Mechanisms for Enhancing the Efficiency of Composite Semiconductor/Metal Photocatalysts

Abstract

The global demand for energy and the consequences of prolonged dependence on fossil fuels are present and future issues that must be addressed. Renewable and clean hydrogen produced from sunlight and water is part of the potential solution. In this dissertation, the processes involved with driving photocatalytic and photoelectrochemical water splitting reactions are investigated, with a particular focus on the hydrogen evolution reaction. The key parameters that govern these systems are identified through the development of simple and transparent models. Using a model system of a planar silicon absorber and platinum nanoparticle electrocatalysts, these key parameters are tuned to identify strategies for optimally incorporating these two components into an efficient composite system. The first part of this dissertation discusses the enhancement of light-harvesting and surface reaction rates through the embedding of the Pt electrocatalysts into the Si absorber. Through this method, the losses in the system due to reflection, parasitic absorption by Pt, and slow surface reaction rates are decreased simultaneously. The last part of this dissertation investigates the transformation of the Si/Pt and Si/electrolyte interfaces and its effect on the transport of charge to the Pt electrocatalysts.