Nano- and micro-structural control of WO(3) photoelectrode films through aqueous synthesis of WO(3)·H(2)O and (NH(4))(0.33)WO(3) precursors

Nano- and micro-structured tungsten trioxide (WO(3)) photoelectrode films were prepared through an aqueous solution route. WO(3) precursor layers were deposited on glass substrates through heterogeneous nucleation from (NH(4))(10)W(12)O(41) aqueous solutions at 50–60 °C. The crystal phase of the precursors changed from WO(3)·H(2)O to (NH(4))(0.33)WO(3) with increasing (NH(4))(10)W(12)O(41) concentration (x), which involved a morphological change from micron-scale plates to nano-scale fine particles. The WO(3)·H(2)O and (NH(4))(0.33)WO(3) layers were thermally converted to the monoclinic WO(3) phase. The fine-particle WO(3) films obtained from (NH(4))(0.33)WO(3) 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 WO(3) films were obtained from WO(3)·H(2)O layers, which exhibited strong light scattering in the visible range, and resulted in an enhanced photoanodic response at wavelengths above 375 nm.