The visible light photoelectrical properties of different p-type mesoporous metal oxide (MMO) supports were investigated upon the decoration of size controlled, 1.6 nm, 6.4 nm and 7.9 nm Pt nanoparticles. The near room temperature photoelectrical response of the MMOs was 3-4 times higher after decoration of Pt nanoparticles with a loading of 1 wt%. MMOs decorated with smaller Pt nanoparticles showed the highest photoresponse.<br/>The surrounding atmosphere has striking effect on the photoelectrical behavior, as adsorbed oxygen induced lower photoelectrical response compared to that of argon. The noble metal nanoparticles show both electronic and chemical sensitization: the first functioning as an electron sink resulting in a new band structure of the photocatalyst, and the second interacting chemically with the oxygen and argon adsorbed from the environment.<br/>A conceptual model has been proposed in which adsorbed oxygen induces a new potential in the heterojunctions lowering the corresponding potential barrier and as result some electrons can occupy holes (lower in energy) in the interbands of the metal. Upon irradiation, the electrons in the valence band thus require higher energy to reach the free holes resulting in a lower response in the presence of oxygen. The results showed that not only the presence of the noble metal nanoparticles, but also their size had effect on the photoelectrical properties of nanoparticle decorated heterojunction composites.

Photoelectrical response of mesoporous metal oxides decorated with size controlled platinum nanoparticles under argon and oxygen gas

253rd National Meeting (2017)

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