Browse
Submit Data
Databases
API
Help

Dataset Information

23 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Gas-Phase Fluorination of g-C₃N₄ for Enhanced Photocatalytic Hydrogen Evolution.

ABSTRACT: Graphitic carbon nitride (g-C₃N₄) has attracted much attention because of its potential for application in solar energy conservation. However, the photocatalytic activity of g-C₃N₄ is limited by the rapidly photogenerated carrier recombination and insufficient solar adsorption. Herein, fluorinated g-C₃N₄ (F-g-CN) nanosheets are synthesized through the reaction with F₂/N₂ mixed gas directly. The structural characterizations and theoretical calculations reveal that fluorination introduces N vacancy defects, structural distortion and covalent C-F bonds in the interstitial space simultaneously, which lead to mesopore formation, vacancy generation and electronic structure modification. Therefore, the photocatalytic activity of F-g-CN for H₂ evolution under visible irradiation is 11.6 times higher than that of pristine g-C₃N₄ because of the enlarged specific area, enhanced light harvesting and accelerated photogenerated charge separation after fluorination. These results show that direct treatment with F₂ gas is a feasible and promising strategy for modulating the texture and configuration of g-C₃N₄-based semiconductors to drastically enhance the photocatalytic H₂ evolution process.

SUBMITTER: Sun L

PROVIDER: S-EPMC8746965 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Enhanced photocatalytic hydrogen evolution from organic semiconductor heterojunction nanoparticles.

Project description:Photocatalysts formed from a single organic semiconductor typically suffer from inefficient intrinsic charge generation, which leads to low photocatalytic activities. We demonstrate that incorporating a heterojunction between a donor polymer (PTB7-Th) and non-fullerene acceptor (EH-IDTBR) in organic nanoparticles (NPs) can result in hydrogen evolution photocatalysts with greatly enhanced photocatalytic activity. Control of the nanomorphology of these NPs was achieved by varying the stabilizing surfactant employed during NP fabrication, converting it from a core-shell structure to an intermixed donor/acceptor blend and increasing H2 evolution by an order of magnitude. The resulting photocatalysts display an unprecedentedly high H2 evolution rate of over 60,000?µmol?h-1?g-1 under 350 to 800?nm illumination, and external quantum efficiencies over 6% in the region of maximum solar photon flux.

| S-EPMC7558859 | biostudies-literature

Accelerating Photocatalytic Hydrogen Production and Pollutant Degradation by Functionalizing g-C3N4 With SnO2.

Project description:Energy crises and environmental pollution are two serious threats to modern society. To overcome these problems, graphitic carbon nitride (g-C3N4) nanosheets were fabricated and functionalized with SnO2 nanoparticles to produce H2 from water splitting and degrade 2-chlorophenol under visible light irradiation. The fabricated samples showed enhanced photocatalytic activities for both H2 evolution and pollutant degradation as compared to bare g-C3N4 and SnO2. These enhanced photoactivities are attributed to the fast charge separation as the excited electrons transfer from g-C3N4 to the conduction band of SnO2. This enhanced charge separation has been confirmed by the photoluminescence spectra, steady state surface photovoltage spectroscopic measurement, and formed hydroxyl radicals. It is believed that this work will provide a feasible route to synthesize photocatalysts for improved energy production and environmental purification.

| S-EPMC7039856 | biostudies-literature

Enhanced photocatalytic hydrogen evolution by combining water soluble graphene with cobalt salts.

Project description:There is tremendous effort put in the pursuit for cheap and efficient catalysts for photocatalytic hydrogen evolution systems. Herein, we report an active catalyst that uses the earth-abundant element cobalt and water-dispersible sulfonated graphene. The photocatalytic hydrogen evolution activity of the catalyst was tested by using triethanolamine (TEOA) as electron donor and eosin Y (EY) as the photosensitizer under LED irradiation at 525 nm. Hydrogen was produced constantly even after 20 h, and the turnover number (TON) reached 148 (H2/Co) in 4 h with respect to the initial concentration of the added cobalt salts was shown to be 5.6 times larger than that without graphene.

| S-EPMC4142871 | biostudies-other

Fast and Simple Microwave Synthesis of TiO2/Au Nanoparticles for Gas-Phase Photocatalytic Hydrogen Generation.

