Bimetallic Pt-Pd co-catalyst Nb-doped TiO2 materials for H2 photo-production under UV and Visible light illumination

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–vis spectroscopies, together with microscopy and porosimetry tools. Such characterization was able to show the formation of PtPd alloy particles in the bimetallic catalysts. The mono and bimetallic TiO2-based powders were tested in the photo-production of hydrogen from methanol:water mixtures under UV and visible illumination conditions. Analysis of catalytic properties was carried out through the measurement of the optical properties of the materials and the calculation of the true quantum efficiency parameter. Results indicate that the PtPd co-catalysts have superior performance that the Pt and Pd monometallic counterparts both under UV and visible illumination conditions. Optimum performance was achieved with a material having a Pt:Pd 1:1 atomic ratio. A remarkable increase in the use of the visible range and thus in sunlight utilization is achieved with the 1:1 Pt:Pd bimetallic system with respect to the monometallic counterparts. The evolution of the bimetallic co-catalysts under reaction conditions as well as their key properties to interpret photo-activity were analyzed with the help of the above mentioned techniques as well as photoluminescence spectroscopy and an in-situ infrared analysis of the materials under reaction conditions. Results point out the critical role that both PtPd alloying and the metal-support interface play in the reaction

Recent progress in the quantitative assessment and interpretation of photoactivity

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 measurement, meaning, and analysis of three types of observables. The first family of observables has the reaction rate and closely connected observables as the turnover frequency as central pieces. The second family owns the so-called efficiency observables, starting from the photonic yield and quantum efficiency of the reaction and ending in the global efficiency of the process. Finally, the review studies kinetic constant observables. The contribution focusses on most rencet contribution analyzing these observables in terms of their (adequate) measurement conditions and physico-chemical interpretation, in order to unveil their full potential in the context of the photo-catalysis field.MCIN/AEI PID2019-105490RB-C31ERDF A way of making EuropeEuropean CommissionConsejo Nacional de Ciencia y Tecnologia (CONACyT) SENER-CONACyT 117373UGR PPJIA2019-0

Role of alkali-cyano group interaction in g-C3N4 based catalysts for hydrogen photo-production

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 illumination source characteristics. The measurement of the quantum efficiency was used to quantitatively assess the performance of the catalysts. Outstanding results were obtained, particularly under sunlight illumination. A complete characterization study of the materials was carried out to establish a structure-activity link. This link correlates catalytic activity with the capture of charge carrier species by surface cyano groups directly associated with the presence of alkali ions at the carbon nitride componen

Facile synthesis of B/g-C3N4 composite materials for the continuous-flow selective photo-production of acetone

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 highlighting that the sample preparation was carried out by an environmentally friendly strategy, without a solvent or additional reagents. Samples containing boron in 1–10 wt% were subjected to physico-chemical characterization using XRD, porosimetry, UVvisible spectroscopy, TEM, energy-dispersive X-ray spectroscopy and XPS. The reaction output was analyzed on the basis of the reaction rate, selectivity and quantum efficiency of the process. A correlation analysis between catalytic properties with two observables, the boron phase distribution in the materials and charge handling efficiency (measured using photoluminescence), rationalizes photoactivity. Such an analysis indicates that the presence of an amorphous boron metallic phase and its contact with the carbon nitride component are key to setting up a renewable and easily scalable chemical process to obtain acetone.MINECO (Spain) ENE2016-77798-C4-1-RConsejo Superior de Investigaciones Cientificas (CSIC)Secretaria de Ciencia Tecnologia e Innovacion of CDMX (SECTEI, Mexico)MINECO CTQ2016-78289-PEuropean Union (EU)RUDN University Program 5-10

Boosting Pt/TiO2 hydrogen photoproduction through Zr doping of the anatase structure: a spectroscopic and mechanistic study

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

Foto-termo catalizador para reformado de metanol

Foto termo catalizadores para reformado de metanol. La presente invención se refiere a un foto-termo catalizador para la reacción de reformado de metanol para la obtención de H2, con fórmula general Yy/Ti{sub.1-x}CexO2 donde y tiene un valor de entre un 0,1% y un 2% en peso respecto de la cantidad final de Ti1-xCexO2. La presente invención se enmarca entonces en el campo de las operaciones industriales del reformado de metanol y en el campo de la química catalítica y de la obtención del H2 y su separación y en la reducción de gases de efecto invernadero.Peer reviewedConsejo Superior de Investigaciones Científicas (CSIC)A1 Solicitud de patente con informe sobre el estado de la técnic

Toward the green production of H2: binary Pt-Ru promoted Nb-TiO2 based photocatalysts

Hydrogen photoproduction 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 main experimental variables (methanol:water molar ratio, catalyst concentration, and light intensity) was studied through a Box-Benhken factorial design and the calculation of the true quantum efficiency. The optimum activity is achieved using a bimetallic PtRu (2:1) composition, which provides outstanding efficiency under ultraviolet (UV), visible, and sunlight illumination, as well as long-term stability. The interpretation of the activity was performed using characterization results, the outcome of an analysis of charge recombination with photoluminescence spectroscopy and of an in situ infrared study under reaction conditions. This proves that the photophysical and chemical properties of metallic Pt particles in contact with Ru oxidized particles are key to render highly active systems

Hydrogen photogeneration using ternary CuGaS2-TiO2-Pt nanocomposites

In this contribution we synthesized ternary CuGaS2-TiO2-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 sacrificial agent. The testing under UV and visible illumination conditions together with the calculation of the true quantum efficiency of the process demonstrate the outstanding performance of these ternary materials under sunlight operation. Optimum activity was achieved for samples having a 3 to 5 wt % of the chalcogenide and a selective interaction of the noble metal with the major oxide component. The physico-chemical characterization and particularly the use of photoluminescence spectroscopy showed that photo-activity is controlled by charge separation under illumination, which drives to charge location of electrons and holes in different components of the powders and the efficient use of charge carriers in the chemical reaction

Hydrogen photogeneration using ternary CuGaS2-TiO2-Pt nanocomposites

In this contribution we synthesized ternary CuGaS-TiO-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 sacrificial agent. The testing under UV and visible illumination conditions together with the calculation of the true quantum efficiency of the process demonstrate the outstanding performance of these ternary materials under sunlight operation. Optimum activity was achieved for samples having a 3 to 5 wt % of the chalcogenide and a selective interaction of the noble metal with the major oxide component. The physico-chemical characterization and particularly the use of photoluminescence spectroscopy showed that photo-activity is controlled by charge separation under illumination, which drives to charge location of electrons and holes in different components of the powders and the efficient use of charge carriers in the chemical reaction