reoxidant

A reoxidant is an oxidizing agent used to reoxidize a reduced species or material, typically after a reduction step in a chemical or materials process. It restores the higher oxidation state and enables cyclic operation or regeneration of catalysts and oxides.

In chemical looping and related redox processes, a reoxidant gas such as air or oxygen is used to reoxidize a reduced oxide, replenishing lattice oxygen and closing the cycle. In these systems, the reoxidant regenerates the active oxide that transfers oxygen to a fuel or reactant during operation.

In semiconductor fabrication and materials engineering, reoxidation describes forming oxide layers after reduction, using oxidants such as O2, water vapor, or ozone to rebuild an oxide film on a surface. The choice of oxidant depends on compatibility with the substrate and the desired oxide properties.

Common reoxidants include molecular oxygen, air, ozone, and oxygen-containing vapors. The selection depends on thermodynamics, kinetics, and selectivity; excessive oxidant can cause over-oxidation or damage interfaces. Process conditions such as temperature and oxygen partial pressure are controlled to balance reoxidation rate with undesired side reactions.

The term is used across disciplines, including metallurgy, catalysis, solid-state chemistry, and photovoltaics, wherever a reduced phase must be restored to its oxidized form to sustain a cycle or maintain material properties.