Nanoparticles are particles in the size range of 1–100 nm, consisting of just a few atoms or molecules. They are characterized by their altered physical and chemical properties, which differ significantly from those of macroscopic materials. In catalysis, nanoparticles are often produced from precious metals such as platinum, palladium, gold, or ruthenium and distributed onto support materials such as oxides, carbons, or zeolites.

A key advantage of nanoparticles lies in their high surface-to-volume ratio (A/V ratio), which increases significantly with decreasing particle size. Since heterogeneous catalytic reactions take place on the surface of a catalyst, smaller particles allow for more efficient use of expensive precious metals. This results in consistent or even improved catalytic performance with a reduced amount of material.

Gold nanoparticles are a well-known example of nanocatalysts. They are widely used in the catalysis of oxidation reactions, such as the conversion of carbon monoxide (CO) to carbon dioxide (CO₂). This reaction, which is particularly important in exhaust gas purification, illustrates the high activity of gold nanoparticles, especially at low temperatures. Another example is palladium nanoparticles, which are used in the hydrogenation of hydrocarbons. This process for the production of bio-based fuels converts unsaturated hydrocarbons (e.g., ethylene) into saturated alkanes (e.g., ethane). Palladium nanoparticles are distinguished by their high selectivity and efficiency, making them one of the most important catalysts in the petrochemical industry.