Rate Of H2O2 Production Research Articles

Spaced Double Hydrogen Bonding in an Imidazole Poly Ionic Liquid Composite for Highly Efficient and Selective Photocatalytic Air Reductive H2O2 Synthesis

AbstractPhotocatalytic oxygen reductive H2O2 production is a promising approach to alternative industrial anthraquinone processes while suffering from the requirement of pure O2 feedstock for practical application. Herein, we report a spaced double hydrogen bond (IC−H‐bond) through multi‐component Radziszewski reaction in an imidazole poly‐ionic‐liquid composite (SI‐PIL‐TiO2) and levofloxacin hydrochloride (LEV) electron donor for highly efficient and selective photocatalytic air reductive H2O2 production. It is found that the IC−H‐bond formed by spaced imino (−NH−) group of SI‐PIL‐TiO2 and carbonyl (−C=O) group of LEV can switch the imidazole active sites characteristic from a covered state to a fully exposed one to shield the strong adsorption of electron donor and N2 in the air, and propel an intenser positive potential and more efficient orbitals binding patterns of SI‐PIL‐TiO2 surface to establish competitive active sites for selectivity O2 chemisorption. Moreover, the high electron enrichment of imidazole as an active site for the 2e− oxygen reduction ensures the rapid reduction of O2. Therefore, the IC−H‐bond enables a total O2 utilization and conversion efficiency of 94.8 % from direct photocatalytic air reduction, achieving a H2O2 production rate of 1518 μmol/g/h that is 16 and 23 times compared to poly‐ionic‐liquid composite without spaced imino groups (PIL‐TiO2) and TiO2, respectively.

Spaced Double Hydrogen Bonding in an Imidazole Poly Ionic Liquid Composite for Highly Efficient and Selective Photocatalytic Air Reductive H2O2 Synthesis.

Photocatalytic oxygen reductive H2O2 production is a promising approach to alternative industrial anthraquinone processes while suffering from the requirement of pure O2 feedstock for practical application. Herein, we report a spaced double hydrogen bond (IC-H-bond) through multi-component Radziszewski reaction in an imidazole poly-ionic-liquid composite (SI-PIL-TiO2) and levofloxacin hydrochloride (LEV) electron donor for highly efficient and selective photocatalytic air reductive H2O2 production. It is found that the IC-H-bond formed by spaced imino (-NH-) group of SI-PIL-TiO2 and carbonyl (-C=O) group of LEV can switch the imidazole active sites characteristic from a covered state to a fully exposed one to shield the strong adsorption of electron donor and N2 in the air, and propel an intenser positive potential and more efficient orbitals binding patterns of SI-PIL-TiO2 surface to establish competitive active sites for selectivity O2 chemisorption. Moreover, the high electron enrichment of imidazole as an active site for the 2e- oxygen reduction ensures the rapid reduction of O2. Therefore, the IC-H-bond enables a total O2 utilization and conversion efficiency of 94.8 % from direct photocatalytic air reduction, achieving a H2O2 production rate of 1518 μmol/g/h that is 16 and 23 times compared to poly-ionic-liquid composite without spaced imino groups (PIL-TiO2) and TiO2, respectively.

Custom-Design of Strong Electron/Proton Extractor on COFs for Efficient Photocatalytic H2O2 Production.

The development of photocatalysts with continuous electron extraction and rapid proton transfer could kinetically accelerate the artificial photosynthesis, but remains a challenge. Herein, we report the topology-guided synthesis of a high-crystalline triazine covalent organic framework (COF) decorated by uniformly distributed polar oxygen functional groups (sulfonic group or carboxyl) as the strong electron/proton extractor for efficient photocatalytic H2O2 production. It was found that the polarity-based proton transfer as well as electron enrichment in as-obtained COFs played a crucial role in improving the H2O2 photosynthesis efficiency (i.e., with an activity order of sulfonic acid- (SO3H-COF)>carboxyl- (COOH-COF)>hydrogen- (H-COF) functionalized COFs). The strong polar sulfonic acid group in the high-crystalline SO3H-COF triggered a well-oriented built-in electric field and more hydrophilic surface, which serves as an efficient carrier extractor enabling a continuous transportation of the photogenerated electrons and interfacial proton to the active sites (i.e., C atoms linked to -SO3H group). As-accelerated proton-coupled electron transfer (PCET), together with the stabilized O2 adsorption finally leads to the highest H2O2 production rate of 4971 μmol g-1 h-1 under visible light irradiation. Meanwhile, a quantum yield of 15 % at 400 nm is obtained, superior to most reported COF-based photocatalysts.

