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[Display omitted] • Quantitative assessment of electron and hole transfer dynamics at anatase nanocrystalline TiO 2 / water interface. • TiO 2 conduction band electron, trapped electron and trapped hole absorption spectra were derived by comparing TA spectra. • Water reduction occurs with two single exponential components with difference in time scale of 6∼7 orders of magnitudes. • Water oxidation: Water oxidation reactions occur multi-exponentially in 25 ns to 200 ms. • Pt nanoparticle on the TiO 2 surface catalyses both water reduction and oxidation reaction. Quantitative assessments of electron and hole transfer dynamics with water on anatase nanocrystalline TiO 2 films were conducted by employing a series of transient absorption spectrometers. For water reduction reactions, both conduction band and trapped electrons decay with two different single exponential components with the difference in time scale of 6∼7 orders of magnitudes. The faster reaction occurs in 8–16 ns, while the slower component shows a lifetime of 0.1∼1.4 s. Pt nanoparticle deposition on the TiO 2 surface switches the slower single exponential reaction to a stretched exponential with an accelerated half lifetime of 2–7 ms, indicating that this slower reaction is limited by the electron trapping-detrapping movements inside the TiO 2. Water oxidation reactions occur multi-exponentially from 100 ns to 200 ms with a half lifetime of 10 μs. Pt on the TiO 2 surface catalyses water oxidation, occurring from 25 ns with a half lifetime of 8 μs. [ABSTRACT FROM AUTHOR]