Marcos Fernández-García

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Verified

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• Professor
• Professor (Full) at Spanish National Research Council

The combination of kinetic and spectroscopic tools has become a key scientific methodology for the understanding of catalytic behavior but its application in photocatalysis has inherent difficulties due to the nature of the energy source of the reaction. This review article provides an overview of its use by, first, presenting mechanistically deriv...

The combination of thermal and photonic energy sources to carry out catalyzed chemical reactions appears as a new avenue to optimize current industrial-oriented processes as well as to open new ones. Here we analyze the contribution of novel oxide-based composite systems to the thermo-photo catalysis field. In first place, the review article gives...

The development of the photo-catalysis field is limited by a deficient quantitative assessment of photo-activity. The interplay between mass and momentum transport together with radiative transfer phenomena taking place at any photo-catalytic reaction or process makes complex such quantitative assessment. To reach this goal, the review studies the...

In this research, composite catalysts based on mixtures of titanium and cobalt oxides were synthesized and tested in the thermo-photo reduction of carbon dioxide. The cobalt loading varied between 2% and 8 M %, providing an outstanding activity in the selective production of carbon monoxide through the reverse water gas reaction. The sample doped w...

The synthesis and properties of stoichiometric, reduced, and Co-doped In2O3 are described in the light of several experimental techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)–visible spectroscopy, porosimetry, and density functional theory (DFT) methods on appropriate models. DFT-based calcula...

Hydrogen generation through a photocatalytic process appears to be a promising technology to produce this energy vector through a novel, efficient, green, and sustainable process. The fruitful use of sunlight as an excitation source and renewable bio-derived reactants as well as the development of highly efficient catalysts are required to achieve...

The synthesis, physicochemical, and functional properties of composite solids resulting from the surface spread of oxidized indium species onto nanoplatelets of anatase were investigated. Both the size and the interaction between the indium- and titanium-containing components control the functional properties. In the reduction of CO2 to CO, the bes...

Statistical procedures to analyse sets of X-ray absorption near-edge structure (XANES) spectra are briefly described. Correlation and factor-analysis procedures are among the most widely used. Representative examples of their application to XANES analysis in a broad range of scientific disciplines are discussed.

In this study, the CuxO/TiO2 (x=1,2) nanocomposite photocatalyst was prepared via chemical-thermal oxidation followed by the sol-gel method on the copper wire. The characterization analysis indicated the co-existence of two types of copper oxides along with TiO2 and proved the formation of multicomponent heterostructure between semiconductors. A mi...

Structure-sensitive catalyzed reactions can be influenced by a number of parameters. So far, it has been established that the formation of Pd-C species is responsible for the behavior of Pd nanoparticles employed as catalysts in a butadiene partial hydrogenation reaction. In this study, we introduce some experimental evidence indicating that subsur...

In this contribution, a series of Pd-promoted Nb-doped titania samples were essayed in the gas-phase thermo-photo production of syngas from methanol/water mixtures. The Pd loading was tested in the 0.1 to 2.5 wt % range, leading to the presence of metallic nanoparticles under reaction. Reaction rates exceeding 52 mmol H 2 g −1 h −1 and quantum effi...

For improving the photocatalytic activity of titania under UV or sunlight (SL) irradiations in the gaseous phase degradation of 2-propanol, M−TiO2 catalysts were synthesized by the sol–gel method (with M = Zr, Zn and Nb) and characterized by various techniques. It was found that the solids show only the diffraction peaks of TiO2 anatase phase with...

Enhanced performance of Pd in the photocatalytic production of green hydrogen from methanol:water mixtures is achieved through the use of a Sn-containing binary co-catalyst. For a Pd:Sn molar ratio of 1:1, the binary co-catalyst leads to an outstanding enhancement of activity under UV, visible and sunlight illumination, rendering a quantum efficien...

Measuring and interpreting the efficiency of a thermo–photocatalytic reaction is key in the quest to define synergy for chemical reactions taking place under dual thermo–photo excitation. The analysis of the efficiency parameter requires multiple facets of the problem to be taken into account, demanding a detailed study of the chemical, photon and...

In this paper, the fabrication of Cu2O-CuO/TiO2 nanocomposite photocatalysts on Cu wire was performed successfully via chemical-thermal oxidation and sol-gel process. The chemical-thermal oxidations were applied for Cu2O-CuO nanostructure fabrication on the Cu wire surface. The sol-gel process was utilized for TiO2 nanoparticles decoration as a sur...

