Serious concerns about the climate change make particularly attractive the reutilization of CO 2 , being one option the electroreduction of CO in acetonitrile solutions on a range of electrode materials. Among them, transition metal oxides stand out as cost effective alternatives. In this context, the electrocatalytic activity of nanostructured WO 3 electrodes for carbon dioxide reduction in both humid and dry acetonitrile media has been addressed by using electrochemical and spectroelectrochemical measurements. Importantly the cathodic faradaic process starts at potentials as high as-0.16 V vs SHE. Gas chromatography measurements show CO as being the main product in both dry and humid acetonitrile, together with formate in the presence of humidity. Interestingly, purging with CO 2 not only causes the appearance of cathodic faradaic currents, but also an increase in capacitive currents, which are directly associated with an enhanced electrochromic effect. The ICP-MS determination of tungsten upon electrolysis confirms a minor electrodissolution of WO 3 electrode. On the basis of these observations, a mechanism is proposed in which WO 3 is not only the electrode material, but also a mediator in the CO 2 reduction process
Graphical and textual abstract for the Table of contents entrySol-gel prepared copper chromium delafossite electrodes behave as stable and efficient photocathodes for water reduction without the need of co-catalysts.
Please cite this article as: Ana Korina Díaz-García, María Isabel Díez-García, Teresa Lana-Villarreal, Roberto Gómez, A comparative photophysical and photoelectrochemical study of undoped and 2-aminothiophene-3-carbonitrile-doped carbon nitride, Electrochimica Acta http://dx. Graphical abstract Research highlights The effect of molecular doping on carbon nitride is revealed by means of photoelectrochemical and luminescence spectroelectrochemical measurements. The effect of pH on the photoelectrochemical response of pristine and doped carbon nitride is presented.2 The intensity of the emission band appearing as a result of molecular doping depends in a reversible way on the applied potential. Doped carbon nitride exhibits stronger light absorption and enhanced photocurrents for hydrogen generation. AbstractIntroducing 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 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.
Please cite this article as: Ana Korina Díaz-García, Roberto Gómez, Improvement of sol-gel prepared tungsten trioxide photoanodes upon doping with ytterbium, Journal of Photochemistry and Photobiology A: Chemistry https://doi. HIGHLIGHTS A sol-gel method for the preparation of Yb-doped WO3 photoanodes is presented. Ytterbium modification induces an increase in the photoresponse of WO3 electrodes. Yb changes WO3 morphology and surface charge without increasing carrier density. AbstractThe development of efficient and stable photoelectrodes keeps on being critical in the development 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 on 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.
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