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In this research study, the impact of adding zirconium oxide to titanium oxide-supported gold systems on photocatalytic hydrogen production was analyzed. The activity was evaluated as a function of the zirconium content, with up to 5 mol.% tested under UV, visible light, and sunlight illumination. It was found that the highest activity was achieved with a 1.75 mol.% zirconium oxide, as measured using reaction rate and quantum efficiency parameters under various illumination conditions. The results showed a quantum efficiency close to 1.9% under sunlight, which represents a substantial improvement of over two orders of magnitude compared to the original titanium system. The addition of zirconium influenced the recombination of charge carriers and boosted photoactivity through the interaction between gold and zirconium. [Display omitted] • Hydrogen production using Au/ZrOx-TiO 2 under UV and visible illumination. • Zr promotes activity over the bare titania catalyst by two orders of magnitude. • Zr optimizes activity with a 1.75 mol%, presenting a quantum efficiency of 1.9%. • Zr presence influences charge recombination and surface chemistry. [ABSTRACT FROM AUTHOR]

A series of catalysts with growing quantities of Niobium were prepared using Pd as co-catalyst and a high surface area titania support. All samples displayed a constant Pd particle size of ca. 4.6 nm and a support where Niobium appears to be present in the pores of anatase without altering the main oxide primary particle size. The activity of the samples in the hydrogen production under UV and visible illumination was tested and measured using the reaction rate and quantum efficiency parameters. The optimum system has a 1 mol. % of Niobium and is particularly akin to profit from sunlight, showing a quantum efficiency value of 2.8%. The physico-chemical analysis of the activity ground unveils a direct correlation between change handling capability of the samples and the optimization of activity. [Display omitted] • Hydrogen production using Pd/NbOx-TiO 2 under UV and visible illumination. • Nb optimizes activity with a 1 mol. %, presenting a quantum efficiency of 2.8%. • Nb promotes activity over the bare titania catalyst by a 3.3 factor. • Nb presence influences charge recombination, directly driving photoactivity. [ABSTRACT FROM AUTHOR]

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–vis and photoluminescence spectroscopies, electron paramagnetic resonance, and transmission electron microscopy. The catalytic performance was evaluated taking into account the measurement of the corresponding reaction rates and the computation of the quantum efficiency values. Optimization of the catalytic output upon UV and visible excitation was carried out as a function of the Nb content of the material and using an experimental design taking as factors the methanol:water ratio, and catalyst concentration at liquid phase. The performance of the materials and the optimum for a catalyst containing a 2.5 mol% of Nb upon UV, visible light and sunlight was examined. The characterization results concerning both the charge carrier species recombination and the fate of such species at the catalytic surface were used to elucidate the physico-chemical roots for maximizing activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt and Pd co—catalysts tested in hydrogen photo-production. • UV and Visible performance tested in gas and liquid phase. • Analysis of activity by means of the true quantum efficiency parameter. • Pd appears as an optimum choice under UV but not under visible illumination. 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 photoluminescence spectroscopies and transmission electron microscopy, and their photocatalytic performance assessed through the analysis of the optical properties, the measurement of the reaction rates and subsequent computation of the true quantum efficiency in both liquid and gas phase reactors. Using Pt and Pd containing catalysts having similar primary noble metal particle size we compare the two co-catalysts performance in terms of the carbon containing product selectivity of the methanol photo-transformation and the overall performance of the materials in the photon to chemical transformation as measured through the true quantum efficiency. The work shows that Pd displays competitive performance with respect to Pt under UV illumination but not under visible light. The physico-chemical analysis of the solids and particularly the measurement of the charge carrier handling and recombination through photoluminescence at several wavelengths indicate the important role played by charge recombination upon UV illumination but also that other phenomena need to be considered under visible illumination to fully explain the photo-catalytic evolution of hydrogen in noble metal containing catalysts. [ABSTRACT FROM AUTHOR]