The influence of the reaction pathway of the sacrificial molecule oxidation to generate hydrogen is here investigated for lean and rich methanol reaction mixtures. Pt-TiO2 powders promoted or not with tin sulfide were used as catalysts. With the help of in situ infrared experiments under reaction conditions, methanol evolution was shown to take pla...

Optimization of Pt-promoted TiO2-based is key to promote the photocatalytic production of hydrogen using sacrificial alcohol molecules. Combination of doping and surface decoration of the mentioned base photoactive material is here exploited to maximize hydrogen yield. Using the quantum efficiency parameter, it is shown that the resulting composite...

The photocatalytic activity in the 2-propanol degradation, under UV and sunlight (SL)-type irradiations, of a series of Zr-TiO2materials, prepared using the sol-gel method, with a Zr content ranging from 0.25 to 1 wt. %, was evaluated in this work. The physicochemical properties of the solids were characterized using X-ray diffraction, BET and poro...

The complex interplay between photons and catalytic powders in liquid-phase photocatalytic degradation reactions requires combined computational and experimental approaches to render a quantitative assessment of the light harvesting and handling properties the system. The full assessment of the light-to-chemical efficiency is here presented for the...

This research evaluated the potential photocatalytic efficiency of synthesized Cu–Fe/TiO2 photocatalysts against organic contaminants and biocontaminants through various synthesis methods (Cu-to-Fe ratio, metal loading, and calcination temperature) and reaction parameters (photocatalyst dose, irradiation time, and different initial methyl orange (M...

The use of efficiency observables to measure activity is of critical importance in order to progress in the quantitative assessment of the functional properties of photo-catalysts in energy and environmental related applications. In this quest, the analysis of the experimental/computational procedures to obtain efficiency observables and the associ...

Carbon nitride based materials incorporating K and Na alkali ions were used as support(s) to deposit platinum. The systems were tested in the photo-production of hydrogen using methanol as a sacrificial molecule. Tests under UV and sunlight-type illumination conditions showed an important promoting effect of the alkali ions irrespective of the illu...

Carbon nitride based materials doped with boron were used as support to deposit platinum. The systems were tested in the photo-production of hydrogen using methanol as a sacrificial molecule. Tests under UV and sunlight-type illumination conditions showed an important promoting effect of boron, irrespective of the illumination nature. The measureme...

The silver/graphitic carbon nitride (Ag/g-C3N4) composite system exerts biocidal activity against the pathogenic bacterium Escherichia coli 1337-H that is stronger than that of well-known silver and titanium oxide (TiO2)-based composites. However, whether the Ag/g-C3N4 composite system has biocidal properties that the parent components do or do not...

The gas phase thermo-photo production of hydrogen from methanol:water mixtures was tested using platinum ceria-titania ternary solids. This contribution focusses on the analysis of the role of ceria and the usefulness of combining heat and light sources in order to boost catalytic activity. To this end, we provide a quantitative assessment of therm...

In this work, the synthesis of the CuO-Cu2O nanocomposites decorated with TiO2 nanoparticles was performed by chemical-thermal oxidation and subsequently by the sol-gel method. The X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) showed using different furnace atmospheres lead to the formation of nanocomposit...

This chapter presents an overview of the new field of thermo-photocatalysis, which combines light and heat energy sources. This is carried out in multiple forms with the simultaneous use of conventional heating and light as well as multiphotonic processes including photons from the UV to the IR electromagnetic ranges. The latter is closely connecte...

A main driver in the progress of the photocatalytic field is the development of catalytic materials able to profit from the whole spectrum of the sun. To do it, such materials need to handle efficiently photons of the UV, visible and infrared regions. This contribution analyzes successful technologies to utilize each type of these photons as well a...

In this study, multicomponent CuxO–TiO2 (x = 1 or 2) nanocomposite was used as a photocatalyst to eliminate 2-propanol in gas-phase media under both UV and sunlight-type irradiation. The specimens were fabricated by a two-step synthesis including solution treatment–thermal oxidation for CuxO and consequently sol–gel method for applying TiO2 nanopar...

Photo-catalysis is a research field with broad applications in terms of potential technological applications related to energy production and managing, environmental protection, and chemical synthesis fields. A global goal, common to all of these fields, is to generate photo-catalytic materials able to use a renewable energy source such as the sun....

The decomposition of formic acid to obtain hydrogen has been studied using molybdenum carbides supported on an activated carbon and two high surface area graphites, H200 (200 m2/g) and H400 (400 m2/g). Particular attention is paid to the effect of Mo loading. The catalysts were prepared in situ using a mixture of CH4 and H2 up to 700°C. Under these...

