Preparation of LSPR enhanced Z-scheme Pd/WO3@SnO2 for photocatalytic decomposition of organic compounds under simulated sunlight

Abstract

The decoration of semiconductor photocatalysts with metal nanoparticles (NPs) is an efficient strategy for improving their performance via localized-surface-plasma-resonance (LSPR). For this study, a LSPR enhanced Z-scheme Pd/WO3@SnO2 photocatalyst was synthesized, which revealed excellent photocatalytic performance and reusability against Rhodamine B (RhB) with degradation rate of 100 % after 1 h under simulated sunlight. The reaction rate constants (k) of the Pd/WO3@SnO2 were ∼4.9, 3.5, and 2.1 times higher than those of the WO3, SnO2, and WO3@SnO2, respectively. In this Z-scheme-structure, the transfer efficacy of photogenerated electrons was significantly promoted due to integrated electric-field between the SnO2 and WO3, which was supported by experimental results and theoretical calculations. The deposited Pd nanoparticles served as an electron-transfer-bridge, as well as a LSPR excitation source, which played significant role in the degradation of RhB. The photodecomposition pathway of RhB was explored, and the toxicities of the intermediates were evaluated. Moreover, tetracycline (TC), chlortetracycline-hydrochloride (CTC), doxycycline-hydrate (DOX), and oxytetracycline (OTC) were tested as common antibiotic models to verify the effectiveness of the catalysts. The degradation efficiencies for TC, CTC, DOX, and OTC over Pd/WO3@SnO2 attained 90.98 %, 96.33 %, 75.37 %, and 50.90 %, respectively, under simulated sunlight, which confirmed its strong potential for the removal of recent pollutants. Experiments and electron paramagnetic resonance (EPR) tests indicated that •O2– served as the major active species in the photocatalysis process, while •OH and h+ played secondary roles. Finally, an LSPR enhanced direct Z-scheme mechanism was proposed. This study provides a rational design strategy for the development of more efficient Z-scheme photocatalysts that exploit the LSPR-effect for photodecomposition of organic pollutant compounds.