Owing to global warming and fast depleting fossil reserves, the world is currently witnessing an energy transition into cleaner and greener energy sources like the wind and solar energy. At present, most of this clean energy is converted into electricity and used up directly or stored in the grids or batteries to be used later. Chemical storage of this energy is an attractive alternative due of its high energy density. Artificial photosynthesis is a hot field wherein researchers try to mimic the photosynthesis process of plants and try to convert solar energy into chemicals that can be stored. Photo-electrochemical (PEC) water splitting is one such pathway that is extensively investigated. However, the ideal semiconductor required to make this conversion efficient and economical is yet to be discovered. A big share of research also focuses on materials or techniques to improve the performance of these PEC devices independent of the semiconductor. Plasmonics, or plasmonic hot electron injection in particular, is such a technique that is being extensively investigated. Plasmonic hot electron injection is a relatively new phenomenon that could have potential application in many fields including photo-electrochemistry and photovoltaics. It is coveted as one of the techniques that could directly improve the performance efficiencies of solar and photo-electrochemical cells. But a fundamental understanding of this phenomenon is still lacking. This is crucial for improving and optimizing this technology before it can have any practical application. In this thesis, photo-electrochemistry is used as a tool to study the plasmonic hot electron injection and shed more light on the fundamental aspects, at the nanoscale, involved in the excitation and injection of hot electrons into the conduction band of a semiconductor. Silver, gold and 50% silver – 50% gold alloy nanoparticles are used in this work to systematically
study the effect of composition, size and concentration of these nanoparticles on the hot electron injection efficiency. Through this work, some fundamental understanding of the factors affecting the energy of the excited hot electron and hot electron injection process is obtained.