Hierarchal Nanorod-Derived Bilayer Strategy to Enhance the Photocurrent Density of Sb₂Se₃ Photocathodes for Photoelectrochemical Water Splitting

For practical H2 production via photoelectrochemical (PEC) water splitting, a proper nanostructure strategy allowing sufficient light absorption and effective charge carrier transport is of immense importance. In this study, via the unique sequential use of two different molecular inks, a bilayer nanostructure for a photocathode composed of vertically oriented nanorods Sb2Se3 on top of a bottom compact Sb2Se3 layer is produced. The hierarchical nanorod bilayer structure possesses light-trapping ability owing to the scattering effect, resulting in the enhancement of light absorption. The bilayer Sb2Se3 photocathode also exhibits better charge-transport capability owing to the synergetic effects of the favorable crystallographic orientation and the enlarged surface area of the vertically aligned nanorods. The bilayer Sb2Se3 photocathode achieves a photocurrent density of nearly 30 mA cm–2 at 0 V vs the reversible hydrogen electrode. This observation implies that the proposed solution-processed Sb2Se3-based hierarchical bilayer structure is a promising candidate for an efficient PEC water splitting tandem device.