Light-assisted surface reactions on metal nanoparticles
Surface catalytic reactions typically occur on metal nanoparticles deposited on inert supports with high surface area. Recently, many studies have reported that the catalytic activity of metal nanoparticles can be enhanced significantly under light irradiation. This ‘light-assisted surface reaction’ can lower reaction temperature, potentially reducing the energy use. Light can be absorbed via intra- or inter-band transition within metal nanoparticles or direct photoexcitation of adsorbates on the surface. The absorbed energy can be relaxed through a radiative or non-radiative process; the non-radiative relaxation can produce heat or energetic electrons, enhancing the surface catalytic reaction with lower activation energy. The enhancement depends on the light intensity or wavelength. Plasmonic metals Au, Ag, and Cu have been widely studied for the ‘light-assisted surface reaction’, but composites of plasmonic metals with semiconductors or other metals such as Pt, Pd, or Ni have also been used for the surface reaction. Most recently, non-plasmonic metal Pt has shown an enhancement upon light irradiation due to the photoexcitation of electrons in the orbitals of adsorbates. The light-assisted surface reaction is still in the infancy stage, but it would surely provide more facile ways to control surface reactions and minimize the overall energy use.