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[EN] In the present manuscript, the influence of the zeolite structure and crystal size on bifunctional tandem catalysts combining K-promoted iron oxide (K/Fe3O4) with different zeolites has been studied for the CO(2)hydrogenation reaction at 320 degrees C and 25 bar. First, to evaluate the influence of the zeolite structure on CO(2)conversion, three different zeolite topologies have been evaluated (BEA, MFI and CHA) with similar Si/Al molar ratios. The combination of K/Fe(3)O(4)with MFI maximizes the formation of aromatic products, while its combination with CHA and BEA increases the C-1-C(4)gas fractions, with a high olefin selectivity. In addition, aromatics and aliphatic hydrocarbons are present in the condensed liquids of the tandem catalysts containing BEA, while no aromatics are observed for those with CHA. These different product selectivities can be ascribed to the different consecutive reactions within the three zeolites, where MFI favors the aromatization of alkenes, and BEA and CHA favor oligomerization/cracking reactions leading to an increase of light olefin yield. Second, the evaluation of the nanosized form of the three proposed zeolite frameworks has also been carried out. The reduction of the particle size allows for increasing light olefin selectivity in all cases as compared to zeolites with larger crystals. Shorter intracrystalline diffusion paths facilitate the egression of light olefins before being involved in consecutive oligomerization reactions. In the particular case of the tandem catalysts with nanosized MFI zeolites, the C-2-C(4)fraction and its olefinicity are increased while maintaining the overall aromatic selectivity comparable to that obtained with micron-sized MFI zeolites. ; This work was supported by the Spanish Government through "Severo Ochoa" (SEV-2016-0683, MINECO) and RTI2018-101033-B-I00 (MCIU/AEI/FEDER, UE), by the Fundacion Ramon Areces through a research contract (CIVP18A3908) and by Generalitat Valenciana (AICO/2019/060). A. R. F. acknowledges the Spanish ...

In this dissertation, hydroxyapatite-based and hydroxyapatite with carbon composite materials have been rationally designed, synthesized, characterized and applied to processes of environmental concern, namely wastewater remediation (as sorbents) and electrochemical CO2 reduction reaction, CO2RR (as electrocatalysts). Pristine hydroxyapatite (HAP, Ca10(PO4)6(OH)2) and composite HAP/carbon materials have been synthesized according to a simple wet co-precipitation route. Composition, structure and morphology of samples have been investigated by a plethora of physical-chemical techniques (i.e. ICP/OES elemental analyses, N2 adsorption/desorption isotherms, XRD, TEM (and STEM) imaging, TEM/EDX mapping, transmittance FT-IR and Raman spectroscopies, and XPS). Since adsorption onto materials' surface is crucial in both sorption and catalytic applications, a special attention has been devoted to surface properties, determined by means of zeta potential measurements, gas-solid calorimetric/volumetric titrations, and liquid-solid volumetric titrations, thus assessing the amphoteric nature of HAP-based surfaces. At first, pristine pristine HAP has been studied as sorbent for the remediation of inorganic pollution in wastewater (i.e. heavy metal cations such as Cu(II), Pb(II), Cr(III), Ni(II) and Co(II)). Stirred batch adsorption tests and collection of adsorption isotherms in solutions containing both individual and mixtures of heavy metal cations allowed to quantitatively assess HAP sorption ability. Ad-hoc experiments (i.e. microcalorimetric adsorption isotherms) and physical-chemical investigation of metal-loaded samples shed light on the adsorption mechanisms of several polluting species onto HAP surface. Eco-friendly HAP/carbon composites from renewable resources have been instead applied to the remediation of more complex effluents, where simultaneous organic and inorganic pollution may occur. Thanks to their dual nature, HAP/carbon composites exerted outstanding adsorption performances towards both class of polluting species. Both in the form of pristine HAP and HAP/carbon composites, the sorbents exhibited a strict retention of adsorbed pollutants when undergoing leach testing, therefore ensuring no secondary pollution issues. In an exploratory study, HAP/carbon composites have been also implemented as modifiers in self-standing and mechanically stable electrodes for the electrochemical detection of heavy metal cations traces in waterbodies. Benefitting from the pronounced HAP affinity towards such species, encouraging results have been obtained on the detection of some benchmark pollutants, although the registered limits of detection (ca. one order of magnitude improvement to match legislative requirements) and linearity ranges currently limit HAP/carbon modified electrodes applications. Finally, during a 6-months stay at University of California Irvine (UCI), hosted by Prof. Plamen Atanassov group, HAP has been applied as dopant in CO2RR electrocatalysts. The peculiar ability of HAP amphoteric surface to adsorb and destabilize CO2 (i.e. breakage of its linearity) has been exploited in composite electrocatalysts, composed by copper nanoparticles (active phase) and HAP (dopant), supported on N-doped 3D assembly of graphene nanosheets (3D-GNS, carbonaceous support). When tested in a lab scale CO2 electrolyzer, HAP-doped electrocatalysts displayed a faradic efficiency (FE) towards CO2RR ≥ 80% throughout the whole potential range under investigation, minimizing parasitic Hydrogen Evolution Reaction (HER). Interestingly, HAP doping actually altered CO2RR product distribution: in particular, small quantities of C2+ products were produced under low applied overpotential while at higher voltage formate production was boosted. Product distribution alteration has been rationalized taking into account the ability of HAP acid-basic surface groups to stabilize CO2 reduction intermediate species, directing the the selectivity of electrochemical CO2RR processes. Overall, the present study demonstrates that the unique features of HAP make it a versatile material which may be applied for the protection of the environment at 360 degrees, from water to air remediation, as pristine and/or composite material, as sorbent and/or catalysts' dopant.

Electromagnetic (EM) pollution has been evolving as one of the most concerning environmental problems in current society, due to the extensive application of EM technology, from household electronic apparatuses to wireless base stations, as well as military radars [.]

Graphene is the enabling material of the 21st century and there are high expectations for its potential applications. A clear and consistent system describing the various derivatives of graphene promotes a precise vocabulary for the family of graphene-based materials. This will be a prerequisite, for example, to understand structure–activity relationships in the context of human health and safety and to avoid generalizations about the capabilities and limitations of graphenebased materials. Within the European Union's GRAPHENE Flagship project, three physical-chemical descriptors specific for graphene were defined to assist in the classification of graphene-based materials.

International audience ; Graphene is the enabling material of the 21st century andthere are high expectations for its potential applications. Aclear and consistent system describing the various derivativesof graphene promotes a precise vocabulary for the family ofgraphene-based materials. This will be a prerequisite, forexample, to understand structure–activity relationships in thecontext of human health and safety and to avoid generalizationsabout the capabilities and limitations of graphenebasedmaterials. Within the European Union's GRAPHENEFlagship project, three physical-chemical descriptors specificfor graphene were defined to assist in the classification ofgraphene-based materials.

International audience ; Graphene is the enabling material of the 21st century andthere are high expectations for its potential applications. Aclear and consistent system describing the various derivativesof graphene promotes a precise vocabulary for the family ofgraphene-based materials. This will be a prerequisite, forexample, to understand structure–activity relationships in thecontext of human health and safety and to avoid generalizationsabout the capabilities and limitations of graphenebasedmaterials. Within the European Union's GRAPHENEFlagship project, three physical-chemical descriptors specificfor graphene were defined to assist in the classification ofgraphene-based materials.