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.