Large scale synthesis of highly crystallized SnO_2 quantum dots at room temperature and their high electrochemical performance

摘要

In this work, SnO_2 quantum dots with high crystallinity were synthesized on a large scale under mild reaction conditions via an epoxide precipitation route. The SnO intermediate, which was produced in the reactions between epoxide and [Sn(H_2O)_6]~(2+), was converted to SnO_2 quantum dots by the oxidation of H_2O_2. It is believed that the protonation and the following ring opening of epoxide promoted the hydrolysis and condensation of [Sn(H_2O) _6]~(2+) to form the intermediate. The obtained quantum dots had a maximum specific capacitance of 204.4 F g~(-1) at a scan rate of 5 mV s~(-1) in 1 mol l~(-1) KOH aqueous solution. The electrochemical measurements proved that this high specific capacitance of SnO_2 resulted from the Faradaic reactions between SnO_2 and the electrolyte. This demonstrates for the first time that SnO_2 can be used as a pseudocapacitive electrode material.