Juan Carlos Hernandez-Garrido

Universidad de Cádiz | UCA · Department of Material Science and Metallurgy Engineering and Inorganic Chemistry

The removal of acetylene from ethylene streams is key in industry for manufacturing polyethylene. Here we show that a well-defined Pd1–Au1 dimer, anchored to the walls of a metal–organic framework (MOF), catalyses the selective semihydrogenation of acetylene to ethylene with ≥99.99% conversion (≤1 ppm of acetylene) and >90% selectivity in extremely...

Commercially available zeolite Y modulates the catalytic activity and selectivity of ultrasmall silver species during the Buchner reaction and the carbene addition to methylene and hydroxyl bonds, by simply exchanging the counter cations of the zeolite framework. The zeolite acts as a macroligand to tune the silver catalytic site, enabling the use...

The influence of thermal treatment under reducing conditions on the structural and hydrogen evolution reaction (HER) properties of Au@MoS2 structures is reported in this work. After a thermal treatment at 800 °C under H2 atmosphere, the Au@MoS2 nanostructures exhibit remarkable performance with an overpotential of 203 mV vs reversible hydrogen elec...

Copper is one of the goldilocks metals in catalysis. Deciphering the local atomic environment and oxidation state of active centers in supported copper catalysts, as well as the design of materials to control their stability under reaction conditions remains a great challenge today. We show here that a mixed-oxide of copper delafossite with gallium...

Sub‐nanometer metal clusters have special physical and chemical properties, significantly different from those of nanoparticles. However, there is a major concern about their thermal stability and susceptibility to oxidation. In situ X‐ray Absorption spectroscopy and Near Ambient Pressure X‐ray Photoelectron spectroscopy results reveal that support...

The isomerization (chain-walking) reaction of terminal to internal alkenes is catalyzed by part-per-million amounts of practically any Ru source when the reaction is carried out with a neat terminal alkene. Here, we provide evidence that the soluble starting Ru sources evolve to catalytically active peralkene Ru(II) species under reaction condition...

The combination of well-defined Fe3+ isolated single-metal atoms and Ag2 subnanometer metal clusters within the channels of a metal-organic framework (MOF) is reported and characterized by single-crystal X-ray diffraction for the first time. The resulting hybrid material, with the formula [Ag02(Ag0)1.34FeIII0.66]@NaI2{NiII4[CuII2(Me3mpba)2]3}·63H2O...

Simple aluminosilicates, including NaX and NaY zeolites, catalyze the selective halogen exchange reaction between two different alkyl organohalides, either in batch or in flow, without any additive or solvent, simply...

The use of bimetallic nanoparticles as catalysts in complex organic synthesis is rare, despite the widespread use of these materials in thermal C1 chemistry and electrocatalysis. Here we show that...

The aim of this article is to study the catalytic capacities of gold nanoparticles based on a layered double hydroxide prepared by a depo-precipitation method in oxidation. The main interest of this work is to prove the possibility of using these materials as catalysis for selective oxidation for succinic acid production. The textural and morpholog...

Ligand-free sub-nanometer metal clusters (MCs) of Pt, Ir, Rh, Au and Cu, are prepared here in neat water and used as extremely active (nM) antitumoral agents for HeLa and A2870 cells. The preparation just consists of adding the biocompatible polymer ethylene-vinyl alcohol (EVOH) to an aqueous solution of the corresponding metal salt, to give liters...

The aim of this article is to study the catalytic capacities of gold nanoparticles based on a layered double hydroxide prepared by a depo-precipitation method in oxidation. The main interest of this work is to prove the possibility of using these materials as catalysis for selective oxidation for succinic acid production. The textural and morpholog...

Antitumoral Agents In article number 2113028, M. Arturo López‐Quintela, Fernando Domínguez, and co‐workers report that Ag5 clusters show unique catalytic activities to oxidize thiols. They catalyze the complete oxidation of thiols present in cysteine, glutathione, and thioredoxin. This oxidation is tunable by relevant biological oxidants species (h...

The performance of gallium promoted cobalt-ceria catalysts for ethanol steam reforming (ESR) was studied using H2O/C2H5OH = 6/1 mol/mol at 500 °C. The catalysts were synthetized via cerium-gallium co-precipitation and wetness impregnation of cobalt. A detailed characterization by N2-physisorption, XRD, H2-TPR and TEM allowed the normalization of co...

Low atomicity clusters present properties dependent on the size, due to the quantum confinement, with well‐defined electronic structures and high stability. Here it is shown that Ag5 clusters catalyze the complete oxidation of sulfur to S⁺⁶. Ag5 catalytic activity increases with different oxidant species in the order O2 ≪ H2O2 < OH•. Selective oxid...

