The discovery of palladium and its early uses
Palladium is one of the rarest and most valuable metals on the planet – it’s 30 times more scarce than gold. The history of this metal begins in 1802, when English chemist William Hyde Wollaston discovered a new substance while dissolving platinum in a mixture of nitric and hydrochloric acids. Initially, Wollaston was reluctant to announce his discovery to the public, preferring to sell the metal to private buyers as ‘new silver’. It was only after other scientists began to claim that palladium was simply an alloy of existing metals that Wollaston was forced to present his findings to the Royal Society of London.
The metal was named after the asteroid Pallas, which was discovered around the same time. Initially, palladium was used to treat tuberculosis, but this practice had to be abandoned because of side effects. Palladium began to be used in jewellery in 1939, most often as a component of white gold. Thanks to its anticorrosive properties and attractive silvery-white colour, it quickly gained popularity among high-end jewellers.
It wasn’t until the late 1980s, however, that the application of palladium was widely adopted. This was the result of the tightening of environmental standards in the automobile industry, when the introduction of new emissions standards in the US, Europe and Japan required the mass rollout of catalytic converters. Here, palladium proved to be a vital component.
Physical and chemical properties
Palladium has a unique set of properties that make it indispensable in numerous modern technologies. It is a ductile, silvery-white metal that is 12.6% harder than platinum, ensuring high wear resistance. Palladium is also ductile enough that it can be produced in sheets measuring 4 microns thick, which makes it suitable for use in hydrogen fuel cells, hydrogen purification and other high-tech applications.
One of palladium’s most remarkable properties is its ability to absorb as much as 900 times its own volume in hydrogen. This makes it vital in hydrogen purification processes and hydrogen energy. Additionally, palladium has high resistance to chemical corrosion and excellent electrical conductivity.
Key uses for palladium
Automotive industry
Historically, the automotive industry has been the largest consumer of palladium. Catalytic converters, which convert toxic exhaust gases into less harmful substances, use 2–7 grams of the metal. It is worth noting, however, that the development of electric vehicles could ultimately change palladium’s role in the automotive industry significantly. Since electric vehicles do not need catalytic converters, demand for palladium from automakers may decrease in the long term. This creates certain challenges for palladium producers, while incentivising the search for new applications for the metal.
Water purification and wastewater treatment
Palladium opens the door to more efficient and environmentally friendly water purification technologies. Unlike the traditional method of disinfecting water with chlorine, which requires the storage of large volumes of hazardous chemicals, palladium-based technologies allow disinfectants to be produced directly at the point of use.
The process is based on the electrolysis of common table salt, with a palladium catalyst ensuring high reaction efficiency. The catalytic system requires just 0.6 milligrams of palladium per unit, which makes the technology economically viable even taking into account the high cost of the metal. These units are not only safer to operate, but also allow for higher levels of water purification with lower cost inputs.
Hydrogen energy
Against the backdrop of the global transition to clean energy, palladium is playing a key role in the development of hydrogen energy. It is deployed across the entire cycle of hydrogen production and use, from water electrolysis to the purification of the resulting gas and its storage.
Palladium is used as an electrode component and a catalyst for the hydrogen evolution reaction in the production of ‘green’ hydrogen. Palladium membranes play a special role, possessing a unique ability to let only hydrogen molecules pass through them, thus ensuring a very high level of purification. These membranes are capable of operating at high temperatures and pressures, maintaining stability and efficiency for long periods.
Palladium membranes are already being implemented in a number of large-scale projects. For example, the British company Johnson Matthey has developed and implemented a technology for catalytic membranes that are used to produce clean hydrogen through water electrolysis. These catalyst-coated membranes are used in electrolysers and are key components in the production of ‘green’ hydrogen that avoids harmful emissions. This technology can contribute to the decarbonisation of various industries, including transport and heavy industry.
Mitsubishi Heavy Industries is dedicating significant resources to the development of hydrogen energy technologies, including solid-state electrolysis cells and anode exchange membranes, which are used to generate hydrogen for fuel cells. These technologies allow for the efficient production of hydrogen, which can be used as a clean energy source. Russia's Nornickel, meanwhile, is investing heavily in the development of palladium membranes, with a focus on increasing their service life and efficiency.
Solar power
The latest research has been positive when it comes to potential applications for palladium in solar power. A newly synthesised compound of palladium and selenium has demonstrated unique photoelectric properties. The compound has a higher efficiency when converting light energy into electrical energy compared with traditional materials used in solar panels such as copper, indium and selenium.
Although this technology is still in its fundamental research stage, scientists are already studying a number of its aspects, including the chemical stability of the new synthesised compound and how its properties change depending on particle size and layer thickness. It is expected that a prototype of a new active element for solar panels using palladium will be developed in the near future.
Chemical industry
Palladium has proven itself as an effective catalyst in the chemical industry, and is used in many processes. It plays a particularly important role in the production of glycolic acid, a substance widely used in the pharmaceutical, cosmetic and textile industries. The traditional method of producing glycolic acid through the oxidation of formaldehyde with nitric acid is environmentally harmful. With palladium catalysts, the more environmentally friendly process of liquid-phase oxidation of ethylene glycol can be used.
Current research is focused on creating new catalytic systems based on palladium and gold nanoparticles on a carbon carrier. Laboratory tests show that these catalysts outperform existing commercial solutions in terms of both activity and selectivity, providing higher yields of the target product.
Global production and the palladium market
Global palladium production is concentrated in a handful of countries. Russia leads the way, producing about 92 tonnes of the metal per year, while South Africa is ranked second with 71 tonnes. Canada (16 tonnes), Zimbabwe (15 tonnes) and the United States (9 tonnes) also make significant contributions to global production.
Palladium prices have historically been highly volatile. The metal fluctuated in the $100–150 per ounce range between 1986 and 1996, and the first significant price jump occurred in 2001. In subsequent years, the price showed significant fluctuations and, as of 2016, it has begun to grow steadily, exceeding $1,500 per ounce in February 2019. In February 2022, the price reached an all-time high of around $3,000 per ounce.
Growth forecasts and new areas of research
Despite the potential reduction in demand from the automotive industry resulting from the development of electric transport, prospects for applications of palladium remain very optimistic. Research is actively underway to create new materials and technologies using palladium in a number of fields:
In hydrogen energy, scientists are working to improve palladium membranes by increasing their service life and efficiency. Particular attention is being paid to the development of new alloys of palladium with other platinum group metals (PGMs) to achieve a synergistic effect from their catalytic properties.
In water purification, research is aimed at optimising the composition of catalytic coatings to increase activity and reduce the amount of palladium required. New methods for applying palladium to electrodes are being developed to ensure better adhesion and a longer service life for the coatings.
In solar energy, new palladium compounds that can convert light energy into electrical energy more efficiently are being studied. Researchers are working to optimise the structure and composition of these compounds in order to achieve the maximum possible energy conversion efficiency.
Conclusion
Despite its high cost, palladium remains one of the most important metals for the development of new technologies. Its unique properties make it indispensable in a number of critical applications, from water purification to clean energy generation. Although the advent of EVs may lead to a decrease in demand from the automotive industry, the emergence of new applications and improvements in existing technologies are creating a sustainable future for this rare metal.
Current research and development efforts are aimed at optimising the use of palladium, which will help to reduce the amounts of the metal required in various applications while maintaining or even improving efficiency. This makes palladium-based technologies more accessible and suitable for widespread implementation, which is of vital importance in the context of the global transition to cleaner and more sustainable technologies.
