http://hdl.handle.net/10366/4165 2026-07-14T23:18:12Z http://hdl.handle.net/10366/172072 [EN]An advanced oxidation heterogeneous process completely degrades 4-nitrophenol in weak acid ambient aqueous conditions using post-synthetically iron-doped nickel azolate frameworks. The framework crystallinity, porosity and reactivity of the redox-active iron (II/III) sites, hydroxyl anions and radicals upon H2O2 pretreatment are discussed based on spectroscopic analysis of the reaction mixture and pretreated MOF. 2024-01-01T00:00:00Z http://hdl.handle.net/10366/172071 [EN]The oil sands industry generates large volumes of oil sands process water (OSPW). There is an urgent need for OSPW treatment to reduce process water inventories and to support current reclamation approaches. This study discusses how efficient ozone (O3)-based combined advanced oxidation processes (AOPs), including hydrogen peroxide (H2O2) and UV-C, are at achieving mineralization while reducing the toxicity arising from such organic components as naphthenic acids (NAs) in OSPW. The results showed that the dissolved organic carbon (DOC) removals of 45%, 84%, 84% and 98%, obtained after 90-min treatments with O3, O3/H2O2, UVC/O3 and UVC/O3/H2O2, respectively, at a production rate of 6 g/L·h O3 were considerably higher than at lower O3 production rates. The acute toxicity on Vibrio fischeri was significantly reduced by all the treatments, which explains the high percentages of NA removal (up to 99% as confirmed by UPLC-QTOF-HRMS.) Mineralization (expressed as DOC removal) was highest with UVC/O3/H2O2 at ca. 2 mg C/L in the treated effluent, which means that it could be used as cooling/boiling process water in bitumen upgrading units. However, considering the energy demand of the treatments tested, the treatment using O3/H2O2 was found to be the most realistic for large-scale applications. 2022-01-01T00:00:00Z http://hdl.handle.net/10366/172070 [EN]High aluminum loading incorporation in the SBA-15 silica structure was investigated. Different Si/Al molar ratios (15, 10, and 2) were evaluated. The SBA-15 and the aluminum-containing materials (Al-SBA-15) were prepared by the “pH adjusting” method with modifications. The mesoporous structure of the materials was demonstrated by the type IV isotherms. The SBA-15 pore changed from a cylindrical to a slit-like structure in the presence of higher aluminum content. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) pointed out that the structural order is compromised in the presence of a higher aluminum load in the Al-SBA-15 materials, although the mesoporous structure was preserved. Higher Al loading increases the total quantity of Lewis acid sites as well as generates Brönsted acid sites. CO adsorption FTIR spectroscopy suggests aluminum incorporation into the SBA-15 and generation of acid sites. The Si–O–Al linkage in the aluminum-containing materials was corroborated by UV–Vis DRS due to the presence of a peak centered at 241 nm related to the Al-O bond, which is ascribed to four-coordinated framework aluminum in the SBA-15 structure. XPS spectra of Al 2p suggested that the Al species are less oxidized than the Al2O3 phase giving some indication of Al incorporation into the SBA-15 framework. 27Al MAS NMR results revealed that the aluminum species are in a tetrahedral oxygen coordination environment for Al-SBA-15 with Si/Al molar ratios of 15 and 10. Aluminum species in both tetrahedral and octahedral environments were evidenced for Al-SBA-15 with a Si/Al molar ratio of 2. 2023-01-01T00:00:00Z http://hdl.handle.net/10366/172069 [EN]We present a green procedure for the synthesis of metal-organic frameworks (having either Zn, Ni and Co) in graphene oxide aqueous suspension (obtained with graphitized or non-graphitized carbon nanofibers) avoiding organic solvents and high temperatures. The materials were thoroughly characterized using XRD, SEM, N2/CO2-physisorption, Raman and XPS spectroscopies, and TGA. Our results demonstrate that the nature of the metal (electronegativity) and graphene oxide (oxygen-containing defects) are key in the size, porosity and defectivity (free non-coordinated linkers and open metal sites) of the MOF and significantly affect their CO2 adsorption energy (up to 6 kJ·mol-1 increase), uptake (up to 5·mmolCO2·g-1 increase) and catalytic activity (up to 35% rate increase with respect to bulk MOFs) in the solvent-free ambient pressure CO2 cycloaddition to epoxides. 