Effective Formation of WO₃ Nanoparticle/Bi₂S₃ Nanowire Composite for Improved Photoelectrochemical Performance

Abstract

A well-defined WO 3 /Bi 2 S 3 composite comprised of single-crystalline Bi 2 S 3 nanowire (Bi 2 S 3 NW) layers on top of the WO 3 nanoparticles (WO 3 NP) was synthesized via an in situ hydrothermal reaction. The single-crystalline Bi 2 S 3 nanowires were uniformly grown on the surface of the WO 3 nanoparticle layer. This in situ hydrothermal process is also a general route for the synthesis of well-aligned Bi 2 S 3 nanowires on various metal oxide substrates, such as TiO 2 , BiVO 4 , and ZnO. Compared to the sole Bi 2 S 3 electrode, the resulting WO 3 NP/Bi 2 S 3 NW composite showed enhanced photoelectrochemical activity. The origin of this enhanced activity is mainly attributed to the enhancement of charge separation on the Bi 2 S 3 layer, due to the effective photogenerated electron transfer from the Bi 2 S 3 conduction band to that of WO 3 . Furthermore, the single-crystalline longitudinal structure of the Bi 2 S 3 nanowires can provide a direct electrical pathway through a single domain of nanowires.

In Situ Growth of the Bi2S3 Nanowire Array on the Bi2MoO6 Film for an Improved Photoelectrochemical Performance

“…The flat band potential of Bi 2 MoO 6 , estimated using the MS plot was approximately 0.25 V (vs NHE). The conduction band edge ( E CB ) is considered to be more negative than the flat band potentials by approximately 0.1 V. 23,30 Therefore, the typical E CB and valence band edges ( E VB ) of Bi 2 S 3 are approximately 0.05 and 1.40 eV, respectively, (vs NHE), while those of Bi 2 MoO 6 are approximately 0.15 and 2.95 eV (vs NHE), respectively, which are matched well with the literatures. 30 Figure 6c shows possible photogenerated electron–hole pathways based on the MS plots: (1) electron transfer from the E CB of Bi 2 S 3 to that of Bi 2 MoO 6 , (2) hole transfer from the E VB of Bi 2 MoO 6 to that of Bi 2 S 3 , and (3) electron–hole recombination at the Bi 2 S 3 –Bi 2 MoO 6 interface.…”

“…Furthermore, pure Bi 2 S 3 nanowires (Bi 2 S 3 NW) were fabricated by the hydrothermal method for comparison. 30 Figure S4 shows SEM images of the Bi 2 MoO 6 /Bi 2 S 3 (Dip), Bi 2 MoO 6 /Bi 2 S 3 (Drop), and Bi 2 S 3 NW electrodes. The Bi 2 MoO 6 /Bi 2 S 3 NWA and Bi 2 MoO 6 /Bi 2 S 3 (Drop) samples were adjusted with Bi 2 S 3 layers of the same thickness using their UV−visible absorption spectra (Figure S5).…”

“…The Mott− Schottky (MS) plots were recorded using a Na 2 SO 4 solution (Figure 6a,b). 30 The MS plot indicated that the flat-band potential of Bi 2 S 3 is approximately 0.15 V [vs normal hydrogen electrode (NHE)] with an n-type behavior. The flat band potential of Bi 2 MoO 6 , estimated using the MS plot was approximately 0.25 V (vs NHE).…”

“…The flat band potential of Bi 2 MoO 6 , estimated using the MS plot was approximately 0.25 V (vs NHE). The conduction band edge (E CB ) is considered to be more negative than the flat band potentials by approximately 0.1 V. 23,30 Therefore, the typical E CB and valence band edges (E VB ) of Bi 2 S 3 are approximately 0.05 and 1.40 eV, respectively, (vs NHE), while those of Bi 2 MoO 6 are approximately 0.15 and 2.95 eV (vs NHE), respectively, which are matched well with the literatures. 30 Figure 6c…”

“…The recombination at the surface and in the bulk state of Bi 2 S 3 , leads to a lower PEC conversion efficiency. One-dimensional Bi 2 S 3 structures such as nanorods and nanowires have been studied as photoelectrodes, which can provide the advantages of a reduced hole diffusion length and enhanced charge transport properties. − On the other hand, the Bi 2 S 3 nanowires must be grown on a conductive substrate to enable efficient interactions for improved PEC properties. As most Bi 2 S 3 nanowires are prepared as powdered samples, their deposition on substrates is another challenging process .…”