Internal-electric-field induced high efficient type-I heterojunction in photocatalysis-self-Fenton reaction: Enhanced H₂O₂ yield, utilization efficiency and degradation performance

Herein, a type-I phosphorus-doped carbon nitride/oxygen-doped carbon nitride (P-C₃N₄/O-C₃N₄) heterojunction was designed for photocatalysis-self-Fenton reaction (photocatalytic H₂O₂ production and following Fenton reaction). In P-C₃N₄/O-C₃N₄, the photoinduced charge carriers were effectively separated with the help of internal-electric-field near the interface, ensuring the high catalytic performance. As a result, the production rate of H₂O₂ in an air-saturated solution was 179 μM·h^-1, about 7.2, 2.5, 2.5 and 2.1 times quicker than that on C₃N₄, P-C₃N₄, O-C₃N₄, and phosphorus and oxygen co-doped C₃N₄, respectively. By taking advantage of the cascade mode in photocatalysis-self-Fenton reaction, H₂O₂ utilization efficiency was remarkably improved to 77.7%, about 9.0 times higher than that of traditional homogeneous Fenton reaction. Befitting from the superior yield and utilization efficiency, the degradation performance of P-C₃N₄/O-C₃N₄ was undoubtedly superior than other photocatalysts. This work well addressed two bottlenecks in traditional Fenton reaction: source of H₂O₂ and their low utilization efficiency, and the findings were beneficial to understand the mechanism and advantage of the photocatalysis-self-Fenton system in environmental remediation.