Potassium Poly(heptazine imide) Coupled with Ti₃C₂ MXene-Derived TiO₂ as a Composite Photocatalyst for Efficient Pollutant Degradation

The photocatalytic degradation of pollutants is an effective and sustainable way to solve environmental problems, and the key is to develop an efficient, low-cost, and stable photocatalyst. Polymeric potassium poly(heptazine imide) (K-PHI), as a new member of the carbon nitride family, is a promising candidate but is characterized by a high charge recombination rate. To solve this problem, K-PHI was in-situ composited with MXene Ti3C2-derived TiO2 to construct a type-II heterojunction. The morphology and structure of composite K-PHI/TiO2 photocatalysts were characterized via different technologies, including TEM, XRD, FT-IR, XPS, and UV–vis reflectance spectra. Robust heterostructures and tight interactions between the two components of the composite were verified. Furthermore, the K-PHI/TiO2 photocatalyst showed excellent activity for Rhodamine 6G removal under visible light illumination. When the weight percent of K-PHI in the original mixture of K-PHI and Ti3C2 was set to 10%, the prepared K-PHI/TiO2 composite photocatalyst shows the highest photocatalytic degradation efficiency as high as 96.3%. The electron paramagnetic resonance characterization indicated that the·OH radical is the active species accounting for the degradation of Rhodamine 6G.