Hydroxylation induced defect states and formation of bidentate acetate adstructure of TiO2 catalysts with acetic acid variation for catalytic application

2022 ◽  
Author(s):  
Kazi Hasibur Rahman ◽  
Asit Kumar Kar
Keyword(s):  
Acetic Acid ◽  
Tio2 Nanoparticles ◽  
Active Sites ◽  
Surface Defects ◽  
Advanced Oxidation Process ◽  
Theoretical Calculations ◽  
Xrd Analysis ◽  
Structural Defects ◽  
Condensation Process ◽  
Defect States

Abstract TiO2 is considered a promising candidate for catalysis applications.The addition of acetic acid and its variation creates a strong bonding withoxide surfaces which generates various oxidizing agents. The XRD analysis of the prepared TiO2 nanoparticles reveals the semicrystalline nature. The result shows that holes are captured by surface and subsurface, producing≡〖Ti〗^IV‒〖OH〗^. , ≡〖Ti〗^IV‒O^(.-)‒〖Ti〗^IV≡ and reducing agent =〖Ti〗^III‒, which act as active oxidizersduring photocatalysis confirmingthe occurrence of OH radical by advanced oxidation process. Increasing acetic acid amount leads to disordered structural defects below the conduction band. XPS analysis shows the induction of hydroxylation of surface defects such as Ti‒OH.The results indicate that oxygen vacancy is favourabledue toa large number of surface defects. Detailed discussion of energy band structure with the concept of valence band and CB maximum isimplemented. The electron-withdrawing carboxylic group can affect oxygen vacancies and acetate ligands on the photocatalyst surface. The formation of bidentate acetate adstructure with lower acetic acid concentration leads to an explanation for higher visible light driven Mehtlyne blue (MB) degradation. The mechanism of formation of additional Ti-O-Ti bond by condensation process is also illustrated elaborately. Theoretical calculations of the potential of VB and CB show the effect of active sites on degradation and can be associated with redox reactions for water splitting ability. Possible model of sentisized photocatalysis for hydrogen production with hydrogen and oxygen evolution site is also proposed in this article. Thus, TiO2 nanoparticles with acetic acid variation are promising sources for photocatalytic/catalytic applications.evolution site is also proposed in this article. Thus, pH-dependent TiO2 nanoparticles are promising sources for photocatalytic/catalytic applications.

scholarly journals Lignin-Mediated Biosynthesis of ZnO and TiO2 Nanocomposites for Enhanced Antimicrobial Activity

2019 ◽  
Vol 3 (3) ◽  
pp. 90 ◽  
Author(s):  
Kanchan M. Samb-Joshi ◽  
Yogesh A. Sethi ◽  
Anuradha A. Ambalkar ◽  
Hiralal B. Sonawane ◽  
Suresh P. Rasale ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Antimicrobial Activity ◽  
Tio2 Nanoparticles ◽  
Phase Formation ◽  
Visible Region ◽  
Xrd Analysis ◽  
Structural Defects ◽  
Precipitation Method ◽  
Zno Nps ◽  
Average Size

In this work, we report the synthesis of fragmented lignin (FL) assisted zinc oxide (ZnO) and titanium oxide (TiO2) nanocomposites. The fragmented lignin synthesized from biomass (sugarcane bagasse) was used as a template to generate the morphology and crystallite structure of metal oxide nanomaterial. The nanocomposites were synthesized by a simple precipitation method, wherein fragmented lignin is used in alkaline medium as a template. X-ray diffraction (XRD) analysis shows the phase formation of hexagonal wurtzite ZnO and mixed phase formation of TiO2 as rutile and anatase. The morphology was studied by using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM). The FE-SEM of pristine ZnO nanocomposites showed a cluster of particles whereas FL–ZnO NPs showed self-aligned nanoparticles in the form of rod shaped having average size 30–70 nm. Pristine TiO2 nanoparticles showed clusters of particles and FL–TiO2 nanocomposites showed well crystalline 41nm size nanocomposites. The FL acts as a surfactant which restrict the cluster formations. The band gap determined by diffuse reflectance spectra is 3.10 eV and 3.20 eV for FL–ZnO and FL–TiO2 nanocomposites, respectively. Photoluminescence spectra of both nanocomposites showed structural defects in the visible region. Further, the antimicrobial activity of pristine ZnO and TiO2 nanoparticles, and FL–ZnO and FL–TiO2 nanocomposites against Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923) were studied under UV-A (315-400 nm) (8W) for 30min.

