Platinum(IV) oxide, commonly known as Adams' catalyst, is an inorganic compound with the chemical formula PtO₂. It typically exists as a brown or black powder and is insoluble in water and most common organic solvents. It is a precursor to active platinum metal catalysts. Its primary and most significant application is as a precursor to highly active platinum black or platinum dioxide catalysts used in hydrogenation reactions. Upon reduction, it generates finely divided platinum metal, which serves as a heterogeneous catalyst for the hydrogenation of a wide range of functional groups, including alkenes, alkynes, nitro groups, and carbonyl compounds, under mild conditions. It is a classic and versatile catalyst in organic synthesis and industrial processes. Beyond its role as a catalyst precursor, platinum(IV) oxide itself finds use in specialized applications such as in fuel cells and electrochemical sensors due to its catalytic properties. It is also employed in the synthesis of other platinum compounds. As a heavy metal compound, it requires careful handling, and appropriate safety measures should be observed to avoid inhalation or ingestion.