Project description:The fabrication of small anatase titanium dioxide (TiO2) nanoparticles (NPs) attached to larger anisotropic gold (Au) morphologies by a very fast and simple two-step microwave-assisted synthesis is presented. The TiO2/Au NPs are synthesized using polyvinylpyrrolidone (PVP) as reducing, capping and stabilizing agent through a polyol approach. To optimize the contact between the titania and the gold and facilitate electron transfer, the PVP is removed by calcination at mild temperatures. The nanocatalysts activity is then evaluated in the photocatalytic production of hydrogen from water/ethanol mixtures in gas-phase at ambient temperature. A maximum value of 5.3 mmol·[Formula: see text]h-1 (7.4 mmol·[Formula: see text]h-1) of hydrogen is recorded for the system with larger gold particles at an optimum calcination temperature of 450°C. Herein we demonstrate that TiO2-based photocatalysts with high Au loading and large Au particle size (≈50 nm) NPs have photocatalytic activity.

| S-EPMC5907367 | biostudies-literature

Enhanced Photocatalytic Hydrogen Evolution from Transition-Metal Surface-Modified TiO<sub>2</sub>.

Project description:This study describes the UV solution photodeposition of several earth-abundant 3d transition metals (Co, Ni, and Cu) onto the surface of nanoparticulate TiO2. Irradiated methanolic metal dichloride solutions with suspended Degussa P25-TiO2 (1-2 wt % metal to TiO2) yield visibly colored titanias, whereas the bulk TiO2 structure is unchanged; X-ray photoelectron spectroscopy confirms that metals are present on the titania surface in either reduced metal (Cu/Cu+) or metal cation states (Co2+ and Ni2+), and UV-vis diffuse reflectance spectroscopy shows new visible absorbance features. The analyzed bulk metal contents (∼0.04-0.6 at. %, highest for copper) are lower than the nominal metal solution content. Mixed-metal solution photodeposition reactions roughly parallel observations for single metals, with copper deposition being most favored. These 3d metal surface-modified titanias show significant (∼5-15×) improvement in UV photocatalytic H2 evolution versus unmodified TiO2. H2 evolution rates as high as 85 μmol/h (8500 μmol h-1 g-1) were detected for Cu-coated TiO2 using continuous monitoring of reactor headspace gases by portable mass spectrometry. Control experiments verify the necessity of the methanol sacrificial oxidant in both metal deposition and H2 evolution. In situ metal surface deposition is quickly followed by enhanced H2 evolution relative to TiO2, but at lower levels than isolated metal surface-modified titanias. The photodeposited 3d metal species on the TiO2 surface likely act to reduce electron-hole recombination by facilitating the transfer of photoinduced TiO2 conduction band electrons to protons in solution that are reduced to H2. This study demonstrates a facile method to modify photoactive TiO2 nanoparticles with inexpensive 3d transition metals to improve photocatalytic hydrogen evolution, and it shows the utility of quantitative real-time gas evolution monitoring by portable mass spectrometry.

| S-EPMC6641314 | biostudies-literature

Enhanced Photocatalytic CO2 Reduction in Defect-Engineered Z-Scheme WO3-x /g-C3N4 Heterostructures.

Project description:Oxygen vacancy-modified WO3-x nanorods composited with g-C3N4 have been synthesized via the chemisorption method. The crystalline structure, morphology, composition, band structure, and charge separation mechanism for WO3-x /g-C3N4 heterostructures are studied in detail. The g-C3N4 nanosheets are attached on the surface of WO3-x nanorods. The Z-scheme separation is confirmed by the analysis of generated hydroxyl radicals. The electrons in the lowest unoccupied molecular orbital of g-C3N4 and the holes in the valence band of WO3 can participate in the photocatalytic reaction to reduce CO2 into CO. New energy levels of oxygen vacancies are formed in the band gap of WO3, further extending the visible-light response, separating the charge carriers in Z-scheme and prolonging the lifetime of electrons. Therefore, the WO3-x /g-C3N4 heterostructures exhibit much higher photocatalytic activity than the pristine g-C3N4.

| S-EPMC6761746 | biostudies-literature

PEG-stabilized coaxial stacking of two-dimensional covalent organic frameworks for enhanced photocatalytic hydrogen evolution.

Project description:Two-dimensional covalent organic frameworks (2D COFs) featuring periodic frameworks, extended π-conjugation and layered stacking structures, have emerged as a promising class of materials for photocatalytic hydrogen evolution. Nevertheless, the layer-by-layer assembly in 2D COFs is not stable during the photocatalytic cycling in water, causing disordered stacking and declined activity. Here, we report an innovative strategy to stabilize the ordered arrangement of layered structures in 2D COFs for hydrogen evolution. Polyethylene glycol is filled up in the mesopore channels of a β-ketoenamine-linked COF containing benzothiadiazole moiety. This unique feature suppresses the dislocation of neighbouring layers and retains the columnar π-orbital arrays to facilitate free charge transport. The hydrogen evolution rate is therefore remarkably promoted under visible irradiation compared with that of the pristine COF. This study provides a general post-functionalization strategy for 2D COFs to enhance photocatalytic performances.

| S-EPMC8225615 | biostudies-literature

Synthesis of Novel Kaolin-Supported g-C3N4/CeO2 Composites with Enhanced Photocatalytic Removal of Ciprofloxacin.

