Pyrolysis-tuned carbon nitride with synergistic K-bridged channels and vacancies for boosting H2O2 production and tetracycline degradation

Abstract

Carbon nitride (CN), a promising polymeric semiconductor and photocatalyst, exhibits photocatalytic activity that is notably influenced by the synthesis temperature. In this work, a series of I, K co-doped carbon nitrides (KICN_T) were fabricated under various pyrolysis temperature (450, 500, 550, 600 and 650 °C) conditions and an N₂ atmosphere, which were then subsequently applied to catalytic hydrogen peroxide (H₂O₂) production and tetracycline (TC) degradation. Both oxygen adsorption capacity and photocatalytic activity exhibited an initial increase followed by a decline with rising pyrolysis temperature. The KICN₆₀₀ sample simultaneously exhibits the highest photocatalytic activity for both H₂O₂ production and photodegradation capability for TC. KICN₆₀₀ achieved a H₂O₂ yield of 4382.1 μmol L⁻¹ via a two-step oxygen reduction process in air after 2 h and 11 013.8 μmol L⁻¹ under an oxygen atmosphere and visible light irradiation. Furthermore, the TC degradation over this state-of-the-art KICN₆₀₀ photocatalyst can reach 83.9% within only 2 h under ambient air conditions. The characterizations results showed that the exceptional photocatalytic activity of KICN₆₀₀ can be attributed to the high concentration of K-bridged channels and abundant carbon vacancies. These structural features collectively enhance the oxygen reduction capability and charge carrier separation efficiency.