TiO2 Support Research Articles

Direct Synthesis of Formic Acid from Carbon Dioxide by Hydrogenation Over Ruthenium Metal Doped Titanium Dioxide Nanoparticles in Functionalized Ionic Liquid

Background: Presently worldwide manufacturing of formic acid follows the permutation of methanol and carbon monoxide in presence of a strong base. But due to the use of toxic CO molecule and easy availability of CO2 molecule in the atmosphere, most of the research has been shifted from the conventional method of formic acid synthesis to direct hydrogenation of CO2 gas using different homogenous and heterogeneous catalysts. Objective: To develop reaction protocol to achieve easy CO2 hydrogenation to formic acid using Ionic liquid reaction medium. Methods: We used the sol-gel method followed by calcination (over 250oC for 5 hours) to synthesize two types of ruthenium metal-doped TiO2 nanoparticles (with and without ionic liquids), namely Ru@TiO2@IL and Ru@TiO2. We are reporting the application NR2 (R= CH3) containing imidazolium- based ionic liquids not only to achieve a good reaction rate but also to get agglomeration free ruthenium metal-doped TiO2 nanoparticles along with easy product isolation due to the presence of NR2 (R= CH3) functionality in ionic liquid structure. We synthesized various NR2 (R= CH3) functionalized ionic liquids such as 1-Butyl-3-methylimidazolium Chloride, 1,3-di(N,Ndimethylaminoethyl)- 2-methylimidazolium trifluoromethanesulfonate ([DAMI][TfO]), 1,3-di(N,Ndimethylaminoethyl)- 2-methylimidazolium bis (trifluoromethylsulfonyl) imide ([DAMI][NTf2]) and 1-butyl-3-methylimidazolium chloride ionic liquids which were synthesized as per the reported procedure. Results: We easily developed two types of Ru metal-doped TiO2 nanoparticles using the sol-gel method. After calcination, both Ru@TiO2@IL (3.2 wt% Ru), and Ru@TiO2 (1.7 wt% Ru) materials were characterized by XRD, FTIR, TEM, ICP-AES, EDS, and XANES analysis. After understanding the correct structural arrangement of Ru metal over TiO2 support, we utilized both Ru@TiO2@IL (3.2 wt% Ru) and Ru@TiO2 (1.7 wt% Ru) the materials as a catalyst for direct hydrogenation of CO2 in the presence of water and functionalized [DAMI] [TfO] ionic liquid. Conclusion: Here we demonstrated the preparation and characterization of TiO2 supported Ru nanoparticles with and without ionic liquid. After understanding the correct morphology and physiochemical analysis of Ru@TiO2@IL (3.2 wt% Ru), and Ru@TiO2 (1.7 wt% Ru) catalysts, we examined their application in CO2 reduction and formic acid synthesis. During the optimization, we also noticed the significant effect of functionalized [DAMI] [TfO] ionic liquid and water to improve the formic acid yield. Lastly, we also checked the stability of the catalyst by recycling the same till the 7th run.

Photothermal Catalytic Degradation of Lomefloxacin with Nano Au/TiO2

With the fast development of intensive poultry and aquaculture, the consumption of antibiotics has ever been increasing. Absorbed or metabolized antibiotics usually enter the water environment in the form of active drugs and metabolites, which can enhance the resistance of pathogenic microorganisms and even cause serious water pollution. Considering the bacteriostatic activity of antibiotics, the main biological method used to treat organic waste water has limited efficiency. Herein, we prepared Au/TiO2 for the efficient photocatalytic degradation of lomefloxacin (LOM) antibiotic wastewater. Based on the characteristics of prepared Au/TiO2, the short–wavelength light can be converted into photogenerated carriers with TiO2 support and the long–wavelength light can be converted into heat, likely due to the localized surface plasmon resonance effect of Au, synergistically promoting the LOM degradation. This study not only demonstrates that Au/TiO2 is an efficient photocatalyst for LOM degradation, but also further indicates the effectiveness of photocatalytic technology in the treatment of antibiotic wastewater.

