Improvement of sol-gel prepared tungsten trioxide photoanodes upon doping with ytterbium

The development of efficient and stable photoelectrodes keeps on being critical in the implementation of practical water splitting devices. Sol-gel synthesized tungsten trioxide thin film electrodes modified with ytterbium have been prepared on conducting glass substrates. All the obtained electrodes were found to be composed of monoclinic WO3, which is the photoactive crystal phase of WO3 for water oxidation. The photoelectrochemical behavior of both WO3 and WO3:Yb nanostructured electrodes in 0.1 M HClO4 is apparently characterized by a low degree of recombination. Ytterbium addition to tungsten trioxide improves its photoelectrochemical response as larger photocurrents are obtained without a significant change of the onset potential. This behavior is attributed primarily to a surface effect rather than to bulk doping. The addition of H2O2 to the aqueous electrolyte gives rise to both an increment in photocurrent and a shift of the photocurrent onset potential toward less positive values, which can be linked to the fact that hydrogen peroxide acts as an efficient hole scavenger. The implications of these findings in the mechanism of water photooxidation on WO3 are discussed.Financial support of the Spanish Ministry of Economy and Competitiveness through project MAT2015-71727-R (FONDOS-FEDER) is gratefully acknowledged. A. K. D.-G. thanks the Mexican government (CONACyT) for the award of a doctoral grant

Sol–gel copper chromium delafossite thin films as stable oxide photocathodes for water splitting

Significant effort is being devoted to the study of photoactive electrode materials for artificial photosynthesis devices. In this context, photocathodes promoting water reduction, based on earth-abundant elements and possessing stability under illumination, should be developed. Here, the photoelectrochemical behavior of CuCrO2 sol–gel thin film electrodes prepared on conducting glass is presented. The material, whose direct band gap is 3.15 eV, apparently presents a remarkable stability in both alkaline and acidic media. In 0.1 M HClO4 the material is significantly photoactive, with IPCE values at 350 nm and 0.36 V vs. RHE of over 6% for proton reduction and 23% for oxygen reduction. This response was obtained in the absence of charge extraction layers or co-catalysts, suggesting substantial room for optimization. The photocurrent onset potential is equal to 1.06 V vs. RHE in both alkaline and acidic media, which guarantees the combination of the material with different photoanodes such as Fe2O3 or WO3, potentially yielding bias-free water splitting devices.We are grateful to the Spanish Ministry of Education and Competitiveness for financial support through project MAT2012-37676 (co-financed with FEDER funds by the European Union). A. K. D.-G. thanks the Mexican government (CONACYT) for the award of a doctoral grant

A comparative photophysical and photoelectrochemical study of undoped and 2-aminothiophene-3-carbonitrile-doped carbon nitride

Introducing molecular dopants in carbon nitride has been shown to dramatically modify its electronic structure, resulting in efficient charge separation and improved photocatalytic efficiency. Herein, we have studied the effect of doping carbon nitride with 2-aminothiophene-3-carbonitrile. A fundamental photoelectrochemical characterization has been performed comparing the behavior of the resulting material (ATCN) with undoped carbon nitride (CN). On the one hand, it is shown that the photocurrent onset shifts with the pH up to a value of 8 for both materials, as expected theoretically. On the other, ATCN, which benefits from additional light absorption, shows an improved photoactivity toward hydrogen evolution. In addition, it displays intriguing photoluminescence properties that can be additionally engineered by modulating the potential. In a more general vein, this study illustrates how to shed light on the effects of introducing molecular dopants in the CN matrix.We are grateful to the Spanish Ministry of Education and Competitiveness for financial support through projects MAT2012-37676 and MAT2015-71727-R (co-financed with FEDER funds by the European Union). A.-K.D.G. thanks the Mexican government (CONACYT) for the award of a doctoral grant

Células tándem fotoelectroquímicas para la generación de hidrógeno y otros combustibles solares

Esta tesis tiene como objetivo el diseño de una célula tándem fotoelectroquímica estable para la generación de hidrógeno y otros combustibles solares. Para ello se investiga la factibilidad de diferentes materiales, tales como el CuCrO2 y el CN el para su aplicación como fotocátodos y WO3 para su aplicación como fotoánodo

[Catalogue 59 Antike Münzen Griechen. Römer. Barbaren]

[Vente. Numismatique. 1930-01-31. Munich]Avec mode text