2025-01-01T00:00:00Z http://hdl.handle.net/10366/172068 [EN]Catalytic conversion of glycerol to C3 products using advanced functional materials is an economical and efficient approach to promoting sustainable energy development. Selective glycerol dehydration to hydroxyacetone (HA) is one such alternative and requires an appropriate balance of catalyst texture, structure, and acidity. In this study, different Cu-based catalysts supported on SBA-15 with different Si/Al molar ratios (2, 10, 15 and ∞) were prepared using the “pH-adjusting” method and ammonia evaporation method and they were evaluated for the dehydration of glycerol at high concentration (80 wt%.) in liquid phase to hydroxyacetone under inert N2 atmosphere. The formation of 1,2-propanediol (1,2-PDO) was also observed even under N2 inert atmosphere conditions. The catalysts were characterized by ICP-MS, N2 adsorption-desorption, XRD, HRTEM, H2-TPR, passivation of N2O, NH3-TPD, TPO, FTIR, FTIR-OH, Py-FTIR and XPS. The Al chemical environment and the Si/Al molar ratio of the supports show a remarkable effect on the catalytic performance. The highest catalytic activity was obtained with the SiAl = 15 molar ratio, reaching a conversion of around 35 % at 120 min of reaction and a selectivity of 84 % to hydroxyacetone at 90 min of reaction. While lower Si/Al molar ratios led to a decrease in catalytic activity and an increase in product distribution. The isomorphic incorporation of Al into the SBA-15 promotes the interlinking cooperative between the properties of textural, acidity, structural, and stability of the catalyst. HRTEM and HAADF-STEM images show a well-defined hexagonal arrangement even when the CuO phase is added to the mesoporous materials with high Al loadings. At high heteroatom loadings, the typical hexagonal arrangement of the mesostructure was preserved but a decrease in the long-range order was observed. The presence of mononuclear and oligonuclear Cuδ+ species, which is related to their coordination environment and their position in the mesoporous network, was dependent on the variation of the Si/Al molar ratio. The prominent catalytic performance at the SiAl = 15 ratio can be attributed to an optimal cooperative effect of the structural defects and electronic promotion produced by the Al species, which favors the conversion of glycerol to HA. While the increase in the selectivity of 1,2-PDO observed with the molar ratio SiAl = 2 is associated with a conjugation between the higher availability of acid sites on the surface that promote the dehydration of glycerol and the domain size of copper species which would be acting as dehydrogenating sites of glycerol, forming H2 in-situ leading to the conversion of HA into 1,2-PDO. 2025-01-01T00:00:00Z http://hdl.handle.net/10366/170978 [EN]The development of efficient visible light photocatalysts based on ceria (CeO2) requires precise control over both morphology and electronic band structure. Herein, a facile one-pot hydrothermal method is reported for the preparation of crystallographically well-defined ceria nanocubes featuring enhanced photocatalytic response under visible light irradiation. The proposed approach relies on the in situ structural incorporation of 1,10-phenanthroline during crystal growth. Unlike conventional doping or surface functionalisation strategies, this method yields organic–inorganic nanostructured hybrid materials where the organic moiety is effectively incorporated into the fluorite-type ceria lattice through the formation of Ce–N coordination bonds while preserving the cubic morphology enclosed by reactive {100} facets and simultaneously increasing the specific surface area. Diffuse reflectance UV–Vis spectroscopy and valence band XPS analyses reveal that this integration induces the appearance of N 2p intraband gap states associated with the Ce–N bonds, resulting in a significant narrowing of the optical band gap and extending the light absorption edge into the visible region. Consequently, these organoceria hybrids exhibit a remarkable synergistic enhancement in photocatalytic hydrogen production via ethanol photoreforming under simulated solar irradiation, with hydrogen evolution rates being 7.5 times higher than those of pristine ceria nanocubes. This work demonstrates the potential of organic ligand-assisted lattice engineering as a versatile approach for tailoring the optoelectronic properties of ceria, thus opening new avenues for sustainable solar-to-chemical energy conversion. 2026-03-11T00:00:00Z http://hdl.handle.net/10366/168599 [EN]High durability and activity for the oxygen reduction reaction were demonstrated for oxide-supported platinum catalysts. The supports were antimony-doped SnO2 (ATO) fibres-in-tubes obtained by electrospinning and subsequent calcination. The doping with antimony instead of the already-reported niobium, allowed the preparation of tin oxide with electrical conductivity that was similar to carbon, which also had an increased electrocatalyst loading. Platinum nanoparticles supported on electrospun ATO demonstrated higher electrochemical stability and comparable mass activity to commercial Pt/C during exsitu potential cycling. The in situ fuel cell tests also revealed improved corrosion resistance with no noticeable degradation of the oxide-based membrane electrode assembly (MEA), but a slightly lower performance compared to the MEA with carbon-supported catalysts. 