Strategies for Hot Electron-Mediated Catalytic Reactions: Catalytronics

Abstract

A pulse of high kinetic energy electrons can be generated after deposition of external energy to a metallic surface, such as the absorption of light or exothermic chemical processes. These energetic electrons are not at thermal equilibrium with the phonons of the metal atoms and are called “hot electrons”. The detection of hot electrons on the surface of a catalyst is an active subject in the field of surface science. More significantly, it has been found that surface processes, including desorption, diffusion, and chemical rearrangement of atomic and molecular species, are driven by the flow of hot electrons on the surface. The strong correlation between hot electron generation and surface phenomena suggests that hot electrons can be used to control surface chemical reactions, which is known as hot electron chemistry. In this Perspective, research strategies for electronic control of catalytic reactions by engineering metal–oxide interfaces and manipulating hot electron flux are discussed. Catalytic nanodiodes consisting of a metal catalyst film, semiconductor layers, and Ohmic contact pads have revealed a strong correlation between the hot electron flux (chemicurrent) and catalytic activity under CO oxidation and hydrogen oxidation. We highlight recent results on new architecture for hot electron collection, including a Au/TiO2 nanodiode and a graphene/TiO2 nanodiode, that show that hot electrons can be used for quantitative measurement of catalytic activity. We show that the direct conversion of photon energy to hot electron flows can be achieved in metal–semiconductor nanodiodes. Hot electrons and surface plasmons can be used to change the catalytic activity using metal–oxide nanocatalysts. This strategy requires an understanding of both the electronic and chemical properties of metal–oxide interfaces, as well as the combined measurement of electronic and chemical signals on nanoscale electronic devices during catalytic reactions, and therefore can be referred to as “catalytronics”, which is the combination of catalysis and electronics.