Ytterbium induced surface polarization of graphitic carbon nitride with N vacancies towards enhanced photocatalytic decomposition of tetracycline

The recombination of photogenerated charges is always a hinder for the improvement of photocatalytic efficiency. Herein, as a case of study, graphitic carbon nitride (g-C3N4) modified with N vacancies and Yb doping (YbCN) was synthesized by the thermal polymerization of ytterbium nitrate and melamine. The optimized sample showed a photocatalytic efficiency of 99.9% within 30 min for degrading tetracycline (TC) under visible light irradiation (λ > 420 nm), which was 24 times than pure g-C3N4. The experimental results and density functional theory (DFT) calculations support that the enhanced performance for photocatalytic decomposition of TC was attributed to the doped Yb3+ and the formation of N vacancies. The doped Yb3+ and induced polarization can expand the light responsive range and inhibit the recombination of photogenerated carriers. Moreover, the introduction of Yb3+ in g-C3N4 can accelerate the adsorption and activation of O2 to generate 1O2, O2− and OH. Furthermore, the photocatalytic degradation pathway of TC was revealed by HPLC-MS and DFT calculations. Finally, the optimized sample catalyst was also employed for photocatalytic decomposition of TC in practical conditions including tap, river, and lake water. It was found that inorganic ions in real water can influence the photocatalytic degradation of TC. This work disclosed a strategy for the rational design of efficient g-C3N4-based materials for practical environmental remediation.