LAUSR

Nano- and micro-structured tungsten trioxide (WO3) photoelectrode films were prepared through an aqueous solution route. WO3 precursor layers were deposited on glass substrates through heterogeneous nucleation from (NH4)10W12O41 aqueous solutions at 50–60 °C. The crystal phase of the precursors changed from WO3·H2O to (NH4)0.33WO3 with increasing (NH4)10W12O41 concentration (x), which involved a morphological change from micron-scale plates to nano-scale fine particles. The WO3·H2O and (NH4)0.33WO3 layers were thermally converted to the monoclinic WO3 phase. The fine-particle WO3 films obtained from (NH4)0.33WO3 layers showed a better photoanodic performance in the UV range below 350 nm, which was attributed to the larger surface area arising from the porous structure. On the other hand, platy-particle WO3 films were obtained from WO3·H2O layers, which exhibited strong light scattering in the visible range, and resulted in an enhanced photoanodic response at wavelengths above 375 nm.