Efficient promotion and transfer of excited charge carriers in phosphorus doped and Ni complex modified g-C3N4

Abstract

Solar hydrogen energy generation via photocatalysis can play a vital role in reducing global warming, environmental pollution, and the ever-increasing energy demand. Herein, phosphorus and Ni complex modified g-C3N4 were prepared by a hydrothermal method. The bonding of electron-rich phosphorous heteroatom to the g-C3N4 changed the morphology of the g-C3N4 from nanosheets into nano-rods and significantly altered the electronic structure, as evident by the shift in the conduction band edge and bandgap of g-C3N4. FTIR and XPS measurements revealedthat the triazine ring is oxygen functionalized and the P atom bonded to g-C3N4 via PN bond. Furthermore, EPR, UPS, and UV-DRS measurements revealed that the P and Ni complex reduced the localized π-conjugated structure defects of g-C3N4 and extended the light absorption into the near IR region. The Ni complex in the photocatalysts provided the additional charge transfer band of IMCT and OMCT. EDS color mapping revealed that the Ni complex is distributed uniformly on the P-g-C3N4 surface. These surface embedded Ni complex acts as an electron trap state, thereby suppressing the charge pair recombination rate which was confirmed by the PL and TRPL measurements. The synergetic effect of Ni complex and P resulted in 86 % tetracycline degradation in 20 min. and 3272 μmol/g of H2 production in 4 h. Compared to bulk g-C3N4, 818 times higher H2 production activity was achieved for the P and Ni complex modified g-C3N4.