2D g-C3N4 as a bifunctional photocatalyst for co-catalyst and sacrificial agent-free photocatalytic N2 fixation and dye photodegradation

Abstract

Photocatalytic N₂ fixation is an ecofriendly technology to produce ammonia. In this work, photocatalytic N₂ fixation to generate ammonia in the absence of any co-catalysts or sacrificial agents (SF) is achieved on 2D g-C₃N₄ prepared via thermal exfoliation, for the first time. The formation of 2D g-C₃N₄ is confirmed using several analytical techniques including XRD, SEM, TEM, FT-IR, and XPS analyses. 2D g-C₃N₄ exhibits a blue shift in the bandgap compared to the bulk g-C₃N₄ attributed to the quantum confinement effect. In the absence of SF, 2D g-C₃N₄ shows an NH₃ production rate of 3.9 mg L⁻¹ h⁻¹ under sunlight irradiation, while no NH₃ is generated on bulk g-C₃N₄. In the presence of ethanol as a sacrificial agent, 2D g-C₃N₄ also exhibits a higher NH₃ production rate (12.76 mg L⁻¹ h⁻¹) than bulk g-C₃N₄ (7.58 mg L⁻¹ h⁻¹). Moreover, 2D g-C₃N₄ shows superior photodegradation activity compared to bulk g-C₃N₄ toward the decomposition of methylene blue (MB) and malachite green (MG) under sunlight irradiation. The enhanced photocatalytic activity of 2D g-C₃N₄ could be attributed to its more exposed active sites, high charge separation, and low electron–hole recombination rate.