Heterojunction Bi₂Se₃/Sb₂Se₃ on Flexible Mo Metal Foils for Photoelectrochemical Water Splitting Applications

Nanostructured heterojunctions are an effective approach to enhance the photoelectrochemical (PEC) performance of semiconducting materials, as they facilitate the separation of the photogenerated charge carriers. Here, we report the PEC properties of the Bi₂Se₃/Sb₂Se₃ heterojunction structure on a thin flexible Mo metal foil. Raman spectroscopy confirmed the structural composition of Bi₂Se₃ and Sb₂Se₃ with their corresponding vibrational modes. X-ray diffraction showed a rhombohedral crystal structure for Bi₂Se₃ and an orthorhombic crystal structure for Sb₂Se₃ on polycrystalline substrates. X-ray photoelectron spectroscopy further revealed the formation of Bi₂Se₃ and Sb₂Se₃ compounds corresponding to their chemical and electronic states. PEC measurements were carried out under 100 mW/cm² (AM 1.5G) simulated solar radiation in a 0.5 M Na₂SO₄ aqueous electrolyte solution and demonstrated an enhancement in photocurrent density from the Bi₂Se₃/Sb₂Se₃ heterojunction (127.6 μA/cm²) attributed to more active sites and easy separation of photogenerated charges in comparison to bare Bi₂Se₃ (7.5 μA/cm²) and Sb₂Se₃ (76.5 μA/cm²) thin films at 0.9 V vs RHE. This preliminary study on thin metal foil-based photoelectrodes paves the way toward the futuristic production of large-area PEC water-splitting applications.