A series of samples where platinum is deposited onto titania P25 using a chemical deposition method was tested in the photo-production of hydrogen using methanol as a sacrificial agent. The optimization of the platinum titania contact was analyzed as a function of the synthesis conditions. The catalysts’ structural and electronic properties were measured using a combination of porosimetry, X-ray diffraction, X-ray photoelectron, photoluminescence, and UV–visible spectroscopies, together with a microscopy study of the noble metal particle size distribution and an in situ infrared study of the catalysts under reaction conditions. The measurement of the optical properties of the catalyst suspensions and the subsequent calculation of the true quantum efficiency were used to show that a significant enhancement of ca. 250% can be achieved through the series of Pt-containing catalysts. The study provides solid evidence concerning the physical roots of the photoactivity behavior. For catalysts having equal Pt properties in terms of primary particle size and electron handling capability, a synergy between the noble metal and the oxide support at interface sites is shown to promote the conversion of carboxylate-type surface species into carbon dioxide and maximize the hydrogen yield of the reaction. [ABSTRACT FROM AUTHOR]

A series of TiO 2 samples, prepared by a microwave assisted method followed by spray drying and subjected to further calcination, were tested in gas-phase photodegradation of 2-propanol under UV and Sunlight-type illumination conditions. Samples were characterized using X-ray diffraction, porosimetry, UV–vis and Photoluminescence spectroscopies. This physico-chemical characterization was completed with the in-situ analysis of the sample behavior under illumination conditions using infrared spectroscopy. The photochemical behavior of the samples was analyzed through their reaction rate and particularly efficiency parameters, the later measured as both the apparent and true quantum efficiency. To calculate the efficiency in quantitative basis we carried out a complete analysis of the light-matter interaction in the reaction system as well as the chemical response of the catalysts measuring reaction activity and selectivity. The study measures the differences observed among the most common (including the apparent and true quantum efficiency) approximations used to calculate the efficiency parameter providing evidence that they can differ in a factor of 2–4 and shows that optimum performance in our titania-based catalysts is obtained in presence of anatase-rutile interface contact. However, the analysis of the true quantum efficiency demonstrates that this is not exclusively based in the well-known effect of such interface in charge recombination but also depends critically on the variation of the optical properties of the catalytic solids through the series. [ABSTRACT FROM AUTHOR]

• Hydrogen photoproduction on multicomponent Pd-Sn/NbOx-TiO 2 -based catalysts. • Electronically modified Pd nanoparticles in contact with Sn oxo-hydroxide entities. • 4 % quantum efficiency under simulated sunlight. • An alkoxy-radical route with dioxymethylene as main intermediate maximizes photo-activity. 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 efficiency value of 4 % in the latter case. A core–shell type interaction occurs between Pd metal nanoparticles and Sn oxo-hydroxyde nanoentities, resulting in an electronic modification of both components. The chemical effects of the binary co-catalyst were explored under reaction conditions using infrared spectroscopy. Overall, this study provides evidence that the electronic interaction between Pd and Sn promotes the adsorption and attack of the charge carrier species on the methanol molecule and controls the reaction mechanism, favoring the generation of hydrogen. This new system appears to be a strong candidate in the contribution to the new hydrogen economy through a green and eco-efficient process using renewable energy and reagents. [ABSTRACT FROM AUTHOR]

[Display omitted] • M−TiO 2 catalysts (M = Zr, Zn and Nb) were prepared by the sol–gel method. • M−TiO 2 showed reduced crystallites size and band gap energies compared to TiO 2. • All the samples, show better photocatalytic activity under UV irradiation. • 0.5 %Zr-TiO 2 catalyst had the best activity in the 2-propanol photodegradation. For improving the photocatalytic activity of titania under UV or sunlight (SL) irradiations in the gaseous phase degradation of 2-propanol, M−TiO 2 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 TiO 2 anatase phase with high surface area and porosity. The type of transition metal affects the physicochemical properties and photocatalytic activity of M−TiO 2 catalysts which were found more active and more selective to CO 2 using UV illumination. Only the Nb-TiO 2 solid was less active than TiO 2. However, 0.5 % Zr-TiO 2 sample was the most efficient catalyst for the photodegradation of 2-propanol with 58 % as 2-propanol maximum conversion to CO 2 (54.4 %) and acetone (45.6 %) under UV. This is attributed to its high surface area and porosity, reduced particle size and low band gap energy. [ABSTRACT FROM AUTHOR]