The Influence of High-Energy Faceted TiO2 Supports on Co and Co-Ru Catalysts for Dry Methane Reforming.

The reforming of methane from biogas has been proposed as a promising method of CO2 utilization. Co-based catalysts are promising candidates for dry methane reforming. However, the main constraints limiting the large-scale use of Co-based catalysts are deactivation through carbon deposition (coking) and sintering due to weak metal-support interaction. We studied the structure-function properties and catalytic behavior of Co/TiO2 and Co-Ru/TiO2 catalysts using two different types of TiO2 supports, commercial TiO2 and faceted non-stoichiometric rutile TiO2 crystals (TiO2 *). The Co and Ru metal particles were deposited on TiO2 supports using a wet-impregnation method with the percentage weight loading of Co and Ru of 5% and 0.5%, respectively. The materials were characterized using SEM, STEM-HAADF, XRD, XPS and BET. The catalytic performance was studied using the CH4 : CO2 ratio of 3 : 2 to mimic the methane-rich biogas composition. Our results indicate that the addition of Ru to Co catalysts supported on TiO2 * reduces carbon deposition and influences oxygen mobility. Co and Co-Ru catalysts supported on TiO2 * has superior activity with the highest conversion of CO2 and CH4 of 34.7% and 23.5%, respectively. Despite the improved performance, the Co-Ru/TiO2 * catalyst has limited stability due to the proliferation of nanoparticle growth and TiOx layers on the surface of the nanoparticles indicating the prevalence of the strong-metal support interaction.

Effect of redox promoters (CeOx and CuOx) and surface sulfates on the selective catalytic reduction (SCR) of NO with NH3 by supported V2O5-WO3/TiO2 catalysts

A series of TiO2-supported MOx catalysts (M=V, W, Ce, Cu and S) were investigated for their SCR activity. In situ Raman spectroscopy indicated that the supported MOx phases were completely dispersed as surface sites on the TiO2 support. In situ IR revealed that surface VOx, WOx and SOx sites anchored at both CeOx/CuOx and TiO2 sites. The number of surface Lewis acid sites decreased with the addition of basic (CeOx/CuOx) and acidic (VOx/WOx) sites in all catalysts, and acidic SOx in the unpromoted and Ce-promoted catalysts. The surface VOx, WOx and SOx sites introduced surface Brønsted acid sites. The redox promoters increased the NO conversion, but SOx impregnation inhibited their effect due to acid (SOx)-base (CeOx/CuOx) interactions. The SCR reaction was shown to efficiently proceed via either surface NH3* or NH4+* species, resolving the long-standing dispute on the involvement of these species in the SCR reaction.

Highly Photoactive Titanium Dioxide Supported Platinum Catalyst: Synthesis Using Cleaner Ultrasound Approach

Catalysts increase reaction rates; however, the surface area to volume ratio of catalysts has a vital role in catalytic activity. The noble metals such as platinum (Pt) and gold (Au) are expensive; despite this, they have proven their existence in catalysis, motivating the synthesis of supported metal catalysts. Metal catalysts need to be highly dispersed onto the support. In this investigation, an ultrasound approach has been attempted to synthesise highly photoactive titanium dioxide (TiO2) nanoparticles by the hydrolysis of titanium tetraisopropoxide in an acetone/methanol mixture. To enhance its photocatalytic activity, TiO2 was doped with Pt. The synthesised photocatalyst was characterised by techniques such as particle size analysis (PSA), XRD, FE-SEM, TEM, and EDX. The enhancement in the surface characteristics of Pt-doped TiO2 compared with bare TiO2 support was confirmed with Brunauer–Emmett–Teller (BET) analysis. The enhanced surface area and uniformity in particle size distribution at the nanoscale level were due to the effects of ultrasonic irradiation. The obtained results corroborated the size and composition of the synthesised catalysts. The size of the catalysts is in the nanometre range, and good dispersion of Pt catalysts over the TiO2 support was observed. The UV-Visible spectroscopy analysis was performed to study the optical properties of the synthesised TiO2 and Pt/TiO2 photocatalysts. An increase in the absorbance was noted when Pt was added to TiO2, which is due to the decrease in the band gap energy.

