Editing Palladium (section)

==Applications==
[[File:Aufgeschnittener Metall Katalysator für ein Auto.jpg|thumb|[[Multiview orthographic projection|Cross-section]] of a [[Catalytic converter|metal-core catalytic converter]]]]
[[File:25 rubles palladium 1989 Ivan III.jpg|thumb|The Soviet 25-rouble commemorative [[palladium coin]] is a rare example of the monetary usage of palladium.]]
The largest use of palladium today is in catalytic converters.<ref name="unctad" /> Palladium is also used in jewellery, [[dentistry]],<ref name="unctad" /><ref>{{cite journal |journal=Platinum Metals Review |title=Palladium in Restorative Dentistry: Superior Physical Properties make Palladium an Ideal Dental Metal |first=Roy |last=Rushforth |volume=48 |issue=1 |date=2004 |doi=10.1595/003214004X4813031 |doi-access=free}}</ref> [[watch]] making, blood sugar test strips, aircraft [[spark plug]]s, [[surgical instrument]]s, and [[electrical contact]]s.<ref>{{cite book |title=Jewelrymaking through history: an encyclopedia |first=Rayner W. |last=Hesse |publisher=Greenwood Publishing Group |date=2007 |page=146 |chapter-url=https://books.google.com/books?id=DIWEi5Hg93gC&pg=PA146 |chapter=palladium |isbn=978-0-313-33507-5}}</ref> Palladium is also used to make some professional [[transverse flute|transverse (concert or classical) flutes]].<ref>{{cite book |title=The flute book: a complete guide for students and performers |first=Nancy |last=Toff |publisher=Oxford University Press |date=1996 |page=20 |isbn=978-0-19-510502-5 |url=https://books.google.com/books?id=pCSanDD4CtsC&pg=PA20}}</ref> As a commodity, palladium [[bullion]] has [[ISO currency code]]s of XPD and 964. Palladium is one of only four metals to have such codes, the others being [[gold]], [[silver]] and platinum.<ref>{{cite book |chapter-url=https://books.google.com/books?id=2neeMTPKtEMC&pg=PA34 |chapter=Precious Metals |page=34 |title=Foreign exchange: a practical guide to the FX markets |isbn=978-0-471-73203-7 |author=Weithers, Timothy Martin |date=2006 |publisher=Wiley}}</ref> Because it [[adsorbs]] hydrogen, palladium was a key component of the controversial [[cold fusion]] experiments of the late 1980s.<ref>{{cite journal |last=Fleischmann |first=M |author2=Pons S |author3=Hawkins M |author-link=Martin Fleischmann |title=Electrochemically induced nuclear fusion of deuterium |journal=[[J. Electroanal. Chem.]] |year=1989 |volume=261 |pages=301 |doi=10.1016/0022-0728(89)80006-3 |issue=2}}</ref>

===Catalysis===
{{See also|Palladium-catalyzed coupling reactions}}
When it is finely divided, as with [[palladium on carbon]], palladium forms a versatile [[catalyst]]; it speeds [[Heterogeneous catalysis|heterogeneous]] catalytic processes like [[hydrogenation]], [[dehydrogenation]], and [[petroleum cracking]]. Palladium is also essential to the [[Lindlar catalyst]], also called Lindlar's Palladium.<ref>{{cite book |chapter-url=https://books.google.com/books?id=mTHQB7MkUFsC&pg=PA270 |title=Organic chemistry |author1=Brown, William Henry |author2=Foote, Christopher S |author2-link=Christopher Spencer Foote |author3=Iverson, Brent L |date=2009 |publisher=[[Cengage Learning]] |isbn=978-0-495-38857-9 |page=270 |chapter=Catalytic reduction}}</ref> A large number of [[carbon–carbon bond]]ing reactions in [[organic chemistry]] are facilitated by palladium compound catalysts. For example:
* [[Heck reaction]]
* [[Suzuki coupling]]
* [[Tsuji–Trost reaction|Tsuji-Trost reactions]]
* [[Wacker process]]
* [[Negishi reaction]]
* [[Stille coupling]]
* [[Sonogashira coupling]]

When dispersed on conductive materials, palladium is an excellent electrocatalyst for oxidation of primary alcohols in alkaline media.<ref>{{cite book |page=90 |url=https://books.google.com/books?id=RDT0OUdlj0MC&pg=PA90 |title=Palladium reagents and catalysts: new perspectives for the 21st century |first=Jiro |last=Tsuji |publisher=John Wiley and Sons |date=2004 |isbn=978-0-470-85032-9}}</ref> Palladium is also a versatile metal for [[homogeneous catalysis]], used in combination with a broad variety of [[ligand]]s for highly selective chemical transformations.

