Person: González Calbet, José María
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First Name
José María
Last Name
González Calbet
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Inorgánica
Area
Química Inorgánica
Identifiers
9 results
Search Results
Now showing 1 - 9 of 9
Item Modified Synthesis Strategies for the Stabilization of low n TinO2n–1 Magnéli Phases(Chem. Rec., 2018) Azor Lafarga, Alberto Eduardo; Ruiz González, María Luisa; Parras Vázquez, Marina Marta; D. Portehault; C. Sanchez; González Calbet, José MaríaTitanium reduced oxides TiO2–x occupy, since long time, a prominent place on the landscape of binary metal oxides because of their intriguing ability to form extended defects that affect both the formation of new superlattices and different electronic behaviours. Related to these features, a wide range of practical applications has been achieved. Moved by the conviction of the great potential of understanding the influence of the reactivity, compositional variations and size effects on their functional properties, the aim of this personal account is the optimization of a recently developed strategy for the stabilization of low n TinO2n–1 terms. In particular, we will focus on the Ti4O7 composition as well as the incorporation of transition metals, like Mn, in order to deal with new reduced Magnéli phases.Item Quantitative, Spectro-kinetic Analysis of Oxygen in Electron-Beam Sensitive, Multimetallic Oxide Nanostructures(Microscopy and Microanalysis, 2023) López-Haro, Miguel; Gómez Recio, Isabel; Pan, Huiyan; Delgado, Juan ; Chen, Xiaowei; Cauqui, Miguel ; Pérez-Omil, José ; Ruiz González, María Luisa; Hernando González, María; Parras Vázquez, Marina Marta; González Calbet, José María; Calvino, JoséThe oxygen stoichiometry of hollandite, KxMnO2-δ, nanorods has been accurately determined from a quantitative analysis of scanning-transmission electron microscopy (STEM) X-Ray Energy Dispersive Spectroscopy (XEDS) experiments carried out in chrono-spectroscopy mode. A methodology combining 3D reconstructions of high-angle annular dark field electron tomography experiments, using compressed-sensing algorithms, and quantification through the so-called ζ-factors method of XEDS spectra recorded on a high-sensitivity detector has been devised to determine the time evolution of the oxygen content of nanostructures of electron-beam sensitive oxides. Kinetic modeling of O-stoichiometry data provided K0.13MnO1.98 as overall composition for nanorods of the hollandite. The quantitative agreement, within a 1% mol error, observed with results obtained by macroscopic techniques (temperature-programmed reduction and neutron diffraction) validate the proposed methodology for the quantitative analysis, at the nanoscale, of light elements, as it is the case of oxygen, in the presence of heavy ones (K, Mn) in the highly compromised case of nanostructured materials which are prone to electron-beam reduction. Moreover, quantitative comparison of oxygen evolution data measured at macroscopic and nanoscopic levels allowed us to rationalize beam damage effects in structural terms and clarify the exact nature of the different steps involved in the reduction of these oxides with hydrogen.Item Unambiguous localization of titanium and iron cations in doped manganese hollandite nanowires(Chemical Communications, 2020) Gómez Recio, Isabel; Azor Lafarga, Alberto Eduardo; Ruiz González, María Luisa; Hernando González, María; Parras Vázquez, Marina Marta; Calvino, José Juan; Fernández Díaz, María Teresa; Portehault, David; Sanchez, Clement; González Calbet, José MaríaNew insights into the chemical and structural features of iron or titanium-doped KxMnO2 hollandites are reported. Neutron diffraction and atomically resolved transmission electron microscopy elucidate the localization of the dopant cations that could be one of the key factors governing the functional activity of these nanomaterials.Item Evaluating the impact of iron impurities in KOH on OER performance of BaNiO3 single crystals using scanning electrochemical cell microscopy(Electrochimica Acta, 2024) Gutiérrez Martín, Daniel; Abdelilah Asserghine; Torres Pardo, María De La Almudena; Varela Losada, María Áurea; Joaquín Rodríguez-López; González Calbet, José María; Parras Vázquez, Marina MartaUnderstanding the oxygen evolution reaction (OER) electrocatalysis requires a careful understanding of the surface