Effect of dual-cocatalysts surface modification on photodegradation activity, pathway and mechanisms with highly efficient Ag/BaTiO3/MnOx.

Cocatalyst surface-loading has been regarded as an effective strategy to promote solar-energy-conversion efficiency. However, the potential influence of surface modification with cocatalysts on photodegradation pathway and the underlying mechanisms are still unclear. Herein, we have used ferroelectric BaTiO3 as the substrate, and both reduction cocatalyst Ag and oxidation cocatalyst MnOx have been successfully loaded onto BaTiO3 simultaneously by one-step photodeposition method as evidenced by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM). The influence of dual-cocatalysts surface-loading on photodegradation of Rhodamine B has been systematically investigated for the first time. Firstly, the dual-cocatalyst modified BaTiO3 outperformed over single-cocatalyst loaded BaTiO3, and the photodegradation rate of Ag/BaTiO3/MnOx is about 3 times and 12 times as high as that of Ag/BaTiO3 and BaTiO3/MnOx respectively. The credit is given to the synergetic effect between reduction and oxidation cocatalysts, prompting charge carrier separation and migration as verified by the transient photocurrent, electrochemical impedance and photoluminescence (PL) spectrum investigation. Secondly, in addition to the boosted photodegradation activity, the photodegradation pathway is found to be altered as well when using Ag/BaTiO3/MnOx. The high performance liquid chromatography (HPLC) analysis indicated a highly selective stepwise deethylation process predominate over chromophore cleavage in Ag/BaTiO3/MnOx system while it is reverse for Ag/BaTiO3 system. This phenomenon is attributed to the different dye molecule adsorption mode. Furthermore, the radical trapping experiment shows holes play the major role in the degradation process and the recycle test proves its excellent stability of Ag/BaTiO3/MnOx. Our findings may add another layer of understanding depth to cocatalyst surface modification in photodegradation applications.

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