MODIFICATION OF NANOMATERIALS WITH INTENSE PULSED ION BEAMS FOR PHOTOCATALYTIC APPLICATIONS

Abstract

The world energy problem has been facing harsh challenges in the last few decades due to the increase in energy consumption of the growing world population and decreasing reserves of traditional carbon-based energy resources. Photoelectrochemistry (PEC) based solar water splitting is one of the potential paths for transforming renewable solar energy into green hydrogen fuel to meet energy expectations. In PEC water splitting, hydrogen is generated using semiconductor materials that can absorb sunlight and decompose water molecules into hydrogen and oxygen gases. Fabrication of highly effective, stable, and economically viable semiconductor photoelectrode materials, to increase their performance, and enhancing their photocatalytic activity has been proved to be a vital task for PEC solar water decomposition. Among all the suitable materials, WO3 has been reputed as a promising photoelectrode in the last decade due to the many criteria that it fits. The main current problems in WO3, based PEC water splitting systems are their low solar to hydrogen efficiencies and poor photocatalytic properties. Developing and applying new methods of surface modifications and engineering are favorable strategies to enhance photocatalytic properties of WO3. This thesis work is devoted to the study of surface modification of WO3 photoelectrodes with intense pulsed ion beam (IPIB) irradiation for photocatalytic properties enhancement and studying the effect of IPIB irradiation on solid state dewetting shape formation of plasmonic Ag nanoparticles (NPs). The thesis also reports strategies of combining plasmonic nanoparticles and downshifting photoluminescent NPs with WO3. IPIB irradiation is a method for modification of surfaces of materials with few hundreds keV energetic ions that penetrate deep into 1-2 micrometers. The outcomes of experiments show that surface engineering of WO3 photoelectrode with IPIB can enhance its photocatalytic properties and promote charge-carrier characteristics. The IPIB also gives opportunity to study shape formations of silver NPs and results exhibit huge influence of super-fast annealing on sphericity of the silver NPs. Simultaneous use of plasmonic NPs and fluorescent materials also proven to be effective method of photoactivity enhancement of WO3 thin films.