Applications of Palladium

The largest use of palladium today is in catalytic converters. Palladium is also used in jewelry, in dentistry, watch making, in blood sugar test strips, in aircraft spark plugs and in the production of surgical instruments and electrical contacts. Palladium is also used to make professional transverse flutes. As a commodity, palladium bullion has ISO currency codes of XPD and 964. Palladium is one of only four metals to have such codes, the others being gold, silver and platinum.
Catalysis
When it is finely divided, such as in palladium on carbon, palladium forms a versatile catalyst and speeds up hydrogenation and dehydrogenation reactions, as well as in petroleum cracking. A large number of carbon-carbon bond forming reactions in organic chemistry (such as the Heck and Suzuki coupling) are facilitated by catalysis with palladium compounds. In addition palladium, when dispersed on conductive materials, proves to be an excellent electrocatalyst for oxidation of primary alcohols in alkaline media. In 2010, palladium-catalysed organic reactions were recognised by the Nobel Prize in Chemistry. Palladium is also a versatile metal for homogeneous catalysis. It is used in combination with a broad variety of ligands for highly selective chemical transformations. A 2008 study showed that palladium is an effective catalyst for making carbon-fluoride bonds. Palladium is found in the Lindlar catalyst, also called Lindlar's Palladium.
Electronics
The second biggest application of palladium in electronics is making the multilayer ceramic capacitor. Palladium (and palladium-silver alloys) are used as electrodes in multi-layer ceramic capacitors. Palladium (sometimes alloyed with nickel) is used in connector platings in consumer electronics.
It is also used in plating of electronic components and in soldering materials. The electronic sector consumed 1.07 million troy ounces (33.2 tonnes) of palladium in 2006, according to a Johnson Matthey report.
Technology
Hydrogen easily diffuses through heated palladium; thus, it provides a means of purifying the gas. Membrane reactors with Pd membranes are therefore used for the production of high purity hydrogen. Palladium is a part of the palladium-hydrogen electrode in electrochemical studies. Palladium(II) chloride can oxidize large amounts of carbon monoxide gas, and is used in carbon monoxide detectors.
Hydrogen storage
Palladium hydride is metallic palladium that contains a substantial quantity of hydrogen within its crystal lattice. At room temperature and atmospheric pressure, palladium can absorb up to 900 times its own volume of hydrogen in a reversible process. This property has been investigated because hydrogen storage is of such interest and a better understanding of what happens at the molecular level could give clues to designing improved metal hydrides. A palladium based store, however, would be prohibitively expensive due to the cost of the metal.
Jewelry
Palladium itself has been used as a precious metal in jewelry since 1939, as an alternative to platinum for making white gold. This use resulted in the naturally white color of palladium which required no rhodium plating. Palladium is proportionally much lighter than platinum. Similar to gold, palladium can be beaten into a thin leaf form as thin as 100 nm (1/250,000 in). Unlike platinum, palladium may discolor upon heating to above 400 °C; it is relatively brittle and reacts with strong acids such as nitric acid.
Palladium is one of the three most popular metals used to make white gold alloys (nickel and silver can also be used). Palladium-gold is a more expensive alloy than nickel-gold, but seldom causes allergic reactions (though certain cross-allergies with nickel may occur).
When platinum was declared a strategic government resource during World War II, many jewelry bands were made out of palladium. As recently as September 2001, palladium was more expensive than platinum and rarely used in jewelry also due to the technical obstacle of casting. However the casting problem has been resolved and its use in jewelry has increased because of a large spike in the price of platinum and a drop in the price of palladium.
Prior to 2004, the principal use of palladium in jewelry was the manufacture of white gold. In early 2004, when gold and platinum prices rose steeply, China began fabricating significant volumes of palladium jewelry and used 37 tonnes of palladium for this purpose in 2005. Changes of the relative price between palladium and platinum after 2008 lowered demand for palladium to 17.4 tonnes in 2009.
Photography
With the platinotype printing process photographers make fine-art black-and-white prints using platinum or palladium salts. Often used with platinum, palladium provides an alternative to silver.