Hot Electron Injection in Photocatalytic Plasmon Resonant Nanostructures
Abstract
Early reports of plasmon-enhanced photocatalysis have given rise to a discussion of the nature of this enhancement. There have been several recent theoretical studies concluding that plasmon resonant excitations decay into hot electrons in metal nanostructures. In photocaralysis, hot electrons present the exciting possibility of driving high barrier reactions at lower onset potentials with improved selectivity. Experimentally, however, it is difficult to distinguish between the effects of hot electron injection (HEI) and local field enhancement (LFE). In the case of hot electron injection, the photon is absorbed in the metal, and the excited electron is in jected into the semiconductor. In the case of local field enhancement , the photon is absorbed in the semiconductor and the minority carrier is then swep t out to the metal by the built-in field of the Schottky junction. For wide bandgap semiconductors (like Ti02) under vis ible illum in ation, an electron is photoexcited from a defect state within the bandgap to the conduction band (i.e., sub-band gap abso rption). While both of these mech anis ms produce a photocurrent in the same di rection , the processes are quite different. LFE results purely from classical elec tromagnetism , while HEI is stric tl y a quantum mechanica l phenomenon. High energy barrier e lectrochem ic al reactions, suc h as CO2 reduction, typically require large external voltages to drive them in the desired direction. If successful, the proposed work will provide a detailed understanding of hot electron processes in chemical reactions, improved chemical selectivity, and enable photoelectrochemical reactions to be driven at smaller applied voltages.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 11, 2018
- Source ID
- W911NF1710325
Entities
People
- Stephen B Cronin
Organizations
- Army Contracting Command
- United States Army
- University of Southern California