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

Herein, a type-I phosphorus-doped carbon nitride/oxygen-doped carbon nitride (P-CN/O-CN) heterojunction was designed for photocatalysis-self-Fenton reaction (photocatalytic HO production and following Fenton reaction). In P-CN/O-CN, 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 HO in an air-saturated solution was 179 μM·h, about 7.2, 2.5, 2.5 and 2.1 times quicker than that on CN, P-CN, O-CN, and phosphorus and oxygen co-doped CN, respectively. By taking advantage of the cascade mode in photocatalysis-self-Fenton reaction, HO 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-CN/O-CN was undoubtedly superior than other photocatalysts. This work well addressed two bottlenecks in traditional Fenton reaction: source of HO 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.