Abstract
<jats:p>Most advances in heterogeneous catalysis have been achieved by modifying catalysts, whereas the thermodynamic state of the reactant is rarely treated as an independent design variable. Here, we test whether changing only the allotrope of a feedstock—thereby preserving elemental composition while altering chemical potential and bonding topology—can reshape catalytic thermodynamics and kinetics. Ammonia synthesis provides a stringent model because activation of stable N2 remains a persistent catalytic bottleneck. Using density functional theory calculations combined with kinetic analyses, we compare the activation of N2 and metastable N6 on Fe(111) and Ti3C2Tx(0001). N6 changes the reaction landscape in two complementary ways: its stored chemical energy renders ammonia formation substantially more exergonic, while its bonding network opens low-barrier dissociation pathways that are inaccessible to N2. Consequently, adsorbed nitrogen forms rapidly from N6 under ambient conditions, whereas N2 activation remains strongly hindered. By holding elemental composition and catalyst identity fixed, these results isolate reactant metastability as an independent lever that influences both reaction equilibrium and accessible catalytic pathways. This work therefore provides a proof of principle for metastable-allotrope engineering as a strategy complementary to catalyst design.</jats:p>