Photo-electrochemical cells for green H₂ production: a contribution to scaling up studies

This PhD project focuses on the comparative study of two types of solar fuel generators: a PEC cell based on a bismuth vanadate (BiVO₄) photoanode, and an integrated photoelectrochemical (IPEC) cell combining a solar cell with an electrolyser. Both devices achieve the artificial photosynthesis process of capturing solar energy and storing it in chemical bonds. The goal of the work is to identify the limiting parameters that hinder the large-scale deployment of these photoelectrochemical devices and to propose solutions in order to facilitate research in this field. Two specific scientific questions are at the heart of this research: 1. What is the impact of heterogeneities, inherent to large-scale preparation processes, on the performance of photoactive materials? 2. What role can integration play in transferring performance from the laboratory to the pilot scale? To answer the first question, an experimental parametric study was undertaken on BiVO₄ photoanodes, considered as photoactive semiconductors representative for artificial photosynthesis. In parallel, in order to answer to the second question, an IPEC cell, the combination of a PK/Si tandem solar cell with a proton exchange membrane electrolyser, was realized, tested and optimized. In a second phase, this approach was followed by the design of a monolithic module, integrating 9 IPEC cells. The realization of 5 of these modules enabled the assembly of the EASI Fuel device (European Autonomous Solar Integrated fuel station) for the continuous conversion of H₂ (produced under sunlight by the IPEC cells) and CO₂ into CH₄ within a methanogenesis Archaea-based bioreactor. Thanks to this innovative coupling, the EASI Fuel device was selected and successfully tested for 72 hours of continuous operation in total autonomy, during the final of the Horizon Prize - Fuel from the Sun: Artificial Photosynthesis competition, which took place at the end of the second year of the thesis. (author)