A catalyst is a substance that can be added to a reaction to speed up the process without being consumed by it. Catalysts usually work by lowering the activation energy or modifying the mechanism of a process. They usually work by reducing the energy of the transition state, lowering the activation energy, and/or altering the reaction process. The nature (and energy) of the transition state is likewise altered.
In the chemical and related sectors, catalytic reactions are ubiquitous. A homogeneous or heterogeneous catalyst that provides a different reaction route with lower activation energy and greater selectivity control can have a significant impact on process viability and economics.