Tunable thickness and band structure of SnO sheets for improved photocatalytic activity

Abstract

SnO sheets with tunable thickness were synthesized by a hydrothermal method. The thickness of the SnO sheets could be delicately controlled by adjusting the amount of PEG added. It was found that the thickness of the SnO sheets reduced from 1 μm to 150 nm with the increase in PEG. PEG was preferentially adsorbed on the (001) facets of SnO and thus inhibited the crystal growth in the <001> direction, which determined the final shape to be sheets with reduced thickness. The reduced thickness of SnO offered a shorter pathway along the two-dimensional conducting path and thus induced rapid charge transfer and high separation efficiency. Meanwhile, the reduced thickness of the SnO sheets induced an enlarged band gap and correspondingly increased the redox ability of SnO, which was confirmed by UV-vis absorbance spectroscopy and Mott–Schottky plots. Benefiting from the improved charge separation efficiency and the stronger redox ability, enhanced photocatalytic degradation efficiency was demonstrated by the SnO sheets with reduced thickness. The SnO sheets with the thinnest thickness (150 nm) exhibited optimal photocatalytic activity in the degradation of methylene blue (MB) under fluorescent light irradiation (350–800 nm); the activity was about 3.5 times higher than that of the SnO sheets with 1 μm thickness.