STRATEGIES TO IMPROVE THE STABILITY OF MESOPOROUS SILICON PHOTOCATALYSTS

Abstract

Mesoporous silicon (mp-Si) nanoparticles (NPs) are of interest due to their promising application as photocatalysts for solar-driven hydrogen production via water splitting. While mp-Si NPs have shown promising photocatalytic performance, they have poor cyclability and stability. Under operation, the mp-Si NPs experience oxidation from hole induced photocorrosion and stoichiometrically reacting with water. In this thesis, several strategies to prevent silicon oxidation while maintaining a high photocatalytic performance were investigated. Since silicon does not have the valence band edge position to carry out water oxidation, a sacrificial reagent is added instead to scavenge the photogenerated holes. Several sacrificial reagents were selected based on their oxidation potential and varying polarity as part of the screening process to find the reagent that would facilitate the fastest hole removal and improve the stability. Sacrificial reagents that generate hydroxyl ions were found to generate hydrogen via base catalyzed stoichiometric reaction between silicon and water. Furthermore, increased steric bulk in alcohols was found to increase the stability of mp-Si NPs but also decrease performance. Additionally, several surface modification strategies such as ligand and polymer functionalization and forming type II heterojunctions were explored on mp-Si stability. Polyvinyl alcohol functionalized mp-Si NPs showed improved stability among all the surface ligands explored.