H2O2 Production Ability Research Articles

TCE degradation of modified graphite felt cathode in a flow-through electro-Fenton system and its H2O2 production ability in a real contaminated field

A modified graphite felt (MGF) was prepared with carbon black (CB) and polytetrafluoron (PTFE) for cathodic electrochemical H2O2 production, which was used in a flow-through cathodic electro-Fenton reactor to degrade chlorinated hydrocarbons. Cathode electrode was floating on aqueous surface and 369.1 mg/L H2O2 could be produced after 1 h 150 mA power applied without O2 aeration. The main O2 source for H2O2 production was confirmed from air with this floating position. In a 2.0 L flow-through cathodic electro-Fenton system, 95.97 % degradation efficiency for 5.0 mg/L trichloroethylene (TCE) was achieved in 90 min with 13.4 mL/min influent rate. Reducing the reactor volume to 0.14 L, 5.0 mg/L TCE could be degraded completely in 10 min with continuous 4 L influent. The mixed chlorinated hydrocarbons (TCE, cis-1,1-dichloroethylene, 1,2-dichloroethane, and dichloromethane) were also rapidly degraded in 20 min. The flow-through cathodic electro-Fenton reactor presented excellent degradation ability for chlorinated hydrocarbons with a smaller volume. In the simulated sand tank system, after continuously operated 27 days, H2O2 concentration in electrode well was still remained at 80 mg/L. In the contaminated field in Tianjin, China, H2O2 yield of MGF in groundwater could keep at about 60 mg/L after 220 min operating.

Efficient photocatalytic hydrogen peroxide production over S-scheme In2S3/molten salt modified C3N5 heterojunction

Graphitic phase carbon nitride (g-C3N5), as a novel n-type metal-free material, is employed as a visible light-receptive catalyst because of its narrow band gap and abundant nitrogen. To overcome the low carrier mobility efficiency of g-C3N5, its modification by K ions was adopted. In addition, In2S3 was selected to couple with modified g-C3N5 to overcome the recombination of photogenerated e−/h+. As a novel photocatalytic material, it was proven to possess a high visible light absorption capacity and a strong H2O2 production ability (up to 3.89 mmol⋅L-1 in 2 h). Moreover, a S-scheme heterojunction structure was successfully constructed between the two materials, which was tested and confirmed to be successful in raising the photogenerated e−/h+ separation efficiency. Ultimately, the primary processes of photocatalytic H2O2 production were summarized by superoxide radical and rotating disc electron measurements. This research provides a fresh perspective for the synthesis of C3N5-based S-scheme heterojunction photocatalysts for producing H2O2.

Comparison of the photocatalytic performance of ZnSe nanocrystals with different crystallite sizes

ZnSe nanocrystals were prepared by a hydrothermal method and their photocatalytic properties were investigated as a function of the ZnSe nanocrystal size. At the beginning of the photocatalytic reaction, the smaller-sized ZnSe nanocrystals demonstrated better H2O2 production performance (12.84 mmol g-1h−1) than the larger-sized ones (12.29 mmol g-1h−1). In the long run, the smaller-sized ZnSe nanocrystals suffered from severe photocorrosion and showed inferior H2O2 production ability.

Construction of NM88B(Fe)-POR/Rf equipped with hyperoxia microenvironment as a cascade nanozyme for ultrasensitive electrochemical detection of sarcosine

High detection stability makes sarcosine oxidase (SOx) nanozyme as natural enzyme substitute, a promising sensor for prostate cancer biomarker Sarcosine (Sar). However, its limited catalytic capacity towards product (H2O2) and the following weak signal response significantly restrict the detection sensitivity of Sar. Herein, a novel NH2-MIL88B(Fe)-porphyrin/riboflavin (NM88B-POR/Rf) electrochemical sensor with a hyperoxia microenvironment and cascade reaction functions is proposed to promote catalytic H2O2 production and cascade signal amplification (from H2O2 to •OH). Fe-porphyrin implantation in NM88B-POR/Rf as bionic heme enhanced the O2-carrying capacity, thus effectively improving the sensor's utilization rate of dissolved oxygen and the catalytic H2O2 production ability of Rf. Based on enzymatic cascade strategy, NM88B in NM88B-POR/Rf as peroxidase nanozyme further catalyzed H2O2 to generate •OH. Methyl blue was used to capture •OH and enhance Sar detection sensitivity. Detection results revealed that NM88B-POR/Rf presented as low limit of detection (LOD) as 3.31 pM with detection range of 10 pM∼1 mM. The synergistic effect of the hyperoxia microenvironment and enzyme cascade make LOD about 4 orders of magnitude lower than reported state-of-the-art biosensors. Moreover, NM88B-POR/Rf has good selectivity and stability and hence also be applied to the detection of Sar in real urine.

