Ru TiO2 Research Articles

Boosting photocatalytic water splitting of TiO2 using metal (Ru, Co, or Ni) co-catalysts for hydrogen generation

The photocatalytic activity of titanium dioxide (TiO2) nanoparticles toward hydrogen generation can be significantly improved via the loading of various metals e.g., Ru, Co, Ni as co-catalysts. The metal co-catalysts are loaded into TiO2 nanoparticles via different deposition methods; incipient wet impregnation (Imp), hydrothermal (HT), or photocatalytic deposition (PCD). Among all of the tested materials, 0.1 wt% Ru–TiO2 (Imp) provided the highest initial hydrogen catalytic rate of 23.9 mmol h−1 g−1, compared to 10.82 and 16.55 mmol h−1 g−1 for 0.3 wt% Ni–TiO2 (Imp) and 0.3 wt% Co–TiO2 (Imp), respectively. The loading procedures, co-catalyst metals type, and their loading play a significant role in elevating the photocatalytic activity of pristine TiO2 semiconductors toward hydrogen generation. Redox transition metals e.g., Co and Ni exhibit comparable photocatalytic performance to expensive elements such as Ru.

MOX-TiO2 (M=Pt, Pd, Ru) for alcoholysis reaction from furfuryl alcohol to ethyl levulinate

Simple noble metal oxides (PtOx, PdOx, RuOx) based titanium dioxide (Pt–TiO2, Pd–TiO2, Ru–TiO2) were prepared using a facile sol-gel method. The conversion of furfuryl alcohol (FAL) to ethyl levulinate (EL) was studied. Full characterizations were performed using XRD, XPS, Raman and in situ FT-IR. An in-depth study of acidic strength and sites distribution (Brønsted or Lewis) was conducted by NH3-TPD, pyridine-IR. The profiles of H2-TPR and O2-TPD suggested enhanced reducibility and optimum oxygen storage capacity in Pt–TiO2. Remarkable FAL conversion (94.4%), EL yield (89.6%) with productivity (21.3 × 103 molEL/mmolPt h) and TOF (22.5 × 103 molFAL/mmolPt h) were obtained. Metal productivity follows the order: Pt (21.3 × 103 molEL/mmolPt h) > Ru (11.5 × 103 molEL/mmolRu h) > Pd (3.6 × 103 molEL/mmolPd h). Two different reaction pathways were proposed. From computational calculations of charge density differences and Ead value, a robust electron transfer capacity was found in Pt–TiO2, as well as an advantageous FAL adsorption as compared to other catalytic systems.

Electro-sensing of biocide and its applications based on the Ru-doped TiO2 and reduced GO nanocomposite fabricated electrode

In this study, we utilized a carbon paste electrode (CPE) that had been modified with reduced graphene oxide nanoparticles (rGO) and ruthenium-doped TiO2 nanoparticles (Ru–TiO2) to conduct an electrochemical investigation of triclosan (TCS). To characterize the synthesized Ru–TiO2 nanoparticles, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were utilized. Electrochemical impedance spectroscopy was employed to characterize the fabricated Ru–TiO2/rGO/CPE and bare CPE. “The heterogeneous rate constant, the pH study, the accumulation time, the scan rate, and the concentration fluctuation were investigated. Combining several electrocatalytic modifiers allows for the development of effective electrochemical sensors. Ru–TiO2 and rGO nanostructures are two examples of these modifiers. As a result of its great sensitivity, selectivity, and application to the measurement of TCS, nanostructured Ru–TiO2 and rGO are highly recommended in this research. At a pH of 9.2 in PBS, the sensitivity range of a Ru–TiO2/rGO/CPE was investigated by testing its response to a calibration plot of TCS concentrations ranging from 1.0 × 10−8 M to 2.2 × 10−7 M. Voltammetric techniques such as square wave voltammetry (SWV) and cyclic voltammetry (CV) were used to determine the electrochemical components that comprise TCS. The developed sensor was also employed to detect and analyze TCS levels in actual samples, including those of fruits, vegetables, water, and soil.”