Photodegradation of 2-propanol in gas phase over zirconium doped TiO2: Effect of Zr content

The photocatalytic activity in the 2-propanol degradation, under UV and sunlight (SL)-type irradiations, of a series of Zr-TiO2materials, prepared using the sol–gel method, with a Zr content ranging from 0.25 to 1 wt%, was evaluated in this work. The physicochemical properties of the solids were characterized using X-ray diffraction, BET and porosity measurements, IR, UV–vis, Photoluminescence and X-ray photoelectron spectroscopy. The XRD data showed that the TiO2 was stabilized as anatase phase in all the samples and that the incorporation of Zr4+ into TiO2 lattice has led to a decrease of the crystallite size. The BET analysis confirmed that the addition of zirconium onto TiO2 support affected the surface area which increases with the increase of Zr4+ content. The UV-DRS spectra showed that, the incorporation of zirconium into TiO2 lattice leads to a slight decrease of the band gap energy of TiO2. The results of the photocatalytic test showed an enhancement on the photocatalytic activity of TiO2, in the 2 propanol degradation, by the doping with a low amount of zirconium. All the samples were found more active under UV illumination than under SL. In all cases, the highest efficiency in the 2-propanol photodegradation was observed for the 0.5% Zr-TiO2 sample and was essentially related to its lowest optical band gap energy.

Synthesis of TixSn1-xO2 mixed metal oxide for copper catalysts as high-efficiency NH3 selective catalytic oxidation

A series of y Cu/TixSn1-xO2 catalysts for selective catalytic oxidation (NH3-SCO) were synthesized using TixSn1-xO2 as catalyst support and CuO as active species. Compared with pure TiO2 support, the strong metal-support interaction between Cu active species and TixSn1-xO2 was significantly promoted by the Sn-doping, thereby improving the catalytic activity and N2 selectivity of the catalyst, which meets the demand of diesel vehicles to completely convert NH3. The results of XRD and HRTEM showed that the particle size of 20 Cu/TiSnO2 sample is much more highly dispersed. The results of NH3-TPD and in-situ DRIFTS indicated that the copper species in 20 Cu/TixSn1-xO2 can provide more Lewis acid sites than 20 Cu/TiO2, which is conducive to the adsorption and reaction of NH3. Meanwhile, XPS results proved that adsorbed oxygen on the catalyst surface is the main active oxygen species. Finally, in-situ DRIFTs and kinetic measurements found that the NH3-SCO reaction over 20 Cu/TiSnO2 and 20 Cu/TiO2 follow the i-SCR and imide (–NH) mechanisms, respectively. This catalyst will provide solutions for the future design and application of ammonia slip from mobile and stationary sources.

Synthesis and application of TiO2-supported phosphotungstic acid for ethyl levulinate production

The present study investigates synthesis, characterization, and application of TiO2 supported Keggin phosphotungstic acid in biorenewable transformations. In particular, 10 wt%, 20 wt%, 30 wt% and 40 wt% Keggin phosphotungstic acid was loaded over TiO2 support via wet impregnation method to prepare EPTN-1, EPTN-2, EPTN-3, and EPTN-4 catalysts, respectively. After this, synthesized catalysts were tested in a microwave reactor to measure reactivity trend in order HPW > EPTN-4 > EPTN-3 > EPTN-2 > EPTN-1. A maximum 95% levulinic acid (LA) conversion was measured in the presence of 72 mg EPTN-4 catalyst, two mmol LA in 1:42 LA: EtOH (ethanol) molar ratio at 393 K in 120 min at a stirring speed of 300 rpm. No significant loss in heterogenized EPTN-4 catalyst was measured after five application cycles. A detailed characterization of synthesized catalyst showed that the Keggin structure remained intact after heterogenization.