Revisiting Glycerol Esterification with Acetic Acid over Amberlyst-35 via Statistically Designed Experiments: Overcoming Transport Limitations

2019 ◽  
Author(s):  
Víctor Gabriel Baldovino Medrano ◽  
Karen V. Caballero ◽  
Hernando Guerrero-Amaya
Keyword(s):  
Acetic Acid ◽  
Active Sites ◽  
Batch Reactor ◽  
Catalyst Particle ◽  
Experimental Designs ◽  
Particle Sizes ◽  
Turnover Rates ◽  
Designed Experiments ◽  
Different Temperatures ◽  
Glycerol Esterification

Turnover rates for glycerol esterification with acetic acid over Amberlyst-35 were measured under different temperatures, reactants and active sites concentrations, and catalyst particle sizes. Data were collected in a batch reactor. Experiments were done following a sequence of factorial experimental designs.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

scholarly journals Efficient electrocatalytic nitrogen reduction to ammonia with aqueous silver nanodots

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Wenyi Li ◽  
Ke Li ◽  
Yixing Ye ◽  
Shengbo Zhang ◽  
Yanyan Liu ◽  
...  
Keyword(s):  
Active Sites ◽  
Theoretical Calculations ◽  
Current Collector ◽  
Electrochemical Reactor ◽  
Reduction Reaction ◽  
Solution Ph ◽  
Faradaic Efficiency ◽  
Yield Rate ◽  
Silver Nanodots ◽  
Ti Mesh

AbstractThe electrocatalytic nitrogen (N2) reduction reaction (NRR) relies on the development of highly efficient electrocatalysts and electrocatalysis systems. Herein, we report a non-loading electrocatalysis system, where the electrocatalysts are dispersed in aqueous solution rather than loading them on electrode substrates. The system consists of aqueous Ag nanodots (AgNDs) as the catalyst and metallic titanium (Ti) mesh as the current collector for electrocatalytic NRR. The as-synthesized AgNDs, homogeneously dispersed in 0.1 M Na2SO4 solution (pH = 10.5), can achieve an NH3 yield rate of 600.4 ± 23.0 μg h−1 mgAg−1 with a faradaic efficiency (FE) of 10.1 ± 0.7% at −0.25 V (vs. RHE). The FE can be further improved to be 20.1 ± 0.9% at the same potential by using Ti mesh modified with oxygen vacancy-rich TiO2 nanosheets as the current collector. Utilizing the aqueous AgNDs catalyst, a Ti plate based two-electrode configured flow-type electrochemical reactor was developed to achieve an NH3 yield rate of 804.5 ± 30.6 μg h−1 mgAg−1 with a FE of 8.2 ± 0.5% at a voltage of −1.8 V. The designed non-loading electrocatalysis system takes full advantage of the AgNDs’ active sites for N2 adsorption and activation, following an alternative hydrogenation mechanism revealed by theoretical calculations.

Comparative study of conventional and microwave heating of polyacrylonitrile-based fibres

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guozhen Zhao ◽  
Jianhua Liu ◽  
Lei Xu ◽  
Shenghui Guo
Keyword(s):  
Microwave Heating ◽  
Surface Defects ◽  
Energy Dispersive Spectrometer ◽  
Xrd Analysis ◽  
Economic Benefits ◽  
Heating Time ◽  
Oxidation Temperature ◽  
Conventional Heating ◽  
Heating Method ◽  
Molecular Arrangement

Abstract The effects of the conventional heating method and the microwave heating method on polyacrylonitrile-based fibres in the temperature range of 180–280 °C were investigated. Fourier transform infrared spectroscopy, X-ray wide-angle scattering, Raman spectroscopy, energy-dispersive spectrometer, scanning electron microscopy and bulk density were used to characterise the properties of the samples. Results show that the microwave heating method can shorten the pre-oxidation time, reduce pre-oxidation temperature and reduce the number of surface defects. The pre-oxidised fibres obtained by the microwave heating method exhibit not only good crystallite size but also a smooth surface. Atomic morphology and molecular arrangement are orderly inside the fibre. The FT-IR spectrum shows that the oxidation reaction occurs at 220 °C, and the CI value of PAN fibers stabilised by microwave heating is the larger than the fibers stabilised by conventional heating. XRD analysis shows that fibers stabilised by microwave heating have low stack domains. The SEM and Raman spectra indicate that hydrogen peroxide can improve the surface finish of the fibers and reduce defects. Microwave heating can reduce the pre-oxidation temperature by about 20 °C and shorten the heating time. The economic benefits of using this method are significantly improved.