and activity evolution of well-defined materials. An especially promising candidate is the BaNiO3 hexagonal perovskite, matching strides with benchmark catalysts such as Ba0.5Sr0.5Co0.8Fe0.2O3–δ. Here, we conducted a structural and electrochemical analysis of BaNiO3 single crystals to assess the influence of iron impurities in KOH electrolyte on their OER performance. We used scanning electrochemical cell microscopy (SECCM) for precise measurements on BaNiO3 single crystals in the absence of carbon additives. Cyclic voltammetry (CV) revealed that the presence of iron consistently enhanced the OER current with subsequent cycles, indicating a dynamic improvement in BaNiO3's electrochemical activity. Conversely, in iron-free KOH electrolyte, performance diminished with cycling. These findings not only underscore the critical necessity of KOH purification for BaNiO3 electrochemical studies but also showcase SECCM's unparalleled ability to offer insights into the electrochemical evolution of individual entities such as single crystals. This makes it a powerful operando tool for evaluating forthcoming single crystals, thereby aiding in the design of superior catalysts for OER reactions.Item Exceptional Low-Temperature CO Oxidation over Noble-Metal-Free Iron-Doped Hollandites: An In-Depth Analysis of the Influence of the Defect Structure on Catalytic Performance(ACS Catalysis, 2021) Gómez Recio, Isabel; Pan, Huiyan; Azor Lafarga, Alberto Eduardo; Ruiz González, María Luisa; Hernando González, María; Parras Vázquez, Marina Marta; Fernández-Díaz, María Teresa; Delgado, Juan J.; Chen, Xiaowei; Goma Jiménez, Daniel; Portehault, David; Sanchez, Clément; Cabero Piris, Mariona; Martínez-Arias, Arturo; González Calbet, José María; Calvino, José J.A family of iron-doped manganese-related hollandites, KxMn1–yFeyO2−δ (0 ≤ y ≤ 0.15), with high performance in CO oxidation have been prepared. Among them, the most active catalyst, K0.11Mn0.876Fe0.123O1.80(OH)0.09, is able to oxidize more than 50% of CO at room temperature. Detailed compositional and structural characterization studies, using a wide battery of thermogravimetric, spectroscopic, and diffractometric techniques, both at macroscopic and microscopic levels, have provided essential information about this never-reported behavior, which relates to the oxidation state of manganese. Neutron diffraction studies evidence that the above compound stabilizes hydroxyl groups at the midpoints of the tunnel edges as in isostructural β-FeOOH. The presence of oxygen and hydroxyl species at the anion sublattice and Mn3+, confirmed by electron energy loss spectroscopy, appears to play a key role in the catalytic activity of this doped hollandite oxide. The analysis of these detailed structural features has allowed us to point out the key role of both OH groups and Mn3+ content in these materials, which are able to effectively transform CO without involving any critical, noble metal in the catalyst formulation.Item Hydroxyapatites as Versatile Inorganic Hosts of Unusual Pentavalent Manganese Cations(Chemistry of Materials, 2020) Varela Losada, María Áurea; Gómez Recio, Isabel; Serrador, Laura; Hernando González, María; Matesanz, Emilio; Torres Pardo, María De La Almudena; Fernández-Díaz, María Teresa; Martínez, Jose ; Gonell, Francisco; Rousse, Gwenaelle; Sanchez, Clément; Laberty-Robert, Christel; Portehault, David; González Calbet, José María; Parras Vázquez, Marina MartaContrary to molecular species, only very few solids are reported to host manganese (V) species. Herein, we report three new compounds with a hydroxyapatite structural backbone built on the MnVO43– anion: Sr5[(Mn1–xSix)O4]3(OH)1–3x (x = 0 and 0.053), Sr5(MnO4)3(OH)1–yFy (y = 0.90), and Sr5[(Mn1–xSix)O4]3F1–3x (x = 0.058). These solids are fully characterized using powder X-ray and neutron powder diffraction, scanning transmission electron microscopy, electron energy loss spectroscopy (EELS), thermogravimetric analysis, and magnetic measurements. Especially, we report for the first time EELS Mn–L2,3 spectra of manganese with the oxidation state (V). Contrary to other Mn(V) oxides, these solids and the nominal compound Sr5(MnO4)3OH do not comprise Ba2+ cations but rely only on Sr2+ cations, showing that barium is not a required element to stabilize Mn(V) species in inorganic solids. We show that by tuning soft chemistry conditions on the one hand and post-treatment