In 2010 the [[Nobel Prize in Chemistry]] was awarded "for palladium-catalyzed cross couplings in organic synthesis" to [[Richard F. Heck]], [[Ei-ichi Negishi]] and [[Akira Suzuki]]. A 2008 study showed that palladium is an effective catalyst for [[carbon–fluorine bonds]].<ref>{{cite journal |journal=[[Chemical & Engineering News]] |volume=86 |issue=35 |date=2008 |title=Palladium's Hidden Talent |pages=53–56 |first=Carmen |last=Drahl |doi=10.1021/cen-v086n035.p053}}</ref>
[[File:Kumada Catalytic Cycle.png|thumb|upright=1.8|Catalytic cycle for Kumada cross coupling reaction, which is widely used in the synthesis of fine chemicals]]

Palladium catalysis is primarily employed in organic chemistry and industrial applications, although its use is growing as a tool for [[synthetic biology]]; in 2017, effective ''in vivo'' catalytic activity of palladium [[nanoparticles]] was demonstrated in mammals to treat disease.<ref name="pmid28699627">{{cite journal |doi=10.1038/ncomms15906 |pmid=28699627 |pmc=5510178 |title=Nano-palladium is a cellular catalyst for in vivo chemistry |journal=[[Nature Communications]] |volume=8 |pages=15906 |year=2017 |last1=Miller |first1=Miles A |last2=Askevold |first2=Bjorn |last3=Mikula |first3=Hannes |last4=Kohler |first4=Rainer H |last5=Pirovich |first5=David |last6=Weissleder |first6=Ralph |bibcode=2017NatCo...815906M}}</ref>

Palladium is also used as a catalyst in the production of [[biofuels]].<ref>{{Cite web |date=2017-08-29 |title=Biofuel production boost from catalyst made from palladium and bacteria |url=https://www.theengineer.co.uk/content/news/biofuel-production-boost-from-catalyst-made-from-palladium-and-bacteria/ |access-date=2025-05-01 |website=The Engineer |language=en}}</ref>

===Electronics===
The primary application of palladium in electronics is in [[multi-layer ceramic capacitor]]s<ref>{{cite web |url=http://www.ttiinc.com/object/ME_Zogbi_20030203.html |title=Shifting Supply and Demand for Palladium in MLCCs |first=Dennis |last=Zogbi |date=3 February 2003 |publisher=TTI, Inc.}}</ref> in which palladium (and palladium-silver alloy) is used for electrodes.<ref name="unctad" /> Palladium (sometimes alloyed with nickel) is or can be used for component and connector plating in consumer electronics<ref>{{cite book |author=Mroczkowski, Robert S. |title=Electronic connector handbook: theory and applications |url=https://books.google.com/books?id=XGkw8YR-uXsC&pg=SA3-PA30 |date=1998 |publisher=McGraw-Hill Professional |isbn=978-0-07-041401-3 |pages=3–}}</ref><ref>{{cite book |author=Harper, Charles A. |title=Passive electronic component handbook |url=https://books.google.com/books?id=OtlKBAcFBQAC&pg=PA580 |date=1997 |publisher=McGraw-Hill Professional |isbn=978-0-07-026698-8 |pages=580–}}</ref> and in soldering materials. The electronic sector consumed {{convert|1.07|e6ozt|t|abbr=off|order=flip}} of palladium in 2006, according to a [[Johnson Matthey]] report.<ref name="matthey">{{cite web |date=2007 |publisher=[[Johnson Matthey]] |title=Platinum 2007 |url=http://www.platinum.matthey.com/uploaded_files/2007/07_palladium.pdf |first=David |last=Jollie |archive-url=https://web.archive.org/web/20080216100834/http://www.platinum.matthey.com/uploaded_files/2007/07_palladium.pdf |archive-date=2008-02-16}}</ref> Palladium is used in the production of [[printed circuit boards]].<ref>{{Cite journal |last=Bourgeois |first=Damien |last2=Lacanau |first2=Valentin |last3=Mastretta |first3=Régis |last4=Contino-Pépin |first4=Christiane |last5=Meyer |first5=Daniel |date=2020 |title=A simple process for the recovery of palladium from wastes of printed circuit boards |url=https://hal.umontpellier.fr/hal-03365417v1 |journal=Hydrometallurgy |language=en |volume=191 |pages=105241 |doi=10.1016/j.hydromet.2019.105241}}</ref>

