Synthesis of Ag/TiO2 Nanotube Heterojunction with Improved Visible-Light Photocatalytic Performance Inspired by Bioadhesion

Inspired by the bioadhesion mechanism found in mussel, a catechol derivative, 3-(3,4-dihydroxyphenyl)propionic acid (diHPP), is employed as both linker and reducer of Ag+ to synthesize the Ag/TiO2 nanotube (Ag/TNT) heterojunction under ambient conditions in this study. In the prepared Ag/TNT composite, Ag nanocrystals about 3.8 nm in diameter distribute over the TNT surface uniformly and form the heterojunction structure with TNT. The diHPP first links to the TNT surface through the bidentate chelation of catechol group with Ti4+ and then acts as both an anchor and a reducer to in situ nucleate and grow Ag nanocrystals on the TNT surface. By adjusting the AgNO3 concentration, the loading amount of Ag nanocrystals on the TNT surface can be controlled easily, and the visible-light absorption ability of Ag/TNT heterojunctions enhances with increasing the Ag loading amount. Moreover, their photocatalytic activity was evaluated by the degradation capability of Rhodamine B (RhB) under visible light. The Ag/TNT heterojunctions exhibit the high visible-light photocatalytic activity, which can almost degrade 100% RhB within 2 h. This excellent performance can be attributed to the local electric field caused by the surface plasmon resonance (SPR) of Ag nanocrystals and the high adsorption capability of TNTs with large specific surface area.