In the context of catalytic hydrogen evolution, the hydrogen-metal binding strength exerts a substantial influence on the elementary steps of the reaction. To illustrate, on Pd catalysts, the rate-limiting step is contingent on the size of the particles. For large nanoparticles, the diffusive combination of H* across the metal surface is rate-limiting, while for subnanometer-sized Pd clusters, both 2H* combination and H2 desorption pose significant challenges . This observation underscores the critical role of the enthalpy of adsorption and desorption processes in determining the overall reaction rate.