Understanding the Charge Carrier Dynamics of Metal@TiO2 Core–Shell Nanorods in Photocatalytic Hydrogen Generation

The fast recombination of photogenerated electrons and holes in the pure TiO 2 leads to a low photocatalytic efficiency in hydrogen generation or solar energy conversion. Noble metal nanoparticles have been used to combine with TiO 2 for effective photocatalysis. Herein, Au@Ag@TiO 2 nanorods (NRs) with core–shell structure have been prepared by hydrolysis the precursor of titanium in acid environment. UV light–driven H 2 generation rate of Au@Ag@TiO 2 samples demonstrated 14 times enhancement compared to P25 TiO 2 at the same experimental conditions. The improved photocatalytic performance was due to the charge transfer from the conduction band of excited TiO 2 to Au@Ag NRs leading to effective separation of electron–hole pairs. This mechanism has been proved by transient absorption spectroscopy and photo-electrochemical (PEC) measurements. The time resolved photocurrents of P25 TiO 2 NPs is ~ 13 times higher that of Au@Ag@TiO 2 , indicating that a fraction of the photogenerated electrons of TiO 2 driven by UV light transfer to Au@Ag nanocores instead of transporting entirely to the ITO substrates. The ultrafast transient absorption and pump-probe measurements demonstrated a faster decay in Au@Ag@TiO 2 NRs compared to pure TiO 2 system, indicating that the photogenerated electron–hole recombination in TiO 2 is substantially suppressed by Au@Ag@TiO 2 NRs attributed to the effective trapping of the photogenerated electrons by the Au@Ag cores. Graphic Abstract Au@Ag@TiO 2 nanocomposites with core-shell structure have been prepared and its UV light–driven H 2 generation rate has been demonstrated 14 times enhancement compared to P25 TiO 2 at the same experimental conditions. The improved photocatalytic performance was due to the charge transfer, which has been proved by photocurrent measurement and the ultrafast transient absorption and pump-probe measurements.