Development of Particulate Photocatalysts and Photoelectrodes for Water Splitting Operable in up to Near-Infrared Region

Abstract

  Effective utilization of long wavelength light for photocatalytic and photoelectrochemical water splitting is an important challenge for practical realization of solar energy harvesting in the form of chemical energy, i.e., artificial photosynthesis. Meanwhile, narrowing the band gap of the semiconductor accompanied with the negative or positive shift of the valence band maximum or conduction band minimum, respectively, can cause the decline of the driving force of the photoexcited carriers. To break through this trade-off, innovative approaches to efficiently utilize the photoexcited carries generated inside the semiconductor for the chemical reaction performed outside the material should be necessary. In this study, novel concepts to control several processes with varying time scales involved in photocatalysis: 1) physical process inside the semiconductor, 2) chemical process at the photocatalyst surface, and 3) mass transfer of reactants in the bulk aqueous solution, are proposed with using particulate photocatalytic materials responsive up to near-infrared light.