An effective heterojunction with robust charge separation and enormous degradation efficiency is the major task for photocatalyst preparation. In this study, we have prepared the FeCo₂O₄-loaded g-C₃N₄ nanosheet by the sol–gel-assisted calcination method for photo-Fenton-like degradation under visible-light irradiation by activating persulfate. The nanocomposite exhibits a higher charge separation efficiency than pure g-C₃N₄ and FeCo₂O₄ for the degradation reaction against naproxen drugs. An effective interaction between the nanoparticles increases the degradation efficiency up to 91% with a synergistic index of 73.62%. Moreover, the nanocomposite exhibits a 78% mineralization efficiency against the naproxen pollutant under visible-light irradiation. For practical implementation, the degradation reaction was tested with various pH values, different water sources (DI, lake, and tap water), and light sources (LED (visible)/direct sunlight (UV–visible)). Moreover, the possible degradation mechanism predicted by the elemental trapping experiment and the recycling experiment clearly revealed that the heterojunction composite has a high enough degradation stability.

A graphene–cadmium sulfide (Gr–CdS) nanocomposite was prepared by a chemical solution method, and its material properties were characterized by several analysis techniques. The synthesized pure CdS nanoparticles (NPs) and Gr–CdS nanocomposites were confirmed to have a stoichiometric atomic ratio (Cd/S = 1:1). The Cd 3d and S 2p peaks of the Gr–CdS nanocomposite appeared at lower binding energies compared to those of the pure CdS NPs according to X-ray photoelectron spectroscopy analyses. The formation of the Gr–CdS nanocomposite was also evidenced by the structural analysis using Raman spectroscopy and X-ray diffraction. Transmission electron microscopy confirmed that CdS NPs were uniformly distributed on the graphene sheets. The absorption spectra of both the Gr–CdS nanocomposite and pure CdS NPs thin films showed an absorption edge at 550 nm related to the energy band gap of CdS (~2.42 eV). The Cu(In,Ga)Se₂ thin film photovoltaic device with Gr–CdS nanocomposite buffer layer showed a higher electrical conversion efficiency than that with pure CdS NPs thin film buffer layer. In addition, the water splitting efficiency of the Gr–CdS nanocomposite was almost three times higher than that of pure CdS NPs.

Energy consumption and environmental pollution are major issues faced by the world. The present study introduces a single solution using SnS₂ for these two major global problems. SnS₂ nanoparticles and thin films were explored as an adsorbent to remove organic toxic materials (Rhodamine B (RhB)) from water and an alternative to the toxic cadmium sulfide (CdS) buffer for thin-film solar cells, respectively. Primary characterization tools such as X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), and UV-Vis-NIR spectroscopy were used to analyze the SnS₂ nanoparticles and thin films. At a reaction time of 180 min, 0.4 g/L of SnS₂ nanoparticles showed the highest adsorption capacity of 85% for RhB (10 ppm), indicating that SnS₂ is an appropriate adsorbent. The fabricated Cu(In,Ga)Se₂ (CIGS) device with SnS₂ as a buffer showed a conversion efficiency (~5.1%) close to that (~7.5%) of a device fabricated with the conventional CdS buffer, suggesting that SnS₂ has potential as an alternative buffer.