Fe/W Co-Doped BiVO4 Photoanodes with a Metal-Organic Framework Cocatalyst for Improved Photoelectrochemical Stability and Activity

Abstract

BiVO₄ has been identified as one of the excellent visible light responsive photoanodes for use in photoelectrochemical (PEC) water splitting. However, pristine BiVO₄ usually exhibits relative low photocatalytic properties owing to insufficient charge separation and transport characteristics. Although the marginal n-type doping of higher valence ions can obviously raise the photocurrent value, it by no means improves the PEC stability. In this work, we successfully enhanced the PEC stability of BiVO₄ by doping Fe ions in substitution of Bi. Density functional theory calculations have illustrated that Fe-doping would result in an impurity band in the forbidden gap, and thus narrow its energy gap. More importantly, Fe-doping can synergize with other means to further improve the PEC activities of BiVO₄ . Therefore, we fabricated a nanoporous Fe/W co-doped BiVO₄ photoelectrode, and then loaded the metal-organic framework (MOF) MIL-100(Fe) as cocatalyst to further promote the separation of charge carriers. To the best of our knowledge, MOFs have not yet been utilized as a cocatalyst to facilitate the charge separation, which could increase the photocurrent density of Fe/W co-doped BiVO₄ .

Keywords: charge separation; cocatalyst; iron; metal-organic framework; stability.