The biocidal capability of Ag/g-C 3 N 4 composite photocatalysts against Escherichia coli was evaluated as a function of the Ag content of the material upon UV and visible light excitation. The Ag/g-C 3 N 4 composite system shows significant biocidal activity, presenting a behavior with a strong dependence on the silver content as well as on the excitation wavelength. The physico-chemical characterization of the samples together with a Langmuir–Hinshelwood-type kinetic modelling of biocidal experiments and the (photoluminescence and electron paramagnetic resonance) analysis of charge handling properties of the solids were used to interpret the photocatalytic response of the composite materials. The overall analysis shows that the wavelength dependence observed for all Ag/g-C 3 N 4 composite photocatalysts is strongly correlated with the semiconductor—metal heterojunction effect on charge separation, handling and recombination, indicating the key role of the cooperative action between the two components of the system. Such cooperative effect is studied along the sample series and discussed to be related to the efficient use of both hole and electron related species in the disinfection action. [ABSTRACT FROM AUTHOR]

The influence of different TiO 2 supports on the Cu active species has been studied. It was found that the photocatalytic H 2 evolution is highly affected by the structural and electronic features of surface Cu species. Thus, metal dispersion and oxidation state appears strongly conditioned by the structural and surface properties of the TiO 2 support. We have examined three TiO 2 supports prepared by different synthetic methods; sol–gel, hydrothermal and microemulsion. In addition, we have induced structural and surface modifications by sulfate pretreatment over freshly prepared TiO 2 precursors and subsequent calcination. Notably different copper dispersion and oxidation state is obtained by using these different TiO 2 supports. From the wide structural and surface analysis of the catalysts we are able to propose that the occurrence of highly disperse Cu 2+ species, the sample surface area as well as the crystallinity of the TiO 2 support are directly related to the photocatalytic activity for H 2 production reaction. [ABSTRACT FROM AUTHOR]

The promotion of a TiO 2 photocatalyst by surface species consisting of cerium oxide and metal-promoted carbon nitride (g-C 3 N 4 ) was analyzed to gain insight into the effect of Ca or Fe cationic species of the carbon nitride component in the overall performance of the photocatalytic system. The resulting materials were characterized with X-ray diffraction, time-resolved microwave conductivity (TRMC) and photoelectron, infrared, UV–visible and photoluminescence spectroscopies. The photoactivity of the materials in the gas phase elimination of toluene was evaluated under UV and sunlight-type illumination conditions and the corresponding true reaction quantum efficiency values calculated. The photoluminescence and TRMC analyses provide unequivocal evidence that the presence of Fe and Ca alter charge recombination to a different degree, leading to qualitatively different, promoting photochemical effects. This occurs exclusively in co-presence of ceria species at the titania surface and is thus characteristic of the ternary composite heterostructures. [ABSTRACT FROM AUTHOR]

The ethanol steam reforming (ESR) 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 reaction were investigated by diffuse reflectance infrared Fourier transform spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO 2 lattice, with the remaining Ni forming highly dispersed nano-NiO (<2 nm) outside the Ni–W–Ce oxide structure. The nano-NiO was reduced to Ni under ESR conditions. The Ni–W–Ce system exhibited a much larger lattice strain than those seen for Ni–Ce and W–Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity, and stability (i.e., resistance to coke formation) during ethanol steam reforming. [ABSTRACT FROM AUTHOR]

• Hydrogen photoproduction on multicomponent Pt-TiO2-based catalysts. • Optimization using Zr-doping of anatase and surface decoration by SnSx. • Charge carrier fate analyzed using a multitechnique approach. • Oxygen- and carbon-centered radicals play unexpected roles to control activity. Optimization of Pt-promoted TiO 2 -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 system can boost activity up to 7.3 times within the whole methanol:water mixture ratio, yielding quantum efficiencies in the ca. 13–16 % range. The key role of the different components in generating charge carrier species and their use to trigger the sacrificial molecule evolution and control reaction kinetics are examined through an in-situ spectroscopic study. The study unveils the complex reaction mechanism, with generation of C1 to C3 molecules from different carbon-containing radicals, and interprets the physical origin of the huge H 2 production enhancement occurring in doped-composite titania-based catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] Bi2O3–TiO2 materials were prepared by a single-pot microemulsion procedure. [•] The Bi component is present as an oxidic phase in strong interaction with anatase. [•] Optimum performance achieved with a 5wt.% loading of Bi. [•] UV and visible light performance superior to titania (including P25) references. [•] Improved performance in terms of activity and selectivity to complete mineralization. [Copyright &y& Elsevier]

