Molten salt synthesis of Nb-doped TiO2 rod-like particles for use in bifunctional oxygen reduction/evolution electrodes

摘要

Gas diffusion electrodes (GDEs) that have high stability and high bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) activity are required for producing metal-air secondary batteries with excellent charge/discharge performance. Here, Nb-doped TiO2 rod-like particles were synthesized using NaCl-Na2HPO4 molten salt as a reaction medium and applied as a catalyst support in ORR/OER bifunctional GDEs for use in metal-air batteries. The Nb-doped TiO2 rod-like particles were successfully synthesized when Nb(OH)(5) and TiO2 powder consisting of the anatase and rutile phases were used as the Nb and Ti sources, respectively. Heat treatment with solid NaBH2 at 370 ? nbsp;was able to reduce the Nb-doped TiO2 rod-like particles while avoiding the thermal agglomeration of particles, which led to an increase in the electrical conductivity and OER activity of the Nb-doped TiO2 rod-like particles. The reduced Nb-doped TiO2 nbsp;rod-like particles showed high stability against anodic corrosion during the OER and higher OER activity than reduced graphene oxide (rGO), which has been reported as a catalyst support in ORR/OER bifunctional GDEs. The loading of LaNiO3 as an ORR/OER bifunctional catalyst onto the reduced Nb-doped TiO2 rod-like particles achieved higher ORR/OER bifunctional activity than the loading of LaNiO3 on rGO, indicating that the reduced Nb-doped TiO2 rod-like particles are superior to rGO as the catalyst support in ORR/OER bifunctional GDEs.