Palladium black is a coarse, sponge-like form of elemental palladium

Palladium

Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...

 that offers a large surface area for hydrogen adsorption. It can be used as a catalyst for hydrogenation

Hydrogenation

Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...

reactions.

This term is also used colloquially to refer to a black precipitate of elemental palladium, which forms on decomposition of palladium complexes.

This form of palladium is commercially available in different grades. It may be prepared by the reduction of various palladium(II) compounds.