Copper sulfides based photocatalysts for degradation of environmental pollution hazards: A review on the recent catalyst design concepts and future perspectives

Amongst various metal chalcogenides, CuS (copper sulfides) have been widely explored in past years due to its semiconducting behavior and non-toxic nature. CuS owns remarkable plasmonic effect and apt bandgap energy values (1.2-1.5 eV) with exceptional electronic and optical properties making it an excellent photocatalytic material. Different morphological forms of CuS have been reported with diverse bandgap energy values such as 1.88, 2.06, 2.08, and 2.16 eV for CuS nanoparticles, nanotubes, microspheres, and nanoflakes, respectively. The different forms of CuS photocatalyst mostly exhibit optical absorption in the visible near-infrared (NIR) region. The present review delivers a detailed discussion of structural, optoelectronic features of CuS nanostructures and different synthetic routes with their application in wastewater treatment. The study summarized previously reported literature by explaining innovative methodologies for developing bare CuS nanomaterials with appropriate modulations such as doped CuS photocatalysts and different CuS-based heterostructures by coupling with metal oxides, metal sulfides, and metal-free semiconductors nanomaterials (carbonaceous materials) to enhance the photocatalytic activity of CuS. The heterojunctions of CuS with other photocatalysts have been extensively studied to validate the enhancement in photocatalytic activity of bare CuS photocatalysts towards different pollutants. Concluding perspectives on the challenges and opportunities for CuS-based photocatalysts to degrade environmental pollution hazards are also highlighted.