scholarly journals Nitrile versus isonitrile adsorption at interstellar grain surfaces

2017 ◽  
Vol 608 ◽  
pp. A50 ◽  
Author(s):  
M. Bertin ◽  
M. Doronin ◽  
X. Michaut ◽  
L. Philippe ◽  
A. Markovits ◽  
...  
Keyword(s):  
Density Functional ◽  
Surface Defects ◽  
High Vacuum ◽  
Solid Support ◽  
Ultra High Vacuum ◽  
Structural Defects ◽  
Adsorption Energies ◽  
The Difference ◽  
Temperature Programmed ◽  
Open Question

Context. Almost 20% of the ~200 different species detected in the interstellar and circumstellar media present a carbon atom linked to nitrogen by a triple bond. Of these 37 molecules, 30 are nitrile R-CN compounds, the remaining 7 belonging to the isonitrile R-NC family. How these species behave in their interactions with the grain surfaces is still an open question. Aims. In a previous work, we have investigated whether the difference between nitrile and isonitrile functional groups may induce differences in the adsorption energies of the related isomers at the surfaces of interstellar grains of various nature and morphologies. This study is a follow up of this work, where we focus on the adsorption on carbonaceous aromatic surfaces. Methods. The question is addressed by means of a concerted experimental and theoretical approach of the adsorption energies of CH3CN and CH3NC on the surface of graphite (with and without surface defects). The experimental determination of the molecule and surface interaction energies is carried out using temperature-programmed desorption in an ultra-high vacuum between 70 and 160 K. Theoretically, the question is addressed using first-principle periodic density functional theory to represent the organised solid support. Results. The adsorption energy of each compound is found to be very sensitive to the structural defects of the aromatic carbonaceous surface: these defects, expected to be present in a large numbers and great diversity on a realistic surface, significantly increase the average adsorption energies to more than 50% as compared to adsorption on perfect graphene planes. The most stable isomer (CH3CN) interacts more efficiently with the carbonaceous solid support than the higher energy isomer (CH3NC), however.

scholarly journals Probing the Catalytic Efficiency of Supported Heteropoly Acids for Esterification: Effect of Weak Catalyst Support Interactions

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Ali Alsalme ◽  
Aliyah A. Alsharif ◽  
Hamda Al-Enizi ◽  
Mujeeb Khan ◽  
Saad G. Alshammari ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Active Sites ◽  
Catalyst Support ◽  
Supported Catalyst ◽  
Catalytic Efficiency ◽  
Biodiesel Production ◽  
Effect Of Temperature ◽  
Heteropoly Acids ◽  
Catalyst Loading ◽  
Esterification Activity

Supported heteropoly acids are an interesting class of solid acid catalysts which possess flexible structure and super acidic properties essentially required for the oil-based biodiesel production. In this study, a series of catalysts containing 25 wt.% of heteropolytungstate (HPW) supported on various clays or SiO2 were prepared, and their catalytic efficiency was evaluated for esterification of acetic acid with heptanol. The as-prepared catalysts were characterized by various techniques including FT-IR spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and BET. The catalytic efficiency of both bulk and supported HPW catalysts for the esterification activity strongly depends on the type of support and amount of catalyst; the bulk HPW catalyst and the catalyst supported by kaolinite with 25 wt.% of HPW exhibited highest activity. In order to study the effect of temperature on conversion, all the catalysts were subjected to different reaction temperatures. It was revealed that esterification activity of both bulk and supported HPW catalysts strongly depends upon the temperature variations of the reaction. Besides, the effect of leaching of active sites on the catalysts performance for biodiesel production was also evaluated by inductively coupled plasma studies (ICP). The kaolinite-supported catalyst (25% HPW/kaolinite) demonstrated higher amount of leaching which is also confirmed by the significant decrease in its catalytic activity when it is used for the second time. However, the higher activity demonstrated by HPW/kaolinite maybe because of some homogeneous reaction indicating a weak catalyst support interaction (WCSI) resulting in the leaching of the catalyst during the test. Furthermore, the effects of other reaction variables such as catalyst loading and reaction time on the conversion of acetic acid were also studied.