===Technology===
Hydrogen easily diffuses through heated palladium,<ref name="CRC" /> and [[membrane reactor]]s with Pd membranes are used in the production of high purity hydrogen.<ref>{{cite journal |last1=Shu |first1=J. |last2=Grandjean |first2=B. P. A. |last3=Neste |first3=A. Van |last4=Kaliaguine |first4=S. |title=Catalytic palladium-based membrane reactors: A review |journal=The Canadian Journal of Chemical Engineering |volume=69 |pages=1036 |date=1991 |doi=10.1002/cjce.5450690503 |issue=5}}</ref> Palladium is used in [[palladium-hydrogen electrode]]s in electrochemical studies. [[Palladium(II) chloride]] readily catalyzes carbon monoxide gas to carbon dioxide and is useful in [[carbon monoxide detector]]s.<ref>{{cite journal |last1=Allen |first1=T. H. |last2=Root |first2=W. S. |title=An improved palladium chloride method for the determination of carbon monoxide in blood |url=http://www.jbc.org/content/216/1/319.short |journal=The Journal of Biological Chemistry |volume=216 |issue=1 |pages=319–323 |date=1955 |doi=10.1016/S0021-9258(19)52308-0 |pmid=13252031 |doi-access=free}}</ref>

Palladium has been used to produce [[metallic glass]] by fast cooling alloys, avoiding their crystallisation, thus reducing brittleness and leading to stronger materials.<ref>{{Cite press release |title=Glass that’s Stronger than Steel |url=https://www.technologyreview.com/2011/01/11/197657/glass-thats-stronger-than-steel |language=en |access-date=2025-05-05 |website=[[MIT Technology Review]]}}</ref>

===Hydrogen storage===
{{Main|Palladium hydride}}
Palladium readily [[adsorbs]] hydrogen at room temperatures, forming [[palladium hydride]] PdH<sub>x</sub> with x less than 1.<ref>{{cite journal |doi=10.1007/BF02667685 |title=The H-Pd (hydrogen-palladium) System |date=1994 |last1=Manchester |first1=F. D. |last2=San-Martin |first2=A. |last3=Pitre |first3=J. M. |journal=Journal of Phase Equilibria |volume=15 |pages=62–83 |s2cid=95343702}}</ref> While this property is common to many transition metals, palladium has a uniquely high absorption capacity and does not lose its ductility until x approaches 1.<ref name="gr">{{Greenwood&Earnshaw|pages=1150–151}}</ref> This property has been investigated in designing an efficient and safe hydrogen fuel storage medium, though palladium itself is currently prohibitively expensive for this purpose.<ref name="grochala">{{cite journal |last1=Grochala |first1=Wojciech |last2=Edwards |first2=Peter P. |title=Thermal Decomposition of the Non-Interstitial Hydrides for the Storage and Production of Hydrogen |journal=Chemical Reviews |volume=104 |issue=3 |pages=1283–316 |year=2004 |pmid=15008624 |doi=10.1021/cr030691s}}</ref> The content of hydrogen in palladium can be linked to [[magnetic susceptibility]], which decreases with the increase of hydrogen and becomes zero for PdH<sub>0.62</sub>. At any higher ratio, the [[solid solution]] becomes [[diamagnetic]].<ref>Mott, N. F. and Jones, H. (1958) ''The Theory of Properties of metals and alloys''. Oxford University Press. {{ISBN|0-486-60456-X}}. p. 200</ref>

