Catalysts are not only one of the most influential parts of industrial chemical synthesis, but also play an extremely important role in everyday life. Essentially, catalysts reduce the energy barrier, which needs to be overcome to start a chemical reaction. This makes reactions run at lower temperatures, faster or start easier. The catalysts function by building (multiple) intermediate complexes, making a reaction take a different path, which is lower in energy. [Imagine driving through Switzerland and taking Gotthard tunnel instead driving over the mountain top.] Moreover, catalysts are only used in minimal amounts and recovered after a reaction, making it possible to use expensive materials like platinum in a catalysis complex.

Catalysts can be homogenous i.e., they dissolve in the reaction, or heterogeneous, often in the form of porous solids.

Some of the best-known catalysts are Fe₃O₄ in the Haber Bosch process to make ammonia, platinum in car exhausts or the lactase enzyme breaking down lactose in the human small intestine.

While many catalysts already exist, the quest for more environmentally friendly syntheses and thus more efficient, cheaper catalysts is still very much at the forefront of research. X-ray diffraction is a versatile tool to measure the purity or particle size of catalyst powders or determine the crystal structure of new catalysts. Moreover, high temperature PXRD experiments, for example with the STOE HT2, enable research on intermediate catalyst complexes or following reaction pathways in-situ.