Oxygen vacancy and size controlling endow tin dioxide with remarked electrocatalytic performances towards vanadium redox reactions

Abstract

Nanomaterials have been applied in electrochemistry fields due to advantages of large surface area and high surface activity. Nano mental oxides have been widely used as catalyst in vanadium redox flow battery. In this work, oxygen vacancy and size controlling strategies were used to endow SnO2 with remarked electrocatalytic performances towards vanadium redox reactions, which were realized by facile Cr doping. A series of Sn1-xCrxO2-δ (x = 0.01, 0.02 and 0.04) samples were prepared by using sol-gel method and high-temperature calcination. Cr doping reduces the particle size of SnO2 and increases oxygen vacancies in crystal structure of SnO2. Cr-doped SnO2 displays the improved electrochemical performance for vanadium redox reaction compared with SnO2. It owes to Cr-doped SnO2 with more active sites and larger reaction place than SnO2. SnO2/Cr-2 (Sn0.98Cr0.02O2-δ) exhibits the best electrocatalytic activity for V3+/V2+ redox reaction as well as better electrocatalytic activity for VO2+/VO2+ redox reaction than SnO2. The graphite felt was loaded by SnO2/Cr-2 as bifunctional electrodes in cell. The cell shows the improved electrolyte usage and better electrochemical stability in cycling test compared with pristine cell. SnO2/Cr-2 reduces electrochemical polarization and increases energy and voltage efficiency of the cell. Overall, Cr doped SnO2 is an attractive catalyst for improving electrochemical performance of vanadium redox reaction.