Custom‐Design of Strong Electron/Proton Extractor on COFs for Efficient Photocatalytic H2O2 Production

AbstractThe development of photocatalysts with continuous electron extraction and rapid proton transfer could kinetically accelerate the artificial photosynthesis, but remains a challenge. Herein, we report the topology‐guided synthesis of a high‐crystalline triazine covalent organic framework (COF) decorated by uniformly distributed polar oxygen functional groups (sulfonic group or carboxyl) as the strong electron/proton extractor for efficient photocatalytic H2O2 production. It was found that the polarity‐based proton transfer as well as electron enrichment in as‐obtained COFs played a crucial role in improving the H2O2 photosynthesis efficiency (i.e., with an activity order of sulfonic acid‐ (SO3H‐COF)>carboxyl‐ (COOH‐COF)>hydrogen‐ (H‐COF) functionalized COFs). The strong polar sulfonic acid group in the high‐crystalline SO3H‐COF triggered a well‐oriented built‐in electric field and more hydrophilic surface, which serves as an efficient carrier extractor enabling a continuous transportation of the photogenerated electrons and interfacial proton to the active sites (i.e., C atoms linked to −SO3H group). As‐accelerated proton‐coupled electron transfer (PCET), together with the stabilized O2 adsorption finally leads to the highest H2O2 production rate of 4971 μmol g−1 h−1 under visible light irradiation. Meanwhile, a quantum yield of 15 % at 400 nm is obtained, superior to most reported COF‐based photocatalysts.

Phyto-synthesis of tin oxide nanoparticles using Diospyros mollis leaves extract doped graphitic carbon nitride for photocatalytic methylene blue degradation and hydrogen peroxide production

In this study, tin oxide nanoparticles (SnO2 NPs) were combined with graphitic carbon nitride (gCN) to produce the SnO2/gCN composite for photocatalytic methylene blue (MB) degradation and H2O2 production. Specifically, SnO2 NPs were initially prepared using a biological pathway from Diospyros mollis leaves extract, followed by the incorporation on gCN via calcination treatment. Characterization of SnO2/gCN was conducted through analytical methods, including scanning electron microscopy, energy dispersive X-ray spectroscopy, field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, N2 sorption isotherm, photoluminescence spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS). The optical band gap of the nanocomposite was also evaluated to be 2.44 eV using the Tauc plot and UV-DRS, which is lower than pristine gCN. The photocatalytic performance over the optimal 1.0SnO2/gCN sample was resultingly investigated, reaching over 99.76 % of MB degradation efficiency within 120 min, and 4060.78 μM/g.h of H2O2 production rate under visible light radiation. Insights into the mechanism revealed the vital participation of reactive radicals, especially •O2− and •OH, in the degradation of MB molecules, while the reusability of 1.0SnO2/gCN was also maintained after 4 succeeding photocatalytic cycles. Such findings affirm the promising applicability of the constructed SnO2/gCN material in many industries, namely the environmental remediation and cleaner production sectors.

Laser direct overall water splitting for H2 and H2O2 production

Hydrogen (H2) and hydrogen peroxide (H2O2) play crucial roles as energy carriers and raw materials for industrial production. However, the current techniques for H2 and H2O2 production rely on complex catalysts and involve multiple intermediate steps. In this study, we present a straightforward, environmentally friendly, and highly efficient laser-induced conversion method for overall water splitting to simultaneously generate H2 and H2O2 at ambient conditions without any catalysts. The laser direct overall water splitting approach achieves an impressive light-to-hydrogen energy conversion efficiency of 2.1%, with H2 production rates of 2.2 mmol/h and H2O2 production rates of 65 µM/h in a limited reaction area (1 mm2) within a short real reaction time (0.36 ms/h). Furthermore, we elucidate the underlying physics and chemistry behind the laser-induced water splitting to produce H2 and H2O2. The laser-induced cavitation bubbles create an optimal microenvironment for water-splitting reactions because of the transient high temperatures (104 K) surpassing the chemical barrier required. Additionally, their rapid cooling rate (1010 K/s) hinders reverse reactions and facilitates H2O2 retention. Finally, upon bubble collapse, H2 is released while H2O2 remains dissolved in the water. Moreover, a preliminary amplification experiment demonstrates the potential industrial applications of this laser chemistry. These findings highlight that laser-based production of H2 and H2O2 from water holds promise as a straightforward, environmentally friendly, and efficient approach on an industrial scale beyond conventional chemical catalysis.