Correlating O-Vacancy and Hydrogen Spillover with Activity and Selectivity in Furfural Hydrogenation Using Nanocatalysts Comprised of Ru Nanoparticles Supported on TiO2–SiO2

The nanoengineering of efficient and stable nanocatalysts is highly desired for sustainable biomass valorization toward the selective hydrogenation of furfural. The interaction of supports with metallic nanoparticles and oxygen vacancies has a significant role in the catalytic activity of oxide nanocatalysts. Here, by combining density functional theory (DFT) calculations and catalytic experimental data, we demonstrated that the presence of TiO2 in Ru–SiO2 catalysts might allow an association between oxygen vacancies and the hydrogen spillover effect. Specifically, Ru–TiO2–SiO2 and Ru–SiO2 nanocatalysts displayed improved activities and selectivities toward the reaction mentioned above. The nanomaterials were prepared by a simple, versatile, and single-step modified sol–gel process build upon two different stabilizing agents (P123 and CTAB), which afforded entirely covered surfaces of TiO2–SiO2 and SiO2 supports with uniform small Ru nanoparticles generated in situ. The Ru-TSdc nanocatalyst displayed several interesting promising nanoscale features for hydrogenation of furfural: (i) uniform distribution of Ru, Ti, and Si elements over the entire catalyst surface, (ii) deposition of small Ru nanoparticles with no significant particle agglomeration, (iii) facilitated hydrogen spillover from Ru NPs to the TiO2 support, and (iv) a significant amount of oxygen vacancies at the nanoparticle surface. For these reasons, the Ru-TSdc sample afforded the optimal performance toward the selective hydrogenation of furfural (up to 99% of selectivity), maintaining good conversions in certain reaction conditions. This work demonstrates how the catalytic activity of metallic nanoparticles could be improved by the structural addition of a reducible oxide, leading to more efficient inorganic supports and for preparing nanocatalysts.

Efficient Nitrate Synthesis via Ambient Nitrogen Oxidation with Ru-Doped TiO2 /RuO2 Electrocatalysts.

A facile pathway of the electrocatalytic nitrogen oxidation reaction (NOR) to nitrate is proposed, and Ru-doped TiO2 /RuO2 (abbreviated as Ru/TiO2 ) as a proof-of-concept catalyst is employed accordingly. Density functional theory (DFT) calculations suggest that Ruδ + can function as the main active center for the NOR process. Remarkably doping Ru into the TiO2 lattice can induce an upshift of the d-band center of the Ru site, resulting in enhanced activity for accelerating electrochemical conversion of inert N2 to active NO*. Overdoping of Ru ions will lead to the formation of additional RuO2 on the TiO2 surface, which provides oxygen evolution reaction (OER) active sites for promoting the redox transformation of the NO* intermediate to nitrate. However, too much RuO2 in the catalyst is detrimental to both the selectivity of the NOR and the Faradaic efficiency due to the dominant OER process. Experimentally, a considerable nitrate yield rate of 161.9 µmol h-1 gcat -1 (besides, a total nitrate yield of 47.9 µg during 50 h) and a highest nitrate Faradaic efficiency of 26.1% are achieved by the Ru/TiO2 catalyst (with the hybrid composition of Rux Tiy O2 and extra RuO2 by 2.79 wt% Ru addition amount) in 0.1 m Na2 SO4 electrolyte.

Ru–TiO2 semiconducting nanoparticles for the photo-catalytic degradation of bromothymol blue

Photo-catalytic degradation of bromothymol blue (BTB) in an aqueous medium by Ru–TiO2 using UVC (254 nm) irradiation was investigated for a pH range of 4.0–8.0. The liquid impregnation method was used to synthesize 0.2, 0.4 and 0.8 % ruthenium doped TiO2 (Ru–TiO2) nanoparticles. The characterizations of resulting nanoparticles were done using X-ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy analysis. The crystallite sizes of doped and undoped nanoparticles were determined from X-ray diffraction spectra using Scherrer equation. The average crystallite size of undoped TiO2 was found to be 17.00 nm, whereas the crystallite sizes of 0.2, 0.4 and 0.8 % Ru–TiO2 were 16.67, 15.70 and 14.40 nm respectively. The TEM images confirm the particle sizes to be 10–40 nm. Pseudo-first order rate constants (kobs) determined were found to decrease with increase in pH. The effect of BTB Concentration, catalyst dosage, a percentage of doping of photo catalyst, pH and UV light intensity of BTB on the degradation rate were also examined.

Titania Supported Ru Nanoclusters as Catalysts for Hydrodeoxygenation of Pyrolysis Oils

