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

Abstract

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 μF cm⁻²) is almost twice as large as that of the thermally oxidized plain WO₃ electrode (2930 μF 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 × 10¹⁹vs. 1.28 × 10¹⁸ 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.