Enhanced photoelectrochemical water splitting on novel nanoflake WO3 electrodes by dealloying of amorphous Fe-W alloys

Photocorrosion-resistant tungsten trioxide (WO3) nanoflake arrays were synthesized via a new route which involves the dealloying of an electrodeposited Fe-W amorphous alloy and subsequent thermal treatment in air. Cyclic voltammetry measurements were employed to evaluate the surface capacitive characteristics. The interfacial capacitance measurements showed that the specific surface capacitance of the nanoflake WO3 electrode (5900 mu F cm(-2)) is almost twice as large as that of the thermally oxidized plain WO3 electrode (2930 mu F cm(-2)), displaying a dramatic increase in surface area. UV-Vis absorption spectroscopy revealed that the bandgap of the oxide film increased from 2.2 to 2.75 eV by gradually eliminating iron from the Fe-W compounds. The photoelectrochemical (PEC) measurements of the nanoflake WO3 electrode exhibited a significant enhancement of the photocurrent of 2.25 mA cm(-2) (about 2.5-fold higher than that of thermally oxidized plain WO3) at a bias potential of 1.5 V (vs. SCE) under light illumination of 100 mW cm(-2). Mott-Schottky relation analysis demonstrated that the carrier concentration increased by an order of magnitude (3.19 x 10(19) vs. 1.28 x 10(18) cm(-3)), implying that the enhanced PEC water splitting performance should be attributed to the unique nanoflake architecture, which offers improved light harvesting as well as efficient charge transportation.