The de–novo synthesis of soluble or solid–supported Pd–(CaCO3)n clusters (n = 2–13) and their high catalytic activity for the semi–hydrogenation of internal alkynes compared to terminal alkynes, is presented. Mechanistic studies show that this reactivity, i.e. internal alkynes more reactive than terminal alkynes, comes from the higher electrophilic...

Supported Ni catalysts (4.5 wt%) using a Ce-Zr oxide (18/82 molar ratio and a ceria-rich surface) depicting advanced redox properties, were deposited by washcoating over cordierite honeycombs (230 and 400 cpsi). FIB-STEM unveiled nanostructure details otherwise undistinguishable by conventional techniques. The catalytic performance was evaluated in...

The texture, structure, composition, and electronic state of new and used monolithic Mn-Cu catalysts were studied. Characterisation was performed at different scales and spatial resolution by combining STEM-FIB and imaging techniques (STEM-HAADF) and spectroscopy (STEM-EDX and EELS of space resolution). A thickness of the alumina layer that varies...

The palladium-catalysed cross-coupling reaction between alkenes and aryl halides (the Mizoroki–Heck reaction) is a powerful methodology to construct new carbon–carbon bonds. However, the success of this reaction is in part hampered by an extremely marked regioselectivity on the double bond, which dictates that electron-poor alkenes react exclusivel...

Metal single-atom catalysts (SACs) promise great rewards in terms of metal atom efficiency. However, the requirement of particular conditions and supports for their synthesis, together with the need of solvents and additives for catalytic implementation, often precludes their use under industrially viable conditions. Here, we show that palladium si...

Subnanometer-sized metal clusters often feature a molecule-like electronic structure, which makes their physical and chemical properties significantly different from those of nanoparticles and bulk material. Considering potential applications, there is a major concern about their thermal stability and susceptibility towards oxidation. Cu clusters o...

Subnanometer-sized metal clusters often feature a molecule-like electronic structure, which makes their physical and chemical properties significantly different from those of nanoparticles and bulk material. Considering potential applications, there is a major concern about their thermal stability and susceptibility towards oxidation. Cu clusters o...

Stainless-steel honeycomb monoliths (square cell-shape/230 cpsi cylinders) were 3D-printed and used as support of a Ni/CeO 2-ZrO 2 powder deposited by washcoating. The resulting catalysts were characterized by XRF, SEM-EDX and H 2-TPR, and tested in the dry reforming of methane reaction. In the 750-900 °C range, they showed competitive conversions...

A Ni/CeO2/ZrO2 catalyst with improved redox properties has been washcoated onto a honeycomb cordierite monolith in the form of a nonconventional alumina-catalyst layer, just a few nanometers thick. In spite of the very low active phase loading, the monolith depicts outstanding performance in dry reforming of methane, both in terms of activity, with...

Electron tomography (ET) has rapidly developed into a powerful technique to characterize the three-dimensional (3D) structure of complex materials, with nanometer resolution, for a wide range of applications including heterogeneous catalysis. In these 3D studies, scanning transmission electron microscopy (STEM) has been the most widely used imaging...

Electrochemical synthesis employing porous membranes previously metalized with a gold layer as a template is an easy and widespread method to obtain 1D nanostructures. Nevertheless, experimental factors for tuning the morphology and structural details of such nanostructures are still investigated. The influence of the amount of gold on morphology a...

This work shows an easy and eco-friendly methodology to obtain almost pristine anatase phase of TiO 2 by using furfural, a biomass-derived molecule, as a bio-template. The photocatalytic activity was studied following the degradation of methylene blue and phenol under artificial solar irradiation. Results were compared against those obtained on a c...

Redox and catalytic performance in total methane oxidation of a nanostructured ceria-terbia catalyst supported on magnesia is presented and compared to that of a pure ceria catalyst supported on MgO. The investigated material, Ce0.5Tb0.5Ox (3% mol.)/MgO, features several remarkable properties: a quite low total molar loading of the two lanthanide e...

The assumption that oxidative addition is the key step during the cross-coupling reaction of aryl halides has led to the development of a plethora of increasingly complex metal catalysts, thereby obviating in many cases the exact influence of the base, which is the simplest, inexpensive and necessary reagent for this paramount transformation. Here,...

This paper explores the capability of scanning transmission electron microscopy (STEM) techniques in determining the dispersion degree of graphene layers within the carbon matrix by using simulated high-angle annular dark-field (HAADF) images. Results ensure that unmarked graphene layers are only detectable if their orientation is parallel to the m...

Carbon-containing SiO2-based photocatalysts were prepared by the solvothermal treatment of rice husk as biogenic precursor in the presence and absence of TiO2 and used for the photocatalytic degradation of rhodamine-B under simulated solar light. Data showed that the prepared catalysts are mainly composed of biogenic silica and displayed mesoporous...

