WO3 nanofibrous backbone scaffolds for enhanced optical absorbance and charge transport in metal oxide (Fe2O3, BiVO4) semiconductor photoanodes towards solar fuel generation

Abstract

Producing clean fuel (O2 and H2) using semiconductors through solar driven water splitting process has been considered as a promising technology to mitigate the existing environmental issues. Unlike the conventional single photoabsorbers, heterostructured semiconductors exhibit the merits of improved solar light photon harvesting and rapid charge separation, which are anticipated to result in high quantum yield of solar fuel generation in photoelectrochemical (PEC) cells. In this report, we demonstrate the electrospun derived WO3 backbone fibrous channel as heteropartner to the primary photoabsorber (Fe2O3 and BiVO4) for promoting the electron transport from charge injection point to charge collector as well as photoholes to the electrolyte. We examine structure, optical, photoelectrochemical and charge transfer property of Fe2O3/WO3 and BiVO4/WO3 electrodes. These results were compared with directly coated Fe2O3 and BiVO4 photoabsorber onto conducting substrate without WO3 backbone. The optical results showed that the absorbance and visible light activity of Fe2O3 and BiVO4 is significantly improved by WO3 backbone fibers due to high amount of photo absorber loading. In addition, one dimensional (1-D) WO3 fibers beneficially enhance the optical path length to the photoanode through light scattering mechanism. The electrochemical impedance analysis exhibits WO3 nanofiber backbone reduces charge transfer resistance at Fe2O3 and BiVO4 by rapid charge collection and charge separation compare to backbone-free Fe2O3 and BiVO4. As a result, Fe2O3/WO3 and BiVO4/WO3 fibrous hetero interface structures showed fourfold higher photocurrent generation from PEC cell.