Ultra-Tiny Sb-Doped SnO2 Nanoparticles as a Superior Catalyst for Vanadium Redox Reactions

Herein, ultra-tiny Sb-doped SnO2 nanoparticles were prepared using co-precipitation as superior catalyst for vanadium redox reactions. Different concentrations of Sb in range of 2%, 5%, and 10% were doped in lattice structure of SnO2. The size of nanoparticles decreased, as doping concentration increased. Sb doping also decreased the crystallinity of SnO2, producing structural defects. It is notable that Sb-doped SnO2 showed greatly improved conductivity. However, excessive Sb doping reduced conductivity of SnO2. Sb-doped SnO2 exhibited better electrocatalysis for V3+/V2+ and VO2+/VO2+ reactions. It benefits from Sb-doped SnO2 with smaller size, more structural defects, and higher conductivity, increasing active sites and electron transfer rate for vanadium redox reactions. SnO2/Sb-5% showed the best electrocatalysis. SnO2/Sb-5% was used to modify graphite felt, such that it had better electrochemical performance for vanadium redox reactions. A cell using SnO2/Sb-5% improved electrolyte usage and discharge capacity retention at 50 mA cm−2 for 50 cycles. SnO2/Sb-5% also efficiently reduced electrochemical polarization of cell. The cell using SnO2/Sb-5% had higher energy efficiency compared to pristine cell. At 150 mA cm−2, the energy efficiency of modified cell increased by 9.2% compared with pristine cell (57.3%). Therefore, Sb-doped SnO2 can be used as a promising catalyst for vanadium redox reactions.