Browse
Submit Data
Databases
API
Help

Dataset Information

26 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Mechanism of photocatalytic water oxidation on small TiO₂ nanoparticles.

ABSTRACT: We present the first unconstrained nonadiabatic molecular dynamics (NAMD) simulations of photocatalytic water oxidation by small hydrated TiO₂ nanoparticles using Tully surface hopping and time-dependent density functional theory. The results indicate that ultrafast electron-proton transfer from physisorbed water to the photohole initiates the photo-oxidation on the S₁ potential energy surface. The new mechanism readily explains the observation of mobile hydroxyl radicals in recent experiments. Two key driving forces for the photo-oxidation reaction are identified: localization of the electron-hole pair and stabilization of the photohole by hydrogen bonding interaction. Our findings illustrate the scope of recent advances in NAMD methods and emphasize the importance of explicit simulation of electronic excitations.

SUBMITTER: Muuronen M

PROVIDER: S-EPMC5407260 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Mechanism of photocatalytic water oxidation on small TiO2 nanoparticles.

Muuronen Mikko M Parker Shane M SM Berardo Enrico E Le Alexander A Zwijnenburg Martijn A MA Furche Filipp F

Chemical science 20161207 3

We present the first unconstrained nonadiabatic molecular dynamics (NAMD) simulations of photocatalytic water oxidation by small hydrated TiO2 nanoparticles using Tully surface hopping and time-dependent density functional theory. The results indicate that ultrafast electron-proton transfer from physisorbed water to the photohole initiates the photo-oxidation on the S1 potential energy surface. The new mechanism readily explains the observation of mobile hydroxyl radicals i ...[more]

PMID: 28507672

Similar Datasets

Photocatalytic Degradation Mechanism of the Pharmaceutical Agent Salbutamol Using the Mn-Doped TiO2 Nanoparticles Under Visible Light Irradiation.

Project description:In the present work, the photocatalytic degradation of salbutamol [2-(tert-butylamino)-1-(4-hydroxyl-3-hydroxymethylphenyl)ethanol] under visible irradiation using Mn-doped TiO2 is investigated. The Mn-doped TiO2 nanoparticles were synthesized by the sol-gel method with ratios of 0.1, 0.2, and 0.3%. Significant characteristics, including the rutile/anatase phases ratio, specific surface area, and band gap energy, were due to the amount of Mn doping; the narrowest band gap energy of 2.80 eV was observed in 0.2% Mn-doped TiO2 with specific surface areas of 89.36 m2/g and 10.87/89.13 of rutile/anatase phases. The investigation involved salbutamol photocatalytic degradation, a kinetic study, and the identification of intermediate compounds. The results indicated that 0.2% Mn-doped TiO2 obtained the best salbutamol removal of 95% under an irradiation time of 180 min. Salbutamol slowly degraded to the intermediate compounds in the first 60 min (k = 0.0088 1/min), and these intermediate compounds were dramatically mineralized to small hydrocarbon fragments and carbon dioxide in the later irradiation times (k = 0.0179 1/min). According to the high-performance liquid chromatography-mass spectrometry (HPLC-MS) results, possible degradation pathways of salbutamol were proposed: 2-(tert-butylamino)-1-(3,4-dihydroxyphenyl)ethanone, 2-(tert-butylamino)-ethanol, and 2-(tert-butylamino)-1-(4-hydroxyl-3-hydroxymethylphenyl)ethanone were initially formed and then transformed to 2-(methylamino)-1-(3,4-dihydroxyphenyl)ethanone, 2-(tert-butylamino)-acetic acid, hydroquinone, and 1-(4-hydroxylphenyl)ethanol, respectively. The mineralization of all intermediate compounds was verified by 90% chemical oxygen demand (COD) reduction, and the effluent contained a relatively low COD concentration of 7.8 mg/L.

| S-EPMC10193389 | biostudies-literature

Synthesis, Characterisation, Photocatalytic Activity, and Aquatic Toxicity Evaluation of TiO2 Nanoparticles.

