First, the agglomeration and growth of Pt particles means that Pt nanoparticles often agglomerate into large particles due to their high surface energy relative to large particles. The strength of attraction between molecules depends on the substrate's surface energy, with higher surface energy meaning a stronger molecular attraction and low surface energy meaning a weaker attractive force. Therefore, as Pt nanoparticles have higher surface energy relative to large particles, they will attract each other and agglomerate into larger particles, which reduces the active area and the catalyst's efficiency. This process is called Ostwald ripening, a process through which a larger particle grows at the expense of nanoparticles. Ostwald ripening begins as smaller platinum particles dissolve through the Nafion ionomer phase. Smaller Pt nanoparticles will dissolve into the electrolyte and migrate to neighboring larger particles, releasing platinum ions into the surrounding environment. These platinum ions will then be redeposited onto larger platinum particles due to the relative molecular force between the larger and smaller particles, causing the particle size to grow. Over time, the particle agglomeration of particles will result in less surface area, contributing to the degradation of the platinum catalyst over long periods and impacting the stability and efficiency of the fuel cell ; the speed of this process depends on how much the catalyst is degrading. The time scale of this phenomenon is based on the time scale of the whole catalyst.