Ultra-Tiny Sb-Doped SnO ₂ Nanoparticles as a Superior Catalyst for Vanadium Redox Reactions

Abstract

Herein, ultra-tiny Sb-doped SnO 2 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 SnO 2 . The size of nanoparticles decreased, as doping concentration increased. Sb doping also decreased the crystallinity of SnO 2 , producing structural defects. It is notable that Sb-doped SnO 2 showed greatly improved conductivity. However, excessive Sb doping reduced conductivity of SnO 2 . Sb-doped SnO 2 exhibited better electrocatalysis for V 3+ /V 2+ and VO 2 + /VO 2+ reactions. It benefits from Sb-doped SnO 2 with smaller size, more structural defects, and higher conductivity, increasing active sites and electron transfer rate for vanadium redox reactions. SnO 2 /Sb-5% showed the best electrocatalysis. SnO 2 /Sb-5% was used to modify graphite felt, such that it had better electrochemical performance for vanadium redox reactions. A cell using SnO 2 /Sb-5% improved electrolyte usage and discharge capacity retention at 50 mA cm −2 for 50 cycles. SnO 2 /Sb-5% also efficiently reduced electrochemical polarization of cell. The cell using SnO 2 /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 SnO 2 can be used as a promising catalyst for vanadium redox reactions.