Overview

Copper(II) oxide, commonly called cupric oxide and written CuO, is a dense black solid composed of copper in the +2 oxidation state combined with oxide anions. It occurs in nature as the mineral tenorite and is widely used in industry and research. For general references and introductory data see general compound information.

Structure and physical properties

CuO crystallizes in a monoclinic lattice and is generally described as a p-type semiconductor with a relatively small band gap. It is typically a black to brown-black powder or crystalline mass, insoluble in water under neutral conditions. The compound is stable in air at room temperature but can be reduced to metallic copper under strongly reducing conditions.

  • Chemical formula: CuO.
  • Oxidation state: copper(II), Cu2+ combined with oxide O2−.
  • Appearance: black to brown-black solid.
  • Electrical character: p-type semiconductor.

Chemical behavior and reactions

CuO reacts with mineral acids to form soluble copper(II) salts and water. In the presence of suitable ligands or complexing agents it forms soluble complexes, for example with ammonia to give ammine complexes. Under reducing atmospheres it is readily converted to Cu metal. Additional chemical and analytical details are available at specialized sources: oxidation and reactivity notes.

Preparation and natural occurrence

Laboratory and industrial methods to produce CuO include oxidation of copper metal at elevated temperature, thermal decomposition of basic copper(II) carbonates or hydroxides, and calcination of copper(II) compounds after precipitation. In nature, tenorite forms in the oxidized zones of copper deposits and as an alteration product of other copper minerals. See synthesis and occurrence summaries at preparation references.

Uses and applications

Copper(II) oxide is used as a pigment and colorant in ceramics and glass, as a catalyst or catalyst support in various chemical processes, and as an active material in certain electrode and sensor technologies. It is also investigated for photocatalysis, gas sensing, and energy storage applications. For applied and technical guidance consult technical resources.

Safety, handling and disposal

As with many fine metal oxide powders, CuO dust should not be inhaled and prolonged skin contact should be avoided. Standard laboratory precautions apply: use adequate ventilation, wear gloves and eye protection, and follow institutional or regulatory guidance for disposal. More complete safety data are available from material safety resources: safety and regulatory information.

Distinction from other copper oxides

Copper(II) oxide is distinct from copper(I) oxide (Cu2O), which is typically red or orange and contains copper in the +1 oxidation state. Their colors, electronic properties, solubility behavior, and common uses differ, so correct identification matters for synthesis, application, and safety.