Potassium and phosphorus co-doped g-C3N4 with improved carrier migration for efficient photocatalytic degradation of 2,4-dichlorophenoxyacetic acid under visible light

Abstract

The carrier migration efficiency of photocatalysts is important for the performance of photocatalysis. Hence, element doping was employed to improve the photogenerated carrier separation efficiency of carbon nitride in the graphite phase (CN). Melamine was calcined in order to create potassium (K) and phosphorus (P) co-doped CN (K+PCN) by adding ammonium dihydrogen phosphate and potassium hydroxide. The varying K doping amounts are denoted as 1-K+PCN, 2-K+PCN, and 3-K+PCN, respectively. Under visible light, 2-K + PCN possessed a 12 times faster degradation rate than CN for the photodegradation of 2,4-Dichlorophenoxyacetic acid, as well as good photodegradation performance in actual water. The combination of density functional theory calculations and spectroscopic characterization techniques has demonstrated that K and P doping can facilitate the transfer of electrons to the carbon-nitrogen aromatic heterocyclic framework. This process modulates the electronic band structure, leading to a reduction in the band gap. Consequently, there is a synergistic enhancement of carrier separation from two-dimensional to three-dimensional systems. Specifically, K⁺ ions facilitated the formation of an interfacial charge-transfer pathway within the CN matrix, while P atoms introduced electron-trapping sites that preferentially captured photogenerated electrons, thereby spatially isolating holes and electrons. Additionally, the co-doping approach greatly increased the modified CN surface's ability to adsorb dissolved oxygen, which encouraged the production of superoxide radicals. These radicals were identified as the predominant reactive species responsible for the oxidation of 2,4-dichlorophenoxyacetic acid. Valuable theoretical insights for the logical design of dual-element-doped CN materials to address challenges in environmental remediation and sustainable pollutant degradation are provided by this study.