Size-dependent activity of Pt/yttria-stabilized zirconia catalyst for ethylene and carbon monoxide oxidation in oxygen-free gas environment

Promotion of TiO2 Nanotube-Confined Pt Nanoparticles via Surface Modification with Fe2O3 for Ethylene Oxidation at Low Temperature

A modified confined catalyst with Pt nanoparticles on the interior and Fe₂O₃ on the exterior surface of TiO₂ nanotubes (Pt-in/Fe₂O₃-TNTs) was prepared and investigated for catalyzing the oxidation of ethylene. Compared with the Pt-in/TNTs without Fe₂O₃ modification, the Pt-in/Fe₂O₃-TNTs exhibited a significantly enhanced activity, and the complete conversion temperature of ethylene decreased from 170 to 95 °C. X-ray photoelectron spectroscopy analysis indicated that the Pt nanoparticles were stabilized at higher oxidation states in the Pt-in/Fe₂O₃-TNT catalyst. It was proposed that the modification of Fe₂O₃ on the outer surface can tune the electronic state of the encapsulated Pt particles and accelerate the electrons transferred from Pt to Fe species via TiO₂ nanotubes, thus improving the catalytic oxidation performance of the confined catalyst.

Evaluation of particulate matter emissions from non-passenger diesel vehicles in Qatar

Road traffic is one of the main sources of particulate matter (PM) in the atmosphere. Despite its importance, there are significant challenges in the quantitative evaluation of its contribution to airborne concentrations. In order to propose effective mitigation scenarios, the proportions of PM traffic emissions, whether they are exhaust or non-exhaust emissions, should be evaluated for any given geographical location. In this work, we report on the first study to evaluate particulate matter emissions from all registered heavy duty diesel vehicles in Qatar. The study was applied to an active traffic zone in urban Doha. Dust samples were collected and characterized for their shape and size distribution. It was found that the particle size ranged from few to 600 μm with the dominance of small size fraction (less than 100 μm). In-situ elemental composition analysis was conducted for side and main roads traffic dust, and compared with non-traffic PM. The results were used for the evaluation of the enrichment factor and preliminary source apportionment. The enrichment factor of anthropogenic elements amounted to 350. The traffic source based on sulfur elemental fingerprint was almost 5 times higher in main roads compared with the samples from non-traffic locations. Moreover, PM exhaust and non-exhaust emissions (tyre wear, brake wear and road dust resuspension) were evaluated. It was found that the majority of the dust was generated from tyre wear with 33% followed by road dust resuspension (31%), brake wear (19%) and then exhaust emissions with 17%. The low contribution of exhaust PM₁₀ emissions was due to the fact that the majority of the registered vehicle models were recently made and equipped with efficient exhaust PM reduction technologies.Implication: This study reports on the first results related to the evaluation of PM emission from all registered diesel heavy duty vehicles in Qatar. In-situ XRF elemental analysis from main, side roads as well as non-traffic dust samples was conducted. Several characterization techniques were implemented and the results show that the majority of the dust was generated from tyre wear, followed by road dust resuspension and then brake wear; whereas exhaust emissions were tremendously reduced since the majority of the registered vehicle models were recently made and equipped with efficient exhaust PM reduction technologies. This implies that policy makers should place stringent measures on old vehicle license renewals and encourage the use of metro and public transportation.

A review on the direct effect of particulate atmospheric pollution on materials and its mitigation for sustainable cities and societies

Particulate matter (PM) has gained significant attention due to the increasing concerns related to their effects on human health. Although several reviews have shed light on the effect of PM on human health, their critical adverse effect on material's structure and sustainability was almost neglected. The current study is an attempt to fill this gap related to PM impact on structural materials under the overall consideration of sustainability. More specifically, this review highlights the existing knowledge by providing an overview on PM classification, composition, and sources in different locations around the world. Then, it focuses on PM soiling of surfaces such as solar panels due to an increasing need to mitigate the impact of soiling on reducing photovoltaic (PV) power output and financial competitiveness in dusty regions. This topic is of critical importance for sustainable deployment of solar energy in arid and desert areas around the world to help in reducing their impact on overall climate change and life quality. In addition, this review summarizes climate change phenomena driven by the increase of PM concentration in air such as radiative forcing and acid rain deposition due to their impact on human health, visibility and biodiversity. To this end, this work highlights the role of process management, choice of fuel, the implementation of clean technologies and urban vegetation as some possible sustainable mitigation policies to control PM pollution in cities and urban regions. This research is designed to conduct a comprehensive narrative literature review which targets broad spectrum of readers and new researchers in the field. Moreover, it provides a critical analysis highlighting the need to fill main research gaps in this domain. The findings of this review paper show that PM pollution imposes severe adverse impacts on materials, structures and climate which directly affect the sustainability of urban cities. The advantages of this review include the value of the extensive works that elaborate on the negative impacts of PM atmospheric pollution towards high level of public awareness, management flexibility, stakeholder's involvements, and collaboration between academy, research, and industry to mitigate PM impact on materials and human welfare.

Improved Self-cleaning Properties of an Efficient and Easy to Scale up TiO2 Thin Films Prepared by Adsorptive Self-Assembly

Transparent titania coatings have self-cleaning and anti-reflection properties (AR) that are of great importance to minimize soiling effect on photovoltaic modules. In this work, TiO₂ nanocolloids prepared by polyol reduction method were successfully used as coating thin films onto borosilicate glass substrates via adsorptive self-assembly process. The nanocolloids were characterized by transmission electron microscopy and x-ray diffraction. The average particle size was around 2.6 nm. The films which have an average thickness of 76.2 nm and refractive index of 1.51 showed distinctive anti soiling properties under desert environment. The film surface topography, uniformity, wettability, thickness and refractive index were characterized using x-ray diffraction, atomic force microscopy, scanning electron microscopy, water contact angle measurements and ellipsometry. The self-cleaning properties were investigated by optical microscopy and UV-Vis spectroscopy. The optical images show 56% reduction of dust deposition rate over the coated surfaces compared with bare glass substrates after 7 days of soiling. The transmission optical spectra of these films collected at normal incidence angle show high anti-reflection properties with the coated substrates having transmission loss of less than 6% compared to bare clean glass.

Synthesis of Pt@TiO2@CNTs Hierarchical Structure Catalyst by Atomic Layer Deposition and Their Photocatalytic and Photoelectrochemical Activity

Pt@TiO₂@CNTs hierarchical structures were prepared by first functionalizing carbon nanotubes (CNTs) with nitric acid at 140 °C. Coating of TiO₂ particles on the CNTs at 300 °C was then conducted by atomic layer deposition (ALD). After the TiO₂@CNTs structure was fabricated, Pt particles were deposited on the TiO₂ surface as co-catalyst by plasma-enhanced ALD. The saturated deposition rates of TiO₂ on a-CNTs were 1.5 Å/cycle and 0.4 Å/cycle for substrate-enhanced process and linear process, respectively. The saturated deposition rate of Pt on TiO₂ was 0.39 Å/cycle. The photocatalytic activities of Pt@TiO₂@CNTs hierarchical structures were higher than those without Pt co-catalyst. The particle size of Pt on TiO₂@CNTs was a key factor to determine the efficiency of methylene blue (MB) degradation. The Pt@TiO₂@CNTs of 2.41 ± 0.27 nm exhibited the best efficiency of MB degradation.

Applications of yttria stabilized zirconia (YSZ) in catalysis

The main applications of yttria stabilized zirconia in catalysis are briefly reviewed and analyzed based on its functionalities.