Palladium is used for purification of hydrogen on a laboratory<ref>{{Cite book |url=https://www.worldcat.org/oclc/870962388 |title=Handbook of membrane reactors Vol. 1, Fundamental materials science, design and optimisation |date=2013 |publisher=Woodhead Publishing |editor=Angelo Basile |isbn=978-0-85709-414-8 |location=Cambridge, UK |oclc=870962388}}</ref>{{Rp|pages=183–217}} but not industrial scale.<ref>{{cite book |doi=10.1002/14356007.o13_o04 |chapter=Hydrogen, 3. Purification |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2011 |last1=Häussinger |first1=Peter |last2=Lohmüller |first2=Reiner |last3=Watson |first3=Allan M. |isbn=978-3-527-30385-4}}</ref>

=== Medicine ===
Palladium is used in small amounts (about 0.5%) in some alloys of [[dental amalgam]] to decrease corrosion and increase the [[Lustre (mineralogy)#Metallic lustre|metallic lustre]] of the final restoration.<ref>{{cite journal |last1=Colon |first1=Pierre |last2=Pradelle-Plasse |first2=Nelly |last3=Galland |first3=Jacques |title=Evaluation of the long-term corrosion behavior of dental amalgams: influence of palladium addition and particle morphology |journal=Dental Materials |volume=19 |issue=3 |pages=232–9 |year=2003 |pmid=12628436 |doi=10.1016/S0109-5641(02)00035-0}}</ref><ref>{{Citation |title=Chapter 10 - Restorative Materials: Metals |date=2019-01-01 |url=https://www.sciencedirect.com/science/article/pii/B978032347821200010X |work=Craig's Restorative Dental Materials (Fourteenth Edition) |pages=171–208 |editor-last=Sakaguchi |editor-first=Ronald |place=Philadelphia |publisher=Elsevier |doi=10.1016/B978-0-323-47821-2.00010-X |language=en |isbn=978-0-323-47821-2 |access-date=2023-02-11 |editor2-last=Ferracane |editor2-first=Jack |editor3-last=Powers |editor3-first=John}}</ref> Palladium is also used in the production of [[pacemakers]].<ref>{{Cite patent |number=US4514589A |title=Electrode connecting cable for cardiac pacemaker |gdate=1985-04-30 |invent1=Aldinger |invent2=Bischoff |invent3=Keilberth |invent4=Sperner |inventor1-first=Fritz |inventor2-first=Albrecht |inventor3-first=Richard |inventor4-first=Franz |url=https://patents.google.com/patent/US4514589A/en}}</ref>

===Jewellery===
Palladium has been used as a [[precious metal]] in jewellery since 1939 as an alternative to platinum in the alloys called "[[white gold]]", where the naturally white color of palladium does not require [[Plating#Rhodium plating|rhodium plating]]. Palladium, being much less dense than platinum, is similar to gold in that it can be beaten into [[Metal leaf|leaf]] as thin as 100&nbsp;nm ({{frac|1|250,000}}&nbsp;in).<ref name="CRC" /> Unlike platinum, palladium may discolor at temperatures above {{convert|400|C|F}}<ref>{{cite book |first1=Dinesh C. |last1=Gupta |first2=Paul H. |last2=Langer |author3=((ASTM Committee F-1 on Electronics)) |title=Emerging semiconductor technology: a symposium |url=https://books.google.com/books?id=u-a9LvarW-8C&pg=PA273 |date=1987 |publisher=ASTM International |isbn=978-0-8031-0459-4 |pages=273–}}</ref> due to oxidation, making it more brittle and thus less suitable for use in jewellery; to prevent this, palladium intended for jewellery is heated under controlled conditions.<ref>{{Cite web |last=Mann |first=Mark B. |date=2007 |title=950 Palladium: Manufacturing Methods |url=https://www.ganoksin.com/article/950-palladium-manufacturing-methods/}}</ref>

