Recent theories in literature invoke electrochemical dissolution/recrystallization mechanisms to explain the loss of the electrochemically active area of Pt nanocrystalline catalysts in polymer electrolyte fuel cells, with some significant discrepancies in experimental observations. This paper reports findings in molecular dynamic (MD) simulations of Pt nanocrystallites in a polymer electrolyte environment. The MD simulations reveal that the Pt nanocrystallites can become unstable and undergo instantaneous disintegration under a mainly electric interaction between charged Pt nanocrystallites and a polarized polymer electrolyte during a charging process. These results also indicate that the instantaneous disintegration of charged Pt nanocrystallites results in temperature rises in the interfacial area.