Direct injection of electrons into Cu active sites from porous phosphorus-doped g-C3N4 for enhanced Fenton-like performance

Highlight • A CuOx catalyst supported on P-doped porous g-C3N4 is synthesized easily. • P-doping increases the number of unpaired electrons in the catalyst. • Porous defects increase the catalyst surface area and active sites. • The unpaired electrons in the catalyst can directly inject into Cu active sites. • Catalyst performance and H2O2 utilization efficiency are simultaneously improved. Copper oxides were supported on porous P-doped g-C3N4 (Cu/p-PCN) by a stepwise calcination process. Elemental analysis, XPS, and ESR results show that P atoms enter the network of g-C3N4, and the thus-fabricated configuration could provide additional electrons for the conjugated system of g-C3N4. As verified by TEM, XRD, XPS, and FTIR results, copper is mainly present as oxides on the catalyst surface and undergoes Cu-π interactions with porous P-doped g-C3N4 (p-PCN). During the reaction, unpaired electrons in p-PCN can be injected into the Cu active sites, prompting the decomposition of H2O2 into hydroxyl radicals (•OH). The degradation begins with the activation of H2O2 into •OH radicals by the Cu(I) active center. The depleted Cu(I) centers are then regenerated by electron injection from P atoms rather than by the reaction between H2O2 and Cu(I). Thus, the catalyst performance and H2O2 utilization are greatly enhanced. Equally significantly, the porous structure of Cu/p-PCN also contributes appreciably to its performance by increasing the specific surface area and active sites. Cu/p-PCN exhibits better performance than many reported catalysts in similar conditions, robust resistance to interference from various ions, high degradation efficiency over a wide pH range, and excellent degradation ability for various pollutants.