Boron Reduced Copper Excess-Induced Oxidative Damage in Citrus sinensis by Modulating Reactive Oxygen Species and Methylglyoxal Formation and Their Detoxification Systems.

Citrus is mainly cultivated in acid soil with low boron (B) and high copper (Cu). In this study, Citrus sinensis seedlings were submitted to 0.5 (control) or 350 μM Cu (Cu excess or Cu exposure) and 2.5, 10, or 25 μM B for 24 weeks. Thereafter, H2O2 production rate (HPR), superoxide production rate (SAPR), malondialdehyde, methylglyoxal, and reactive oxygen species (ROS) and methylglyoxal detoxification systems were measured in leaves and roots in order to test the hypothesis that B addition mitigated Cu excess-induced oxidative damage in leaves and roots by reducing the Cu excess-induced formation and accumulation of ROS and MG and by counteracting the impairments of Cu excess on ROS and methylglyoxal detoxification systems. Cu and B treatments displayed an interactive influence on ROS and methylglyoxal formation and their detoxification systems. Cu excess increased the HPR, SAPR, methylglyoxal level, and malondialdehyde level by 10.9% (54.3%), 38.9% (31.4%), 50.3% (24.9%), and 312.4% (585.4%), respectively, in leaves (roots) of 2.5 μM B-treated seedlings, while it only increased the malondialdehyde level by 48.5% (97.8%) in leaves (roots) of 25 μM B-treated seedlings. Additionally, B addition counteracted the impairments of Cu excess on antioxidant enzymes, ascorbate-glutathione cycle, sulfur metabolism-related enzymes, sulfur-containing compounds, and methylglyoxal detoxification system, thereby protecting the leaves and roots of Cu-exposed seedlings against oxidative damage via the coordinated actions of ROS and methylglyoxal removal systems. Our findings corroborated the hypothesis that B addition alleviated Cu excess-induced oxidative damage in leaves and roots by decreasing the Cu excess-induced formation and accumulation of ROS and MG and by lessening the impairments of Cu excess on their detoxification systems. Further analysis indicated that the pathways involved in the B-induced amelioration of oxidative stress caused by Cu excess differed between leaves and roots.

Interface Chemical Bond Enhanced Ions Intercalated Carbon Nitride/CdSe‐Diethylenetriamine S‐Scheme Heterojunction for Photocatalytic H2O2 Synthesis in Pure Water

AbstractPhotosynthesis of hydrogen peroxide (H2O2) is regarded as an economically efficient and environmentally friendly synthesis method. However, the scalability of photocatalytic H2O2 production (PHP) is hindered by the sluggish reaction kinetics and rapid recombination of photogenerated charge carriers. In this study, an organic amine‐constrained ions intercalated carbon nitride/CdSe‐diethylenetriamine (K+/I−‐CN/CdSe‐D) S‐scheme heterojunction is synthesized using an organic–inorganic hybrid approach and employed for PHP for the first time. The optimization of the heterojunction interface by I− and K+ ions contributed to enhanced light absorption capabilities and reduced interlayer charge transfer distance. Concurrently, the synergy of C─Se bonds at interface effectively modulated the electron transfer pathways. The coordination environment and charge transfer mechanism are thoroughly investigated by extended X‐ray absorption fine structure and in situ irradiated X‐ray photoelectron spectroscopy. The H2O2 production rate of 40%K+/I−‐CN/CdSe‐D reached 2240.23 µmol h−1 g−1 in pure water. This study highlights the significance of dual tuning of interface chemical bonds and ionic intercalation as an effective strategy for enhancing the photocatalytic H2O2 , paving the way for further advancements in PHP technology.