topological transformation conditions on the other hand, Mn(V) and hydroxyl groups can be substituted by Si(IV) and fluoride ions, respectively. Hence, we deliver solids with a potentially wide composition range. These compounds show significant oxygen anionic conduction, thus suggesting the emergence of new functional materials built from high-oxidation state manganese cations.Item Nickel-Doped Sodium Cobaltite 2D Nanomaterials: Synthesis and Electrocatalytic Properties(Chemistry of Materials, 2018) Ruiz González, María Luisa; Gonell, Francisco; Laberty-Robert, Christel ; Parras Vázquez, Marina Marta; Sanchez, Clément; Portehault, David; González Calbet, José María; Azor Lafarga, Alberto EduardoABSTRACT: In this work we report a synthetic pathway to two-dimensional nanostructures of high oxidation state lamellar cobalt oxides with thicknesses of only few atom layers, through the combined use of precipitation in basic water at room temperature and gentle solid state topotactic transformation at 120 °C. The 2D nanomaterials are characterized by X-ray diffraction, nitrogen porosimetry, scanning electron microscopy, transmission electron microscopy and especially scanning transmission electron microscopy coupled to energy dispersive X-ray analysis and electron energy loss spectroscopy to assess the composition of the nanosheets and the oxidation state of the transition metal species. We show that the nanosheets preserve high oxidation states Co3+ and Co4+ of high interest for electrocatalysis of the oxygen evolution reaction (OER). By combining high Co oxidation state, surface-to-volume ratio and optimized nickel substitution, the 2D nanomaterials produced in a simple way exhibit high OER electrocatalytic activity and stability in alkaline aqueous electrolyte comparable to standard materials obtained in harsh thermal conditions.Item Multicationic Sr4Mn3O10 mesostructures: molten salt synthesis, analytical electron microscopy study and reactivity(2018) González-Jiménez, Irma N.; Torres Pardo, María De La Almudena; Rano, Simon; Laberty-Robert, Christel; Hernández-Garrido, Juan carlos; López-Haro, Miguel; Calvino, José J.; Varela Losada, María Áurea; Sanchez, Clément; Parras Vázquez, Marina Marta; González Calbet, José María; Portehault, DavidInorganic molten salts are known as fluxes for the synthesis of novel bulk inorganic compounds and of mesostructures and nanostructures with crystal habits different from those observed in more conventional solvents. However, they have not demonstrated the ability to provide mesostructures and nanostructures of complex metal oxides that are currently unreported at the mesoscale and nanoscale. In this report, we show the first occurrence of Sr4Mn3O10 at the mesoscale, as platelets synthesized in molten strontium hydroxide at 600 °C with basal faces of few hundreds of nanometers and thicknesses ranging from 20 to 100 nm. We address carefully the atom-scale structure by transmission electron microscopy, including electron energy loss spectroscopy and electron tomography. We then propose that the final morphology is driven by the surface charge of each facet through surface energy. The reactivity of these platelets is then addressed, highlighting cation leaching when in contact with acidic water, which results in crystalline–amorphous core–shell platelets that are active electrocatalysts towards the oxygen reduction reaction.Item Revisiting the Decomposition Process of Tetrahydrate Co(II) Acetate: A Sample’s Journey through Temperature(Applied Sciences, 2022) Gutiérrez Martín, Daniel; Varela Losada, María Áurea; González Calbet, José María; Matesanz, Emilio; Parras Vázquez, Marina MartaCobalt oxides, CoO and Co3O4, were obtained from Co (II) acetate tetrahydrate. The thermal decomposition pathway of the starting product was followed by combining thermogravimetric analysis and in situ X-ray thermodiffraction. Under a nitrogen atmosphere, cobalt monoxide with Zn-blende and rocksalt polymorphs could be obtained almost as single phases at 330 and 400 °C, respectively. In addition to these oxides, a Co (II) oxyacetate, Co3O(CH3COO)4, was stabilized as an intermediate phase. Under an air atmosphere, Co3O4 (spinel structure type) was obtained as the only final product. The involved phases in this thermal decomposition process were characterized with scanning and transmission electron microscopy (SEM and TEM, respectively).