Efficient Photocatalytic H2 O2 Production Ability of a Novel Graphitic Carbon Nitride/Carbon Composites under Visible Light.

In the present work, using one-step calcination of a mixture made of potassium hydroxide (KOH), melamine, and microplastics, this work prepares a novel graphitic carbon nitride/carbon (g-C3 N4 /C) composite, which can be employed to photo-catalytically produce hydrogen peroxide (H2 O2 ) at a high rate up to 6.146mmol g-1 h-1 under visible light irradiation. By analyzing the energy band structure of the catalyst, the production of H2 O2 in this system consists of two single-electron reactions. The modification of KOH makes abundant N-vacancies caused by cyano-groups in g-C3 N4 , enhancing the electron absorption ability. Moreover, the introduction of graphitic carbon increases its specific surface area and porosity and improves the adsorption ability of O2 . Simultaneously, their synergism reduces the g-C3 N4 band gap, making both the conduction-band and valence-band positions more negative, showing enhanced reduction ability, lowering the energy barrier for oxygen reduction, and greatly improving the photogeneration performance of H2 O2 .

Oxygen-containing surface functional groups, mesoporous structure and photothermal effect co-modulated highly-efficient H2O2 production and pollutant degradation

Carbon-based nanomaterials are well-recognized catalysts for H2O2 production though remain insufficient for practical applications, and their photothermal effect is usually ignored. Herein, two typical carbon nanomaterials, mesoporous carbon hollow spheres (MCHS) and carbon hollow spheres (CHS), are selectively synthesized to explore the influence of oxygen-containing surface functional groups, mesoporous structure and photothermal effect on their electrocatalytic and application ability. It was found that the abundant oxygen-containing surface functional groups in MCHS can optimize the adsorption energy of *OOH while the mesoporous structure of MCHS provides plenty of electrochemical active sites, both of which significantly enhance H2O2 production selectivity of the MCHS (96.0% versus 87.0% for the CHS counterpart). Furthermore, the notable photothermal effect of the MCHS can promote the generation of more ·OH radicals and accelerate related reaction kinetics (3.5 times higher than those without NIR light irradiation) under the in-situ electro-Fenton degradation of methyl orange. As a result, remarkable degradation efficiency of 98.1% was achieved for the MCHS under the illumination of near infrared (NIR) light, outperforming those without NIR light irradiation (70.1% for MCHS and 54.7% for CHS). By integrating oxygen-containing surface functional groups, mesoporous structure and photothermal effect, this work achieves remarkable H2O2 production ability and pollutant degradation application simultaneously, providing a new avenue for the design of advanced electrocatalysts and may promote their energy related applications.

Plasma-induced hierarchical amorphous carbon nitride nanostructure with two N2C-site vacancies for photocatalytic H2O2 production

Carbon nitride (CN) with nitrogen vacancy is a robust photocatalyst with proven enhancing H2O2 production ability. However, nitrogen vacancy control is extremely challenging with the majority of reports representing it as a few vacancies. Herein, for the first time, the amorphous CN (ACN) with two N2C-site vacancies in one CN unit is prepared by a one-step H2 plasma approach. First-principles calculations and experimental results provide consistent evidence that two N2C vacancies are located in one CN unit structure after amorphous transformation. Plasma-induced ACN is stable with a hierarchical continuous nanosheet network structure and exhibits an ultrahigh specific surface area of ~405.76 m2g−1, which is 83 times higher than that of pristine CN (4.89 m2g−1) and significantly enhanced photocatalytic H2O2 production, yielding 1874 μmolg−1h−1. Besides, the existence potential drop of 2.61 eV for the electrostatic potential in ACN is key to charge carrier separation. Moreover, the amorphous transformation leads to a new strong band tail, which remarkably enhances the absorbance edge of ACN up to 593 nm, resulting in a wider range of visible-light absorption to enhance H2O2 production. The results have provided an effective approach for promoting the practical application of ACN in photocatalytic H2O2 production.

