Changing the reaction pathway
Reactants generally pass through higher-energy stages before becoming products. A catalyst participates in an alternative sequence with a lower effective barrier and is regenerated during the cycle. Intermediate compounds can form, so regeneration does not mean the catalyst remains chemically uninvolved throughout every individual step.
References: [1]
Rates and equilibrium
At fixed conditions, catalysis changes conversion rates rather than the thermodynamic difference between reactants and products. Forward and reverse processes share the catalytic route, allowing faster equilibration. Industrial yields also depend on operating conditions and product separation, which remain distinct from the rate improvement itself.
References: [1]
Solutions and solid surfaces
Homogeneous catalysis places catalyst and reactants in one phase. Heterogeneous processes often use solid surfaces that adsorb reacting species. Surface sites, adsorption strengths and transport affect measured rates, so materials with the same bulk composition can behave differently when their exposed structures or preparation methods differ.
From industrial practice to surface science
Industrial processes including ammonia synthesis motivated the search for effective, durable catalysts. Surface science investigates adsorption and elementary reaction steps; Ertl’s work was recognized by the 2007 Nobel Prize. Practical selection also considers selectivity, deactivation and regeneration alongside an initially measured reaction rate.