Self‐Floating Photocatalytic System for Highly Efficient Hydrogen Peroxide Production and Organic Synthesis on Carbon Dots Decorated Conjugated Microporous Polymer

AbstractPhotocatalytic oxygen (O2) reduction to hydrogen peroxide (H2O2) is considered to be a promising method for energy storage. However, it suffers from the rapid recombination of carriers, the limited solubility and slow diffusion of O2, and the self‐decomposition of H2O2 in traditional diphase systems. Here, a self‐floating carbon dots/conjugated microporous polymer (CDs/CMP) photocatalytic system is established for H2O2 production and organic synthesis. Due to the D–π–A structure, porous structure, and hydrophobicity, CMP induced the intramolecular charge transfer, exposed abundant reaction sites, and enhanced O2 adsorption. CDs act as “bridges” for electron transmission and regulate the surface hydrophobicity of CMP, further improving charge transfer and optimizing the reaction interface. CDs/CMP system exhibits a high H2O2 production of 8542.6 µmol g−1 h−1 and concurrent furoic acid production at 2.22 mm h−1. This H2O2 production rate is ≈90% higher than that in the diphase system, exceeding all previously reported photocatalysts in triphase systems. Notably, the CDs/CMP system achieves the relative separation of the photocatalysts and H2O2, suppressing the generated H2O2 self‐decomposition. Theoretical calculations and in situ characterizations reveal the mechanism of H2O2 and furoic acid evolution. This self‐floating system provides insights into exploring the application of metal‐free photocatalysts in heterogeneous reactions.

General and Ultrafast Photothermal Synthesis of Atomic Metal‐Nitrogen‐Carbon Catalysts for H2O2 Electrosynthesis

AbstractAtomic metal‐nitrogen‐carbon catalysts (M‐N‐Cs) are promising electrocatalysts for the two‐electron oxygen reduction reaction (2e− ORR) for the green production of H2O2. However, the conventional synthetic methods of M‐N‐Cs typically suffer from prolonged possessing time and high energy consumption. Herein, a flash light irradiation‐assisted transient pyrolysis strategy is reported for the rapid and facile synthesis of a Co‐N‐C catalyst consisting of atomic Co‐N4 sites supported on graphene. The resultant Co‐N‐C is highly active and selective as an electrocatalyst for the 2e− ORR, with a H2O2 selectivity up to 94.2%, high mass activity of 113.9 A g−1, high turnover frequency of 34.8 s−1, and an average H2O2 production rate of 12.1 mol g−1 h−1 with an accumulated H2O2 concentration up to 15.2 mmol L−1 when evaluated with a three‐phase flow cell setup. Additionally, this synthetic strategy can be readily expanded to prepare other types of M‐N‐Cs (M = Fe, Ni, Cu, and noble metal Ir) with similar M‐N4 configurations by simply changing the metal precursors, demonstrating the generality of this method. The rapid and general flash‐assisted synthetic strategy for M‐N‐Cs can provide a readily accessible material library and platform for investigating their catalytic properties in different energy conversion processes.

Restricting bioenergetic efficiency enhances longevity and mitochondrial redox capacity in Drosophila melanogaster.

Mitochondria are essential for survival and as such, impairments in organelle homeostasis significantly accelerate age-related morbidity and mortality. Here, we determined the contribution of bioenergetic efficiency to life span and health span in Drosophila melanogaster utilizing the mitochondrial uncoupler BAM15. Life span was determined in flies fed a normal diet (ND) or high fat diet (HFD) supplemented with vehicle or BAM15. Locomotor function was determined by negative geotaxis assay in middle-aged flies fed vehicle or BAM15 under ND or HFD conditions. Redox capacity (high-resolution respirometry/fluorometry), citrate synthase (enzyme activity), mtDNA content (qPCR), gene expression (qPCR), and protein expression (western blot) were assessed in flight muscle homogenates of middle-aged flies fed vehicle or BAM15 ND. The molar ratio of H2O2 and O2 (H2O2:O2) in a defined respiratory state was calculated as a measure of redox balance. BAM15 extended life span by 9% on ND and 25% on HFD and improved locomotor activity by 125% on ND and 53% on HFD. Additionally, BAM15 enhanced oxidative phosphorylation capacity supported by pyruvate + malate, proline, and glycerol 3-phosphate. Concurrently, BAM15 enhanced the mitochondrial H2O2 production rate, reverse electron flow from mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) to Complex I, mGPDH, and Complex I without altering the H2O2:O2 ratio. BAM15 upregulated transcriptional signatures associated with mitochondrial function and fitness as well as antioxidant defense. BAM15-mediated restriction of bioenergetic efficiency prolongs life span and health span in Drosophila fed a ND or HFD. Improvements in life span and health span in ND were supported by synergistic enhancement of muscular redox capacity.

