Cobalt based oxides have been comprehensively investigated as electrocatalysts, and the main concern in catalyst design is the clarification of the catalyst structure and reaction site. Herein, the crystal structure of α-Co(OH)2 and its transformations to other cobalt hydroxides were fully elucidated. The α-Co(OH)2 consisted of layered structure with anion intercalations which is identified by Rietveld analysis using X-ray diffraction. The chemical phase transformations of α-Co(OH)2 into various other cobalt hydroxides, such as β-Co(OH)2, γ-CoOOH, and β-CoOOH were selectively performed and characterized their structures. In addition, electrochemical oxidative phase transformation of α-Co(OH)2 into β-CoOOH and γ-CoOOH were successively accomplished. Typically, electrochemical cation intercalations of α-Co(OH)2 were carried out to obtain γ-CoOOH. The cations in electrolyte such as Li+, Na+, K+ were selectively inserted to layered structure and formed γ-CoOOH phase. The prepared cobalt hydroxides were applied to oxygen evolution reaction (OER) and chlorine evolution reaction (CER) to clarify the relationship between crystal structure and catalytic activity. The coordination environment of cobalt sites, and the effect of intercalated cations for electrocatalytic reaction are fully elucidated.

Chemical and electrochemical ion intercalation on cobalt hydroxide: Selective phase transformation and application to electrocatalytic reactions

ACS Spring 2022

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