Synthesis of metal and metal oxide hybrid nanostructures for photocatalytic energy generation

Abstract

Photocatalytic water splitting and CO2 reduction reactions are ideal reactions that convert renewable solar energy to chemical energy. Since Fujishima and Honda reported photoelectro chemical water splitting reaction using TiO2, numerous metal oxide based photocatalysts have been developed. However, a great part of photocatalysts have large band gap energies which can only absorb the ultraviolet region. Moreover, most of studies have conducted with poorly controlled photocatalysts in terms of size and morphology of metal oxide particles and adjacent metal co-catalysts. Recently, researchers have focused on development of photocatalyst working under visible light based on well defined nanostructures. Rational design of the photocatalyst structures using nanosynthetic technology can improve photocatalytic performances including activity, stability, and conversion efficiency. In the present study, we have tried to synthesize metal and metal oxide-semiconductor hybrid nanoparticle structures with well-defined morphologies with Pt-CdSe, Au-TiO2, and CuO2-ZnO systems. These nanostructures were employed as model catalysts for photocatalytic energy generation reactions. Detailed mechanisms and particular factors affecting conversion efficiencies were carefully investigated. Such rational design and well-defined morphology of the hybrid nanostructures would help to understand fundamental chemical nature of the photoinduced catalytic reactions and provide essential information to develop actual processes of energy generation. In Part 2, we demonstrate the effect of noble metals (Au and Pt) with distinct geometric structures on CdSe nanorods for photocatalytic hydrogen production. The choice of metals and their locations significantly affect photocatalytic activity of the hydrogen generation. In part 3, we report the synthesis of TiO2 hollow shell nanoparticles and their hybrid structures with metals including Au and Pt. It is possible that metals attach to TiO2 inner ...