2D/2D nitrogen-doped graphitic carbon nitride/cobalt sulfide nanostructures for fast photodegradation of methylene blue dye and real industrial sewage effluents

Abstract

Currently, the pollution of water and air is causing many diseases in humans and water pollution from textile industries is causing various problems for the livestock. To deal with this, photocatalytic degradation by g-C₃N₄-based nanocomposites has been trending in the scientific world. It is believed that doping with metals or nonmetals and constructing a nanocomposite with a metal sulfide can establish suitable energy band positions and a bandgap as an interface between two semiconductors, thus enhancing photodegradation efficiency. Herein, nitrogen-doped g-C₃N₄/CoS (CSNG) nanocomposites have been synthesized using a facile polycondensation-hydrothermal method by varying the concentration of nitrogen-doped g-C₃N₄ (NG). The CSNG-2 nanocomposite showed maximum photocatalytic efficiency (0.03474 min⁻¹) and adsorption capacity (∼192 mg g⁻¹) as compared to NG and cobalt sulfide (CS). The results suggest that industrial real samples (RS), RS.I and RS.II, were degraded by 60% and 41% in 20 and 70 min, respectively. A mixture of RS.I with Methylene Blue (MB) dye solution, degraded 79% and 98% in 20 min, and RS.II with MB solution degraded 72% and 99% in 40 min. Scavenger and stability studies were performed with the CSNG-2 nanocomposite to determine the roles of organic species and photocatalytic efficiency during the photocatalytic mechanism. Superoxide played an important role in the photodegradation of MB and showed excellent photostability in five consecutive cycles with a loss of just 0.7%. Thus, our research highlights improved photocatalytic activity in the degradation of MB and industrial real samples with the enhanced photostability of CSNG nanocomposites, and the CSNG-2 nanocomposite can also be very useful in water-splitting and CO₂ reduction, etc.