This study evaluates: (1) Ru-containing catalysts for low temperature hydrogenation of acetic acid in aqueous medium to simulate hydrogenating bio-derived oils, and (2) the development of the role of ruthenium–titania (Ru–TiO2) catalytic interaction for this system. A series of 9 catalysts was screened, and a comparison of selectivity versus conversion indicated that selectivity was a function of conversion, with ethanol being the predominant product at low conversion, and light gases being favored at higher conversion by secondary reactions. Exponential trend curves for ethanol (decay) and methane (increase) with conversion were fitted. On a per gram catalyst basis, the most active catalyst under study in the temperature range of 120° through 220 °C with a hydrogen partial pressure of 1000 psi (7.0 MPa) was 5 % Ru on carbon; however, its selectivity for the conversion to ethanol was exceptionally low (5 % selectivity at ~70 % conversion and 180 °C) with the primary products being ethane and methane. This catalyst formulation displayed a negative deviation from the trend curve for ethanol and a higher methane selectivity deviation. On the other hand, a catalyst of Ru prepared by atomic layer deposition (i.e., Ru(ALD)/Ti(ALD)/Nb/Si) was also highly active (~55 % conversion at 180 °C) but displayed a significant positive deviation from the trend curve (~40 % selectivity). These results combined with those of EXAFS suggest that the interface between the deposited Ru and the titania support may be responsible for the increase in selectivity to ethanol. In general, the catalysts prepared by ALD were more active on a per gram catalyst basis than the catalysts prepared by standard aqueous impregnation. Samples of catalyst that were observed using transmission electron microscopy confirmed that the Ru was well dispersed in that no Ru nanoparticle morphology was observed within the resolving power of the JEOL JEM-3010 TEM instrument. Regarding the nanostructure of the support, TEM measurements revealed that the ALD method resulted in support domain sizes that were significantly smaller ( 10 nm), promoting defect formation. EXAFS characterization indicated that the best ALD catalyst (i.e., Ru(ALD)/Ti(ALD)/Nb/Si) had higher dispersion (i.e., smaller nanoparticles and thus greater metal-support interface) than the reference catalysts prepared by aqueous impregnation. A Ru-Osupport contribution was required in order to obtain an acceptable EXAFS fit (‘the long metal–oxygen bond’). Increases in Ru–Ru coordination along with decreases in Ru-Osupport coordination were observed for longer catalyst aging times and higher treatment temperatures. In summary, the selectivity to ethanol during hydrogenation of acetic acid was promoted by preparing finely dispersed Ru particles in close interaction with nanoscale titania domains. The hydrogenation of the bio-model compound, acetic acid, over Ru-deposited catalyst leads to ethanol and methane/ethane. Based on XANES/EXAFS results, the reaction on finely dispersed Ru interacting with titania leads to the preferred product, ethanol, while larger Ru metal particles in the absence of contact between Ru and titania leads towards the formation of light hydrocarbon gases.

In‐situ Raman spectroscopy study of Ru/TiO2 catalyst in the selective methanation of CO

Raman spectroscopic technique has been used to characterize a Ru/TiO2 catalyst and to follow in situ their structural changes during the CO selective methanation reaction (S‐MET). For a better comprehension of the catalytic mechanism, the in‐situ Raman study of the catalysts activation (reduction) process, the isolated CO and CO2 methanation reactions and the effect of the composition of the reactive stream (H2O and CO2 presence) have been carried out. Raman spectroscopy evidences that the catalyst is composed by islands of TiO2–RuO2 solid solutions, constituting Ru–TiO2 interphases in the form of RuxTi1 − xO2 rutile type solid solutions. The activation procedure with H2 at 300 °C promotes the reduction of the RuO2–TiO2 islands generating Ruo–Ti3+ centers. The spectroscopic changes are in agreement with the strong increase in chemical reactivity as increasing the carbonaceous intermediates observed. The selective methanation of CO proceeds after their adsorption on these Ruo–Ti3+ active centers and subsequent C―O dissociation throughout the formation of CHx/CnHx/CnHxO/CHx―CO species. These intermediates are transformed into CH4 by a combination of hydrogenation reactions. The formation of carbonaceous species during the methanation of CO and CO2 suggests that the CO presence is required to promote the CO2 methanation. Similar carbonaceous species are detected when the selective CO methanation is carried out with water in the stream. However, the activation of the catalysts occurs at much lower temperatures, and the carbon oxidation is favored by the oxidative effect of water. Copyright © 2015 John Wiley & Sons, Ltd.

Density Functional Theory Study on the Metal–Support Interaction between Ru Cluster and Anatase TiO2(101) Surface

Density functional theory (DFT) calculations were carried out to study the nucleation and growth mechanism of Ru clusters on the TiO2(101) surface by using supported Run (n = 1–10, 20, 22) cluster models to understand the metal–support interaction and the resulting catalytic performance toward CO oxidation. The results show that the Run cluster prefers a 3D geometry when n ≥ 4 and that the Ru–TiO2 interface is predominantly composed of Ru–O and Ti–O bonds. Calculation studies based on the density of states (DOS), Hirshfeld charge analysis, and electron deformation density (EDD) demonstrate that the electronic interaction is mainly localized at the Ru–TiO2 interface through the electron transfer via the Ru–O bond. Additionally, the investigation on catalytic behavior of Run/TiO2 toward CO oxidation reveals the largely enhanced catalytic activity of the supported Run clusters, which originates from the significant reduction of the activation barrier as a result of the electron transfer from Ru to TiO2.