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

•P-C3N4/g-C3N5 isotypic heterojunction is prepared via coupling P-C3N4 and g-C3N5.•RhB removal of P-C3N4/g-C3N5 is 7.3 and 12.3 times higher than P-C3N4 and g-C3N5.•Internal-electric-field is built at interface of P-C3N4/g-C3N5 type-II heterojunction.•Contributions of ROSs for RhB removal follow the order: •O2− > •OH > h+ > 1O2> e−.•96.4% of degradation efficiency is maintained even after 8 successive cycles. 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. 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. 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. P-C3N4/g-C3N5 photocatalyst was prepared to accelerate electron transfer and improve photocatalytic degradation performance by forming a type-II isotypic heterojunction through internal-electric-field. [Display omitted]