Crystallization time-induced microstructural evolution and photoelectrochemical properties of ternary Ag@AgBr/TiO2 nanorod arrays

Abstract

The plasmonic Ag@AgBr nanoparticles on a well-ordered TiO2 nanorod array (TNR) matrix were successfully constructed by a secondary hydrothermal strategy. Effects of different crystallization time of Ag@AgBr on crystallinity, size and optical properties of the ternary arrays were discussed. The results showed that the crystalline behavior of Ag@AgBr was improved significantly with the increasing crystallization time. The average size of Ag@AgBr nanoparticles attached to top and side of TiO2 nanorods was 15 nm, and increased up to 55 nm at longer time. The surface plasmon resonance (SPR) bands were evident in the Ag@AgBr/TNR (ABT) arrays, and a significant redshift was observed with crystallization time. Especially when the crystallization time is 12 h, 12ABT photoelectrode had the lowest transfer resistance for interfacial charges and the highest transient photocurrent intensity of 130 μA/cm2, which was about 13 times that of bare TNR. In the degradation of methyl orange, 12ABT showed the highest photocatalytic efficiency of 95.6% and rate constant of 0.0167 min−1 under full spectral irradiation, which was 18.6 times of TNR. The favorable sunlight-driven photocatalytic activity originated from synergistic effect of three components in Ag@AgBr/TNR array, such as the improved solar light response through surface plasmon resonance (SPR) and photosensitive effect of Ag and AgBr co-sensitizers, as well as the high-efficiency carrier transfer in the unique heterojunction.