Maria Giorgia Cutrufello

Bio: Maria Giorgia Cutrufello is an academic researcher from University of Cagliari. The author has contributed to research in topics: Catalysis & Adsorption. The author has an hindex of 19, co-authored 47 publications receiving 1128 citations.

Structural and surface approach to the enhanced photocatalytic activity of sulfated TiO2 photocatalyst

Abstract: TiO2 materials prepared by sol–gel method and then impregnated with sulfuric acid and further calcined at different temperatures show high photon efficiencies for the photocatalytic degradation of phenol under UV-illumination. Best photocatalyst was obtained after calcination around 700 °C, giving specific activities (i.e. per m2) significantly higher than those exhibited by similarly prepared non-sulfated TiO2 or by pure Degussa P25. Structural analysis of these new materials by XRD, TG–DTG and Raman spectroscopy shows that once calcined at 700 °C the material was a well-crystallized, high surface area and sulfate-free 90% anatase. Surface characterization in this work by XPS, LEIS and 1H MAS-NMR confirms a complete loss of the sulfate and OH-groups, and a low XPS O/Ti-atomic ratio with the O(1s) peak shifted to higher binding energies (1.7 versus 2 ± 0.1 and 530.4 eV versus 529.8 eV, respectively, against the reference materials). This indicates the existence of oxygen vacancies, which give a broad band at 400–600 nm in the reflectance spectra. However, LEIS spectra show an O/Ti composition at the topmost exposed atomic surface layer similar to that of TiO2 reference materials. Adsorption microcalorimetry of pyridine gives a profile of acid sites quite similar to those found for reference anatase samples, what discards the presence of superacid sites as the origin of its enhanced UV-photoefficiency. A mechanism is proposed, on the basis of earlier results in the literature for acidic TiO2 surfaces, to explain the nature of these materials. We also try to correlate the contribution of the oxygen vacancies within the anatase sub-surface layers to the high photon UV-efficiency of the system and, likely, to an enhanced vis-photoactivity of these materials.

Acid-Base Properties of Zirconium, Cerium and Lanthanum Oxides by Calorimetric and Catalytic Investigation

Abstract: The combined use of calorimetric and catalytic methods for the investigation of the acid-base properties of oxide systems is discussed with reference to the authors' work on pure and doped zirconia samples, ceria-zirconia and ceria-lanthana solid solutions. Adsorption microcalorimetry of ammonia and carbon dioxide had been used to characterize the samples, whose chemical and thermal history was taken into account. The catalytic behavior of these samples in the conversion of 4-methylpentan-2-ol, route to 4-methylpent-1-ene (starting product for the manufacture of polymers of superior technological properties), had also been studied. On the basis of the calorimetric data, a rationale for interpreting the data for the transformation of 4-methylpentan-2-ol is formulated, which takes into account the role of the concentration and strength of the sites in governing the competition among the various mechanisms for dehydration and dehydrogenation.

Effects of potassium addition on the acidity and reducibility of chromia/alumina dehydrogenation catalysts

Abstract: Dehydrogenation catalysts based on chromia supported on γ-alumina, containing about 6 wt.% of chromium and increasing amounts of potassium (up to 1.8 wt.%), were prepared and characterised by means of several techniques, such as N2 adsorption at 77 K, X-ray powder diffraction (XRPD), UV-Vis diffuse reflectance spectroscopy (DRS), electron paramagnetic resonance (EPR), temperature programmed reduction (TPR), microcalorimetry and chemical analyses. The catalytic behaviour of the samples was investigated in the propane dehydrogenation reaction at 813 K and the effect of potassium loading was examined. The addition of increasing amounts of the alkali metal, as expected, determined a general decrease in the surface acidity. The sites strength distribution was greatly influenced, due to the fact that, at loadings above 0.5 wt.%, potassium preferentially caused the disappearance of weak and medium acid sites. EPR showed a decrease of CrIII species (especially α-Cr2O3) on potassium increasing. TPR profiles of the K-containing samples showed the presence of two reduction peaks, ascribable to two different kinds of CrVI surface species with a different reduction behaviour. All catalysts showed a maximum of activity as a function of time-on-stream, due to reduction of CrVI to CrIII species in the first reaction period, and then a decrease, due to deactivation by coking. Propene selectivity was high in all cases and was positively affected by the presence of potassium in concentrations up to 1 wt.%.

ZnO/SBA-15 composites for mid-temperature removal of H2S: Synthesis, performance and regeneration studies

Abstract: ZnO/SBA-15 composites for mid-temperature H2S removal were prepared by both conventional Incipient Wetness and Two-Solvents impregnation techniques. The composites, differing as to the ZnO loading and the calcination treatment, were characterised by X-ray diffraction, transmission electron microscopy (also in the high resolution mode) and N2 physisorption. Characterisation techniques revealed that zinc oxide was highly dispersed into/over the well-ordered mesoporous channels. In all the composites the mesostructure of the support was still retained together with a high surface area, large pore volume and uniform pore size. The sorbent performance for H2S removal from a H2S/He stream was investigated and compared with a commercial ZnO sorbent. The confinement of the active phase in the SBA-15 structure enhances its ability to interact with hydrogen sulphide, which results in improved performance. Temperature-programmed experiments were carried out for selecting appropriate regeneration conditions. The regenerated sorbent showed a sorption capacity even higher than that of the fresh ones. Such behaviour is maintained in repeated sorption/regeneration cycles.

