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

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 (KICNT) 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.