MeOx

MeOx is a generic notation used in inorganic chemistry and materials science to denote metal oxides, where Me represents a metal element and x indicates the oxide content. It is not a single compound but a class of materials formed by metal cations and oxide anions. Depending on the metal and synthesis, MeOx can exhibit a range of oxidation states and non-stoichiometric compositions.

Composition and structure: The crystal structure and stoichiometry of MeOx depend on the metal and the oxide phase. Common motifs include rock-salt, rutile, perovskite, and spinel-type structures, as well as non-stoichiometric variants with oxygen vacancies. MeOx often exist as nanoparticles, thin films, or bulk phases.

Properties and behavior: MeOx materials can be insulating or semiconducting, with properties strongly affected by defects such as oxygen vacancies and dopants. They frequently exhibit catalytic activity for oxidation and reduction reactions, as well as interesting magnetic, optical, or electronic characteristics that are exploited in devices.

Synthesis and characterization: MeOx can be prepared by solid-state reactions, sol-gel and hydrothermal methods, precipitation, or thin-film deposition techniques such as sputtering, chemical vapor deposition, or atomic layer deposition. Characterization typically includes X-ray diffraction, X-ray photoelectron spectroscopy, electron microscopy, and surface area analysis.

Applications and examples: MeOx find use as catalysts, electrode materials for batteries and supercapacitors, gas sensors, and protective coatings. Examples include FeOx, TiO2, NiOx, Co3O4, and mixed-oxide systems such as perovskites (ABO3) and spinels (AB2O4).

See also: metal oxide, oxide semiconductor, spinel, perovskite.