Prior to 2004, the principal use of palladium in jewellery was the manufacture of white gold. Palladium is one of the three most popular alloying metals in white gold ([[nickel]] and silver can also be used).<ref name="unctad">{{cite web |publisher=[[United Nations Conference on Trade and Development]] |url=http://www.unctad.org/infocomm/anglais/palladium/uses.htm |title=Palladium |access-date=5 February 2007 |archive-url=https://web.archive.org/web/20061206003556/http://www.unctad.org/infocomm/anglais/palladium/uses.htm <!--Added by H3llBot--> |archive-date=6 December 2006}}</ref> Palladium-gold is more expensive than nickel-gold, but seldom causes allergic reactions (though certain cross-allergies with nickel may occur).<ref>{{cite journal |last1=Hindsen |first1=M. |last2=Spiren |first2=A. |last3=Bruze |first3=M. |title=Cross-reactivity between nickel and palladium demonstrated by systemic administration of nickel |journal=Contact Dermatitis |volume=53 |issue=1 |pages=2–8 |year=2005 |pmid=15982224 |doi=10.1111/j.0105-1873.2005.00577.x |s2cid=20927683}}</ref>

When platinum became a strategic resource during World War II, many jewellery bands were made out of palladium. Palladium was little used in jewellery because of the technical difficulty of [[Casting (metalworking)|casting]]. With the casting problem resolved<ref>{{cite web |last1=Battaini |first1=Paolo |title=The Working Properties for Jewelry Fabrication Using New Hard 950 Palladium Alloys |url=http://www.santafesymposium.org/2006-santa-fe-symposium-papers/2006-the-working-properties-for-jewellery-fabrication-using-new-hard-950-palladium-alloys |website=SANTA FE SYMPOSIUM PAPERS |date=2006}}</ref> the use of palladium in jewellery increased, originally because platinum increased in price whilst the price of palladium decreased.<ref name="wsj">{{cite news |last=Holmes |first=E. |title=Palladium, Platinum's Cheaper Sister, Makes a Bid for Love |publisher=[[The Wall Street Journal]] (Eastern edition) |date=13 February 2007 |pages=B.1}}</ref> In early 2004, when gold and platinum prices rose steeply, China began fabricating volumes of palladium jewellery, consuming 37 [[tonne]]s in 2005. Subsequent changes in the relative price of platinum lowered demand for palladium to 17.4 tonnes in 2009.<ref name="USGS09YB">{{cite web |publisher=[[United States Geological Survey]] |date=January 2007 |title=Platinum-Group Metals |work=Mineral Yearbook 2009 |url=http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2009-plati.pdf}}</ref><ref name="USGS06YB">{{cite web |publisher=[[United States Geological Survey]] |date=January 2007 |title=Platinum-Group Metals |work=Mineral Yearbook 2006 |url=http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf}}</ref> Demand for palladium as a catalyst has increased the price of palladium to about 50% higher than that of platinum in January 2019.<ref name="JMM">{{cite web |date=2019 |title=Johnson Matthey Base Prices |url=http://www.platinum.matthey.com/prices/price-tables |access-date=7 January 2019}}</ref>

In January 2010, [[hallmark]]s for palladium were introduced by assay offices in the United Kingdom, and hallmarking became mandatory for all jewellery advertising pure or alloyed palladium. Articles can be marked as 500, 950, or 999 parts of palladium per thousand of the alloy.
<!-- Johnson Matthey estimated that in 2004, with the introduction of palladium jewellery in China, demand for palladium for jewellery fabrication was {{convert|920,000|ozt|MT}}, or approximately 14% of the total palladium demand for 2004&nbsp;— an increase of almost {{convert|700,000|ozt|MT}} from the previous year. This growth continued during 2005, with estimated worldwide jewellery demand for palladium of about {{convert|1,400,000|ozt|MT}} 1.4&nbsp;million ounces (44&nbsp;t), or almost 21% of net palladium supply, again with most of the demand centered in China. 37,000&nbsp;kg in 2005 15,500 (2007) 20,200 (2008) 17,400 (2009) -->

[[Fountain pen]] [[nib (pen)|nibs]] made from [[gold]] are sometimes plated with palladium when a silver (rather than gold) appearance is desired. [[Sheaffer]] has used palladium plating for decades, either as an accent on otherwise gold nibs or covering the gold completely.