Preparation and the Catalytic Properties of Attapulgite / TiO2 Nanocomposites

With the rapid development of industry, the discharge of textile printing and dyeing wastewater will cause serious pollution to other pure water bodies. It is imperative to deal with textile printing and dyeing wastewater. In this paper, with titanium tetrachloride as a precursor, attapulgite (ATP) / TiO2 nanocomposites were prepared by a neutralizing hydrolysis method and their catalytic activities were investigated by the oxidative degradation of methylene blue dye using ozone as oxidant. The test results showed that there were significant interactions between TiO2 and ATP support. The effects were also studied of ozone concentration, catalyst amount, reaction temperature, and initial concentration of methylene blue on the degradation rate of methylene blue catalyzed by the prepared attapulgite / TiO2 nanocomposites, and under the optimal conditions, the methylene blue could be degraded more than 90% in 30 minutes. Compared with that of pure ATP, the catalytic activities of ATP / TiO2 nanocomposites were enhenced remarkably. The degradation mechanism of methylene blue was also discussed.

TiO2-supported Co catalysts for the hydrogenation of γ-valerolactone to 2-methyltetrahydrofuran: influence of the support

The TiO2 support phase composition (anatase/rutile ratio) directly impacts key factors such as the metal–support interaction and the nanoparticle size driving the Co catalyst performances in γ-valerolactone hydrogenation to 2-methyltetrahydrofuran.

Effects of TiO2 Support and Cobalt Addition of Ni/TiO2 Catalyst in Selective Hydrogenation of Furfural to Furfuryl Alcohol

An effect of phase compositions (rutile, Rut and anatase, Ant) of TiO2 supports on the selective hydrogenation of furfural to furfuryl alcohol was investigated. The 15%wt Ni/TiO2 catalysts were prepared by incipient impregnation method. The result showed that Ni supported on anatase-rutile mixed phase TiO2 (91% Rut and 9% Ant, A2) provided the highest furfuryl alcohol yield at 43.8% due to the relatively strong Ni-TiO2 interaction, its appropriate crystallite sizes, and high average pore sizes. Furthermore, the effect of cobalt as a promoter on Ni/ TiO2-A2 catalysts was studied. The result showed that the Ni-Co/TiO2-A2 catalysts exhibited poorer catalyst performances compared to the monometallic Ni/TiO2, probably because addition of cobalt can lower the reduction temperatures of Ni/TiO2 and weaken the metal-support interaction.

Fe and Mn mixed oxide catalysts supported on Sn-modified TiO2 for the selective catalytic reduction of NO with NH3 at low temperature

FeMn/SnxTiO2 catalysts were synthesized by introducing Sn as an additive to modify TiO2 supports, and the Sn doping could improve the SO2 tolerance and low-temperature SCR activity significantly.

High electrocatalytic activity of Pt on porous Nb-doped TiO2 nanoparticles prepared by aerosol-assisted self-assembly.

This study explores an aerosol-assisted method to prepare an efficient support for the Pt catalyst of polymer electrolyte membrane fuel cells (PEMFCs). Titania nanoparticles and mesoporous niobium-doped titania nanoparticles were prepared by aerosol-assisted self-assembly using titanium(iv) isopropoxide and niobium(v) ethoxide as the titanium and niobium sources for application as non-carbon supports for the platinum electrocatalyst. The structural characteristics and electrochemical properties of the supports were investigated by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, inductively coupled plasma optical emission spectrometry, and dynamic light scattering. The Brunauer–Emmett–Teller method was used to calculate the specific surface areas of the samples, and the pore size distribution was also examined. The results demonstrated that under a radial concentration gradient, the aerosol droplets self-assembled into a spherical shape, and mesoporous supports were obtained after subsequent removal of the surfactant cetyltrimethylammonium bromide by annealing and washing. The hydrothermal technique was then used to deposit platinum on the TiO2-based supports. The electrical conductivity of the non-carbon support was enhanced by the strong metal–support interaction effect between the platinum catalyst particles and the porous niobium-doped TiO2 support. The half-wave potential, electrochemical surface area, mass activity, and specific activity of the obtained Pt/Nb-TiO2 catalyst all surpassed those of commercial Pt/C.

