Nanowire morphology control in Sb metal-derived antimony selenide photocathodes for solar water splitting

We report a facile method to enhance the photoelectrochemical (PEC) performance of Sb₂Se₃ photocathodes by controlling the growth of bilayer Sb₂Se₃ consisting of vertically oriented nanorods on a compact Sb₂Se₃ layer. Sb₂Se₃ thin films with controllable nanorod diameters were achieved by manipulating the substrate temperatures during metallic Sb thin film deposition. The lower temperature-derived Sb₂Se₃ photocathode, with a larger nanorod diameter (202 ± 48 nm), demonstrated a photocurrent density of -15.2 mA cm^-2 at 0 V_RHE and an onset potential of 0.21 V_RHE. In contrast, the higher temperature-derived Sb₂Se₃ photocathode, with a smaller nanorod diameter (124 ± 28 nm), exhibited an improved photocurrent density of -22.1 mA cm^-2 at 0 V_RHE and an onset potential of 0.31 V_RHE. The enhanced PEC performance is attributed to reduced charge recombination, facilitated by a shorter charge transport path in the [hk0] direction. This study highlights the significance of morphology control in optimizing Sb₂Se₃ photocathodes, providing insights for future material and device design.