Co-decorated reduced graphene/titanium nitride composite as an active oxygen reduction reaction catalyst with superior stability

Preparing a cost-effective, active, stable, non-precious catalyst, especially at the cathode, is one of the basic requirements for the commercialization of fuel cells (FCs). In this study, cobalt nanoparticles composite with titanium nitride (TiN) were prepared on the surface of reduced graphene oxide, using a facile hydrothermal method, followed by heat treatment under an inert atmosphere. The surface morphology, surface composition, and crystalline structure are investigated with the use of field emission-scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. The oxygen reduction reaction (ORR) activity is examined in sulfuric acid (0.5 M H₂SO₄), under nitrogen and oxygen bubbling. Results showed that there is an optimum ratio of the Co and the TiN that maximizes the ORR activity. A high onset potential of 0.926 V vs Ag/AgCl is obtained in the case of CoTiN (30)/Gr. This is much higher than that of commercial Pt/C catalyst (0.576 V vs Ag/AgCl). The prepared catalyst has no activity towards methanol oxidation, unlike the Pt/C catalyst. Thus, it considered a promising cathode catalyst for direct alcoholic FCs. Furthermore, the composite catalyst has a high stability, with no activity degradation occurring even after 1000 cycles. This is extremely effective compared to the 20% loss of Pt/C activity under the same operating conditions. The high performance of the prepared catalyst is related to the synergetic effect between the TiN and the Cobalt.