scholarly journals Nanobelts-constructed Porous TiO2-B@SnS2 Heterostructure Hybrids for Enhance Lithium Storage Performance

2021 ◽  
Author(s):  
Chao Cai ◽  
Meiyu Song ◽  
Qixiang Ou ◽  
Jianmei Li ◽  
changsheng an
Keyword(s):  
Active Sites ◽  
Electrode Materials ◽  
Theoretical Calculations ◽  
Electronic Conductivity ◽  
Lithium Ion ◽  
Cycle Performance ◽  
Electrode Structure ◽  
Lithium Storage ◽  
Volume Collapse ◽  
Alloy Type

Abstract Alloy-type anodes materials possess broad prospects for excellent electrochemical property lithium-ion batteries owing to its high theoretical capacity and excellent electronic conductivity. However, this type electrode materials experience poor kinetics and tremendous volume collapse during the repeated lithiation-delithiation process. Herein, an efficient method to provide a fast transmission channel and suppress the volume collapse during the discharge/charge process by constructing the heterostructure between porous TiO2-B nanoblets and few-layer SnS2 nanosheets interface, which provides high-active sites for the nucleation and growth of SnS2 nanosheets, and inhibits the agglomeration of SnS2 nanosheets. Both experimental results and theoretical calculations definite that porous TiO2 nanobelts provides more chemical active sites for the adsorption and transmission of lithium ion and then effectively improve the stability the electrode structure. As a result, TiO2-B@SnS2 hybrid exhibits excellent rate and cycle performance. This work paves a way to design and construction of high performance alloy-type anode materials.

Effect of TiO2 surface treatment on electron transfer in dye-sensitized solar cells

2022 ◽  
Author(s):  
Suping Jia ◽  
Tong Cheng ◽  
Huinian Zhang ◽  
Hao Wang ◽  
Caihong Hao
Keyword(s):  
Solar Cells ◽  
Electron Transport ◽  
High Efficiency ◽  
Surface Defects ◽  
Dye Sensitized Solar Cells ◽  
Charge Recombination ◽  
Defect States ◽  
Transport Pathway ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

Defect states in the TiO2 nanoparticles can cause severe charge recombination and poor electron-transport efficiency when used as a photoanode in dye-sensitized solar cells (DSSCs). Herein, we report a simple and practical way to passivate the surface defects of TiO2 through hydrothermal treating with acetic acid and H2SO4, introducing a high percentage of 101 facets and sulfonic acid functional groups on the TiO2 surface. A high efficiency of 8.12% has been achieved, which is 14% higher than that of untreated TiO2 under the same condition. EIS results prove that the multiacid-treated TiO2 can promote electron transport and reduce charge recombination at the interface of the TiO2 and electrolyte. This work provides an efficient approach to engineer the electron-transport pathway in DSSCs.

Triclinic boron nanosheets high-efficient electrocatalysts for water splitting

2021 ◽  
Author(s):  
Maoping Xu ◽  
Rui Wang ◽  
Kan Bian ◽  
Chuang Hou ◽  
Yaxing Wu ◽  
...  
Keyword(s):  
Active Sites ◽  
Theoretical Calculations ◽  
Chemical Properties ◽  
Chemical Vapor ◽  
Energy Storage And Conversion ◽  
High Efficient ◽  
Long Time ◽  
Time Cycle ◽  
Metal Properties ◽  
Physical And Chemical

Abstract Recently, two-dimensional (2D) boron nanosheets have been predicted to exhibit exceptional physical and chemical properties, which is expected to be widely used in advanced electronics, optoelectronic, energy storage and conversion devices. However, the experimental application of 2D boron nanosheets in hydrogen evolution reactiuon (HER) has not been reported. Here, we have grown ultrathin boron nanosheets on tungsten foils via chemical vapor deposition (CVD). The prepared triclinic boron nanosheets are highly crystalline, which perfectly match the structure in the previous theoretical calculations. Notably, the boron nanosheets show excellent HER performance. The Tafel slope is only 64 mV/dec-1 and the nanosheets can maintain good stability under long-time cycle in acidic solution. The improvement of performance is mainly due to the metal properties and a large number of exposed active sites on the boron nanosheets, which is confirmed by first-principle calculations.

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