2015-01-01T00:00:00Z http://hdl.handle.net/10366/168597 [EN]A family of novel carbon materials with intermediate surface area and varying morphology and surface chemistry were used to prepare Pt/C catalysts by two different preparation procedures; a chemical impregnation method and a microwave-assisted polyol method. The catalysts were thoroughly characterized, and their electrochemical performance and stability were investigated with rotating disc electrode (RDE) cyclic voltammetric (CV) measurements. The intermediate-surface-area carbon supports gave catalysts with much greater support stability than a widely used standard catalyst. The novel catalysts had lower electrochemical surface area than the reference, but their specific electrocatalytic activity towards the oxygen-reduction reaction (ORR) was much higher, and some of them also featured higher mass-specific ORR activity than the reference. The series of catalysts prepared by the microwave-assisted polyol method featured smaller Pt nanoparticles and higher activities than those prepared by impregnation. On the other hand, the impregnated catalysts showed better durability of the Pt particles. The most promising catalysts were selected and elaborated in further optimized preparation procedures to obtain quantities sufficient for their use in proton-exchange membrane fuel cells (PEMFCs). 2017-01-01T00:00:00Z http://hdl.handle.net/10366/168596 [EN]Electrocatalyst supports stable to high potential are required for the proton exchange membrane fuel cell cathode. Electrocatalyst supports based on tantalum-doped tin oxide (Ta/SnO2) were prepared by electrospinning. The dopant amount was varied between 0 (undoped SnO2) and 7.5 at. %, and the resulting materials were characterized for their morphology, composition, structure, porosity, and electrical properties. Platinum nanoparticles prepared by a microwave-assisted polyol method were deposited with different loadings on 1 at. % Ta-doped SnO2 (1Ta/SnO2), selected for its highest electrical conductivity of 0.09 S cm–1. Their electrocatalytic properties toward the oxygen reduction reaction (ORR) were compared with those of the same particles deposited on carbon black and those of a commercial carbon-supported Pt catalyst. Pt/1Ta/SnO2 showed higher ORR activity and stability at high potential than Pt/C. In particular, the electrocatalyst with the lowest Pt loading (7 wt %) presented high mass activity and stability which, from XPS analysis, is suggested to result from very strong metal–support interaction. These results indicate that amongst tin oxides doped with pentavalent metals such as niobium (Nb/SnO2), antimony (Sb/SnO2), and tantalum, Ta/SnO2 has the advantage of both higher conductivity than Nb/SnO2 and greater stability in the fuel cell voltage range than Sb/SnO2. 2020-01-01T00:00:00Z http://hdl.handle.net/10366/168595 [EN]This study investigates the activity and stability of a Prussian blue analogue (PBA) as an inexpensive anode catalyst for Polymer Electrolyte Membrane Water Electrolysis (PEMWE). While some PBAs have recently been reported to catalyze the oxygen evolution reaction (OER) in acidic electrolytes, the present study focuses on their integration in a PEMWE device. Cobalt hexacyanoferrate nanoparticles were interfaced with an electrically conductive support that withstands the PEMWE anodic conditions, namely Sb-doped SnO2. The OER activity of the composite materials was first verified in liquid electrolytes and then in PEMWE. A promising current density of 50–100 mA cm−2 was reached at 2 V cell voltage. The PBA/Sb–SnO2 anode was stable up to 1.9 V, but showed more and more instability at higher potentials. Increasing leaching rates of Sn and Sb observed above 1.9 V suggest that the material instability above 1.9 V can mainly be assigned to Sb-doped SnO2 conductive support. These results are overall promising for the use of PBAs as catalytic sites at the anode of PEMWE. The study also identifies the need for more active PBAs in order to reach a higher current density at a cell voltage of 1.6–1.9 V, a potential range necessary for an acceptable energy efficiency of the PEMWE. 2018-01-01T00:00:00Z http://hdl.handle.net/10366/168594 [EN]The electrocatalyst support antimony doped tin oxide (ATO) was investigated at low and high potentials with ex situ and in situ electrochemical techniques to assess its stability in proton exchange membrane fuel cell (PEMFC) and water electrolysis (PEMWE) operating conditions. 2019-01-01T00:00:00Z http://hdl.handle.net/10366/168592 [EN]Niobium and antimony doped tin oxide loose-tubes decorated with Pt nanoparticles present outstanding mass activity and stability, exceeding those of a reference carbon-based electrocatalyst. Physico-chemical characterisation and in particular X-ray photoelectron spectroscopy demonstrate that this observation can be ascribed to the strong metal–support interaction promoting electroactivity and Pt anchoring on doped metal oxide supports. 