Project description:Imidacloprid (IMD) is a toxic pesticide, and is one of the eight most widely used pesticides globally. Heterogeneous photocatalysis has often been investigated in recent years and can be successfully applied to remove imidacloprid from water. However, less investigated is the toxic effect of both the photocatalyst and the pesticide on aquatic life. Titanium dioxide (TiO2) remains the most effective photocatalyst, provided it is not toxic to the aquatic environment. This study investigated the TiO2 synthesis, characterisation, and photocatalytic activity on imidacloprid degradation and the toxicity of TiO2 nanoparticles and imidacloprid on the green algae Chlorella vulgaris. In the photodegradation process of IMD (initial concentration of 20 mg/L), electrons play an essential role; the degradation efficiency of IMD after 6 h increased from 69 to 90% under UV irradiation when holes (h+) scavengers were added, which allowed the electrons to react with the pollutant, resulting in lowering the recombination rate of electron-hole charge carriers. Growth inhibition of Chlorella vulgaris and effective concentration (EC50) were determined to study the toxic effect of TiO2 nanoparticles and imidacloprid. The EC50 increased from 289.338 mg/L in the first 24 h to 1126.75 mg/L after 96 h Chlorella vulgaris algal age, when the toxicant was TiO2. When IMD was the aquatic toxicant, a decrease in EC50 was observed from 22.8 mg/L (24 h) to 0.00777 mg/L (120 h), suggesting a long-term high toxicity level when pesticides in low concentrations are present in an aquatic environment.

| S-EPMC8709270 | biostudies-literature

Visible light-induced photocatalytic and antibacterial adhesion properties of superhydrophilic TiO2 nanoparticles.

Project description:Bacterial infections triggered by patient or healthcare worker contact with surfaces are a major cause of medically acquired infections. By controlling the kinetics of tetrabutyl titanate hydrolysis and condensation during the sol-gel process, it is possible to regulate the content of Ti3+ and oxygen vacancies (OVs) in TiO2, and adjust the associated visible light-induced photocatalytic performance and anti-bacterial adhesion properties. The results have shown that the Ti3+ content in TiO2 was 9.87% at the calcination temperature of the reaction system was 300 °C and pH was 1.0, corresponding to optimal photocatalytic and hydrophilic properties. The formation of a hydrated layer on the superhydrophilic surface provided resistance to bacterial adhesion, preventing cross-contamination on high-touch surfaces. The excellent photocatalytic self-cleaning performance and anti-bacterial adhesion properties can be attributed to synergistic effects associated with the high specific surface area of TiO2 nanoparticles, the mesoporous structure, and the presence of Ti3+ and OVs. The formation of superhydrophilic self-cleaning surfaces under visible light can serve as the basis for the development of a new class of anti-bacterial adhesion materials.

| S-EPMC10995203 | biostudies-literature

Human Health Risk Assessment of the Photocatalytic Oxidation of BTEX over TiO2/Volcanic Glass.

Project description:This study demonstrates rapid photocatalytic oxidation of a benzene, toluene, ethylbenzene, and xylene (BTEX) mixture over TiO2/volcanic glass. The assessment of the photocatalytic oxidation of BTEX was conducted under conditions simulating those found in indoor environments affected by aromatic hydrocarbon release. We show, under UV-A intensities of 15 mW/cm2 and an air flow rate of 55 m3/h, that low ppmv levels of BTEX concentrations can be reduced to below detectable levels. Solid-phase microextraction technique was employed to monitor the levels of BTEX in the test chamber throughout the photocatalytic oxidation, lasting approximately 21 h. Destruction of BTEX from the gas phase was observed in the following sequence: o-xylene, ethylbenzene, toluene, and benzene. This study identified sequential degradation of BTEX, in combination with the stringent regulatory level set for benzene, resulted in the air quality hazard indexes (Total Hazard Index and Hazard Quotient) remaining relatively high during the process of photocatalytic oxidation. In the practical application of photocatalytic purification, it is crucial to account for the slower oxidation kinetics of benzene. This is of particular importance due to not only its extremely low exposure limits, but also due to the classification of benzene as a Group 1 carcinogenic compound by the International Agency for Research on Cancer (IARC). Our study underscores the importance of taking regulatory considerations into account when using photocatalytic purification technology.

| S-EPMC10745685 | biostudies-literature

Synthesis of Double-Shell Hollow TiO2@ZIF-8 Nanoparticles With Enhanced Photocatalytic Activities.

