Surface defect-engineered silver silicate/ceria p-n heterojunctions with a flower-like structure for boosting visible light photocatalysis with mechanistic insight

Abstract

Charge carrier separation of photocatalysts can be accelerated by p-n heterojunctions and surface defect engineering. Here, novel silver silicate/ceria p-n heterojunction photocatalysts with a hierarchical flower-like structure were successfully synthesized through an in situ deposition-precipitation method in which p-type silver silicate (Ag6Si2O7) nanoparticles were evenly decorated on the sheets of n-type ceria (CeO2) nanoflowers prepared via an ice-bath coprecipitation process. Mott-Schottky plots and morphological studies indicated that p-n heterojunctions were constructed between Ag6Si2O7 and CeO2. This led to the generation of abundant surface defects (Ce3+ ions or oxygen vacancies) in the heterojunctions as confirmed by XPS and Raman. The photocatalytic properties are markedly improved under visible light irradiation and can be regulated by the Ag6Si2O7 content in the composites. The sample with 40 wt% Ag6Si2O7 loading had optimal photocatalytic elimination efficiency for the colorless contaminant tetracycline, the cationic dye rhodamine B, and the anionic dye methyl orange. As evidenced by various characterization techniques, the decoration of Ag6Si2O7 nanoparticles can promote the formation of a surface defect structure, increase visible light harvesting, and improve the separation of charge carriers driven by the internal electric field established between two semiconductors, thus leading to a remarkably enhanced photocatalytic activity. This work offers a reliable strategy for designing efficient p-n heterojunctions for photocatalytic applications in energy and the environment.