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

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 similar to 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.