arises from the surface energy difference owing to more exposed undercoordinated atoms on the surface of small nanoparticles. The detailed process may involve the atomic dissolution from smaller particles into electrolytes and subsequent redeposition of dissolved atoms on larger particles. Similarly, the agglomeration process of nanocatalysts via initial detachment from support and subsequent coalescence with each other would be affected by the size as a consequence of the surface energy difference. Apart from particle size, chemical composition (related to ΔHmig), facet, and curvature will have a strong influence on the free energy change.