Effects of Traps on the Photo-induced Interfacial Charge Transfer of Ag-TiO2: Photoelectrochemical, Electrochemical, and Spectroscopic Characterization

Zhihao Liang, State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
Jiazheng Wang, State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
Dan Wang, State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
Jianzhang Zhou, State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
Deyin Wu, State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China

Abstract

In the field of metal-semiconductor composites based plasmon-mediated chemical reactions, a clear and in-depth understanding of charge transfer and recombination mechanisms are crucial for improving plasmonic photocatalytic efficiency. However, the plasmonic photocatalytic reactions at the solid-liquid interface of the electrochemical systems involve complex processes with multiple elementary steps, multiple time scales, and multiple controlling factors. Herein, the combination of photoelectrochemical and electrochemical as well as spectroscopic characterizations have been successfully used to study the effects of traps on the photo-induced interfacial charge transfer of Ag-TiO2. The results show that the increase of surface hydroxyl groups may be the key reason that leads to the increase of traps after Ag deposition on the surface of TiO2. The increased traps of Ag-TiO2, including deep and shallow traps, subsequently lead to the quenching of fluorescence and the reduction of photocurrent in the UV region. But enhanced trap recombination may also prolong the lifetime of carriers. The modulation of traps is bound to affect the interfacial charge transfer and thus change the amount and lifetime of hot carriers, which can be exploited to manipulate the molecular reactions at the Ag surface. Our work highlights the importance of traps at metal-semiconductor electrodes that may help utilize the hot carriers in plasmonic mediated chemical reactions.