In this work versatile boron–carbon nitride composite materials were synthesized and utilized in a sustainable process using sunlight as the energy source for the continuous-flow selective photocatalytic production of acetone from 2-propanol. It is worth to highlight that the samples preparation were carried out by environmentally friendly strategy...

Here we analyzed the photocatalytic degradation of toluene using composite systems consisting on a tungsten oxide component supported on a pure anatase phase. To scrutinize the photocatalytic process, here we presented a new method with combine spectroscopic and kinetic tools to render novel and quantitative information mostly obtained in situ unde...

Novel composite photo-catalysts having (NH4)4[NiMo6O24H6]·5H2O Polyoxometalate (POM) species deposited over g-C3N4 are synthesized. Materials were characterized through a multitechnique approach showing the stability of the carbon nitride component both through the synthesis process and under reaction. Contrarily, the POM component evolves under re...

Photocatalytic materials have complex nature, frequently with participation of multiple or complex multi-atom components. These materials need to be synthesized with stringent control of their structural, morphological and electronic properties in the quest to optimize functional properties. This is a challenge tackled with the help of the microemu...

The article provides an overview of the most relevant characterization results of heterogeneous photo-catalytic materials available in the literature. First, we present a summary of the ex situ utilization of physico-chemical characterization techniques. In the majority of current works, pre and post-reaction samples are subjected to ex situ analys...

In this contribution we synthesized ternary CuGaS 2-TiO 2-Pt materials. The semiconductor components were surface functionalized with mercapto-alifatic acids to drive their linking and were platinized prior to or after contact between the semiconductors. The corresponding samples were utilized in the photo-production of hydrogen using methanol as a...

In this work we analyze the photocatalytic performance of Mn+ (M]Cu, Ni, Zn, Mn) - g-C3N4 materials in toluenephoto-oxidation under UV and Sunlight-type illumination conditions.The characterization of the solids showed that Cu and Mn containing samples have an oxide type environment, while Ni has a hydroxide type and Zn shows an oxynitride type loc...

The article provides an overview of the most relevant characterization results of heterogeneous photo-catalytic materials available in the literature. First, we present a summary of the ex situ utilization of physico-chemical characterization techniques. In the majority of current works, pre and post-reaction samples are subjected to ex situ analys...

Hydrogen photo-production using methanol:water mixtures was essayed with PtRu titania-based materials. All materials contain a high surface area Nb-doped anatase support. Six bimetallic formulations with Pt:Ru ratios from 4:1 to 1:4 and two (Pt and Ru) monometallic reference samples were utilized. The catalytic response of the materials to three ma...

In this study, Cu2O nanostructures on Cu wire were formed with in situ chemical and then thermal oxidation to obtain the desirable structure, morphology and optical properties in order to enhance visible-light photocatalytic activity. The findings suggested that the procedure involved solution phase treatment and formation of Cu2O on pure Cu wire w...

The interaction between carbon nitride and titania in g-C3N4/TiO2 materials is analyzed from a new perspective. The composite materials are prepared using a well crystallized anatase substrate over which carbon nitride (0.5 to 4 wt.%, promoted or not with Mn) is deposited. The catalysts are characterized using a multitechnique approach. In addition...

A series of ruthenium – anatase solids with noble metal loadings from 1 to 10 wt. %. was tested in the gas phase thermo-photo production of hydrogen using methanol as a sacrificial agent. Samples were characterized using X-Ray diffraction, UV–vis, X-ray photoelectron and absorption spectroscopies as well as transmission electron microscopy. A pure,...

A new cell for in situ combined X-ray absorption, diffuse reflectance IR Fourier transform and mass spectroscopies (XAS–DRIFTS–MS) is presented. The cell stands out among others for its achievements and flexibility. It is possible to perform XAS measurements in transmission or fluorescence modes, and the cell is compatible with external devices lik...

Catalysis is an integral part of a majority of chemical operations focused on the generation of value‐added chemicals or fuels. Similarly, the extensive use of fossil‐derived fuels and chemicals has led to deterioration of the environment. Catalysis currently plays a key role in mitigating such effects. Thermal catalysis and photocatalysis are two...

In this work we analyze two series of samples containing tungsten and titania as cations with a W/Ti atomic ratio from 0 to 0.5. The samples are prepared by a single-pot procedure, rendering in all cases high surface area powders having a dominant anatase crystalline phase. The materials were characterized by a combination of X-ray diffraction and...

A series of composite materials based on titania and growing quantities of the (NH4)4[NiMo6O24H6]·5H2O heteropolyacid (NiMo6 HPA) was tested in the gas-phase toluene photo-oxidation reaction. Materials were characterized with the help of chemical analysis, X-ray diffraction, porosimetry, electron transmission and scanning microscopies, as well as X...