Effect of Tio2 Support for Co Nanoparticle Catalysts for Hydrogen Generation from Nabh4 Hydrolysis

Effect of Tio2 Support for Co Nanoparticle Catalysts for Hydrogen Generation from Nabh4 Hydrolysis

Effect of Au loading on Schottky barrier height in TiO2 + Au plasmonic photocatalysts

Composites of TiO2 and different amounts of plasmonic noble metal Au (0.25–2 wt%) were synthesized by employing the wet impregnation technique. The results of SEM, TEM, XRD and N2 physisorption analyses reveal that the morphologies of the prepared composites are similar to the morphology of bare TiO2 support and are not influenced by the increasing amount of deposited Au nanoparticles. On the other hand, the size of Au ensembles in the TiO2 + Au composites increased from 27.1 to 54.9 nm with the increasing amount of Au. With the increase of the diameter of Au ensembles, the intensity of the surface plasmon resonance (SPR) effect of Au ensembles in the UV–Vis diffuse reflectance spectra of the composites increased. The X-ray photoelectron spectroscopy (XPS) analysis of the valence band maxima (VBM) of the investigated photocatalysts revealed that the height of the Schottky barrier (SBH) at the Au/TiO2 junction in the investigated TiO2 + Au composites decreased from 0.4 to 0.15 eV with the increasing amount of Au (and their size). Therefore, the visible-light-generated “hot electrons” in Au ensembles of TiO2 + 2% Au composite have to overcome a lower energy barrier during the injection into the conduction band (CB) of the TiO2 support than “hot electrons” in the Au ensembles in the TiO2 + 0.25% Au composite. This makes the “hot electrons” in the TiO2 + 2% Au composite less accessible for the recombination with the visible-light generated holes, as the “hot electrons” do not agglomerate at the Schottky barrier (SB). This phenomenon was well expressed in the results of electrochemical impedance spectroscopy (EIS) analysis: under visible-light illumination, the TiO2 + 2% Au composite generated the highest amount of charge carriers among all investigated photocatalysts. The beneficial effect of the low SBH in the TiO2 + 2% Au solid was also expressed in the photoluminescence (PL) emission spectra, where the TiO2 + 2% Au composite showed the lowest charge carrier recombination rate. Further, the TiO2 + 2% Au composite expressed the highest visible-light triggered photocatalytic activity in the hydroxyl radical (OH·) generation and water-dissolved bisphenol A (BPA) oxidation test.

Photodeposition of alloyed Au-Pt nanoparticles on TiO2 for the enhanced catalytic oxidation of HCHO at room temperature

Catalytic oxidation has been considered as one of the most promising strategies for the removal of indoor HCHO which causes multiple health problems. Alloyed Au-Pt showed potential for catalytic oxidation reactions, but the reports on HCHO oxidation are limited. In addition,understanding on the catalytic mechanism is lacking. In this work, a sodium citrate assistant photodeposition process was developed to fabricate highly dispersed dual Au-Pt alloy with 2–3 nm on the surface of TiO2. The turnover frequency of Au-Pt/TiO2 (68.6 h-1) is much higher than that of Pt/TiO2 (19.9 h-1). This enhancement was also confirmed on different TiO2 supports and with different Pt loading. Based on the experimental and density functional theory calculations, it was found that the alloyed Au-Pt has more metallic Pt and is beneficial for the adsorption and dissociation of oxygen. Therefore, the rapid conversion of dioxymethylene species to formate species, with reduced reaction barrier, promotes the performance in catalytic oxidation of HCHO.