The synthesis and reactivity of single metal atoms in low–valence state bound to just water, rather than to organic ligands or surfaces, is a major experimental challenge. Here, we show a gram–scale wet synthesis of Pt11+ stabilized in a confined space by a well–defined crystallographic first water sphere, and with a second coordination sphere link...

The synthesis and reactivity of single metal atoms in low–valence state bound to just water, rather than to organic ligands or surfaces, is a major experimental challenge. Here, we show a gram–scale wet synthesis of Pt11+ stabilized in a confined space by a well–defined crystallographic first water sphere, and with a second coordination sphere link...

Resumen Se prepararon por impregnación a humedad incipiente catalizadores de níquel soportado sobre un óxido mixto de Ce-Zr (de relación molar 15/85 y rico superficialmente en cerio) con un 4.5% en peso de Ni, que se depositaron después por washcoating sobre honeycombs de cordierita de 230 celdas/pulgada 2. Los catalizadores, en polvo y monolitos,...

The gram‐scale synthesis, stabilization and characterization of well‐defined ultrasmall subnanometric catalytic clusters on solids represent a challenge. Here, we report the chemical synthesis and X‐ray snapshots of Pt20 clusters, homogenously distributed and densely‐packaged within the channels of a metal‐organic framework. This novel hybrid mater...

The gram‐scale synthesis, stabilization and characterization of well‐defined ultrasmall subnanometric catalytic clusters on solids represent a challenge. Here, we report the chemical synthesis and X‐ray snapshots of Pt20 clusters, homogenously distributed and densely‐packaged within the channels of a metal‐organic framework. This novel hybrid mater...

Ceria‐zirconia mixed oxides are widely used as catalysts and catalytic supports. Nevertheless, due to economic and geo‐strategic concerns, reducing and optimizing the lanthanide content in these formulations while preserving or even improving their excellent redox and catalytic properties has become a challenge for current research. In this context...

Inorganic 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 current...

Copper-iron mixed oxides with Fe/Cu molar ratios ranging from pure CuO to Fe2O3 were synthesised by a low temperature co-precipitation method, and tested in the CO-PROX reaction. The extensive characterization performed by means of different techniques showed the progressive variation of physical and chemical properties including composition, textu...

A BaFeO3-d (d≈0.22) perovskite was prepared by a sol-gel method and essayed as catalyst in the CO oxidation reaction. BaFeO3-d (0.22 ≤ d≤ 0.42) depicts a 6H perovskite hexagonal structural type with Fe in both (III) and (IV) oxidation state and oxygen stoichiometry accommodated by random distribution of anionic vacancies. The perovskite with the hi...

Nature uses enzymes to dissociate and transfer H2 by combining Fe²⁺ and H⁺ acceptor/donor catalytic active sites. Following a biomimetic approach, it is reported here that very small planar Fe2,3+ oxide nanoparticles (2.0 ± 0.5 nm) supported on slightly acidic inorganic oxides (nanocrystalline TiO2, ZrO2, ZnO) act as bifunctional catalysts to disso...

The interplay between chemical inhomogeneities and magnetic properties in iron alloys is a subtle question that affects several nanoalloys with potential technological and biomedical applications. Herein below, we focus on the FCC palladium rich–iron nanoparticle system, specifically in three samples that reflect the key influence of synthesis cond...

Supplementary material.

Amorphous magnesium-substituted calcium phosphate (AMCP) nanoparticles (75–150nm) form constitutively in large numbers in the mammalian gut. Collective evidence indicates that they trap and deliver luminal macromolecules to mucosal antigen presenting cells (APCs) and facilitate gut immune homeostasis. Here, we report on a synthetic mimetic of the e...

Restructuration of AuPd/CeO2 catalysts is observed during 1,5-cyclooctadiene hydrogenation, with gold surface segregation in which gold acts as a diluent of Pd surface sites. The composition of the catalyst influences the catalytic behavior, and an optimum is observed at a Pd/Au molar ratio of 0.13, as determined by X-EDS STEM. Pd-Au/CeO2 shows hig...

Palladium-rich Iron nanoparticles in the 4-8 nm range have been produced by a combination of two methods: the thermal decomposition of organometallic precursors and the reduction of metallic salts by a polyol. Herein, it is shown how the details of the synthesis have a striking impact on the magnetic and morphological properties of the final produc...

In humans and other mammals it is known that calcium and phosphate ions are secreted from the distal small intestine into the lumen. However, why this secretion occurs is unclear. Here, we show that the process leads to the formation of amorphous magnesium-substituted calcium phosphate nanoparticles that trap soluble macromolecules, such as bacteri...

Co3O4/La-modified-CeO2/Al2O3 powders washcoated onto ceramic and metallic monolithic catalysts have been compared in order to evaluate the contribution of both the type of substrate and the total washcoat loading on the actual surface structure of the corresponding monolithic devices. Detailed structural and chemical characterization studies have b...