The performance of binary PtPd co-catalysts supported on Nb-TiO2 was tested in the gas and liquid phase photo-reforming of methanol. Co-catalyst formulations having Pt:Pd ratios from 2:1 to 1:4 were tested and the activity measured through the calculation of the quantum efficiency. Characterization of the initial and post-reaction materials showed...

The combination of complementary techniques in the characterization of catalysts under working conditions is a very powerful tool for an accurate and in-depth comprehension of the system investigated. In particular, X-ray absorption spectroscopy (XAS) coupled with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectro...

The Cover Feature illustrates the potential use of hydrogen as a fuel, obtained using g‐C3N4‐based nanomaterials and an annular flow photoreactor. The colour map of the reactor describes the local superficial rate of photon absorption of the catalyst. More information can be found in the Article by M. J. Muñoz‐Batista et al. on page 870 in Issue 10...

Heterogeneous photocatalysts are rarely employed in industry for the synthesis of commodity chemicals due to efficiency problems. Now, a photochromic Bi2WO6–x/amorphous-BiOCl composite is reported, which features a remarkable activity for the photocatalytic oxidation of toluene into benzaldehyde and benzoic acid. © 2018, The Author(s), under exclus...

In the context of bandgap engineering of the ZnO photoactive material for solar harvesting applications via W doping, a number of a priori discrepant experimental observations in the literature concerning ZnO c axis expansion/contraction, bandgap red- or blue-shifting, the Zn-substitutional or interstitial nature of W atoms, or the W6+ charge compe...

In this work binary Sn-Ti samples having Sn:Ti atomic ratios from zero to one were prepared through a hydrothermal method. The resulting high surface area powders were characterized using a combination of X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, UV–vis spectroscopy and porosimetry techniques. The series...

The use of operando spectroscopic tools in heterogeneous photocatalysis has experienced a strong drive in recent years. The use of operando tools needs however to consider carefully the fraction of the system to be probed in an in situ cell, that is the volume under the simultaneous influence of the excitation light and the reactants. This is not a...

A series of ruthenium catalysts supported into pure anatase titania were tested in the photo-production of hydrogen from methanol:water mixtures under UV and visible illumination conditions. Catalysts containing 1, 2, 3 and 5 wt.% of ruthenium were subjected to a characterization study with the help of X-ray diffraction, Raman, X-ray photoelectron...

In this work we synthesized a series of binary PtPd co-catalysts supported on a Nb-doped TiO2 support. The catalytic solids and corresponding monometallic reference systems are characterized using X-ray diffraction, X-ray photoelectron, and UV-visible spectroscopies, together with microscopy and porosimetry tools. Such characterization was able to...

Green energy production from renewable sources is an attractive but challenging topic to face the likely energy crisis scenario in the future. In the current work, a series of versatile Ru/TiO2 catalysts were simply synthesized and employed in continuous flow catalytic transfer hydrogenation of industrially derived methyl levulinate biowaste (from...

The effect of using two different promoter precursors on the Fischer-Tropsch synthesis was studied over cesium promoted ruthenium catalysts supported on a high surface area graphite support. In this work we reveal significant modifications in the selectivity values for Fischer-Tropsch reaction depending on the Cs promoter precursor (CsCl vs CsNO3)....

Simple modifications of g‐C3N4 (CN) have been studied to maximise hydrogen production under sunlight irradiation conditions. The relatively low surface area CN obtained was subjected to an exfoliation process which increases 1) available catalytic area and 2) modulates the semiconductor charge photo‐handling. MnOx and metallic Pt, which can act as...

In this work we analyzed the photo-production of hydrogen using titania-based systems able to profit from UV and visible light photons. For this purpose, we prepared Niobium-doped titania and a titania reference by a microemulsion method, subjected these oxide precursors to calcination and subsequently introduced Pt as co-catalyst by a chemical red...

Understanding how a photocatalyst modulates its oxidation state, size and structure during a photocatalytic reaction under operando conditions is strongly limited by the mismatch between (catalyst) volume sampled by light and, to date, the physico-chemical techniques and probes employed to study them. Here we present a synchrotron micro-beam X-ray...

This work describes a study carried out to construct and determine a kinetic formalism for the gas-phase degradation of 2-propanol using a combined thermo-photo based process. Outstanding catalytic performance was observed for a composite ceria-titania system with respect its parent ceria and titania reference systems. Thermo-photo as well as paral...

