Crystallographic interface control of the plasmonic photocatalyst consisting of gold nanoparticles and titanium(iv) oxide

A big question in the field of plasmonic photocatalysis is why a typical photocatalyst consisting of gold nanoparticles and rutile titanium(iv) oxide (Au/R-TiO(2)) usually exhibits activity much higher than that of Au/anatase TiO(2) (Au/A-TiO(2)) under visible-light irradiation. Shedding light on the origin should present important guidelines for the material design of plasmonic photocatalysts. Au nanoparticles (NPs) were loaded on ordinary irregular-shaped TiO(2) particles by the conventional deposition precipitation method. Transmission electron microscopy analyses for the Au/TiO(2) particles ascertain that faceting of Au NPs is induced on R-TiO(2) by using a domain-matching epitaxial junction with the orientation of (111)(Au)//(110)(R-TiO(2)), whereas non-faceted hemispherical Au NPs are exclusively formed on A-TiO(2). The faceting probability of Au NPs (P(f)) on R-TiO(2) increases with decreasing Au particle size (d(Au)) to reach 14% at d(Au) = 3.6 nm. A clear positive correlation between the photocatalytic activity and P(f) in several test reactions indicates that the heteroepitaxial junction-induced faceting of Au NPs is the principal factor for governing the plasmonic photocatalytic activity of Au/TiO(2). In light of this finding, R-TiO(2) nanorods with a high percentage (95%) of {110} facets were hydrothermally synthesized and used for the support of Au NPs. Consequently, the P(f) value increases to as much as 94% to enhance the photocatalytic activity with respect to that of Au/R-TiO(2) with P(f) = 14% by factors of 2.2–4.4 depending on the type of reaction.