Effect of multi-walled carbon nanotubes on the visible light photocatalytic activity of AgInS2 for Rhodamine B degradation

Visible-light responsive AgInS2 (AIS) nanoparticles modified with either pristine multi-walled carbon nanotubes (p-MWCNTs) or mixed-acid (H2SO4 and HNO3) oxidized multi-walled carbon nanotubes (o-MWCNTs) were synthesized using a low-temperature liquid phase method. The resulting nanocomposites are denoted as p-MWCNTs/AIS or o-MWCNTs/AIS. The structure, morphology, and optical properties of the samples were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), photoluminescence spectroscopy (PL), and ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis DRS). The photocatalytic activity of p/o-MWCNTs/AIS towards the degradation of Rhodamine B (RhB) was investigated, and the optimal proportion of p/o-MWCNTs introduced on AIS was determined. A possible degradation mechanism of RhB over p/o-MWCNTs/AIS was proposed. The results demonstrated that p/o-MWCNTs were successfully incorporated into AIS, and the addition of an appropriate amount of p/o-MWCNTs improved the visible-light photocatalytic activity of AIS. Among the samples, 2 % o-MWCNTs/AIS exhibited the highest visible-light catalytic activity, achieving a degradation efficiency of 95 % within 40 min. The·⋅O2− species were identified as the main active species during the photocatalytic degradation process. The introduction of o-MWCNTs not only facilitated the separation of photogenerated electron-hole pairs (e−/h+) in AIS but also enhanced the visible-light absorption of AIS, leading to a significant improvement in its photocatalytic performance. Furthermore, the incorporation of o-MWCNTs greatly enhanced the cycling stability of AIS for reuse.