Extended Data Fig. 6. Optical and electronic properties and photocatalytic hydrogen evolution activity.
a, EPR studies showed a single Lorentzian line centred at a g value of 2.006 for RC-COF-1, which intensified dramatically upon light excitation, suggesting an effective light-induced charge carrier generation, whereas DP-COF-1 displayed much lower signal intensity under same test conditions. b, Transient photocurrents with on-off light intermittent irradiation (λ > 420 nm) for RC-COF-1, DP-COF-1 and Urea-COF-1, conducted with a bias potential of – 0.35 V vs Ag/AgCl. RC-COF-1 produced an enhanced photocurrent compared to its semi-crystalline counterpart, DP-COF-1, indicating more efficient separation of photogenerated charge carriers. c, Time courses of sacrificial photocatalytic hydrogen production for RC-COF-1, FS-COF, DP-COF-1, Urea-COF-1 and g-C3N4 (2.5 mg catalyst in water with 3 wt.% Pt loading, λ > 420 nm for RC-COF-1, FS-COF, DP-COF-1 and Urea-COF-1, and λ > 295 nm for g-C3N4). d, Time course of photocatalytic hydrogen evolution for RC-COF-1 from three different synthetic batches under visible light irradiation; inset is corresponding hydrogen evolution rate (HER). There is good batch-to-batch reproducibility in terms of photocatalytic performance for materials prepared by this reconstruction route. e, The external quantum efficiencies (EQEs) of RC-COF-1 were estimated to be 6.39% at 420 nm, 5.92% at 490 nm, 5.20% at 515 nm, and 1.62% at 595 nm, respectively. By comparison, DP-COF-1 exhibited a much-lower EQEs of 1.97%, 1.61%, 1.37%, and 0.54% at the same wavelengths. f, Long-term photocatalytic hydrogen evolution stability test for RC-COF-1 over 60 h under visible light (λ > 420 nm). The dashed vertical lines denote degassing and addition of a further 1.25 mmol of ascorbic acid. No obvious decrease in activity was observed during this 60-h period.