Gibbs free energy (ΔG) is a key indicator of the spontaneity of a reaction. In catalysis, a catalyst does not alter the ΔG of a reaction but lowers the activation energy, making the reaction proceed faster. If ΔG is negative, the reaction is spontaneous. However, even non-spontaneous reactions (positive ΔG) can proceed with the help of a catalyst if coupled with a more favorable reaction.