Improved H2O2 Electrosynthesis on S-doped Co-N-C through Cooperation of Co-S and Thiophene S.

Co-N-C based catalysts have emerged as a prospective alternative for H2O2 electrosynthesis via a selective 2e- oxygen reduction reaction (ORR). However, conventional Co-N-C with Co-N4 configurations usually exhibits low selectivity toward 2e- ORR for H2O2 production. In this study, the S-doped Co-N-C (Co-N-C@S) catalysts were designed and synthesized for enhancing the electrosynthesis of H2O2, and their S doping levels and species were tuned to investigate their relationship with the H2O2 yield. The results showed that the S doping greatly enhanced the activity and selectivity of Co-N-C@S for H2O2 production. The optimal Co-N-C@S(12) displayed a high H2O2 production rate of 395 mmol gcat-1 h-1, H2O2 selectivity of 76.06%, and Faraday efficiency of 91.66% at 0.2 V, which were obviously better than those of Co-N-C (H2O2 production rate of 44 mmol gcat-1 h-1, H2O2 selectivity of 26.63%, and Faraday efficiency of 17.37%). Moreover, the Co-N-C@S(12) based electron-Fenton system displayed effective rhodamine B (RhB) removal, significantly outperforming the Co-N-C-based system. Experimental results combined with density functional theory unveiled that the enhanced performance of Co-N-C@S(12) stemmed from the combined effect of Co-S and thiophene S, which jointly enhanced electron density of the Co center, reduced the desorption energy of the *OOH intermediate, and then promoted the production of H2O2.

Impact of Pt-Loading and Carbon Support of Pt/C Anode Catalysts on Membrane Degradation Rate in Fuel Cells

In order to clarify the effect of both the Pt-loading and carbon supports in various commercial Pt/C anode catalysts on the chemical degradation rate of polymer electrolyte membranes (PEMs) in fuel cells, the membrane lifetime and fluoride emission rate (FER) were examined in a single cell with an accelerated stress test (AST) at 90 °C, while the H2O2 production rates, j(H2O2), at the Pt/C catalysts were measured in a half cell with 0.1 M HClO4 solution at 90 °C. It was demonstrated that the PEM degradation rate decreased with decreasing amount of adsorbed hydrogen atoms (Had) at the Pt/C−PEM interface by lowering the Pt-loading and using a porous carbon support (locating Pt nanoparticles within pores). The use of a graphitized carbon black (GCB) support was found to be very effective to increase the lifetime due to it having the lowest j(H2O2), although this was accompanied by the disadvantage of decreased mass activity for the hydrogen oxidation reaction. We also found good correlations between the j(H2O2) measured in a half cell and FER, as well as lifetime in a single cell, so that the lifetime of the PEM can be estimated in a shorter time.

Highly Efficient Photocatalytic H2O2 Production over a Zn0.3Cd0.7S/MXene Photocatalyst for Degradation of Emerging Pollutants under Visible-Light Irradiation.

Hydrogen peroxide (H2O2) is an ideal green product with a broad range of applications, and visible-light-driven photocatalytic H2O2 production is deemed a sustainable and eco-friendly strategy. Herein, various ZnxCd1-xS/MXene photocatalysts with a Schottky junction were prepared for photocatalytic H2O2 production. The obtained Zn0.3Cd0.7S/MXene (ZCM-0.3) hybrid presented the highest photocatalytic H2O2 production rate in pure neutral water of 1160 μmol h-1 g-1, which was further improved to 2178.58 μmol h-1 g-1 in the presence of isopropanol as the sacrificial reagent. The experimental results demonstrated that the sufficient visible-light-harvesting ability and appropriate conduction band potential of the Zn0.3Cd0.7S solid solution, the excellent conductivity and two-electron selectivity of MXene, and the construction of Schottky junctions at the Zn0.3Cd0.7S/MXene interface resulted in the fast transfer and separation of the photogenerated charge carriers and the targeted reduction of oxygen to H2O2. The photocatalytic mechanism for H2O2 production was studied and proposed. Moreover, a simple photo-Fenton system consisting of ZnxCd1-xS/MXene and ferrous ions (Fe2+) was constructed and applied for the degradation of various emerging pollutants, which also performed effectively and exhibited universality across different pollutants. Overall, this study presents a novel and useful strategy to convert solar energy into chemical energy through efficient H2O2 production and provides an effective alternative for the degradation of emerging pollutants.

