TiO2-based Photocatalysts for Solar Fuel Production

Abstract

Nature has always been a source of inspiration and from a scientific perspective, it has already solved many of our dilemmas regarding sustainability. As we advance in technology and development, it is important to blend our advancements with nature to coexist sustainably. However, a fossil fuel-dependent economy is causing disastrous changes to our planet, consequently elevating global CO<SUB>2</SUB> emissions and intensifying global warming. Thus, to combat climate change, reduce our dependency on fossil fuels and ensure a stable and clean energy supply for future generations, advancing a sustainable energy economy remains one of the key challenges of the 21st century. One plausible solution to satisfy humanity’s ever increasing energy demands is efficiently harnessing solar power. Due to the diurnal cycle and the intermittency of sunlight, the quantity of sunlight reaching different latitudes on Earth’s surface varies drastically. As a result, it is obligatory to develop strategies to efficiently harness solar energy and store it into chemical bonds for subsequent use as a transportation fuel and to generate electricity. The process of converting solar energy into chemical fuels by artificial photosynthesis is a key step and a sustainable solution to reduce our reliance on fossil fuels.

This Thesis aims to boost the efficiency of TiO<SUB>2</SUB>-based photocatalysts by optimizing their light absorption properties, charge transfer dynamics and crystallization processes. The results show that the photodeposition sequence of Ag and Au metal co-catalysts has a significant effect on solar light absorption, morphology, particle size distribution and photocatalytic efficiency of bimetallic Ag–Au/TiO<SUB>2</SUB> photocatalysts, with the Au-core–Ag-shell/TiO<SUB>2</SUB> being the most efficient. The results demonstrate that TiO<SUB>2</SUB> thin film crystallization can be precisely controlled by optimizing the growth temperature for atomic layer deposition (ALD) and post-deposition treatment temperature, impacting photocatalytic activity, by influencing precursor trace amounts. The best photocatalytic activity is achieved with 30 nm thick TiO<SUB>2</SUB> films grown at 200 °C, where precursor traces are minimized, enhancing the overall efficiency. This Thesis offers new insights into TiO<SUB>2</SUB>-based photocatalyst synthesis and modification thereby significantly enhancing their applications.