A stable CoSP/MWCNTs air-diffusion cathode for the photoelectro-Fenton degradation of organic pollutants at pre-pilot scale

CoS2/MWCNTs have been previously described as potentially viable catalysts to enhance the classical two-electron H2O2 production from O2 reduction reaction (ORR) for in situ water treatment, but their poor stability still limits their large-scale application. Here, the synthesis and characterization of a novel electrocatalyst made of CoSP nanoparticles supported onto multi-walled carbon nanotubes (MWCNTs) is reported. X-ray diffraction data demonstrated the much higher stability conferred upon partial sulfur substitution by phosphorus. Linear and cyclic voltammograms of CoSP/MWCNTs showed a potential window from 0.9 to 0.1 V for the ORR at pH 3.0, along with greater H2O2 production ability. Large area air-diffusion cathodes were manufactured by depositing the catalyst onto carbon paper, being further used in a pre-pilot filter-press cell containing a boron-doped diamond anode. A stable H2O2 accumulation, with maximum current efficiency of 72.0%, was found upon electrolysis of 2.5 L of 0.050 M Na2SO4 at pH 3.0 and 25 mA cm−2. As a crucial finding, Co leaching was negligible. Solutions with 20 mg L−1 of the herbicide bentazon in the same electrolyte could not be mineralized by electrochemical oxidation, whereas photoelectro-Fenton with an UVA lamp and 0.50 mM Fe2+ led to total removal of the herbicide with 77.0% mineralization.

Hydrothermal Synthesis of Band Gap-Tunable Oxygen-Doped g-C3N4 with Outstanding “Two-Channel” Photocatalytic H2O2 Production Ability Assisted by Dissolution–Precipitation Process

Here, band gap-tunable oxygen-doped graphitic carbon nitride (g-C3N4) with outstanding “two-channel” photocatalytic H2O2 production ability was prepared via hydrothermal treatment assisted by dissolution–precipitation process. XRD, N2 adsorption, UV–Vis, Fourier-transform infrared spectra, SEM, electrochemical impedance spectra, XPS and photoluminescence were used to characterize the obtained catalysts. The photocatalytic H2O2 production ability of as-prepared catalyst was investigated. The results show that oxygen doping not only changes the morphology of catalyst, decreases the band gap energy and promotes the separation efficiency of photogenerated electrons and holes, but also tunes the CB and VB potentials. As-prepared oxygen-doped g-C3N4 displays a H2O2 concentration of 3.8[Formula: see text]mmol[Formula: see text]L[Formula: see text], more than 7.6 times higher than that of neat g-C3N4. Because of the shift of CB and VB potentials, not only the CB electrons of oxygen-doped g-C3N4 reduce O2 to form H2O2, but also the VB holes can oxidize OH− to form [Formula: see text]OH, which subsequently react with each other to form H2O2. Such “two-channel pathway” causes the remarkably promoted H2O2 production ability.

Synthesis of halogen doped graphite carbon nitride nanorods with outstanding photocatalytic H2O2 production ability via saturated NH4X (X = Cl, Br) solution-hydrothermal post-treatment

Doping is a very effective method to promote the photocatalytic performance of graphitic carbon nitride (g-C3N4) based catalyst. However, the traditional co-condensation method causes the large particle size, small surface area and low separation rate of electrons-holes. In this work, halogen doped g-C3N4 nanorods with outstanding photocatalytic H2O2 production ability were prepared via saturated NH4X (X = Cl, Br) solution-hydrothermal post-treatment. XRD, N2 adsorption, UV–Vis, SEM, XPS, EPR, EIS and PL were used to characterize the obtained catalysts. Saturated salt solution-hydrothermal post-treatment changed the morphology and surface area of as-prepared g-C3N4 catalyst, as well as doped the halogen atoms into g-C3N4 lattice simultaneously. Br doped g-C3N4 catalyst displayed higher photocatalytic H2O2 production ability than that of Cl doped g-C3N4 catalyst. Compared with traditional co-condensation method, the catalyst prepared via saturated salt solution-hydrothermal post-treatment exhibited larger surface area, more effective separation rate and higher photocatalytic H2O2 production ability. This work can provide a new strategy for doping heteroatoms into g-C3N4 based catalyst.

