Synthesis and microstructure of single‐crystalline cobalt oxyhydroxide and topotactic transformation to cobalt oxide

• Published in: Journal of the American Ceramic Society Vol. 103; no. 12; pp. 7240 - 7246
• Main Authors: Kusano, Yoshihiro, Kawasaki, Shuji, Takada, Jun, Azuma, Masaki
• Format: Journal Article
• Language: English
• Published: Columbus Wiley Subscription Services, Inc 01.12.2020
• Subjects: Cobalt; Cobalt oxides; Cobalt oxyhydroxide; Cobalt plating; Crystal growth; Crystals; Diameters; Heat exchange; Ion exchange; microstructure; oxonium; Porosity; Room temperature; Single crystals; Sodium; sodium cobalt oxide; sodium cobalt oxyhydrate; topotaxy; Water chemistry
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.17140

ABSTRACT Plate‐like cobalt oxyhydroxide (β‐CoOOH, heterogenite) single crystals, with a width of ~5 mm and a thickness of ~100 μm, were successfully synthesized using a simple method of heating a mixture of Co3O4 and NaOH in air at 650°C, and then soaking the resultant crystals in water at room temperature. The crystals were topotactically formed from sodium cobalt oxyhydrate (Na0.2(H3O)0.54CoO2·0.48H2O) by ion exchange between Na+ and H3O+, and by intercalation of water molecules in the as‐grown NaCoO2 crystals. The sodium cobalt oxyhydroxide crystals had spherical nanopores with diameters of ~5 nm. Single‐crystalline sodium cobalt oxyhydroxide, β‐NaxCo4+yCo3+1−yOOH1−x−y (x = 0.08, y = 0.07), with a width of ~5 mm and a thickness of ~100 μm, was successfully synthesized using a novel and simple method. These crystals were formed from sodium cobalt oxyhydrate. The sodium cobalt oxyhydroxide crystals had spherical nanopores with diameters of ~5 nm.