Photoactive Silicon gas diffusion electrodes for solar assisted electrochemical conversion of CO2 – SIROCCO

The main goal of SIROCCO is to design high efficiency photocathodes for the photoelectrochemical reduction of CO2 (PEC-CO2RR) by advantageously combining gas diffusion photoactive supports based on silicon micropillars to bimetallic nanocatalysts (specifically, PdCu and AgCu). The aim is to improve the performances at the level of the photocurrent by overcoming CO2 mass transport limitations, and at the level of selectivity and lifetime by selecting specific bimetallic compositions and structures. As far as we know, designing and implementing gas diffusion photoelectrodes in an integrated photoelectrochemical system has never been studied and hence represents an innovative approach.
The project fits well within the challenge: "Une énergie durable, propre, sûre et efficace" in “Sciences de l’Énergie et des Matériaux” (Axis 2.2 in the AAPG), in particular regarding the production of hydrocarbons and precursors from CO2 and the capture and utilization of renewable energy. Specific challenges are: 1) to design and implement for the first time GD Si photocathodes; 2) to increase the photocurrents densities by a factor of 4 (from diffusion limitation, ~ 10 mA/cm2, up to Si solar cell performances, ~ 40 mA/cm2), 3) to guide the selectivity towards alcohols and hydrocarbons (CH3OH, CH4, C2H4) by adjusting the catalytic properties of PdCu and AgCu via their composition and structure, 4) to rationalize the collection of photocarriers at the level of bimetallic nanoparticles by determining the modulation of the bands at the Si/Bimetallic and Si/Electrolyte parallel junctions, 5) to explore the viability of coupling PEC-CO2RR with urea oxidation to further reduce the cell potential.
The originality of SIROCCO lies mainly in (i) the presentation of a completely new concept, the GD Si photoelectrode (of general interest for the PEC community) (ii) the use of Si pn+ micropillar arrays combined with PdCu and AgCu bimetallics to guide the selectivity (iii) the implementation of an unusual combination of modelling tools : electrochemical and electrical simulations in parallel, to report and optimize the CO2 diffusion regimes in the micropillar network (COMSOL) and the collection of photo-carriers (SILVACO). This original, multidisciplinary approach should provide a deep physical understanding of this type of systems, non-existing in applied PEC today. The results could certainly be extended to other reactions of interest, such as PEC assisted hydrogen evolution or pollutant remediation.
The project is divided in three tasks: T1/ Elaboration of Si 3D structures, T2/ PEC characterization of photocathodes and photoelectrolysis tests and T3/ Electrochemical and electrical simulations. For some parts we will benefit from the expertise of two external partners: the ESYCOM laboratory (T. Bourouina, F. Marty and A. Rezgui, Univ. Gustave Eiffel, Service for microelectronics and microsystems of ESIEE) for the elaboration of micro-structured Si supports and COMSOL simulations, and the GeePs laboratory for the electric simulations by 2D-band bending modelling (Sylvain Le Gall, Univ. Paris-Sud).
The original aspects mentioned above distinguish SIROCCO from most national and international research in the field of integrated PEC-CO2RR. From a personal point of view, the project will strengthen my research profile providing me with skills in research management, personnel coordination and knowledge dissemination. It will allow me as well to develop new skills in the field of multiscale modeling by COMSOL, a new expertise for my institution that will certainly impact my ability to establish new collaborations with researchers at ICMPE and outside. Finally, SIROCCO will deepen a fruitful collaboration with ESYCOM and GeePs and increase the development and the visibility of our line of research at the national and international level.