<i>In-situ</i> UV–Vis Spectroscopy Examination of the Synthesis of Cobalt Oxychloride and Hydroxides

Cobalt hydroxide and cobalt oxychloride are very promising materials for batteries and electrocatalysis, but the reaction mechanism for inducing the formation of both using epoxides is currently unclear. This study focused on synthesizing cobalt oxychloride and cobalt hydroxides from CoCl[Formula: see text]H 2 O using a precipitation reaction triggered by propylene oxide (PO) in ethanol and water. The precipitation reaction process was described using hitherto unexplored UV–Vis technology. In the water system, Co[Formula: see text] existed as [Co(H 2 O) 6 ][Formula: see text] with octahedral coordination, while in alcohol, it was [CoCl n (H 2 O)[Formula: see text]][Formula: see text]. The water content and pH of the reaction system played crucial roles in determining the coordination compounds formed by Co[Formula: see text] ions, impacting the reaction’s course. These findings provide both experimental groundwork and theoretical insights for effectively regulating the synthesis of products in such systems.