Anna Kubacka

Spanish National Research Council | CSIC · Institute of Catalysis and Petrochemistry

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...

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...

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...

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 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...

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...

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...

Measuring and interpreting efficiency of a thermo-photo catalytic reaction appear as central pieces in the quest to define synergy for chemical reactions taking place under dual thermo-photo excitation. The analysis...

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 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 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...

A series of NiCu based catalysts were prepared using different carbon nanostructure as support and loading 2.5 wt% of each metal. The studied nanocarbon materials were: reduced graphene oxide (rGO), N-doped reduced graphene oxide (NrGO), high surface area graphite (HSAG), single and multiwalled carbon nanotubes (SWCNT and MWCNT), N-doped carbon nan...

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...

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...

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...

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....

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...

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...

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,...

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...

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...

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 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 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...

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...

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...

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...

Catalysts of copper (1 wt. %) supported on a CeO2/MgAl2O4 mixed support have been prepared by using different pH values (pH ∼ 4, 8 and 10) in the impregnating solution of copper with the aim of favoring different situations of interaction between copper and the two support components. The catalysts have been characterized in detail by XRD, SBET mea...

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...

The ethanol steam reforming (ESA) reaction was studied over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in situ techniques including X-ray diffraction, pair distribution function, X-ray absorption fine structure, and transmission electron microscopy; while possible surface intermediates for the ESR...

The enhancement of TiO2-based catalysts activity by effect of surface species is analyzed in the photo-elimination of toluene in a complex, ternary system having ceria and Mn-modified carbon nitride in contact with a major anatase phase. With a combination of kinetic and spectroscopic tools applied to the ternary system and corresponding binary/sin...