Real-time observation of phase transition from layered to spinel phase under electron beam irradiation

Transition metal hydroxides (TM(OH) 2 ) have drawn significant attention for their potential applications in the environmental and energy field. In this study, we investigated the phase transition of cobalt hydroxide (Co(OH) 2 ) under electron beam irradiation using in situ high-resolution transmission electron microscopy. Both the α- and β-Co(OH) 2 phases underwent a phase transition to a spinel Co 3 O 4 phase, forming nanograins with a porous morphology. However, the α-Co(OH) 2 showed a faster phase transition and dramatic volume shrinkage during the phase transition. Our results provide a detailed explanation of the mechanism behind the deterioration of the layered structure and the emergence of defects during the phase transition.