Dual Regulation of Charge Separation and the Oxygen Reduction Pathway by Encapsulating Phosphotungstic Acid into the Cationic Covalent Organic Framework for Efficient Photocatalytic Hydrogen Peroxide Production.

Previous research on covalent organic framework (COF)-based photocatalytic H2O2 synthesis from oxygen reduction focuses more on charge carrier separation but less on the electron utilization efficiency of O2. Herein, we put forward a facile approach to simultaneously promote charge separation and tailor the oxygen reduction pathway by introducing phosphotungstic acid (PTA) into the cationic COF skeleton. Experiments verified that PTA, as an electron transport medium, establishes a fast electron transfer channel from the COF semiconductor conductor band to the substrate O2; meanwhile, the reaction path is optimized by its catalytic cycle for preferable dioxygen capture and reduction in oxygen reduction reaction (ORR) kinetics. The existence of PTA promotes the rate and tendency of converting O2 into •O2- intermediates, which is conducive to boosting the photocatalytic activity and selectivity toward the sequential two-step single-electron ORR. As expected, compared to the pristine TTB-EB, the optimal PTA0.5@TTB-EB achieves a 2.2-fold improvement of visible-light-driven photocatalytic performance with a H2O2 production rate of 897.94 μmol·L-1·h-1 in pure water without using any sacrificial agents. In addition, owing to the robust electrostatic interaction and the confinement effect of porous TTB-EB channels, the PTA@TTB-EB composite possessed favorable stability.

A computational model of endogenous hydrogen peroxide metabolism in hepatocytes, featuring a critical role for GSH

This paper presents an ordinary differential equation (ODE) model of endogenous H2O2metabolism in hepatocytes that is unique, at the time of writing, in its ability to accurately compute intracellular H2O2concentration during incidents of oxidative stress and in its usefulness for constructing PBPK/PD models for ROS-generating xenobiotics. Versions of the model are presented for rat hepatocytes in vitro and mouse liver in vivo. A generic method is given for using the model to create PBPK/PD models which predict intracellular H2O2concentration and oxidative-stress-induced hepatocyte death; these are identifiable from in vitro data sets reporting cell mortality following xenobiotic exposure at various levels. The procedure is demonstrated for the trivalent arsenical dimethylarsinous acid (DMAIII), which is produced in liver as part of the arsenic elimination pathway. This is the first model of H2O2metabolism in hepatocytes to feature values for the endogenous rates of H2O2production by mitochondria and other organelles which are inferred from the physiology literature, and to feature a detailed, realistic treatment of GSH metabolism; the latter is achieved by incorporating a minimal version of Reed and coworkers’ pioneering model of GSH metabolism in liver. Model simulations indicate that critical GSH depletion is the immediate trigger for intracellular H2O2rising to concentrations associated with apoptosis (>1μM), that this may only occur hours after the xenobiotic concentration peaks (“delay effect”), that when critical GSH depletion does occur, H2O2concentration rises rapidly in a sequence of two boundary layers, characterized by the kinetics of glutathione peroxidase (first boundary layer) and catalase (second boundary layer), and that intracellular H2O2concentration >1μM implies critical GSH depletion. There has been speculation that ROS levels in the range associated with apoptosis simply indicate, rather than cause, an apoptotic milieu. Model simulations are consistent with this view. In a result of interest to the wider physiology community, the delay effect is shown to provide a GSH-based mechanism by which cells can distinguish transient elevations in H2O2concentration, of use in intracellular signaling, from persistent ones indicative of either pathology or the presence of toxins, the second state of affairs eventually triggering apoptosis.

Benzotrithiophene-based covalent organic frameworks as efficient catalysts for artificial photosynthesis of H2O2 in pure water

Direct synthesis of hydrogen peroxide (H2O2) using oxygen and water through the photocatalytic route is a prospective approach for the on-site production of H2O2. However, the limited varieties of photocatalytic sites and ambiguous structure-active relationship impede the development of environmentally friendly technology. Herein, we report a active compound (benzotrithiophene, BTT) for the photosynthesis of H2O2 using oxygen and water, and design four benzotrithiophene-based 2D covalent organic frameworks (BTT-COFs) linked with aromatic amines linkers. Significant enhancement in photocatalytic activity has been observed via the introduction of BTT struct into 2D COFs. The high crystallinity of COFs increases the visible light absorption ability and photostability of BTT. The suitable distance of BTT struct in COFs and the construction of donor–acceptor (D-A) structure further promote the carrier generation and transfer. The COF-BTT-TAPT exhibited the highest H2O2 production rate of 620 μmol g−1 h−1. Mechanism investigation experiments have given the validation that BTT-COFs efficiently reduce oxygen in pure water to form H2O2 under visible-light irradiation. This work paves a revolutionary way for designing and fabricating high-performance metal-free photocatalysts for visible-light-driven H2O2 production.

