Performance of Ni-doped BaTiO3 hollow porous spheres supported reduced graphene oxide as an efficient bifunctional electrocatalyst for oxygen evolution reaction and oxygen reduction reaction

Perovskite oxides are promising and effective electrocatalysts for various energy related applications due to their low cost, versatile structures, as well as interesting catalytic activity. Herein, aerosol spray pyrolysis was used to synthesize hollow spherical structure of BaTiO3, Ni-doped BaTiO3 and Ni-doped BaTiO3 supported on reduced graphene oxide (rGO). The prepared nanocomposites were used as bifunctional electrocatalysts simultaneously for oxygen reduction and oxygen evolution reactions. Several characterization techniques were utilized for characterizing the prepared materials. The morphological analysis revealed that the produced spheres consisted of nanoparticles ranging in size from 5 to 20 nm, while the Brunauer–Emmett–Teller surface analysis assured the high mesoporous features of the prepared hollow spheres. The oxygen evolution reaction (OER) results exhibited an exceptional current density up to 80 mA cm−2 at potential 1.6 V vs. RHE, this performance was five times higher than the pure BaTiO3 (BTO). The Tafel slope was reduced by 75.5 % compared to BaTiO3. Ni-doped BaTiO3/rGO hollow porous spheres show excellent OER electrocatalytic activity compared to the commercial IrO2 electrocatalyst in basic medium. Moreover, the prepared Ni-doped BaTiO3/rGO hollow porous spheres presented excellent catalytic activity for oxygen reduction reaction (ORR), mainly favored a direct four-electron pathway, enhanced the charge transfer, led to the lowest onset potential (0.77 V vs RHE), and also achieved excellent long-term durability. The results demonstrated that the prepared perovskite/rGO composites effective bifunctional electrocatalysts.