Construction of P-C₃N₄/C₃N₅ isotypic heterojunction for effective degradation of organic pollutants

Background: Photocatalysis was an effective method for organic pollutant degradation, and graphitic carbon nitride g-C₃N₄ and g-C₃N₅ were famous two-dimensional semiconductors. Compared to the allotypic heterojunction, the band alignment and compatibility of isotypic heterojunction were superior. Methods: In this work, an organic isotypic heterojunction was constructed via coupling phosphorus-doped C₃N₄ (P-C₃N₄) and g-C₃N₅. The characteristics were evaluated using transmission electron microscope, Fourier transform infrared, X-ray diffractometer, X-ray photoelectron spectrum, ultraviolet-visible (UV–vis) diffuse reflection spectrum, electronic spin resonance (ESR) analysis, photoluminescence spectrometer, electrochemical impedance spectroscopy, and photocurrent analysis. Significant: Isotypic heterojunction displayed high UV–vis light harvest, high separation efficiency of photo-induced charge carriers, and low surface resistance. Additionally, an internal-electric-field was established at the interface, which was beneficial for spatial separation of photo-induced charge carriers. As expected, the Rhodamine B (RhB) degradation efficiency was 7.3 and 12.3 times higher than that of the P-C₃N₄ and g-C₃N₅. Radical trapping experiment and ESR analysis indicated that ^•O₂⁻, ^•OH, hole, ¹O₂, and electron played joint role in RhB degradation. In this work, a photocatalyst with excellent photocatalytic degradation properties was designed, and it provided a simple and novel strategy for environmental remediation.