The PI seeks to test the hypothesis: A nature-inspired ?tree-like? architecture consisting of 1D oxide nanotubes-1D chalcogenide nanowires will facilitate 1) broad spectrum light absorption, 2) a significant improvement in photogenerated charge separation, transport, and utilization, and 3) enhanced photocatalytic processes. The key objectives of this 2-year activity is to i) test this hypothesis using a TiO2 nanotube?CdS/PbS nanowire as a representative photocatalyst and ii) use the content in a) 2 courses, b) a book, and c) educating a minority student. An experimental approach to hypothesis validation will be implemented. The methods will involve synthesis, characterization, and testing the applicability of the photocatalysts in solar-related energy conversion processes.
To test the hypothesis, a suite of complementary tools that provide further insights into optical, electronic, photoelectrochemical, and photocatalytic properties of the nanocomposites, will be employed. Preparing and testing various TiO2/CdS nanocomposites by combining 0D oxide and 1D oxide separately with 0D chalcogenide forming 0D/0D oxide-chalcogenide and 1D/0D oxide-chalcogenide composites will ensure a systematic baseline comparison and rigorous hypothesis testing. The examination of the structure- property relationships will involve evaluation of a) the role of the physical dimensions of the nanowire/nanotube towards facilitating broad spectrum absorption, b) charge separation and transport using standard and specialized (photo)electrochemical techniques, and c) improvement in the performance efficiencies of 1D oxide-1D chalcogenide nanocomposites compared to the performances of 0D equivalents. Further, experiments that provide insights into the applicability of these nanocomposites in a lesser-known sustainable approach - solar-driven waste-to-fuel production (H2 generation) - will be conducted. The aforementioned strategy to seek a fundamental understanding of the 1D nanocomposite properties, will address the principal challenges currently faced in photocatalysis: maximize visible light absorption by the photocatalyst and employ it for efficient and sustainable solar energy utilization.
This project will facilitate a transformative impact on basic as well as applied science aspects of solar-driven energy generation. From a basic science standpoint, it will help answer questions on whether grain boundary reduction can help realize the formation of superhighways for charges to travel and significantly reduce recombination rates to promote redox reactions. From an applied science standpoint, improved charge separation can directly and immediately benefit a multitude of solar-related applications including: i) solar cells, ii) photocatalysis for fuel production, and iii) environmental remediation. Allied technologies such as energy conversion (fuel cells) and energy storage (batteries and capacitors) will benefit from i) being able to template the synthesis strategies developed herein and ii) draw from the insights on the role of physical dimensions on charge mobility and customize experimental protocols based on these insights for further application-specific improvements. The research efforts will be incorporate into the educational and outreach efforts.
