CoTiO3/NrGO nanocomposites for oxygen evolution and oxygen reduction reactions: Synthesis and electrocatalytic performance

Oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts play an important role in energy conversion and storage devices, but highly active and robust nonprecious metal catalysts are required to address the cost and durability issues. In this work, a modified gel methodology has been used to obtain nanocomposites of perovskite CoTiO3 and N-doped reduced graphene oxide (NrGO). Moreover, the influence of the annealing extent in the synthesis has been studied. The composites show higher activity in oxygen evolution and reduction reactions in alkaline environment compared to sole ilmenite, which is related to a strong interaction between cobalt titanate and NrGO carbon matrix. The annealing duration appears as a key variable to modulate the physicochemical properties and the electrochemical behavior. The composite prepared at the largest duration (3 h) exhibit enhanced bifunctional properties for ORR and OER, with onset potentials of 0.93 V and 1.53 V vs. RHE respectively, which is mainly attributed to higher concentration of nitrogen, larger extent of defects and/or the presence of more oxidized Co species in the nanocomposite. (c) 2019 Elsevier Ltd. All rights reserved.