Dual S-scheme CuSe-Cu3Se2/Ag-PANI heterostructures for the impressive degradation of dye pollutants

Abstract

A dual S-scheme structure for the photocatalytic activity of copper selenide (CuxSey)/Ag-polyaniline (CuxSey/Ag-PANI) nanocomposites to degrade dye pollutants under visible light illumination conditions has been proposed. In the first step, PANI composites have been decorated by Ag nanoparticles (NPs) with different concentrations of Ag NPs. Then, a cost-effective and straightforward co-precipitation method has synthesized the CuxSey/Ag-PANI nanocomposites with different Ag NPs concentrations. Additions of the CuxSey/Ag-PANI nanocomposites, pristine CuxSey nanostructures, and CuxSey/PANI nanocomposites have also been synthesized with the same conditions. X-ray diffraction patterns (XRD) and high-resolution transmission electron microscopy (HRTEM) images indicated the CuxSey nanostructures in the nanocomposites included two phases that were CuSe nanodisks with a few nanometers in thickness and Cu3Se2 NPs with average diameters of 10±2 nm. In contrast, the pristine CuxSey nanostructures have included several extra phases. These microscopy images showed the Cu3Se2 NPs have decorated the CuSe nanodisks. According to the UV–vis results, the Ag NPs in the CuSe-Cu3Se2/Ag-PANI nanocomposites showed surface plasmon resonance (SPR) effects, and this factor became one of the most critical factors for the better photocatalytic performance of the CuSe-Cu3Se2/Ag-PANI nanocomposites. By comparing the Fermi level (Ef) of the structures that make up the CuSe-Cu3Se2/Ag-PANI heterostructures, these structures had the conditions for forming the dual S-scheme structure. Based on this structure and also the synergistic effect of the plasmonic properties of the Ag NPs, the reason for the better photocatalytic performance of the CuxSey/Ag-PANI nanocomposites compared to the pristine CuxSey nanostructures and CuxSey/PANI nanocomposites has been explained.