Ni-Doped CoTiO3 Ilmenite Oxides as Durable and Methanol-Tolerant Electrocatalysts for Oxygen Reduction Reaction

Abstract

Developing cost-effective, methanol-tolerant oxygen reduction reaction (ORR) electrocatalysts is critical for alkaline fuel cells and metal–air batteries. This study presents the synthesis of CoTiO3 and Co1–xNixTiO3 (x = 0.1 and 0.2) ilmenite oxides via a sol–gel method and thoroughly examines the influence of Ni substitution in CoTiO3 on its ORR performance. XRD, FTIR, Raman, and XPS analyses confirmed the formation of the ilmenite CoTiO3 framework, successful Ni incorporation, and Ni-induced modulation of the metal–oxygen environment. TEM and FE-SEM analyses revealed nearly spherical nanoparticles, while EDAX verified the expected constituent elements. BET analysis showed that Co0.9Ni0.1TiO3 possessed the highest surface area and pore volume, supporting improved active-site accessibility. Electrocatalytic ORR studies in O2-saturated 1 M KOH demonstrated that Co0.9Ni0.1TiO3 exhibited the best ORR activity among the investigated oxides, with higher cathodic current density, lower charge-transfer resistance, lower Tafel slope, higher exchange current density, increased ECSA, and an apparent near-four-electron ORR pathway, comparable to Pt/C. Co0.9Ni0.1TiO3 also showed excellent methanol tolerance, retaining 84.36% current after 10,000 s in 1 M KOH containing 1 M methanol and 89.98% after 20,000 s in methanol-free 1 M KOH, highlighting its potential as a cost-effective ORR electrocatalyst.