Nanoparticles are particles in the size range of 1–100 nm that consist of 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 made from precious metals such as platinum, palladium, gold or ruthenium and distributed on carrier materials such as oxides, carbons or zeolites.

A key advantage of nanoparticles is their high surface-to-volume ratio (A/V ratio), which increases sharply with decreasing particle size. Since heterogeneous catalytic reactions take place on the surface of a catalyst, smaller particles enable more efficient use of expensive precious metals. This leads to consistent or even increased 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, for example in 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 impress with their high selectivity and efficiency, which makes them one of the most important catalysts in the petrochemical industry.