000264972 001__ 264972
000264972 005__ 20190710103658.0
000264972 0247_ $$a10.5075/epfl-thesis-9394$$2doi
000264972 037__ $$aTHESIS
000264972 041__ $$aeng
000264972 088__ $$a9394
000264972 245__ $$aLinking Morphology and Multi-Physical Transport in Structured Electrodes
000264972 260__ $$aLausanne$$bEPFL$$c2019
000264972 269__ $$a2019
000264972 300__ $$a168
000264972 336__ $$aTheses
000264972 502__ $$aProf. Jeremy Luterbacher (président) ; Prof. Sophia Haussener (directeur de thèse) ; Prof. Raffaella Buonsanti, Prof. Avner Rothschild, Prof. Roland Marschall (rapporteurs)
000264972 520__ $$aMotivated to advance the renewable energy production and diversify the technologies for storable energy carriers, my work is concentrated on the characterization and the optimization of electrode morphologies applicable in photoelectrochemical water-splitting and electrochemical carbon dioxide reduction. The geometry of the electrode-electrolyte interface affects the multi-physical transport properties in a chemical energy conversion device. The structuring of the solid-liquid interface can improve the light management and assist to overcome the limiting charge transport in a semiconductor electrode. However, it also has implications on the species concentration, the pH and the diffusive mass transport in the electrolyte. Characterizing and quantifying the link between the morphology and those multi-physical transport processes are fundamental to design electrode geometries that enhance the energy conversion efficiency. 
In order to study photoelectrodes with complex and anisotropic morphologies, accurate representations of the 3D electrode structures are required. A coupled experimental-numerical approach was developed to digitalize the morphology of two photoelectrodes, a particle-based lanthanum titanium oxynitride (LTON) and a ‘cauliflower-like’ structured hematite (α-Fe2O3) electrode, using high-resolution FIB-SEM tomography. Key morphological parameters were extracted from the digital model.
Simulations using the exact geometry of the LTON electrode investigated the correlation between the morphology and the multi-physical transport properties in a photoelectrochemical water-splitting device. Light absorption, local current densities and ion concentration distributions in the electrolyte have been computed to link material bulk properties to the incident-light-to-charge-transfer-rate-conversion by morphology-dependent parameters.
The developed numerical tools were adapted for electrochemical carbon dioxide reduction on an inverse-opal silver electrode, where concentration gradients played a more significant role. The species mass transport in the electrolyte determined the selectivity of the competing surface reactions, where mesoporous structuring of the electrode favored the carbon dioxide reduction. The calculations reproduced experimental results from the literature, supporting and quantifying the intrinsic pH-dependency of the unwanted water-splitting reaction.
Lastly, the light management in thin film metal oxide photoelectrodes for water-splitting was optimized by numerical simulations of electromagnetic wave propagation. Wedge patterns of thin film hematite with a reflective backing layer on a flexible polyimide substrate were used to enhance the light absorption by resonant and geometric light trapping. In order to fabricate the patterned thin film photoelectrodes with precise control over the microstructure, an experimental platform was developed based on a template-stripping method.
In conclusion, the methods developed in this work have been proven to characterize and quantify the effects of the morphology on multi-physical transport. Furthermore, design guidelines on the morphology and the operating conditions were derived from the numerical results in order to optimize the electrode performance. Novel electrode architectures were proposed to enhance the reaction selectivity in mesoporous electrodes for the CO2 reduction and improve the light trapping in thin film water-splitting photoelectrodes.
000264972 592__ $$b2019
000264972 6531_ $$aPhotoelectrochemical water-splitting
000264972 6531_ $$aElectrochemical CO2 reduction
000264972 6531_ $$aMorphology
000264972 6531_ $$aFIB-SEM tomography
000264972 6531_ $$aPore-level simulation
000264972 6531_ $$aElectromagnetic wave propagation
000264972 6531_ $$aMass transport
000264972 6531_ $$aDesign guidelines
000264972 6531_ $$aTemplate-stripping
000264972 6531_ $$aLight trapping
000264972 700__ $$aSuter, Silvan$$g234754
000264972 720_2 $$aHaussener, Sophia$$edir.$$g207354
000264972 8564_ $$uhttps://infoscience.epfl.ch/record/264972/files/EPFL_TH9394.pdf$$s8189295
000264972 909C0 $$pLRESE
000264972 909CO $$pSTI$$pDOI$$ooai:infoscience.epfl.ch:264972$$pthesis
000264972 918__ $$aSTI$$cIGM$$dEDEY
000264972 919__ $$aLRESE
000264972 920__ $$a2019-04-05$$b2019
000264972 970__ $$a9394/THESES
000264972 973__ $$sPUBLISHED$$aEPFL
000264972 980__ $$aTHESIS