Ruthenium

Ruthenium (symbol Ru, atomic number 44) is a rare, silvery-white transition metal belonging to the platinum group elements (PGEs). It is hard, brittle, and chemically inert, resisting oxidation even at high temperatures. Despite being among the rarer elements in the Earth’s crust, ruthenium holds substantial industrial, technological, and economic importance due to its exceptional electrical, catalytic, and chemical properties. It is often used in alloys, electronics, catalysis, and advanced materials that underpin modern technology and manufacturing.

Occurrence and Extraction

Ruthenium is primarily obtained as a by-product of platinum, nickel, and copper refining. It occurs naturally in ores of platinum, iridium, and osmium, and is sometimes found in alluvial deposits. Major producers include Russia, South Africa, Canada, and the United States, with South Africa being the leading source due to its vast platinum-group metal reserves.
Extraction involves multiple chemical steps to separate ruthenium from other PGEs, often using oxidation and precipitation methods. The refined metal is then converted into various forms, including powders, alloys, and compounds, for industrial and commercial use.

Physical and Chemical Characteristics

Ruthenium is extremely hard and has a high melting point of about 2334 °C. It exhibits excellent corrosion resistance, especially against strong acids and atmospheric oxidation. In the chemical sense, ruthenium can exist in several oxidation states (from +1 to +8), allowing it to form diverse compounds with catalytic and electronic applications.
These properties—combined with its conductivity and inertness—make ruthenium invaluable in situations where materials must withstand extreme conditions or function with high precision.

Everyday Applications

Although ruthenium is not commonly visible in daily life, its presence is embedded in many everyday technologies and products through its use in electronics, coatings, and precision devices:

• Electronics and computers: Ruthenium is used to coat electrical contacts and connectors in computers, smartphones, and other electronic devices. It enhances conductivity, prevents corrosion, and prolongs component life.
• Data storage: Thin layers of ruthenium are employed in magnetic hard disk drives to separate recording layers and improve storage density.
• Jewellery and watches: Ruthenium is used as a durable, dark-grey plating material for gold and platinum jewellery, as well as for luxury watch components, providing both aesthetic appeal and scratch resistance.
• Writing instruments: Premium pen nibs and mechanical components may be plated with ruthenium for hardness and corrosion resistance.
• Electrical contacts: In consumer and industrial switches, ruthenium-plated contacts ensure long-term performance and oxidation resistance, especially where sparks or high currents are involved.

These applications illustrate how ruthenium enhances performance, longevity, and precision in everyday electronic and luxury items.

Industrial Applications

Ruthenium’s industrial significance extends across multiple sectors, particularly electronics, catalysis, energy, and advanced materials.

1. Catalysis and Chemical Industry
   • Ruthenium is one of the most versatile industrial catalysts, used in hydrogenation, ammonia synthesis, and fuel cell technologies.
   • It plays a role in the Haber–Bosch process, where it can replace iron catalysts to increase efficiency under specific conditions.
   • Ruthenium dioxide (RuO₂) serves as a catalyst in chlorine production, chemical synthesis, and supercapacitor electrodes.
   • In organic chemistry, ruthenium complexes such as Grubbs’ catalysts are used in olefin metathesis, a key reaction in pharmaceuticals, plastics, and fine chemical manufacturing.
2. Electronics and Semiconductor Industry
   • Ruthenium is used as a platinum substitute in chip manufacturing due to its superior adhesion, conductivity, and oxidation resistance.
   • It forms part of thin-film resistors, integrated circuits, and semiconductor components in advanced electronics.
   • In microchips, ruthenium acts as a diffusion barrier and conductive layer, critical for miniaturised devices.
3. Alloy Production
   • Small amounts of ruthenium (0.1–1%) are added to platinum and palladium alloys to improve hardness and wear resistance.
   • Ruthenium–titanium alloys are used in aerospace and medical components for their durability and biocompatibility.
   • In electrical contacts, ruthenium–platinum alloys are favoured for long-term reliability.
4. Electrochemical Applications
   • Ruthenium dioxide and its mixed oxides are used as coatings for titanium anodes in the chlor-alkali industry to produce chlorine and caustic soda.
   • These dimensionally stable anodes (DSAs) offer excellent conductivity, chemical stability, and long life, reducing maintenance and energy consumption.
5. Energy and Renewable Technologies
   • In fuel cells, ruthenium is used as a catalyst for hydrogen oxidation and oxygen reduction reactions.
   • It also improves the performance of lithium-ion and lithium–air batteries, contributing to higher energy density and longer lifespans.
   • Ruthenium-based solar dyes are used in dye-sensitised solar cells (DSSCs) to enhance light absorption and energy conversion efficiency.

Economic Importance

Ruthenium plays a pivotal role in the global economy through its contributions to high-value, high-tech industries.

• Market value: Ruthenium is one of the more affordable platinum-group metals but remains expensive due to its rarity and extraction costs. Prices fluctuate based on demand from the electronics and catalytic sectors.
• Production scale: Global production averages 30–40 tonnes per year, with the majority derived from South Africa’s PGM mines.
• Economic sectors: Key sectors driving ruthenium demand include electronics (contacts, data storage), chemical catalysis, and energy systems.
• Strategic metal: Ruthenium is classified as a critical raw material due to its scarcity, concentrated supply, and importance to renewable energy and microelectronics.
• Recycling: Used ruthenium catalysts and electronic components are increasingly recycled to ensure sustainable supply, given the metal’s economic and strategic significance.

Environmental and Health Considerations

Ruthenium is generally non-toxic in its metallic form and poses little environmental risk when properly managed. However, some of its compounds—especially volatile oxides and organometallics—can be toxic and carcinogenic if inhaled or ingested.