Temperature Effect on the Topotatic Synthesis of Spinel MnCoO Nanoparticles for Efficient Oxygen Reduction Electrocatalyst

In this study, we demonstrated the temperature effect of our previously developed topotatic catalysis for the formation of Mn_0.005Co_2.995O₄ (MnCoO) spinel nanoparticles. Topotatic catalysis induces spinel MnCoO nanoparticles through the redox reaction of the metal cation (Co²⁺ and Mn²⁺) on the Co(OH)₂ nanosheet surface, acting as a growth template. This study particularly elucidates the temperature effect on spinel MnCoO nanoparticles' size, morphology, and crystallinity based on their electrocatalytic performance in an oxygen reduction reaction (ORR). We found that lower temperature produces an amorphous phase, whereas higher temperature induces a large aggregate. We obtained the monodispersed MnCoO nanocubes at approximately 90°C, exhibiting the best ORR performance with an electron-transfer number of 3.86.