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 temperature 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 VRHE and an onset potential of 0.21 VRHE. 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 VRHE and an onset potential of 0.31 VRHE. 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.