Composite Plasmonic Metal/Semiconductor Photoelectrodes for Overall Water Splitting

The efficient conversion of solar energy into useful chemical energy, for example through processes such as water splitting and CO₂ reduction, is of critical importance for the development of sustainable, long-term solutions to society’s energy problems. These and other photochemical processes require the development of novel photo-catalysts that can efficiently make use of the solar spectrum. Conventional semiconductor photocatalysts suffer from range of issues that limit their ability to efficiently convert solar into chemical energy, including low absorption coefficients, large band gap energies and especially high rates of charge carrier recombination.

In this contribution we show that the photocatalytic activity of a semiconductor can be significantly enhanced by the addition of optically active Ag nanostructures of targeted size and shape to form composite metal/semiconductor photocatalysts. The observed activity enhancement is attributed to the transfer of energy from Ag surface plasmon (SP) states, increasing the steady-state concentration of e/h pairs in the semiconductor, thereby increasing the reaction rate. The ability to predictably tune the energy of Ag SP states by controlling particle shape and size allows for the rational design of optimized metal/semiconductor composite photocatalysts and photo-electro-catalysts wherein the overlap of the metal nanostructure SP states, semiconductor band gap, and energy of the light source is maximized.