Highlights: [•] Kinetic analysis of CeO2-TiO2 materials in toluene and E. coli photo-elimination. [•] Modelling of chemical and biological degradation processes under UV and Visible light illumination. [•] The Ce-Ti systems outperforms titania (including P25) and ceria single oxide references. [•] The Ce-Ti system shows potential for general application in the elimination of pollutants. [Copyright &y& Elsevier]

[Display omitted] • Zr-TiO 2 was successfully synthesized by the one-step controlled sol–gel route. • Zr doping enhanced the photocatalytic activity of TiO 2 by reducing its band gap. • Zr-TiO 2 show small sized particles, high surface area and good photocatalytic activity. • 0.5% Zr-TiO 2 catalyst exhibits the best photocatalytic degradation of 2-propanol. The photocatalytic activity in the 2-propanol degradation, under UV and sunlight (SL)-type irradiations, of a series of Zr-TiO 2 materials, 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 porosity measurements, IR, UV–vis, Photoluminescence and X-ray photoelectron spectroscopy. The XRD data showed that the TiO 2 was stabilized as anatase phase in all the samples and that the incorporation of Zr4+ into TiO 2 lattice has led to a decrease of the crystallite size. The BET analysis confirmed that the addition of zirconium onto TiO 2 support affected the surface area which increases with the increase of Zr4+ content. The UV-DRS spectra showed that, the incorporation of zirconium into TiO 2 lattice leads to a slight decrease of the band gap energy of TiO 2. The results of the photocatalytic test showed an enhancement on the photocatalytic activity of TiO 2, in the 2 propanol degradation, by the doping with a low amount of zirconium. All the samples were found more active under UV illumination than under SL. In all cases, the highest efficiency in the 2-propanol photodegradation was observed for the 0.5% Zr-TiO 2 sample and was essentially related to its lowest optical band gap energy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stable and highly active hydrogen thermo-photo production with Pt/CeO 2 -TiO 2. • Activity interpretation using excess functions and energy efficiency. • In-situ XAS proves Pt and Ce properties under reaction conditions. • In-situ infrared unveils the reaction mechanism under dual energy excitation. 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 thermo-photo activity as well as a detailed characterization of the catalytic solids with emphasis in the use of in-situ X-ray absorption and infrared spectroscopies. The adequate combination of components in the platinum ceria-titania ternary system renders highly active and stable catalysts, maximizing hydrogen production (rate of ca. 45 mmol g-1h−1) for a solid having a 1/2.5 wt% of platinum/ceria supported on titania. The characterization shows that this occurs through a synergetic effect among components of the solids and takes place with a critical role of defects located at the ceria-titania interface and the noble metal component. The cooperative action between components promotes the evolution of specific carbon-containing intermediates (related to the step-wise hole-triggered oxidation of the methanol molecule, decarbonylation of intermediates and the water gas shift) and the concomitant production of hydrogen. [ABSTRACT FROM AUTHOR]

• Composite (NH4)4[NiMo6O24H6].5H2O Anderson – g-C3N4 catalyst. • Outstanding UV, visible and Sunlight activity measured through the quantum efficiency. • Selective transformation of C O and C C bonds. • Charge carrier fate analyzed with Photoluminescence and EPR. • Activity and Selectivity connected with interface sites with redox capability. Novel composite photo-catalysts having (NH 4) 4 [NiMo 6 O 24 H 6 ]·5H 2 O Polyoxometalate (POM) species deposited over g-C 3 N 4 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 reaction conditions to maximize the interaction with the support. Such a behavior renders, as measured by the quantum efficiency, highly active photo-catalysts in the photo-oxidation of 2-propanol and styrene both under UV and sunlight illumination, setting up the basis for a green catalytic process. The material having a 4 wt. % POM showed improved activity with respect to both parent constituents but also higher selectivity to the partial oxidation of the alcohol and the aromatic hydrocarbon to generate added value chemical compounds. A multitechnique approach investigating charge carrier fate demonstrates the key role played by the interaction between components to promote activity and selectivity in selective oxidation reactions. [ABSTRACT FROM AUTHOR]