Acid–base properties and catalytic activity of nanophase ceria–zirconia catalysts for 4-methylpentan-2-ol dehydration

Abstract: The room-temperature high energy ball-milling technique was used to prepare nanophase Ce1-xZrxO2 (x=0; 0.2; 0.5; 0.8; 1) catalysts. The acid–base properties of these catalysts were investigated by means of adsorption microcalorimetry, using NH3 and CO2 as probe molecules. The catalytic activity for 4-methylpentan-2-ol dehydration was tested at atmospheric pressure in a fixed-bed flow microreactor. The inclusion of increasingly high contents of zirconium into the ceria lattice has a complex influence on the acidity and basicity of the pure parent oxide, in terms of both number and strength of the sites. A maximum in 1-alkene selectivity is observed for the ceria-rich catalyst and a minimum for the zirconia-rich sample. Catalytic results are correlated with the acid–base properties and can be interpreted in the light of the mechanism formerly proposed for zirconia, ceria and lanthania. Surface conditioning of the zirconia-rich catalyst occurs during the run, resulting in a remarkable variation of selectivity.

Advanced Nanoarchitectures for Solar Photocatalytic Applications

Abstract: UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

A surface science perspective on TiO2 photocatalysis

Abstract: The field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO2 photocatalysis. This review highlights, from a surface science perspective, recent literature that provides molecular-level insights into photon-initiated events occurring at TiO2 surfaces. Seven key scientific issues are identified in the organization of this review. These are: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form. This review ends with a brief examination of several chemical processes (such as water splitting) in which TiO2 photocatalysis has made significant contributions in the literature.

Recent Advances in the Catalytic Oxidation of Volatile Organic Compounds: A Review Based on Pollutant Sorts and Sources.

Abstract: It is well known that urbanization and industrialization have resulted in the rapidly increasing emissions of volatile organic compounds (VOCs), which are a major contributor to the formation of secondary pollutants (e.g., tropospheric ozone, PAN (peroxyacetyl nitrate), and secondary organic aerosols) and photochemical smog. The emission of these pollutants has led to a large decline in air quality in numerous regions around the world, which has ultimately led to concerns regarding their impact on human health and general well-being. Catalytic oxidation is regarded as one of the most promising strategies for VOC removal from industrial waste streams. This Review systematically documents the progresses and developments made in the understanding and design of heterogeneous catalysts for VOC oxidation over the past two decades. It addresses in detail how catalytic performance is often drastically affected by the pollutant sources and reaction conditions. It also highlights the primary routes for catalyst deactivation and discusses protocols for their subsequent reactivation. Kinetic models and proposed oxidation mechanisms for representative VOCs are also provided. Typical catalytic reactors and oxidizers for industrial VOC destruction are further discussed. We believe that this Review will provide a great foundation and reference point for future design and development in this field.

Catalytic combustion of VOCs on non-noble metal catalysts

Abstract: Volatile organic compounds (VOCs) are toxic and contribute significantly to the formation of the photochemical smog, which has remarkable impact to the air quality; therefore, the research on the removal of VOCs has attracted increasing interests during the last decade. This review covers the recent developments in catalytic combustion of VOCs over non-noble metal catalysts including mixed metal oxide catalysts, perovskite catalysts and Au-containing catalysts. The effect of water vapor, coke formation and the effect of supports on the catalytic combustion process will be discussed. The concept of an adsorption/catalytic combustion dual functional system is introduced and several examples of such systems are evaluated. To develop efficient and cost effective VOC removal technologies, further research in catalytic combustion needs to develop novel non-noble metal catalysts and adsorbents, and improve the understanding of catalytic mechanisms involved.

A review on non metal ion doped titania for the photocatalytic degradation of organic pollutants under UV/solar light: Role of photogenerated charge carrier dynamics in enhancing the activity

Abstract: The multifunctional and advanced semiconductor titania with superior physicochemical and opto-electronic properties is extensively investigated in wastewater purification mainly due to its non-toxicity, favorable band edge positions, water insolubility, multifaceted electronic properties, surface acid–base properties, super hydrophilicity and so on. However, large band gap and massive photogenerated charge carrier recombination hinders its wide application under natural solar light. Thus, altering the surface-bulk structure of titania is a major goal in the area of both materials and environmental chemistry for its better applications. The substitution of p block elements (B, C, N, F, S, P, and I) either at Ti 4+ and O 2− sites is a promising approach to overcome the aforementioned drawbacks. This review focuses on the photocatalytic activity of non metal doped titania for a wide variety of pollutants degradation under UV/visible light, with special emphasis on nitrogen doped TiO 2 . Further improvement in photoactivity of N–TiO 2 is achieved via depositing with noble metals, co-doping with foreign ions, sensitization, surface modifications and heterostructuring with other semiconductors. The mechanism governing the photocatalytic reactions is discussed in the light of charge carrier generation–separation–transfer–recombination dynamics together with pollutant adsorption and their reactions with reactive oxygenated species in liquid or gaseous regime. We are positive that this review article will further stimulate our research interest on this intriguing hot topic.