Thesis presented December 13, 2021

Abstract:
In addition to the mature renewable electricity production, solar fuels production possibly combined with fuel cells devices promises a sustainable and environmentally friendly solution to answer both the global ever-increasing energy demand and the damages to the biosphere brought by the abuse of fossil fuels. Countless efforts have been made in improving the individual materials and components required to drive the overall water splitting for solar H₂ fuel production. However, the ultimate goal of this research field is the fabrication of operational devices and prototypes. Through the collaboration between the two laboratories in France and Vietnam, we successfully construct two types of unassisted solar fuels generators. The first device is a monolithic integrated PV-electrolyzer in artificial leaf configuration, which was made famous by Dr. Nocera (Harvard University), that is capable of producing hydrogen fuel through direct solar water splitting. The leaf features a pair of water electrolysis catalysts deposited on a commercial triple junction silicon solar cell through a novel self-assembly approach from a single deposition solution. The second device is a tandem hybrid photoelectrochemical cell based on a dye-sensitized photocathode and a BiVO₄^--based photoanode that can produce syngas without any external bias. Performance study of the devices was done employing an operando setup comprises of multiple potentiostats coupled with gas chromatography. It was shown that the artificial leaf exhibits comparable performance to the similar but more complex to fabricate one featured by Dr. Nocera. However, the degradation of the light harvesting unit in the electrolyte is a big problem and suitable protection is required to increase the overall stability of the device. For the tandem device, the photocathode is currently the limiting component due to desorption of the dye from the corresponding electrode. Nevertheless, the successful fabrication of the devices and the implementation of an experimental setup to monitor their important parameters during operation is a prominent milestone for future improvements.

Keywords:
Water electrolysis, Artificial leaf, Catalysis, Hydrogen

On-line thesis.