• Ternary Pt-SnS 2 -TiO 2 hydrogen photo-production tested under UV and Visible light. • Analysis of activity by means of the true quantum efficiency. • Control of component interfaces optimizes activity under all illumination conditions. • Sulfide presence promotes activity by both charge carrier and chemical effects. The production of hydrogen from the photoreforming of sacrificial alcohols was essayed using an anatase-based ternary system having Pt nanoparticles and SnS 2 nanoplatelets at the surface of the oxide support. Contact between phases was optimized to achieve optimum functional properties under UV and visible illumination, providing the basis for an excellent profit of solar light as measured by the evaluation of the quantum efficiency of the process. The study of the charge carrier fate using photoluminescence and the reactants under reaction conditions using infrared spectroscopy demonstrated that the outstanding photoactivity is connected with the occurrence of multiple cooperative effects between the components of the ternary system, taking place under all (UV and visible) illumination conditions and: i) facilitating charge carrier separation as well as ii) driving the evolution of the carbon-containing intermediates and concomitant hydrogen production. [ABSTRACT FROM AUTHOR]

• Pt/Zr:TiO 2 tested under UV and Visible light hydrogen photo-production. • A 2.5 mol. % of Zr optimizes activity under all illumination conditions tested. • Zr does not affect the mechanism of the reaction. • Zr alters charge carrier recombination and hole-related generation of OH radicals. • Zr doping renders the up-to-date maximum quantum efficiency value. The production of hydrogen from the photoreforming of methanol was essayed using an anatase-based system, having Pt nanoparticles and a Zr-doped anatase high surface area support. The production of hydrogen was quantitatively analyzed using the quantum efficiency parameter under UV and visible illumination conditions. The study showed that a 2.5 mol. % of Zr renders an outstanding material (4.6% quantum efficiency) for the fruitful use of sunlight as a green source of energy of the process. The outstanding promotion of activity orginated by Zr doping of the anatase structure was studied using in-situ infrared, photoluminescence and electron paramagnetic resonance spectroscopies. The multitechnique spectroscopic investigation of the reaction mechanism demonstrates that this occurs through a complex reforming plus water gas shift path. The study also unveils that optoelectronic properties of the solids derived from Zr incorporation drive activity of the system by controlling light absorption and, mainly, charge carrier recombination and interaction with the reactant molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modification of g-C 3 N 4 by surface deposition of Mn+ species. • Analysis of photoactivity by means of the quantum efficiency parameter. • Optimum activity for Zn oxynitride sharing N atoms with the support. • Interpretation of activity through analysis of charge carrier fate and radical formation. In this work we analyze the photocatalytic performance of Mn+ (M Cu, Ni, Zn, Mn) - g-C 3 N 4 materials in toluene photo-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 local order. The photo-activity of the samples under UV and sunlight excitation(s) was evaluated in terms of activity and selectivity, and the subsequent calculation of the quantum efficiency. Optimum activity was obtained with the Zn-containing catalyst. The charge carrier(s) handling and fate through interfaces and recombination was measured and correlated with the structural characterization of the solids. This indicates that the interface contact between the Zn oxynitride and carbon nitride components has significant influence in charge carrier processes and it is at the core of the good photocatalytic properties owned by this sample. [ABSTRACT FROM AUTHOR]

• g-C 3 N 4 /TiO 2 composite materials tested in toluene photo-oxidation. • Activity optimum interpreted through an intrinsic kinetic study. • Reaction rate quantitatively linked with surface rate of OH production. • Progression and selectivity of the photo-oxidation linked with toluene – OH interaction. The interaction between carbon nitride and titania in g-C 3 N 4 /TiO 2 materials is analyzed from a new perspective. The composite materials are prepared using a well crystallized anatase substrate over which carbon nitride (0.5–4 wt%, promoted or not with Mn) is deposited. The catalysts are characterized using a multitechnique approach. In addition, a kinetic formalism using a rigorous intrinsic expression of light was developed in order to reveal information concerning the chemical and charge carrier effects occurring in the materials. Together with the measurement of the adsorption of the main organic molecules involved in the reaction showed that toluene photo-oxidation follows a hydroxyl-mediated mechanism. Moreover, the work shows that the rate of available hydroxyl radicals at the surface of the solids controls activity in the g-C 3 N 4 /TiO 2 catalysts. The contact between components also affects the hydroxyl radical interaction with the reactant and intermediate molecules of the photo-oxidation, modulating the selectivity. [ABSTRACT FROM AUTHOR]