Site-selective emission spectra of Eu3+-doped CeO2 nanoparticles up to the 5D0–7F5 transition were recorded under cryogenic conditions to identify the local structure around the Eu3+ dopants in ceria. It is found that pretreatment conditions are crucial for the redistribution of dopants from a broad variety of environments to six well-defined latti...

On the basis of calculated thermodynamic species distribution diagrams and by appropriately controlling the pH of aqueous HAuCl4 solutions, it has been possible to prepare, using a Speciation-controlled Incipient Wetness Impregnation (ScIWI) approach, Au catalysts supported on ceria-zirconia mixed oxides featuring both high gold loadings and excell...

In the design and engineering of functional core-shell nanostructures, materials characterization at small length scales remains one of the major challenges. Here we show how electron tomography in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mode can be applied successfully to perform nano-metrological chara...

Two commercial high BET surface areas CeO2 are characterized, as received and after calcination at different temperatures, to better understand the relationship between reducibility and micro- and nanostructure. Combination of TPR data, Rietveld analysis of XRD diagrams and HREM/HAADF-STEM suggest that the nano-particles are responsible for Ce4+ re...

The invention relates to catalysts having a structure comprising nanostructured oxides arranged in layers, the surface of which is formed by a cerium-zirconium mixed oxide with a pyrochlore-type structure (phase ĸ) that can activate the hydrogen molecule at a low temperature, and the nucleus is formed by a zirconium oxide or a zirconium oxide stabi...

A novel Co (15 wt.%)/La-modified-CeO2 catalyst was prepared for the oxidation of toluene and ethyl acetate, showing lower light-off temperature (around 20-40 degrees C) than that of a Pt (3 wt.%)/La-CeO2 catalyst under the same experimental conditions. Upon washcoating onto cordierite it was still more active than the noble metal reference. The act...

Cyclohexanone oxime is formed from nitrobenzene with 97% yield in a one-pot reaction catalysed by palladium and gold nanoparticles on carbon. The reaction is carried out under hydrogen at 60 °C and the overall transformation involves a multi-step catalysed mechanism from which intermediates and catalytically active species have been identified.

The current study reports on the prepara-tion of 10–13 nm ZnO nanoparticles homoge-neously doped with Fe 2+ ions ((Zn 0.97 Fe 0.03)O) and the manipulation of their ferromagnetic response at room temperature with an appropriate post-processing. The homogeneous spatial distribution of iron is studied at atomic column level through high-resolu-tion tr...

A detailed structural and chemical characterization study has been performed, both at the micrometer and nanometer scale levels, throughout the different steps of preparation of a catalytic device consisting in Co3O4/La-modified-CeO2/Al2O3 powders washcoated onto a honeycomb-type cordierite monolith. High-resolution transmission electron microscopy...

Pt impregnated on a Sn-beta catalyst results in a very promising catalyst for the selective hydrogenation of α,β-unsaturated aldehydes, compared to the PtSn co-impregnated beta catalysts. Framework tin ions in the Sn-beta sample stabilize the nucleation of platinum nanoparticles inside the zeolite channel. These Pt(0)-Sn(4+) sites, which are only o...

On the basis of detailed previous knowledge about the correlation existing between the Oxygen Storage Capacity (OSC) of ceria–zirconia mixed oxides, the nature of redox pretreatments and the nanostructure of this family of complex materials, it has been possible to design a synthetic strategy allowing one to prepare ceria–zirconia and ceria–yttria-...

Nanocrystalline C-doped TiO2 hybrid hollow spheres were prepared by solvothermal synthesis by controlling calcinations of mixtures of furfural, chitosan or saccharose with titanium isopropoxide. The origin of the carbon influences the texture, the crystalline framework, and the optical and photoelectrochemistry properties of the TiO2. The results i...

CeO2-based redox nanomaterials are widely used in automotive catalysts, solid oxide fuel cell systems and many other applications as highly efficient redox systems. However, these properties suffer thermal deactivation under real operating conditions and accordingly thermal stability is a highly desirable property. We report that highly dispersed a...

A mesoporous TiO(2)-SiO(2) nanocomposite photocatalyst has been prepared from TiO(2) nanoparticles and ethoxysilane oligomers in the presence of a non-ionic surfactant (n-octylamine). The 2D and 3D structure properties of the resulting nanomaterial are described. The use of 3D techniques, particularly HAADF-STEM electron tomography, together with 3...

This study reports an improvement of the stability of steam reforming catalysts at relatively low temperatures, such as for pre-reforming, and reforming of biomass derived compounds, by enhanced stabilization of Ni nanoparticles through spatial confinement in a mixed oxides matrix. We revealed a simple approach of three dimensional engineering of N...