Designing New Materials for Converting Solar Energy to Fuels via Quantum Mechanics.

摘要

This grant was the first to the PI to use first principles quantum mechanics to characterize key atomic-scale elementary processes involved in photocatalysis by novel materials comprised of abundant elements. In particular, we performed computer simulations to evaluate the efficacy of doped and alloyed first-row transition metal oxides for use as catalysts for renewable fuels production. Our work began with extensive testing of methods to calculate properties of interest in photocatalytic production of fuels. These preliminary studies were necessary to establish a quantitatively accurate set of theories to employ when performing photocatalyst modeling, which entails a complicated series of events starting from sunlight absorption to produce electronic excited states (electron-hole pairs), subsequent electron-hole pair separation and transport, followed by redox chemistry at the surface of the catalyst to produce fuels. Properties to be optimized include the material's band gap (which determines the amount of sunlight absorbed), valence and conduction band edge positions (which control whether, e.g., photocatalytic water splitting is thermodynamically allowed), electron-hole pair lifetimes and charge carrier mobilities (which determine whether the charge carriers survive to reach an interface where they can react), and overpotentials for redox reactions at the surfaces of catalysts (which largely control the kinetics of the photoelectrocatalysis). We have examined all of these properties for a number of candidate catalyst materials, and have elucidated important design principles from these studies for future optimization of photocatalysts.