• Thermo-photo production of hydrogen by Ru/TiO 2. • Analysis of activity by means of the excess rate and quantum efficiency. • Co-catalyst core-shell morphology structure. • In-situ infrared unveils the reaction mechanism and the role of the Ru-Anatase interface. 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, high surface area anatase was present in all catalysts. It supports a ruthenium co-catalyst displaying a core-shell structure having an hcp metallic core and a RuO 2 -type shell structure. Activity, particularly under the combined use of light and heat, was analyzed by means of "excess" functions; the reaction rate and the quantum efficiency of the process were studied for thermo-photo vs. thermo/photo processes to provide conclusive evidence that the ruthenium-anatase materials display a strong synergistic use of both energy sources when utilized simultaneously. Optimum thermo-photo performance was achieved with a 5 wt. % Ru/TiO 2 catalyst. An in-situ infrared study of the behavior of the gas-solid interface under the isolate or simultaneous action of heat and light was carried out to interpret the activity and analyze reaction mechanism. The study points out the key role of the ruthenium-anatase interface in activating carbon-containing species leading to carbon monoxide species subsequently transformed through a water gas shift type reaction. Activity seems directly correlated with the promotion of this step by light and heat within the context of a mechanism where methanol is previously oxidized in titania sites and such species evolves at the mentioned interface to generate hydrogen and carbon oxide molecules. [ABSTRACT FROM AUTHOR]

The valorization of CO 2 is an important challenge within the current panorama, since this molecule is probably the main contributor to climate change. In this study, the synthesis of materials based on a nanostructured batonnet-type indium oxide is carried out. In them, different amounts of Co are introduced, varying between 2 and 8% mol. It is verified that the most active sample in the transformation of carbon dioxide to carbon monoxide contains 6 mol %. of Co. This sample's activity under dual excitation exceeds the thermal counterpart by more than 30%. After carrying out a complete physical and chemical characterization with the help of X-ray absorption spectroscopy and other techniques, it is shown that catalysts with amounts of cobalt equal to or below 4 mol % contain isolated single-atom species, while those with higher amounts of metal display a Co-Co interaction which triggers the evolution of the samples under reaction conditions. The optimum control of this Co-Co interaction and the nature of the final cobalt-containing species determine dual photothermal catalytic properties. This work establishes a structure-activity relationship to interpret the catalytic behavior of highly dispersed subnanometric cobalt species, and thus an avenue to optimize the photothermal valorization of carbon dioxide.

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 CO 2 to CO, the best samples have an indium content between ca. 2 and 5 mol % and showed an excess rate over the photo and thermo-alone processes above 33% and an energy efficiency of 1.3%. Subnanometric (monomeric and dimeric) indium species present relatively weak thermal catalytic response but strong thermo-photo promotion of the activity. A gradual change in functional properties was observed with the growth of the indium content of the solids, leading to a progressive increase of thermal activity but lower thermo-photo promotion. The study provides a well-defined structure-activity relationship rationalizing the dual thermo-photo properties of the catalysts and establishes a guide for the development of highly active and stable composite solids for the elimination and valorization of CO 2 .

The synthesis and properties of stoichiometric, reduced, and Co-doped In 2 O 3 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 calculations provide an accurate prediction of the atomic and electronic structure of these systems. The computed lattice parameter is linearly correlated with the experimental result in the Co concentration ranging from 1.0 to 5.0%. For higher Co concentrations, the theoretical-experimental analysis of the results indicates that the dopant is likely to be preferentially present at surface sites. The analysis of the electronic structure supports the experimental assignment of Co 2+ for the doped material. Experiments and theory find that the presence of Co has a limited effect on the material band gap.

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 efficiencies above 33% were obtained. The optimum sample having a 0.5 wt % of Pd provided an outstanding synergy between light and heat under reaction conditions, facilitating the boost of activity with respect to the single-source processes and achieving high selectivity to syngas. The spectroscopic analysis of the physico-chemical ground of the activity unveiled that the noble metal interaction with the Nb-doped anatase support triggers a cooperative effect, promoting the evolution of formic acid-type methanol-derived carbon-containing species and rendering a significant enhancement of syngas production. The proposed thermo-photo system is thus a firm candidate to contribute to the new green circular economy., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

