-TiO2 nanosheets as a surface multifunctional photocatalyst for enhanced degradation of gaseous toluene

The relatively weak activity and serious deactivation of anatase TiO2 nanosheet catalysts with highly exposed {001} facets ({001}-TiO2) limits its wide application in photocatalytic degradation of gaseous pollutants. Herein, we propose a hybrid photocatalyst composed of {001}-TiO2 and SiO2 with numerous hydroxyl groups (denoted as {001}-TiO2/HO-SiO2). The catalyst showed excellent performance for gaseous toluene degradation under UV illumination, with 99.2 % removal efficiency and 204.7 μmol L−1 CO2 yield (about 85.9 % mineralization efficiency) within 120 min. It also demonstrated superior durability over five consecutive cycles of toluene photodegradation. The modification of HO–SiO2 on {001}-TiO2 facilitate the selective adsorption of toluene on the catalyst surface by H-bonding interaction, and make the major poisoning species, benzoic acid, easily desorb from the surface, reducing the catalyst inactivation. Most importantly, we found that the formed TiOSi bond promotes the separation of photogenerated electron–hole pairs, and provides abundant available electrons for the formation of reactive oxygen radicals and the left holes for the conversion of toluene to benzyl radicals or oxidation of H2O to hydroxyl radicals, which results in the improved activity. This study highlights the importance of the introduction of secondary components with special functions on TiO2, which is helpful for the design of photocatalysts with high performance and anti-deactivation ability for treatment of volatile organic compounds.

Enhancement of 2-hydroxy-3-naphthyl hydroxamic acid adsorption on bastnaesite and monazite surfaces using H2O2 pre-oxidation for improved flotation process

Rare earth elements have been widely applied in various sectors. Bastnaesite and monazite are crucial rare earth minerals, and flotation is a vital technique for recovering fine-grained rare earth minerals and separating them from associated gangue minerals such as fluorite and apatite. Flotation collectors play a key role in selectively adsorbing valuable minerals, enhancing their surface hydrophobicity, which has prompted considerable research interest. However, the interaction between minerals and reagents relies on the reactivity and selectivity of the reagent groups, as well as the reactive properties of the surface atoms of the minerals. This study proposes the use of H2O2 oxidation to enhance the flotation process of rare earth minerals. The flotation experiments demonstrated that pre-adding H2O2 before introducing the flotation collector significantly improved the grade and recovery of rare earth concentrates. The adsorption mechanisms of 2-hydroxy-3-naphthyl hydroxamic acid collector on rare earth mineral surfaces before and after H2O2 pre-oxidation were studied. The 2-hydroxy-3-naphthyl hydroxamic acid interacts with Ce3+ on the surface of unoxidized rare earth minerals, forming chelate compounds with five-membered ring structures. The H2O2 exhibited potent oxidizing properties and oxidized the Ce3+ on the bastnaesite and monazite surfaces to more stable Ce4+, which demonstrated stronger binding capability with hydroxamic acid.

Label-free photosensitization colorimetric detection of microRNA by utilizing cascade toehold assembly amplification

The sensitive and label-free detection of microRNA (miRNA) is crucial for the comprehension of miRNA-related pathological process, such as glioma. Here, we utilized a SYBR Green I (SG) catalytic photosensitization colorimetric reaction in conjunction with target recognition-induced exonuclease-iii (Exo-iii) assisted cascade toehold assembly amplification to achieve highly sensitive and label-free miRNA detection. In this research, the photosensitized generation of 1O2 by SG could directly oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) without the need for H2O2 oxidation or enzyme catalysis, which simplifies the experimental procedures and renders the method highly stable. Furthermore, the Exo-iii enhances the target recognition induced catalytic chain assembly, thereby forming cascade signal amplification and providing the method with a significantly higher level of sensitivity than conventional colorimetric miRNA detection methods. Based on this, the proposed method exhibits a low limit of detection of 2.1 fM for miRNA-212 detection. Taking the merit of the high sensitivity, portability, and simplicity, the proposed method can serve as a highly effective nucleic acid detection tool and can facilitate the advancement of biosensors for point-of-care testing (POCT) and clinical disease diagnosis.

Synergistic Surface Engineering of BiVO4 Photoanodes for Improved Photoelectrochemical Water Oxidation.

Surface engineering of BiVO4 photoanodes is effective and feasible for photoelectrochemical (PEC) water splitting. To achieve superior PEC performance, however, more than one surface engineering method is usually indispensable, for which a positive synergistic effect is vital and thus highly desired. Herein, it is reported that the incorporation of borate moieties into ultrathin p-type NiOx catalysts can induce the reconfiguration of surface catalytic sites to form new highly active species, in addition to enhanced fast charge separation and transfer. The photocurrent density of BiVO4 photoanodes is enhanced from 1.49 to 5.76 mA cm-2 at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5G illumination, which is achieved by successive modifications of NiOx and borate moieties. It is found that BO3 groups anchored to Ni atoms by replacing the surface hydroxyl sites of NiOx catalysts not only increase the relative ratio of Ni3+ species to facilitate charge transfer but also provide efficient active sites for H2O molecule adsorption and oxidation reactions. This work demonstrates the positive synergistic effect of these two surface engineering methods and provides an effective pathway to construct highly efficient and stable photoanodes for PEC water splitting.