One-step calcination synthesis of accordion-like MXene-derived TiO2@C coupled with g-C3N4: Z-scheme heterojunction for enhanced photocatalytic NO removal

This work explored an effective treatment method for removing NO from simulated flue gas at normal temperature. We synthesized accordion-like MXene-derived TiO2@C coupled with g-C3N4 (TiO2@C/g-C3N4) via one-step calcination utilizing Ti3AlC2, fluoride salts and melamine as raw materials in CO2 atmosphere. One-step calcination process simultaneously achieved the etch of Al layers of Ti3AlC2 by molten fluoride salts, the generation of g-C3N4 with melamine as precursor and the oxidation of Ti3C2 by CO2. TiO2@C/g-C3N4 for photocatalytic activation of hydrogen peroxide (H2O2) had as high as 94.0% removal rate of NO at parts per million level in a normal temperature environment. This efficiency was 5.3 times and 8.0 times that of TiO2@C/g-C3N4 and H2O2 individually, due to the synergy between photocatalysis and H2O2 oxidation. Meantime, TiO2@C/g-C3N4 exhibited an enhanced performance compared with g-C3N4 (40.3%) and TiO2@C (64.1%) for Z-type heterojunction accelerating the separation of electron-hole pairs. The mechanism was proposed that Z-type TiO2@C/g-C3N4 heterojunction activated H2O2 under visible light to generate hydroxyl radical and superoxide radical for oxidation of NO.