Role of the Morphology and Surface Planes on the Catalytic Activity of Spinel LiMn1.5Ni0.5O4 for Oxygen Evolution Reaction

The electrocatalytic activity of the spinel oxide LiMn1.5Ni0.5O4 withdifferent morphologies (cubic, spherical, octahedral, and truncated octahedral) has beeninvestigated for the oxygen evolution reaction (OER) in alkaline solutions that is ofinterest for metal−air batteries. The OER activity increases in the order truncatedoctahedral the spherical sample compared to nearly similar surface areas (0.3−0.7 m2 g−1) for theother three samples. The high activity of the octahedral sample is attributed to theregular octahedral shape with low-energy {111} surface planes, whereas the lowestactivity of the truncated octahedral sample is attributed to the high-energy {001} surfaceplanes. The octahedral sample also exhibits the lowest Tafel slope of 70 mV dec−1 withthe highest durability whereas the truncated octahedral sample exhibits the highest Tafelslope of 120 mV dec−1 with durability similar to the cubic and spherical samples. Thestudy demonstrates that the catalytic activities of oxide catalysts could be tuned andoptimized by controlling the surface morphologies/planes via novel synthesis approaches.