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 (O 2 and H 2 ) 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 WO 3 backbone fibrous channel as heteropartner to the primary photoabsorber (Fe 2 O 3 and BiVO 4 ) 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 Fe 2 O 3 /WO 3 and BiVO 4 /WO 3 electrodes. These results were compared with directly coated Fe 2 O 3 and BiVO 4 photoabsorber onto conducting substrate without WO 3 backbone. The optical results showed that the absorbance and visible light activity of Fe 2 O 3 and BiVO 4 is significantly improved by WO 3 backbone fibers due to high amount of photo absorber loading. In addition, one dimensional (1-D) WO 3 fibers beneficially enhance the optical path length to the photoanode through light scattering mechanism. The electrochemical impedance analysis exhibits WO 3 nanofiber backbone reduces charge transfer resistance at Fe 2 O 3 and BiVO 4 by rapid charge collection and charge separation compare to backbone-free Fe 2 O 3 and BiVO 4 . As a result, Fe 2 O 3 /WO 3 and BiVO 4 /WO 3 fibrous hetero interface structures showed fourfold higher photocurrent generation from PEC cell.