Understanding how a photocatalyst modulates its oxidation state, size and structure during a photocatalytic reaction under operando conditions is strongly limited by the mismatch between (catalyst) volume sampled by light and, to date, the physico-chemical techniques and probes employed to study them. Here we present a synchrotron micro-beam X-ray...

A series of composite systems based on titania and growing quantities of tungstophosphoric acid are prepared and characterized using infrared, nuclear resonance, UV–visible, photoluminescence, and photoelectron spectroscopies, transmission electron microscopy as well as x-ray diffraction and porosimetry techniques. These techniques showed evolution...

A series of highly-active catalysts were obtained from the same precursor and calcined at different temperatures to generate single-phase anatase and anatase-rutile composite powders. Performance of the catalysts was compared with the P25 reference and assessed through the measurement of the optical properties of the materials and calculation of th...

In this work we compare the performance of platinum and palladium co-catalysts supported on Nb-doped titania materials for the photo-generation of hydrogen using methanol as sacrificial agent. Liquid and gas phase processes are considered. The catalysts physico-chemical properties were characterized by a combination of X-ray diffraction, UV–vis and...

The aim of this work is to understand the role of oxygen surface groups during the preparation, activation and reaction of heterogeneous ruthenium catalysts supported on activated carbon materials. Hence, non-promoted and sodium promoted ruthenium catalysts supported on two different activated carbon materials, with and without oxygen surface group...

Nb-doped titania nanopowders active under UV and visible light were used as supports of platinum and tested in the photo-production of hydrogen using methanol as sacrificial agent in liquid phase. Samples were characterized using X-ray diffraction and photoelectron spectroscopy, UV-visible and photoluminescence spectroscopies, electron paramagnetic...

A relatively low surface area graphitic carbon nitride produced by a standard melamine calcination procedure was subjected to an exfoliation process and/or surface deposition of Mn-containing species. The resulting catalysts were characterized using X-ray diffraction and photoelectron spectroscopies, transmission electron microscopy, UV-visible and...

A new series of electrocatalysts consisting of Ag nanoparticles supported on graphitic carbon nitride (g-C3N4) are presented. The combination of nanostructured silver and a carbon nitride support results in the direct generation of synthesis gas (CO+H2) during the electrocatalytic reduction of CO2 in water. By using a state-of-the-art electrocataly...

The enhancement of active triggered by surface deposition of Cu, Bi and Ce containing oxidic species onto a high surface area anatase is analyzed through the calculation of the quantum efficiency for toluene photo-degradation under UV and Sunlight-type illumination. To this end, series of Cu, Bi and Ce containing oxides supported onto anatase were...

The initial stages in the field of the structure determination focused on the development of diffraction crystallographic techniques both in the single crystal and powder modes. This chapter provides an overview of how the potentialities of X-ray absorption spectroscopy (XAS), and by extension, X-ray emission spectroscopy (XES), can be expanded by...

Here we present a time resolved in situ X-ray absorption spectroscopy investigation of the local chemical environment and the electronic structure of the active metal (Ru) and the promoter (Cs) present in catalysts supported over a high surface area graphite. These catalysts were submitted to a reduction treatment in hydrogen gas and then to altern...

Metallic silver (ranging from 1 to 10 wt. %) was deposited onto a graphite like carbon nitride photocatalyst through a microemultion method. Surface, morphological and structural properties of the resulting materials were characterized using BET and porosity measurements, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron mi...

The role of the interface in Cu,Ni-CeO2 catalysts used for novel hydrogen purification and production processes (preferential oxidation of CO, water–gas shift reactions, and the reforming of bio-alcohols) is analyzed with an emphasis on the description of the physico-chemical properties of the interface that have a critical influence on the catalyt...

Two series of Cu2+ and V4+ doped anatase TiO2 samples were prepared using the microemulsion synthetic route by varying the metal/Ti ratio. The samples were characterized by UV-vis absorption, nitrogen physisorption, XRD, XPS, Raman and EPR spectroscopy. Their photocatalytic activity against toluene photo-oxidation was evaluated under both sunlight-...

A new procedure for preparation of palladium sulfide nanoparticles, which are deposited and anchored over highly graphitized carbon nanofibers, is presented. The preparation method is based on the use of PdSO 4 as metal precursor or alternatively in the previous functionalization of the carbon surfaces with sulfonic groups by treatment with fuming...

A series of ZnO nanostructures with variable morphology were prepared by a microemulsion method and their structural, morphological, and electronic properties were investigated by a combined experimental and theoretical approach using microscopy (high resolution transmission electron microscopy) and spectroscopic (X-ray diffraction, Raman, and UV-v...