Palladium is also used by the luxury brand [[Hermès]] as one of the metals plating the hardware on their handbags, the most famous of which is Birkin.

===Photography===
In 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.<ref>{{cite journal |first=Mike |last=Ware |title=Book Review of : Photography in Platinum and Palladium |journal=Platinum Metals Review |volume=49 |issue=4 |pages=190–195 |date=2005 |doi=10.1595/147106705X70291 |doi-access=free}}</ref> But palladium is more inert than the silver used in [[silver bromide]] prints, so such photographs are better archived than conventional prints and convey details more clearly.<ref>{{Cite web |last=McCabe |first=Constance |title=Noble Metals for the Early Modern Era:  Platinum, Silver- Platinum, and Palladium Prints |url=https://www.moma.org/interactives/objectphoto/assets/essays/McCabe.pdf |website=[[MoMA]]}}</ref><ref>{{Cite web |last=Ware |first=Mike |title=The Technical History and Chemistry of Platinum and Palladium Printing |url=https://www.culturalheritage.org/docs/default-source/publications/books/platinum-and-palladium-photographs/46-83_ware_technicalhistorychemistry.pdf |website=Culturalheritage.org}}</ref>
<!--
This is very minimal application and is not widely adopted

===Art===
Palladium leaf is one of several alternatives to [[silver]] leaf used in [[manuscript illumination]]. The use of silver leaf is problematic because it tarnishes quickly, dulling the appearance and requiring constant cleaning. Palladium is a suitable substitute owing to its resistance to tarnishing. [[Aluminium]] leaf is another inexpensive alternative, but aluminium is much more difficult to work than gold or silver and results in less-than-optimal results when employing traditional metal leafing techniques, so palladium leaf is considered the best substitute despite its considerable cost. Platinum leaf may be used to the same effect as silver leaf with similar working properties, but it is not as commercially available on demand in leaf form.<ref>{{cite book |first=Margaret |last=Morgan |title=The Bible of Illuminated Letters |publisher=Barron's Educational Series |isbn=978-0-7641-5820-9 |page=50 |year=2007}}</ref><ref>{{cite web |publisher=[[Theodore Gray]] |title=Palladium Leaf |url=http://www.theodoregray.com/PeriodicTable/Samples/046.6/index.s12.html}}</ref>
-->
<!--

==Research==
===Cold fusion===
{{Main|Cold fusion}}
Palladium plays an important role in the ongoing research into cold-fusion energy.

===Super tough metallic glass===
Research is being done to develop metallic glass as a microalloy featuring palladium, a metal with a high "bulk-to-shear" stiffness ratio that counteracts the intrinsic brittleness of glassy materials. The initial samples of the new metallic glass were microalloys of palladium with [[phosphorous]], [[silicon]] and [[germanium]] that yielded glass rods approximately one millimeter in diameter. Adding [[silver]] to the mix enabled the Cal Tech researchers to expand the thickness of the glass rods to six millimeters.<ref>{{cite news |url=http://www.scientificcomputing.com/news/2011/01/new-glass-stronger-any-known-material |title=New Glass Stronger than Any Known Material |date=2011-01-11}}</ref>

===Alternatives===
[[Pseudo palladium]] (RhAg) is a binary alloy consisting of equal parts of rhodium (atomic number 45) and silver (atomic number 47). This alloy exhibits properties of palladium (atomic number 46).<ref>{{cite journal |last1=Kusada |first1=Kohei |last2=Yamauchi |first2=Miho |last3=Kobayashi |first3=Hirokazu |last4=Kitagawa |first4=Hiroshi |last5=Kubota |first5=Yoshiki |title=Hydrogen-Storage Properties of Solid-Solution Alloys of Immiscible Neighboring Elements with Pd |journal=Journal of the American Chemical Society |volume=132 |issue=45 |pages=15896–8 |year=2010 |pmid=20979361 |doi=10.1021/ja107362z}}</ref>
-->