Integrated sol-gel and hydrothermal synthesis of V2O5–TiO2 nanocatalysts for enhanced catalytic removal of H2S

Hydrogen sulfide (H2S) emitted from the petroleum refinery process, landfills, or biogas purification is severely corrosive and has harmful health effects on the human body when inhaled at even small concentrations. Selective catalytic oxidation using V2O5–TiO2 is considered to be a benchmark technology for removing H2S. This paper presents a novel preparation method to synthesize V2O5–TiO2 nanocatalysts to improve desulfurization performance. Compared with the conventional sol-gel or wet-impregnation method, the integrated sol-gel and hydrothermal synthesis allows for a substantial increase in the specific surface area, which is mainly attributed to the highly reduced sizes of the primary particles. The enhanced surface area contributes to effective dispersion of the vanadium (V) species on the TiO2 support, by which the interactions between V and titanium (Ti) are strengthened. Accordingly, the redox properties of the catalysts are improved with increased concentrations of the chemisorbed oxygen species on the catalyst surfaces. Finally, the properties of the V2O5–TiO2 nanocatalysts are improved by the new preparation conditions, resulting in significantly enhanced catalytic activities in the selective oxidation of H2S: the best catalyst exhibits excellent activity even at 50 °C. It was also observed that the temperature during the hydrothermal reaction severely affected the catalytic performance of the V2O5–TiO2 nanocatalysts. This study suggests the importance of the preparation conditions for manipulating the physicochemical properties and performances of catalysts.

Analysis and modeling of high-performance polymer electrolyte membrane electrolyzers by machine learning

In this study, box and whisker and principal component analysis, as well as classification and regression tree modeling as a part of machine learning were performed on a database constructed on PEM (polymer electrolyte membrane) electrolysis with 789 data points from 30 recent publications. Box whisker plots discovered that pure Pt at the cathode surface, Ti at the anode support, the existence of Pt, Ir, Co, Ru at the anode surface, Ti porous structures at the electrodes, pure water-electrolyte and Nafion and Aquivion type membranes in proton exchange electrolyzer provide the highest performances. Principal component analysis indicated that when cathode surface consists of mostly pure Ni, when anode electrode has no support or vanadium (10–20%) doped TiO2 support and when anode electrode surface consists of cobalt-iron alloys (0.5:0.5 and 0.333:0.666 mol ratio) or RuO2, there is a risk for low-performance. Classification trees revealed that other than current density and potential, cathode surface Ni mole fraction, anode surface Co mole fraction are the most important variables for the performance of an electrolyzer. Finally, the regression tree technique successfully modeled the polarization behavior with a RMSE (root mean square error) value of 0.18.

TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Driven Water-Splitting

The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and cost-effective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) A large bandgap between optical and acoustic phonon modes and (2) No electronic bandgap, which allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.

Controlling the Production of Acid Catalyzed Products of Furfural Hydrogenation by Pd/TiO2

AbstractWe demonstrate a modified sol‐immobilization procedure using (MeOH)x/(H2O)1‐x solvent mixtures to prepare Pd/TiO2 catalysts that are able to reduce the formation of acid catalyzed products, e. g. ethers, for the hydrogenation of furfural. Transmission electron microscopy found a significant increase in polyvinyl alcohol (PVA) deposition at the metal‐support interface and temperature programmed reduction found a reduced uptake of hydrogen, compared to an established Pd/TiO2 preparation. We propose that the additional PVA hinders hydrogen spillover onto the TiO2 support and limits the formation of Brønsted acid sites, required to produce ethers. Elsewhere, the new preparation route was able to successfully anchor colloidal Pd to the TiO2 surface, without the need for acidification. This work demonstrates the potential for minimizing process steps as well as optimizing catalyst selectivity – both important objectives for sustainable chemistry.