Fig. 4: Charge lifetime of photocatalysts.

a TRPL spectra of BTO in different etching time evolution processes, from top to bottom: BTO-2, BTO-1, BTO-0.5, BTO-0.25, and BTO. The empty dots represent the decay curves and the straight lines are the corresponding fit curves. b Lifetime evolution with the extended etching time. c Etched depth evolution with the extended etching time.