Improving charge transfer in phosphate ion-modified hematite photoanode via decoration with gold nanostructures

Herein, we report a unique synergistic behavior between the phosphate ions (Pi) layer and the plasmonic gold nanostructures to enhance the PEC performance of the hematite photoanode. Under such a combined effect, the lifetime of the photogenerated holes is enhanced by a factor of 3-fold relative to that of pristine hematite. The Au/Pi–hematite photoanode illustrates a stable photocurrent of 1.32 mA cm^–2 at 1.23 V_RHE under standard illumination conditions, which is 3.1, 2.1, and 1.7 times higher than those of pristine hematite, Au/hematite, and Pi–modified hematite photoanodes, respectively. The enhanced photocurrent of Au/Pi–hematite is attributed to the improved hole lifetime and charge transfer kinetics as confirmed by transient photocurrent (TPC), photoelectrochemical impedance spectroscopy (PEIS), and intensity-modulated photocurrent spectroscopy (IMPS) measurements. Au nanostructures have a dual function. They enhance the light absorption ability and more importantly improve the charge transfer efficiency.