Preparation of N-vacancy-doped g-C3N4 with outstanding photocatalytic H2O2 production ability by dielectric barrier discharge plasma treatment

Dielectric barrier discharge (DBD) plasma is considered to be a promising method to synthesize solid catalysts. In this work, DBD plasma was used to synthesize a nitrogen-vacancy-doped g-C3N4 catalyst in situ for the first time. X-ray diffraction, N2 adsorption, ultraviolet–visible spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, electron paramagnetic resonance, O2 temperature-programmed desorption, and photoluminescence were used to characterize the obtained catalysts. The photocatalytic H2O2 production ability of the as-prepared catalyst was investigated. The results show that plasma treatment influences the morphology, structure, and optical properties of the as-prepared catalyst. Nitrogen vacancies are active centers, which can adsorb reactant oxygen molecules, trap photoelectrons, and promote the transfer of photoelectrons from the catalyst to the adsorbed oxygen molecules for the subsequent reduction reaction. This work provides a new strategy for synthesizing g-C3N4-based catalysts.

The effect of phosphate modification on the photocatalytic H2O2 production ability of g-C3N4 catalyst prepared via acid-hydrothermal post-treatment

Protonation of graphitic carbon nitride (g-C3N4) based catalyst by acid treatment is proved to benefit for its photocatalytic performance. However, acid-hydrothermal method to synthesize g-C3N4 was seldom reported. In this work, phosphate-modified g-C3N4 as efficient photocatalyst for H2O2 production was prepared via acid-hydrothermal method. XRD, N2 adsorption, UV–Vis, FT-IR, SEM, XPS, TPD, EIS, and PL were used to characterize the obtained catalysts. Phosphate modification not only influences the morphology, structure property and optical property, but also promotes the O2 adsorption ability, leading to the improved separation rate of electrons-holes. Phosphate modified g-C3N4 catalyst shows the H2O2 concentration of 5.4 mmol L−1, more than 13.5 times higher than that of neat g-C3N4. The possible reaction mechanism is proposed.

The effect of embedding N vacancies into g-C3N4 on the photocatalytic H2O2 production ability via H2 plasma treatment

Dielectric barrier discharge plasma was used to prepare N vacancies embedded g-C3N4 catalyst in situ under H2 atmosphere for the first time. XRD, N2 adsorption, UV–Vis, SEM, TEM, XPS, EIS, EPR, O2-TPD, photocurrent and PL were used to characterize the obtained catalysts. The photocatalytic H2O2 production ability of as-prepared catalyst was investigated. The results show that, compared with traditional roasting method, H2 plasma treatment can embed more N vacancies into g-C3N4 lattice. Nitrogen vacancies are the active centers, which can adsorb reactant oxygen molecules as well as trap photoelectrons and promote the transfer of photoelectrons from the catalyst to adsorbed oxygen molecules for the subsequent reduction reaction. This work provides a new strategy to modify g-C3N4 based catalyst.

Synthesis of band gap-tunable alkali metal modified graphitic carbon nitride with outstanding photocatalytic H2O2 production ability via molten salt method

Band gap-tunable alkali metal modified graphitic carbon nitride was prepared by a molten salt method. X-ray diffraction, N2 isothermal sorption, ultraviolet-visible spectroscopy, scanning electron microscope, X-ray photoelectron spectroscopy and photoluminescence were used to characterize the obtained catalysts. The photocatalytic H2O2 production ability of as-prepared catalyst was investigated. The results indicate that K+ and Na+ are doped into g-C3N4 lattice simultaneously by the molten salt method. Alkali metal modification not only promotes the specific surface area, visible light absorption and separation of electron-hole pairs, but tunes the conduction band and valence band edge positions of as-prepared catalysts by controlling the weight ratio of eutectic salts to melamine. The tunable band edge positions result in the photocatalytic H2O2 production from “single channel pathway” to “two channel pathway”, leading to the promoted H2O2 production ability.

