A tree-like nanoporous WO3 photoanode with enhanced charge transport efficiency for photoelectrochemical water oxidation

Abstract

We report a tree-like nanoporous tungsten trioxide (WO₃) photoanode that largely improves the photoelectrochemical water oxidation performance. These novel WO₃ photoanodes were prepared using a pulsed laser deposition method and their porosity was controlled by adjusting the oxygen partial pressure during the deposition process. The tree-like nanoporous WO₃ photoanode has a nanoporous structure with a partially preferred alignment of the individual WO₃ nanocrystals, which greatly improves the charge transport efficiency. Under simulated solar light illumination, the aforementioned features resulted in ∼9 times higher photocurrent density (1.8 mA cm⁻² at 1.23 V vs. RHE) than a dense WO₃ photoanode. An incident photon-to-current conversion efficiency of over 70% was also obtained at wavelengths of 350–400 nm.