Improving dispersion of indium polyphthalocyanine on carbon nanotube via molecular modification for efficient oxygen reduction to hydrogen peroxide

Molecular catalysts have emerged as the promising candidate for oxygen reduction to hydrogen peroxide (H2O2). Dispersing homogeneously molecular catalyst on carbon support is the prerequisite for actual electrocatalysis application. Herein, we proposed a novel strategy of modification with sodium dodecylbenzenesulfonate (SDBS) to improve dispersion of indium polyphthalocyanine (InPPc) on carbon nanotube (CNT). The SDBS modification induces the matched surface hydrophilicity of CNT with InPPc, preventing InPPc aggregation. As a result, the InPPc/SDBS@CNT exhibits a remarkable onset potential of 0.84 V vs. RHE and selectivity of > 95 %, superior to InPPc/CNT and most recently reported catalysts. In situ Raman spectrum identifies the critical *OOH intermediate during H2O2 formation on InPPc/SDBS@CNT. Importantly, the InPPc/SDBS@CNT presents a prominent H2O2 production rate of 24.88 mg/cm2/h over 12 h in flow cell. This work provides an effective strategy to promote practical application of molecular catalysts.

Revealing the impact of different precursors and solvents for supramolecular complex formation and in-situ C-doping in g-C3N4 with enhanced photocatalytic H2O2 production

The reinforced light-harvesting capability suppresses photocarrier recombination and increases the specific surface area, representing the possibility of excellent photocatalytic performance for graphitic carbon nitride (CN) photocatalysts. Herein, the remarkable photocatalytic properties of porous carbon-doped g-C3N4 (CCN) were enhanced through the incorporation of a supramolecular complex, M-CA-U (melamine-cyanuric acid-urea), in DMSO as the carbon dopant source. Through the diverse characterization methods, the successful formation of the supramolecular g-C3N4 using varying polarity of solvent was verified, achieved through a simple hydrothermal/solvothermal process. The CCN-MCAU-DMSO photocatalyst achieved the maximum photocatalytic H2O2 production rate, 1.3-fold higher than other prepared samples. The outstanding performances of CCN-MCAU-DMSO were probably attributed to the extended specific surface area, robust visible light response, adjusted electronic band structure, accelerated charge separation, and limited charge recombination. The photocurrent response and photoluminescence spectroscopy analysis confirmed excellent charge carriers and separation. Overall, this work provided a new idea to design and construct high-efficiency porous supramolecular assembly of CCN photocatalysts for photocatalytic studies.

Single-Atom Co─O4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H2O2 Electrosynthesis.

The production of hydrogen peroxide (H2O2) via the two-electron electrochemical oxygen reduction reaction (2e- ORR) is an essential alteration in the current anthraquinone-based method. Herein, a single-atom Co─O4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O4@PC). The Co─O4@PC electrocatalyst shows promising potential in H2O2 electrosynthesis via 2e- ORR, providing a high H2O2 selectivity of 98.8% at 0.6V and a low onset potential of 0.73V for generating H2O2. In situ surface-sensitive attenuated total reflection Fourier transform infrared spectra and density functional theory calculations reveal that the electronic and geometric modification of Co─O4 induced by defective carbon sites result in decreased d-band center of Co atoms, providing the optimum adsorption energies of OOH* intermediate. The H-cell and flow cell assembled using Co─O4@PC as the cathode present long-term stability and high efficiency for H2O2 production. Particularly, a high H2O2 production rate of 0.25molg-1 cath-1 at 0.6V can be obtained by the flow cell. The in situ-generated H2O2 can promote the degradation of rhodamine B and sterilize Staphylococcus aureus via the Fenton process. This work can pave the way for the efficient production of H2O2 by using Co─O4 single atom electrocatalyst and unveil the electrocatalytic mechanism.