- Cobalt(II) oxide, with the chemical formula CoO, is a binary inorganic compound composed of cobalt in the +2 oxidation state and oxide ions (O²⁻).
- It typically appears as an olive-green to black crystalline powder and is one of the most stable and commonly encountered cobalt oxides. CoO is a significant compound in the fields of materials science, ceramics, and catalysis, as well as in electrochemical applications.
- Structurally, cobalt(II) oxide adopts the rock salt (NaCl-type) crystal structure, in which cobalt ions and oxide ions are arranged in a face-centered cubic lattice. This structure gives CoO important magnetic and electronic properties. It is antiferromagnetic at low temperatures (below its Néel temperature of ~290 K) and exhibits semiconducting behavior, which has made it a subject of interest in condensed matter physics and materials research.
- Cobalt(II) oxide is commonly produced by thermal decomposition of cobalt(II) carbonate (CoCO₃) or cobalt(II) hydroxide (Co(OH)₂) in a controlled oxygen environment. It can also be formed by reducing cobalt(II,III) oxide (Co₃O₄) at moderate temperatures in a hydrogen or carbon monoxide atmosphere.
- CoO has a number of important industrial and technological applications. It is widely used in the ceramics and glass industries as a colorant, where it imparts blue, green, or gray hues to glazes and enamels depending on the firing conditions and composition. It also serves as a precursor for lithium cobalt oxide (LiCoO₂), a vital cathode material in lithium-ion batteries, which are used in electronics, electric vehicles, and energy storage systems.
- In chemical synthesis, cobalt(II) oxide is employed as a catalyst or catalyst precursor in various oxidation reactions and in the production of other cobalt salts. Its ability to undergo redox reactions makes it valuable in heterogeneous catalysis and ceramic coatings. Additionally, its semiconducting and magnetic properties are being explored in spintronics and magnetoresistive devices.
- From a safety perspective, cobalt(II) oxide, like other cobalt compounds, can be toxic if inhaled or ingested, particularly in fine particulate form. Chronic exposure may affect the lungs and lead to systemic toxicity, and it is classified as a potential carcinogen. Therefore, it must be handled with appropriate personal protective equipment (PPE) and within well-ventilated or controlled environments.
