Extremely rapid high temperature annealing (ER-HTA) was used to boost the photoelectrochemical (PEC) performance of hematite thin film deposited on a TiO2 nanosheet-modified SnO2:F substrate (FTO-TN-HM). The PEC performance of FTO-TN-HM photoanodes were strongly enhanced with increasing ER-HTA temperatures from 700 to 820 degrees C with a holding time as short as 30 s. The photocurrent density of FTO-TN-HM photoanode treated by ER-HTA at 800 degrees C was 0.49 mA cm(-2) and interfacial hole transfer efficiency of 32% was achieved at 1.23 V vs. RHE, which were 18.8 and 16 times as great as FTO-TN-HM photoanodes annealed at 500 degrees C for 30 min, respectively. The effect of ER-HTA on the PEC performance of FTO-TN-HM photoanodes were studied comparatively, which suggested that the improved crystallinity, decreased recombination through surface states, and enhanced interfacial Ti4+ diffusion all contributed to their advanced PEC performance. Our studies confirm that the ER-HTA treatment is an effective method to improve the PEC properties of hematite photoanodes with TiO2 underlayer and might be applicable for other semiconducting photoelectrodes to get better PEC performance. (C) 2017 Elsevier B.V. All rights reserved.