The mechanism of deactivation and regeneration of the Pt/b-TiO₂ NFs photocatalyst in photocatalytic pure water splitting was studied systematically. The photocatalyst is deactivated due to the accumulation of product H₂ inhibits the forward reaction and gradual substitution of H₂O₂ for H₂O in the absorption site on the Pt/b-TiO₂ NFs surface. Timely removal of H₂ allows the photocatalysts to operate stably for more than 500 h. And the H₂O₂ can be desorbed by bubbling with Ar gas at 120 ℃.