One step synthesis of high-efficiency AgBr-Br-g-C3N4 composite catalysts for photocatalytic H2O2 production via two channel pathway.

In this work, a two-component modified AgBr–Br–g-C3N4 composite catalyst with outstanding photocatalytic H2O2 production ability is synthesized. XRD, UV-Vis, N2 adsorption, TEM, XPS, EPR and PL were used to characterize the obtained catalysts. The as-prepared AgBr–Br–g-C3N4 composite catalyst shows the highest H2O2 equilibrium concentration of 3.9 mmol L−1, which is 7.8 and 19.5 times higher than that of GCN and AgBr. A “two channel pathway” is proposed for this reaction system which causes the remarkably promoted H2O2 production ability. In addition, compared with another two-component modified catalyst, Ag–AgBr–g-C3N4, AgBr–Br–g-C3N4 composite catalyst displays the higher photocatalytic H2O2 production ability and stability.

Photocatalytic oxygen reduction to hydrogen peroxide over copper doped graphitic carbon nitride hollow microsphere: The effect of Cu(I)-N active sites

H2O2 is produced industrially by the anthraquinone method, in which energy consumption is high because of its multistep hydrogenation and oxidation reactions. In this work, hollow copper-doped graphitic carbon nitride (g-C3N4) microspheres with outstanding photocatalytic H2O2 production ability are prepared. The characterization results demonstrate that Cu+ is not present as the oxide but instead inserts at the interstitial position through coordinative Cu(I)-N bonds. These Cu(I)-N active sites can act as chemical adsorption sites to activate molecular O2. Moreover, as an “electron transfer bridge”, Cu(I)-N active sites promote electron transfer from the catalyst to the adsorbed O2 molecules. The as-prepared copper-doped g-C3N4 displays much higher H2O2 equilibrium concentration and formation rate than neat g-C3N4 prepared by calcination does, as well as excellent structural stability. Density functional theory simulations show that Cu(I)-N active sites can adsorb the O2 molecules with high adsorption energy and elongate the OO bond. Charge density difference results confirm the electron transfer from the Cu+ doping sites to the O2 molecules. The Mulliken charge is −0.51 when the O2 adsorbed on Cu+ doping sites. This electron-rich environment is beneficial to the H+ attack to form H2O2.

Evaluation of different cathodes and reaction parameters on the enhancement of the electro-Fenton process

In this study, the degradation of pyrimethanil, a pesticide considered as a model pollutant, by electro-Fenton process was optimized. Thus, three different carbonaceous cathode configurations were selected: taffeta carbon fiber (TCF), unidirectional carbon fiber (UCF), and graphite felt (GF). Initially, the H2O2 production ability of these cathodes was evaluated showing results that varied from around 27 to 12mg/L for UCF and TCF, respectively. These results are in accordance with the cyclic voltammetry study and the hydrophilic behavior of the different cathodes. The degradation of pyrimethanil by anodic oxidation shows to be significantly less efficient than electro-Fenton treatments with any cathode. However, the best results were obtained when UCF was used, achieving the total removal after 45min. Working with the best cathode, an estimation of the treatment cost was performed based on the electric consumption and mineralization efficiency of the system working at different intensity values. After 120min, total degradation of the selected pollutant and total organic carbon reduction between 25 and 45% were achieved. Furthermore, different intermediates generated during the degradation process were identified and suitable degradation pathway was proposed. Finally, a continuous treatment system was evaluated at different flow rates and modeled, showing a good agreement between the theoretical and the experimental data.

The effect of Ni(i)–N active sites on the photocatalytic H2O2 production ability over nickel doped graphitic carbon nitride nanofibers

This work provides a strategy to improve the photocatalytic H2O2 production ability by embedding Ni(i)–N sites into the g-C3N4 lattice.