Project description:Synthesis of semiconductor-MOF heterostructure photocatalysts has attracted considerable attention for their thermal stability, controllable crystallinity, and enhanced photocatalytic activity. In this work, the hollow nanostructure of anatase TiO2 was prepared by etching SiO2 from core-shell SiO2@TiO2 nanoparticles. ZIF-8, one of the metal-organic frameworks (MOFs), was hybrid synthesized on the surface of hollow TiO2 and formed double-shell hollow nanoparticles. The photocatalytic activity of the double-shell hollow TiO2@ZIF-8 nanoparticles toward methylene blue (MB) under UV light irradiation was processed, and the highest photocatalytic efficiency of 99.1% was shown compared with TiO2 and SiO2@TiO2 nanoparticles. This study suggests a promising approach to achieve an advanced photocatalytic performance toward dye degradation using MOFs for the surface engineering of semiconductors.

| S-EPMC7645166 | biostudies-literature

Soft Zr-doped TiO2 Nanofibrous Membranes with Enhanced Photocatalytic Activity for Water Purification.

Project description:Self-standing photocatalytic membranes constructed from TiO2 nanofibers hold great promise in environmental remediation; however, challenges still remained for the poor mechanical properties of polycrystalline TiO2 nanofibers. Herein, soft Zr-doped TiO2 (TZ) nanofibrous membranes with robust mechanical properties and enhanced photocatalytic activity were fabricated via electrospinning technique. The Zr4+ incorporation could effectively inhibit the grain growth and reduce the surface defects and breaking point of TiO2 nanofiber. The as-prepared TZ membranes were composed of well-interconnected nanofibers with a high aspect ratios, small grain size and pore size, which exhibited good tensile strength (1.32 MPa) and showed no obvious damage after 200 cycles of bending to a radius of 2 mm. A plausible bending deformation mechanism of the soft TZ membranes was proposed from microscopic single nanofiber to macroscopical membranes. Moreover, the resultant TZ membranes displayed better photocatalytic performance for methylene blue degradation compared to a commercial catalyst (P25), including high degradation degree of 95.4% within 30 min, good reusability in 5 cycles, and easiness of recycling. The successful preparation of such fascinating materials may open up new avenues for the design and development of soft TiO2-based membranes for various application.

| S-EPMC5431652 | biostudies-literature

TiO2 decorated functionalized halloysite nanotubes (TiO2@HNTs) and photocatalytic PVC membranes synthesis, characterization and its application in water treatment.

Project description:In this study photocatalyst, TiO2@HNTs were prepared by synthesizing TiO2 nanoparticles in situ on the functionalized halloysite nanotubes (HNTs) surface. Photocatalytic PVC membrane TiO2@HNTs M2 (2 wt.%) and TiO2@HNTs M3 (3 wt.%) were also prepared. Photocatalyst TiO2@HNTs and photocatalytic PVC membranes were used to study the photocatalytic activity against the methylene blue (MB) and rhodamine B (RB) dyes in UV batch reactor. The structure and morphology of photocatalyst and photocatalytic PVC membrane were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), UV-Vis spectrophotometer and photoluminescence (PL). The PL study showed that the oxygen vacancies and surface hydroxyl groups present on the surface of TiO2@HNTs act as excellent traps for charge carrier, reducing the electron-hole recombination rate.TiO2@HNTs 2 (2 wt.%) and TiO2@HNTs 3 (3 wt.%) degraded MB dye up to 83.21%, 87.47% and RB dye up to 96.84% and 96.87%, respectively. TiO2@HNT photocatalyst proved to be stable during the three consecutive cycle of photocatalytic degradation of the RB dye. TiO2@HNTs M2 and TiO2@HNTs M3 degraded MB dye up to 27.19%, 42.37% and RB dye up to 30.78%, 32.76%, respectively. Photocatalytic degradation of both the dyes followed the first-order kinetic model. Degradation product analysis was done using the liquid chromatography-mass spectrometry (LC-MS) and the results showed that the dye degradation was initiated by demethylation of the molecule. MB and RB dye degradation reaction were tested by TBA and IPA as OH* and H+ scavengers respectively. Mechanism of photocatalytic activity of TiO2@HNTs and photocatalytic PVC membrane were also explained.

