Iodinated SnO2 Quantum Dots: A Facile and Efficient Approach To Increase Solar Absorption for Visible-Light Photocatalysis

Efficient visible-light-driven photocatalysis can be achieved over conventional wide band gap semiconductor, in which iodinated SnO2 quantum dots (QDs) are synthesized via hydrolysis of crystalline SnI4 in the absence of any additives or templates. The formation of SnO2 QDs reveals a wide preparation window and a very fast growth rate in minute scale. The iodine species may only exist on the surface of SnO2 QDs, which can be completely removed through heat treatment. SnO2 QDs reveal the light absorption in visible range which increases the limited optical absorption of bulk SnO2. Notably, the iodination can further enhance the visible light absorption due to the formation of band tail states. Therefore, iodinated SnO2 QDs exhibit significantly enhanced visible-light-driven photocatalytic activity toward degradation of rhodamine B and oxidation of NO in ppb level. Time-resolved spectroscopic studies reveal that the iodine species in QDs can not only server to passivate the surface traps to prolong the lifetime of the excited states when excited above the band gap, but they can also effectively absorb visible light and generate enhancement for photocatalytic reactions. The present study highlights the surface modification of wide band gap semiconductor for exploring efficient visible-light-active photocatalysts.