2018-01-01T00:00:00Z http://hdl.handle.net/10366/168523 [EN]Mesoporous aluminium doped MCM-41 silica catalysts were prepared by a sol–gel method in two reaction steps (acid and alkaline hydrolysis) from joint hydrolysis of tetraethylortosilicate (TEOS) and aluminium triisoproxide, using n-dodecylammonium chloride as surfactant, at room temperature, and subsequent calcination at 550 °C. Two solids with different Si/Al molar ratios (5 and 10) were synthesized, which possess high specific surface area and acidity, with both Brönsted and Lewis acid sites. By using a biphasic water/MIBK as reaction medium and a 30 wt.% of the 10Al-MCM catalyst with respect to the substrate weight (glucose), 87% of glucose conversion and 36% of HMF yield were achieved at 195 °C after 150 min of reaction time. The reaction is quite selective toward HMF, since only fructose was detected as by-product, but neither levulinic acid nor furfural were found. Moreover, the use of a sodium chloride aqueous solution (20 wt.%) and MIBK ameliorates the partition coefficient between the organic and the aqueous phases up to 1.9, leading to an enhancement of the glucose conversion and HMF yield, attaining values of 98% and 63%, respectively, in a time as short as 30 min. The catalytic performance of this acid solid, associated to the presence of strong acid sites, is well maintained after three catalytic cycles. 2015-01-01T00:00:00Z http://hdl.handle.net/10366/167189 [EN]The present work is aimed at shedding light on the evolution of surface chemistry of a commercial activated carbon (AC) support during the preparation of supported metal oxide (MO) catalysts by the conventional wet impregnation method. Particular attention is paid to the chemical changes of oxygen-containing surface functionalities across three preparation stages of impregnation, oven-drying, and thermal treatment. AC was impregnated with aqueous solutions of several MO precursors (Al(NO3)3, Fe(NO3)3, Zn(NO3)2, SnCl2, and Na2WO4) at 80 °C for 5 h, oven-dried at 120 °C for 24 h, and heat-treated at 200 °C and 850 °C for 2 h under an inert atmosphere. The surface chemistry of the resulting catalyst samples, classified in three series by the thermal treatment, was mainly studied by FT-IR spectroscopy, complemented by elemental analysis and pH of the point of zero charge (pHpzc) measurements. During impregnation, phenolic hydroxyl and carboxylic acid groups were predominantly formed by wet oxidation of chromene, 2-pyrone, and ether-type structures found in the pristine AC. The extent of these oxidations correlated with the oxidising power of the precursor solutions. As expected, thermal treatment at 850 °C brought about markedly stronger chemical changes, with most of the above oxygen functionalities decomposing and forming less acidic structures, such as 4-pyrone groups, metal carboxylates, and C-O-M atomic groupings. All these surface chemical modifications result in a lowering of the strong basicity of the raw carbon support (pHpzc ≈ 10.5), thus leading to pHpzc values for the catalysts widely ranging from 1.6 to 9.7. 2025-09-22T00:00:00Z http://hdl.handle.net/10366/165934 [EN]Herein, we report the first example of MOF synthesis employing aluminum slags as a waste resource. This synthesis was exclusively carried out from waste materials, under ambient conditions in water, thus aligning with the guiding principles of Green Chemistry. The resulting MIL-53(Al) material was further functionalized with SnO2 nanoparticles and tested as catalyst for the dehydration of glucose to 5-hydroxymethylfurfural (5-HMF), showing a tenfold increase in catalytic efficiency compared to unsupported SnO2 2025-01-01T00:00:00Z http://hdl.handle.net/10366/163123 [EN]Stable sulfated zirconia can be prepared by impregnation with sulfuric acid of a zirconium doped mesoporous MCM-41 silica and ulterior calcination at 750 °C. Two catalysts with nominal sulfur contents of 1.3 and 4 wt.% were prepared. After the thermal activation at this temperature, some sulfate ions (sulfur content of 0.15 and 0.69 wt.%) are strongly retained onto the superficial zirconia, thus generating acidic catalysts which are able to produce the esterification of oleic acid with methanol at 75 °C in 5 h. The experimental results reveal that the unique way to obtain stable catalysts without leaching of sulfate species to the liquid medium of reaction is by thermal treatment at high temperature as 750 °C. Only with 1 g of this stable catalyst a conversion close to 98% was attained. The conversion of this catalyst is well maintained in a high extend (76%) after three cycles of catalysis without any treatment and is stable in the presence of 5 wt.% of water. 2012-01-01T00:00:00Z