This research evaluated the potential photocatalytic efficiency of synthesized Cu-Fe/TiO 2 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 (MO) concentrations). In addition, the best photocatalysts were characterized through Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), differential reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) analysis techniques. The best metal loading was 1 wt % with 5:5 Cu/Fe ratio and 300 °C calcination temperature (5Cu-5Fe/TiO 2 -300) having 97% MO decolorization. Further analysis indicates that the metal presence does not generate new channels for de-excitation but clearly affects the intensity and decreases charge recombination. The behavior of the photoluminescence intensity is (inversely) proportional to the activity behavior through the series, indicating that the main catalytic effect of Fe and Cu relates to charge recombination and that the Cu-Fe bimetallic catalyst optimizes such function. Moreover, the best-engineered photocatalysts asserted impactful bacteriostatic efficacy toward the tested Escherichia coli strain (in 30 min), and therefore, molecular docking studies were used to predict the inhibition pathway against E. coli β-lactamase enzyme. The photocatalyst had a high negative docking score (-5.9 kcal mol -1 ) due to intense interactions within the active site of the enzyme. The molecular docking study revealed that the ligand could inhibit β-lactamase from producing its bactericidal activity., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Introduction: The silver/graphitic carbon nitride (Ag/g-C 3 N 4 ) 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 (TiO 2 )-based composites. However, whether the Ag/g-C 3 N 4 composite system has biocidal properties that the parent components do or do not have as separate chemical entities and whether they differ from those in Ag/TiO 2 composite photocatalysts have not been clarified., Objective: We investigated the chemical (cooperative charge handling and electronic properties) and biological (metabolic) effects exerted by the addition of Ag to g-C 3 N 4 and to TiO 2 ., Methods: In this work, we undertook metabolome-wide analysis by liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry to compare the metabolite profiles of untreated E. coli 1337-H cells or those subjected to disinfection with Ag, g-C 3 N 4 , 2Ag/g-C 3 N 4 , TiO 2 and 2Ag/TiO 2 ., Results: While Ag or g-C 3 N 4 moderately affected microbial metabolism according to the mean of the altered metabolites, multiple cell systems contributing to rapid cell death were immediately affected by the light-triggered radical species produced when Ag and g-C 3 N 4 were as xAg/g-C 3 N 4. The effects include drastically reduced production of small metabolites essential for detoxifying reactive oxygen species and those that regulate DNA replication fidelity, cell morphology and energy status. These biological consequences were different from those caused by Ag/TiO 2 -based biocides, demonstrating the uniqueness of the Ag/g-C 3 N 4 system., Conclusions: Our results support the idea that the unique Ag/g-C 3 N 4 biocidal properties are based on synergistic action and reveal new directions for designing future photocatalysts for use in disinfection and microbial control.

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. As most active photocatalysts such as titanium oxides are essentially UV absorbers, they need to be upgraded in order to achieve the fruitful use of the whole solar spectrum, from UV to infrared wavelengths. A lot of different strategies have been pursued to reach this goal. Here, we selected representative examples of the most successful ones. We mainly highlighted doping and composite systems as those with higher potential in this quest. For each of these two approaches, we highlight the different possibilities explored in the literature. For doping of the main photocatalysts, we consider the use of metal and non-metals oriented to modify the band gap energy as well as to create specific localized electronic states. We also described selected cases of using up-conversion doping cations. For composite systems, we described the use of binary and ternary systems. In addition to a main photo-catalyst, these systems contain low band gap, up-conversion or plasmonic semiconductors, plasmonic and non-plasmonic metals and polymers.

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 physicochemical techniques and probes employed to study them. A synchrotron micro-beam X-ray absorption spectroscopy study together with the computational simulation and analysis (at the X-ray cell) of the light-matter interaction occurring in powdered TiO 2 -based monometallic Cu, Ni and bimetallic CuNi catalysts for hydrogen production from renewables was carried out. The combined information unveils an unexpected key catalytic role involving the phase contact between the reduced and oxidized non-noble metal phases in all catalysts and, additionally, reveals the source of the synergistic Cu-Ni interaction in the bimetallic material. The experimental method is applicable to operando studies of a wide variety of photocatalytic materials., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The incorporation of TiO2 nanoparticles into (ethylene-vinyl alcohol)-based food packaging copolymers affords an opportunity to synthesize polymer-based nanocomposite materials with novel and powerful biocidal and photodegradability properties, resulting in the production of an advanced, environmentally friendly system prepared using a cost-effective synthesis method via a simple melt compounding without the need of a coupling agent incorporation. The presented materials display an unprecedented performance in the killing of both Gram positive and negative bacteria without the necessity of being release to the media and an easy degradation under sunlight which favorably competes with biodegradation procedures.