Project description:Herein, novel ternary kaolin/CeO2/g-C3N4 composite was prepared by sol-gel method followed by hydrothermal treatment. The self-assembled 3D "sandwich" structure consisting of kaolin, CeO2 and g-C3N4 nanosheets, was systematically characterized by appropriate techniques to assess its physicochemical properties. In the prerequisite of visible-light irradiation, the removal efficiency of ciprofloxacin (CIP) over the kaolin/CeO2/g-C3N4 composite was about 90% within 150 min, 2-folds higher than those of pristine CeO2 and g-C3N4. The enhanced photocatalytic activity was attributed to the improved photo-induced charge separation efficiency and the large specific surface area, which was determined by electrochemical measurements and N2 physisorption methods, respectively. The synergistic effect between the kaolin and CeO2/g-C3N4 heterostructure improved the photocatalytic performance of the final solid. The trapping and electron paramagnetic resonance (EPR) experiments demonstrated that the hole (h+) and superoxide radicals (•O2-) played an important role in the photocatalytic process. The photocatalytic mechanism for CIP degradation was also proposed based on experimental results. The obtained results revealed that the kaolin/CeO2/g-C3N4 composite is a promising solid catalyst for environmental remediation.

| S-EPMC7503662 | biostudies-literature

Coordination Complex Transformation-Assisted Fabrication for Hollow Chestnut-Like Hierarchical ZnS with Enhanced Photocatalytic Hydrogen Evolution.

Project description:Hierarchical nanostructures (HNs) are possibly endowed with novel properties due to their complex three-dimensional (3D) structures. Here, we provide a novel stepwise growth strategy of Coordination Complex Transformation-Assisted Growth for fabricating HNs. By using this, we prepare a new wurtzite ZnS HNs-hollow chestnut-like hierarchical microspheres (HCHMs), which are mesoporous hollow microspheres with single crystalline nanorods arrayed densely and radially from the centre. The HCHMs formation depends on the stepwise decomposition of the two Zn2+ complexes ([Zn(en)m(H?O)2(3-m)]2+ and [Zn(en)m(NH?)2(3-m)]2+, natural number m < 3). As the reaction proceeds, [Zn2+] has been distinctly reduced due to the transformation from [Zn(en)m(H?O)2(3-m)]2+ to [Zn(en)m(NH?)2(3-m)]2+ with a high stability constant, leading to a low crystal growth rate to obtain single crystalline nanorods. Additionally, the generated bubbles (CO?, NH?) acting as a template can induce the generation of hollow structure. The as-prepared ZnS HCHMs show an enhanced photocatalytic hydrogen evolution activity due to the single crystalline wurtzite phase and the high surface area contributed by the hollow hierarchical structures, as well as the mesoporosity. The versatility of the coordination complex transformation-assisted growth strategy will open up new possibilities for fabricating HNs, especially for those transition metal ions with excellent complex capabilities.

| S-EPMC6409558 | biostudies-literature

Enhanced Photocatalytic Activity and Stability in Hydrogen Evolution of Mo6 Iodide Clusters Supported on Graphene Oxide.

Project description:Catalytic properties of the cluster compound (TBA)2[Mo6Ii8(O2CCH3)a6] (TBA = tetrabutylammonium) and a new hybrid material (TBA)2Mo6Ii8@GO (GO = graphene oxide) in water photoreduction into molecular hydrogen were investigated. New hybrid material (TBA)2Mo6Ii8@GO was prepared by coordinative immobilization of the (TBA)2[Mo6Ii8(O2CCH3)a6] onto GO sheets and characterized by spectroscopic, analytical, and morphological techniques. Liquid and, for the first time, gas phase conditions were chosen for catalytic experiments under UV-Vis irradiation. In liquid water, optimal H2 production yields were obtained after using (TBA)2[Mo6Ii8(O2CCH3)a6] and (TBA)2Mo6Ii8@GO) catalysts after 5 h of irradiation of liquid water. Despite these remarkable catalytic performances, "liquid-phase" catalytic systems have serious drawbacks: the cluster anion evolves to less active cluster species with partial hydrolytic decomposition, and the nanocomposite completely decays in the process. Vapor water photoreduction showed lower catalytic performance but offers more advantages in terms of cluster stability, even after longer radiation exposure times and recyclability of both catalysts. The turnover frequency (TOF) of (TBA)2Mo6Ii8@GO is three times higher than that of the microcrystalline (TBA)2[Mo6Ii8(O2CCH3)a6], in agreement with the better accessibility of catalytic cluster sites for water molecules in the gas phase. This bodes well for the possibility of creating {Mo6I8}4+-based materials as catalysts in hydrogen production technology from water vapor.

| S-EPMC7407389 | biostudies-literature