Anion exchange and successive ionic layer adsorption and reaction-assisted coating of BiVO with BiS to produce nanostructured photoanode for enhanced photoelectrochemical water splitting.

Photoelectrochemical water splitting is an environmentally benign way to store solar energy. Properties such as fast charge recombination and poor charge transport rate severely restrict the use of BiVO as a photoanode for photoelectrochemical water splitting and many attempts were made to improve the current performance limit of the photoanode. To address these disadvantages, a highly efficient BiVO/BiS heterojunction was fabricated applying facial anion-exchange (AE) and successive ionic layer adsorption and reaction (SILAR). The deposition of BiS on BiVO nanoworms by both AE and SILAR was confirmed through morphological, structural, and optical analyses. The morphological analysis indicated that BiS grown through SILAR has relatively more crystalline-amorphous phase boundaries than BiS generated using the anion-exchange method. The highest photocurrent density was observed for the SILAR-coated BiS on BiVO, which is three times the value of the pristine BiVO measured under 1 sun illumination (100 mW cm with Air mass (AM) 1.5 filter) in a 0.5 M NaSO electrolyte at 1.6 V vs. RHE. In addition, the deposition of BiS through AE results in a twofold higher photocurrent density compared to uncoated BiVO. The comparison of the two cost-effective AE and SILAR methods to deposit BiS on BiVO showed a negative shift in the flat band Mott-Schottky values, which coincides with the drifted onset potential values of the current density-voltage (J-V) curve. Furthermore, photoelectrochemical impedance spectroscopy (PEIS) analyses and band alignment studies revealed that SILAR-grown BiS creates an effective heterojunction with BiVO, which leads to an efficient charge transfer.