A time-resolved emission technique was employed to study the photoprotolytic cycle of the 2-naphthol-6,8-disulfonate (2N68DS) photoacid in the presence of a low concentration of a strong HCl acid. We found that an excess of protons in ice has a very large and profound effect on the photoprotolytic cycle. The excess proton reacts with the deprotonated form of the photoacid. An analysis of the experimental data reveals that the proton diffusion constant in ice in the temperature range of 240-270 K is much larger than in the liquid state. Under certain assumptions and approximations, the calculated proton diffusion constant in ice is 10 times larger than in water at 295 K, i.e., DH+ice = 1.2 × 10-3 cm 2/s.