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.