2D/2D Z-scheme WO3/g-C3N4 heterojunctions for photocatalytic organic pollutant degradation and nitrogen fixation

Abstract

Two-dimensional/two-dimensional (2D/2D) Z-scheme WO₃/g-C₃N₄ heterojunctions were successfully prepared by facile rapid calcination, which exhibited considerable photocatalytic performance in environmental application and energy application without any cocatalyst. The synthesized 2D/2D Z-scheme WO₃/g-C₃N₄ significantly improved the visible-light photocatalytic degradation of tetracycline hydrochloride (TC-HCl), and 40%WO₃/g-C₃N₄ had the best photocatalytic degradation effect. 40%WO₃/g-C₃N₄ could also degrade rhodamine B (RhB), methylene blue (MB) and methyl orange (MO), and RhB was almost completely degraded after 20 min irradiation. ˙O₂⁻ was the main active species in the degradation process of 40%WO₃/g-C₃N₄. The 2D/2D Z-scheme heterostructure enhanced the photogenerated electron–hole separation and transfer ability and possessed good photocatalytic stability. The 2D/2D Z-scheme WO₃/g-C₃N₄ heterojunction system was first used in nitrogen fixation. 40%WO₃/g-C₃N₄ can simultaneously achieve photocatalytic nitrogen reduction reaction (NRR) and nitrogen oxidation reaction (NOR) to produce NH₄⁺ and NO₃⁻, respectively, using air as a nitrogen source. However, in the presence of a hole sacrificial agent and N₂ as a nitrogen source, the photocatalytic nitrogen fixation reaction of 40%WO₃/g-C₃N₄ was dominated by NRR. The nitrogen fixation products and their possible mechanisms were also discussed. This study confirms that the designed 2D/2D Z-scheme WO₃/g-C₃N₄ heterojunctions have great potential in the photocatalytic degradation of different-type organic pollutants and regulable photocatalytic NRR and NOR reactions.