An ultra-porous g-C3N4 micro-tube coupled with MXene (Ti3C2TX) nanosheets for efficient degradation of organics under natural sunlight

Abstract

It remains as a challenge for realizing efficient photo-responsive catalysts towards large-scale degradation of organic pollutants under natural sunlight. This work reports a new pore engineering strategy for creating ultra-porous g-C₃N₄ micro-tubes with an unprecedentedly high specific surface area of 152.96 m²/g. This is mainly associated with releasing internal vapor pressure in the autoclave where the hydrothermal treatment of the urea/melamine mixture is processed. Supported by microscopic observation, porosity measurement and spectroscopic characterization, it is found that releasing the pressure at halfway of hydrothermal process is vital for forming exfoliated rod-like precursors and the de-aggregation of these rods presents substantial benefits on the production of mesopores on g-C₃N₄ micro-tubes during the calcination of precursors. This offers a large number of reactive sites required by photocatalytic reaction. Coupling these micro-tubes with Ti₃C₂T_X nanosheets via electrostatic interaction yields a 1D/2D heterojunction with a close interfacial contact. The addition of metallically conductive Ti₃C₂T_X nanosheets accelerates the separation between electrons and holes, and also enhances the light absorption. All these merits of structural design lead to forming a group of highly efficient catalysts demonstrating an excellent photocatalytic degradation rate of k = 0.0560 min⁻¹ for RhB dyes under 100 mW/cm² visible light radiation that micks sunlight outdoors. This laboratory valuation is further supported by an outdoor test that shows a fast degradation rate of 0.0744 min⁻¹ under natural sunlight.