Cellule photoélectrochimique

Résumé

Une cellule photoélectrochimique utilise la lumière et des réactions chimiques pour produire de l'électricité. La cellule à photolyse C'est un composant électronique qui, exposé à la lumière (photon), décompose l'eau en oxygène et hydrogène. On peut ensuite utiliser cet hydrogène dans des piles à combustible ou des moteurs à hydrogène. Une telle cellule photoélectrochimique est formée d'une électrode photosensible immergée dans un électrolyte ou dans de l'eau. Ce procédé de photolyse présente l'avantage sur la filière photovoltaïque de supprimer la nécessité de transport du courant électrique entre la centrale solaire photovoltaïque et les installations de production de l'hydrogène par hydrolyse (la conversion directe apportant en outre un rendement supérieur). La corrosion limite actuellement (2006), à 240 heures la durée de vie de ces composants alors que leur seuil de rentabilité serait de (soit plus de 41 fois plus). La cellule solaire nanocristalline à colo

Source officielle

https://fr.wikipedia.org/wiki/Cellule_photo%C3%A9lectrochimique

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Defects on surface and interface for photoelectrochemical properties of hematite photoanodes

Yelin Hu

Hydrogen is a highly versatile fuel that may become one of the key solutions to face our future energy challenges. Among all these methods for hydrogen production, solar water splitting offers possible advantages regarding components integration, stability and costs. The key component for photoelectrochemical (PEC) water splitting is the semiconductor photoelectrode, which requires many material requirements in a single component, such as light absorption, charge separation, charge transport, H2 or O2 evolution kinetics at surface and stability for wide pH range. One of the materials of interest as photoanode for water splitting is hematite (alpha-Fe2O3) because of its suitable bandgap, low-cost and good resistance to corrosion. Considerable effort has been devoted to improving the efficiency of hematite but a complete understanding is still necessary for further application. In this thesis, I focused on investigation of correlation between defects and photoelectrochemical properties of hematite. Several strategies were proposed to modify the defects in hematite bulk, at hematite/substrate interface or on hematite surface, and their impacts on the PEC performance of hematite were studied. In addition, an in-situ operando cell was designed for ambient pressure X-ray spectroscopy to study photoelectrochemical processes occurring at hematite/H2O interface with different bias voltages applied.

EPFL2017

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Scale-up of photo-anodes of Fe2O3 on titanium substrates for photo-electrochemical production of hydrogen

Fabien Petter

2013

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Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

Artur Braun, Yelin Hu

Hematite (alpha-Fe2O3) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. alpha-Fe2O3 thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 degrees C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of alpha-Fe2O3 nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FESEM. The average grain size was observed to increase from similar to 57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV-visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry. (C) 2015 Elsevier B.V. All rights reserved.

Elsevier Science Bv2016

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