Nanostructured hematite photoanodes have been intensively studied in photoelectrochemical (PEC) water splitting for sustainable hydrogen production. Whereas many previous efforts have been focused on doping elements in nanostructured hematite (α-Fe(2)O(3)), we herein demonstrated an alternative approach to enhance the PEC performance by exploiting intrinsic nanostructuring properties of hematite. We found that the introduction of lattice defects effectively decreased the flatband potential and increased the charge transport mobility of nanostructured hematite, hence enhance the light harvest for more efficient hydrogen production via PEC. The nanostructured hematite photoanodes with lattice defects yielded water-splitting photocurrent density of 1.2 mA/cm(2) at 1.6 V vs reversible hydrogen electrode (RHE), which excelled defect-free ones by approximately 1.5 folds. This study thus provides a new strategy for finely tuning properties of nanostructured hematite photoanodes and enhancing the water-splitting ability of PEC.