WO₃ nanorod arrays decorated with isolated Fe active sites for photoelectrocatalytic water oxidation

Herein, a WO₃ nanorod array photoanode is controllably synthesized via a urea-modulated hydrothermal process, after which iron phthalocyanines (FePcs) with tunable Fe centers (H-FePc) are in situ deposited onto the surface of WO₃ nanorods through electrodeposition, followed by a hydrogen reduction treatment. The optimized H-FePc/WO₃ photoanode exhibits a remarkable photocurrent density of 2.44 mA cm^-2 at 1.23 V_RHE while showing robust stability under AM 1.5 G irradiation, which is ∼10-fold enhancement in comparison with that of pristine WO₃ nanorod arrays. The one-dimensional array structure of WO₃ nanorods can enhance light harvesting by virtue of the light trapping effect, provide large surface area for electrolyte penetration and offer a short diffusion path for electrons. Moreover, the modified FePcs considerably facilitate charge transfer and separation by extracting holes to the electrode-electrolyte interface. In addition, the isolated Fe(II)/Fe(0) catalytic sites synergistically expedite water oxidation kinetics. This study offers a feasible route to designing and fabricating high-performance photoanodes for water oxidation.