A catalytic decomposition reaction is a transformation in which a single compound is broken into two or more simpler species at a catalyst that lowers the barrier to bond cleavage and is regenerated after the fragments are released. In catalysis and oxidation chemistry the concept is bounded by a net decrease in molecular complexity of one substrate—rather than by a coupling of two different reactants—and by the requirement that the catalyst participate in the cleavage but not appear in the stoichiometric products. Essential features are an adsorption or coordination event that weakens a targeted bond, an elementary scission (homolytic, heterolytic, or redox-coupled), and desorption of the fragments that restores the active site. Efficient catalytic decomposition of formic acid illustrates selective scission of a single substrate at a molecular catalyst, with hydrogen and carbon dioxide as the fragments ^[1]. Catalytic decomposition of hydrogen peroxide at iron oxide surfaces is a related case in which one oxidant is cleaved into simpler products at a regenerated active site ^[2]. The concept is distinguished from catalytic oxidation of a substrate that remains a single molecule of comparable size, and from pyrolysis, in which no catalyst is required.