Smart Bifunctional Sb₂Se₃ Nanorods for Integrated Water Purification: Insoluble Liquid Separation and Photoelectrochemical Degradation

Antimony selenide (Sb₂Se₃) nanostructures enable bifunctional water purification by a single membrane through i) physical separation of water-insoluble oil and ii) photoelectrocatalytic degradation of water-soluble organic compounds. Sb₂Se₃ nanorods with exposed surfaces of {h 0 0} and {h 0 l} planes exhibit superhydrophobicity (water contact angle of ≈159°) owing to extremely low surface energy of those dangling-bond-free van der Waals planes. Based on crystallographic understanding, superhydrophobic Sb₂Se₃ nanorods were produced on a mesh-type substrate for utilization as a membrane for physical water/oil separation. Sb₂Se₃ exhibited an optimal photocathodic response with p-type electrical conductivity under visible light along the longitudinal crystal direction. This indicated that the nanorods could be used as photoelectrocatalytic material for chemical water purification. A smart membrane with Sb₂Se₃ nanostructures was proposed as a candidate for integrated water purification that can simultaneously accomplish water/oil separation and photoelectrocatalytic degradation of organic compounds in wastewater. Linear sweep voltammetry measurements of the Sb₂Se₃-membrane showed cathodic photocurrent generation (up to approximately 10 mA cm⁻² at 0 V vs. reversible hydrogen electrode), which was enough to reduce O₂ to an oxygen radical (O₂^.−) for degradation of methyl orange. Consequently, solar-driven integrated water purification was demonstrated for the first time by using a single material with a dual function of superhydrophobicity and photoactivity.