| S-EPMC6416328 | biostudies-literature

TiO2 Nanotubes for Solar Water Splitting: Vacuum Annealing and Zr Doping Enhance Water Oxidation Kinetics.

Project description:Herein, we report the cooperative effect of Zr doping and vacuum annealing on the carrier dynamics and interfacial kinetics of anodized TiO2 nanotubes for light-driven water oxidation. After evaluation of different Zr loads and different annealing conditions, it was found that both Zr doping and vacuum annealing lead to a significantly enhanced light harvesting efficiency and photoelectrochemical performance. The substitution of Zr4+ by Ti4+ species leads to a higher density of surface defects such as oxygen vacancies, facilitating electron trapping on Zr4+, which reduced the charge recombination and hence boosted the charge transfer kinetics. More importantly, vacuum annealing promoted the presence of surface defects. Furthermore, the mechanistic study through impedance spectroscopy revealed that both charge transfer and surface conductivity are significantly enhanced due the presence of an oxygen-deficient TiO2 surface. These results represent an important step forward in the optimization of nanostructured TiO2-based photoelectrodes, with high potential in photocatalytic applications, including solar fuel production.

| S-EPMC6777075 | biostudies-literature

Heating-Induced Transformation of Anatase TiO2 Nanorods into Rock-Salt TiO Nanoparticles: Implications for Photocatalytic and Gas-Sensing Applications.

Project description:Anatase TiO2 nanocrystals (NCs) play a vital role in photocatalytic applications due to their high catalytic activity and in gas-sensing applications due to their high chemical sensitivity. Here, we report the transformation at elevated temperature of anatase nanorods (NRs) with a length of 25 nm into rock-salt TiO nanoparticles with an average size of 9.2 ± 2.1 nm investigated by means of in situ heating in the transmission electron microscope. The NRs were completely transformed to titanium monoxide NCs after heating to a temperature of 1200 °C. We also identified an intermediate stage in the temperature range of 950-1200 °C, during which not only the anatase and rock-salt phases were found but also the brookite phase. Understanding of the phase and morphology evolution at high temperatures is of essence to the functionality of the NRs in various applications, as discussed in this work. Moreover, the high-temperature transformation to titanium monoxide is of interest as rock-salt TiO (γ-TiO) is known to exhibit superconducting properties. We propose the heating-induced transformation as a physical route to synthesize TiO NCs of very small size.

| S-EPMC8805116 | biostudies-literature

Sintering Rate and Mechanism of TiO2 Nanoparticles by Molecular Dynamics.

Project description:Titania is the dominant white pigment and photocatalytic material, a key component of sunscreens and has promising applications in photovoltaics and sensors of organic vapors. The growth of TiO2 nanoparticles by sintering, the critical step during their large scale manufacture and processing, is elucidated and quantified by molecular dynamics. Highly mobile ions from the particle surface fill in the initially concave space between nanoparticles (surface diffusion) forming the final, fully-coalesced, spherical-like particle with minimal displacement of inner Ti and O ions (grain boundary diffusion) revealing also the significance and sequence of these two sintering mechanisms of TiO2. A sintering rate for TiO2 nanoparticles is extracted that is much faster than that in the literature but nicely converges to it for increasing particle size.

| S-EPMC3667479 | biostudies-literature