References of "Toussaint, Caroline"
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See detailComparison of structural features of spin-coated and USP-deposited templated α-Fe2O3films
Toussaint, Caroline ULg; Chatzikyriakou, Daphne; Cloots, Rudi ULg et al

Poster (2015)

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See detailCombining mesoporosity and Ti-doping in hematite films for water splitting
Toussaint, Caroline ULg; Tran, Hoang Son ULg; Colson, Pierre ULg et al

in Journal of Physical Chemistry C (2015), 119(4), 1642-1650

(Graph Presented). In this study, we report the synthesis of Ti-doped mesoporous hematite films by soft-templating for application as photoanodes in the photoelectrolysis of water (water splitting ... [more ▼]

(Graph Presented). In this study, we report the synthesis of Ti-doped mesoporous hematite films by soft-templating for application as photoanodes in the photoelectrolysis of water (water splitting). Because the activation of the dopant requires a heat treatment at high temperature (≥800°C), it usually results in the collapse of the mesostructure. We have overcome this obstacle by using a temporary SiO2 scaffold to hinder crystallite growth and thereby maintain the mesoporosity. The beneficial effect of the activated dopant has been confirmed by comparing the photocurrent of doped and undoped films treated at different temperatures. The role of the mesostructure was investigated by comparing dense, collapsed, and mesoporous films heated at different temperatures and characterized under front and back illumination. It turns out that the preservation of the mesotructure enables a better penetration of the electrolyte into the film and therefore reduces the distance that the photogenerated holes have to travel to reach the electrolyte. As a result, we found that mesoporous films with dopant activation at 850°C perform better than comparable dense and collapsed films. [less ▲]

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See detailInfluence of mesoporosity in hematite films on water splitting efficiency
Toussaint, Caroline ULg; Cloots, Rudi ULg; Henrist, Catherine ULg

Poster (2014)

Solar energy is inexhaustible but variable during the day and the seasons. Photoelectrolysis of water (water splitting) convert this energy into hydrogen to obtain an energy that can be stored and ... [more ▼]

Solar energy is inexhaustible but variable during the day and the seasons. Photoelectrolysis of water (water splitting) convert this energy into hydrogen to obtain an energy that can be stored and transported on demand. Hematite is a promising material for the photoanode in water splitting because of its high stability in water, cheapness, abundance and its band gap that enables the absorption of visible light (Eg: 2,1eV). Nevertheless, hematite has also some drawbacks including a short diffusion length of holes and a bad electronic conductivity. We have implemented spin coating and templating to produce doped mesoporous hematite films. The nanostructuration can improve the performances in water splitting by reducing the diffusion length of holes and increasing the specific surface between the film and the electrolyte. To suppress the collapse of the mesoporosity at high temperature (requested for dopant activation), we have used a temporary silica confinement scaffold that reduces the crystallite growth. To show the impact of the nanostructure, we have compared three films (mesoporous, collapsed and dense) in terms of hematite content (elemental analysis), nanostructure (electron microscopy), crystallinity (X-ray diffraction) and water splitting efficiency. We have also test two thermal treatments. This study highlights the effect of the effective interface with the electrolyte, through the preservation or not of open porosity and the different evolutions of the nanostructures as a function of the heat treatment. [less ▲]

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See detailThe effect of the mesoporosity on the crystalline growth of hematite films used as photoelectrodes in water splitting
Toussaint, Caroline ULg; Cloots, Rudi ULg; Henrist, Catherine ULg

Poster (2013)

The environmental effect of atmospheric CO2 associated with other geopolitical and economic problems linked to fossil fuels have urged the research and the development of new and clean sources of energy ... [more ▼]

The environmental effect of atmospheric CO2 associated with other geopolitical and economic problems linked to fossil fuels have urged the research and the development of new and clean sources of energy. The photoelectrolysis of water is an interesting way to produce clean fuel by converting solar energy into hydrogen. Hematite is a particularly attractive material for the photoelectrolysis of water thanks to its abundance, high stability in water and absorption in the visible part of the solar spectrum. Furthermore, the position of its valence band affords the oxidation of water into O2. Nevertheless, hematite has some drawbacks like a too low conduction band to reduce water, a bad conduction of electrons and a very short diffusion length of holes (2-10 nm). The application of a bias resolves the positioning of the conduction band, while the conduction of electrons is improved by adding a dopant (SiO2 or TiO2). The short diffusion length, for its part, is improved by reducing the distance electrode-electrolyte. For this purpose, we developed mesoporous hematite films doped by TiO2 by spin coating, based on the EIMP principle (Evaporation Inducing Micelles Packing). For the sake of comparison, a non mesoporous film was prepared. The crystallinity, the mesostructure and the performance in water splitting of the films were then characterized. Due to the high temperature of crystallization of the hematite, we had to proceed to the fine tuning of the thermal treatment to obtain a crystallized film and to preserve its mesoporosity, which was confirmed by TEM. Based on XRD analysis, it comes out that the mesoporosity leads to smaller grains than without mesoporosity. The water splitting performances were evaluated by measuring the photocurrent density under illumination (AM 1.5G, 100mW/cm²) and the mesoporous film showed promising efficiencies (1.9mA/cm²). [less ▲]

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