Two-dimensional Ga₂S₃/g-C₃N₄ heterojunction composites with highly enhanced photocatalytic activity and stability

In contrast to most composite nanostructured catalysts, two-dimensional Ga₂S₃ semiconductors and ultrathin graphitic-related materials, g-C₃N₄ heterojunction photocatalysts, are highly efficient photocatalysts for the removal of methylene blue from aqueous solutions because of their extraordinarily stable absorption and physical and optoelectrical properties. The activities of Ga₂S₃ nanosheet catalysts are 40% higher than those of commercial P25-TiO₂ catalysts. In comparison with the performances of Ga₂S₃ and g-C₃N₄ photocatalysts, light absorption by the Ga₂S₃/g-C₃N₄ heterostructures in the visible region was at least 2.53 and 2.97 times higher, and their photocatalytic efficiencies increased by more than 2.23 and 2.96 times, respectively. The efficient separation and prolonged lifetimes of photogenerated charge carriers enhanced the photocatalytic activity for degradation. In addition, the parameters of the synthesis process for finely uniform, promising Ga₂S₃/g-C₃N₄ heterostructured nanomaterials were investigated; such parameters included the precursor amount (Ga, S, and melamine), annealing temperature, and reaction time, and their effects on the structural properties and photocatalytic performance were studied. The detailed mechanism of the photocatalytic system was evaluated through a free radical scavenging experiment, electron paramagnetic resonance spectroscopy, and time-resolved fluorescence spectroscopy. Pseudo-first-order kinetics models were used to describe the efficient photocatalysis of methylene blue photodegradation by the Ga₂S₃/g-C₃N₄ heterostructures over different reaction times. e⁻, •OH, and •O₂^– radicals were confirmed as the major reactive oxidative species, and the degradation products were determined. This study is beneficial because it will promote future research on the use of renewable, sustainable resources in photocatalytic applications. Graphical Abstract: [Figure not available: see fulltext.]