Nanostructured WO3 /BiVO4 photoanodes for efficient photoelectrochemical water splitting

Abstract

Nanostructured photoanodes based on well-separated and vertically oriented WO3 nanorods capped with extremely thin BiVO4 absorber layers are fabricated by the combination of Glancing Angle Deposition and normal physical sputtering techniques. The optimized WO3 -NRs/BiVO4 photoanode modified with Co-Pi oxygen evolution co-catalyst shows remarkably stable photocurrents of 3.2 and 5.1 mA/cm(2) at 1.23 V versus a reversible hydrogen electrode in a stable Na2 SO4 electrolyte under simulated solar light at the standard 1 Sun and concentrated 2 Suns illumination, respectively. The photocurrent enhancement is attributed to the faster charge separation in the electronically thin BiVO4 layer and significantly reduced charge recombination. The enhanced light trapping in the nanostructured WO3 -NRs/BiVO4 photoanode effectively increases the optical thickness of the BiVO4 layer and results in efficient absorption of the incident light.

Keywords: BiVO4; WO3; glancing angle deposition; nanorods; photocatalytic water splitting.