Alkali Metal-Assisted Synthesis of Graphite Carbon Nitride with Tunable Band-Gap for Enhanced Visible-Light-Driven Photocatalytic Performance

The development of high-performance semiconductor photocatalysts using solar energy has become a hot topic, which is crucial for a sustainable future. However, construction of a nontoxic and efficient catalyst still remains an enormous challenge. Here, we uncover a simple hydrothermal recalcination method to prepare a novel potassium (K)-doped porous ultrathin g-C3N4 (denoted as KMCN) photocatalyst with efficient catalytic performance, eco-friendly characteristics, and excellent stability. The obtained KMCN nanosheets were applied to the photodegradation of tetracycline (TC) under different reaction condition to simulate practical wastewater treatment. It was found, that the porous structure and K+ addition of g-C3N4 enhanced the pore size and specific surface area, and they increased the photoabsorption region and activity sites. The optical properties of KMCN nanosheets were systematically characterized by PL, UV-DRS, etc. The results revealed that the KMCN(0.05) sample possessed a narrowed band gap, lower recombination of photogenerated charges, and higher electron and hole transfer efficiency. Benefiting from these advantages, KMCN(0.05) photocatalysts demonstrated excellent photocatalytic performance for TC degradation (85.13%), which was approximately a 2.88-fold and 1.40-fold increase compared to bare g-C3N4 (29.60%) and porous ultrathin g-C3N4 (60.84%), respectively. These results suggest a reasonable way for the design of economic and high-efficiency photocatalysis.