Fabrication of three-dimensional hierarchical porous 2D/0D/2D g-C3N4 modified MXene-derived TiO2@C: Synergy effect of photocatalysis and H2O2 oxidation in NO removal.

A novel three-dimensional multi-level porous g-C3N4 modified MXene-derived TiO2@C aerogel (g-C3N4/TiO2@C aerogel) was synthesized for NO removal. Through SEM analysis, 2D g-C3N4 and 2D Ti3C2 nanosheets were constructed into an interconnected macroscopic framework with continuous macropores via ice template. OD TiO2 nanoparticles uniformly covered 2D C nanosheets with irregular mesopores and macropores in in-situ oxidation of Ti3C2 nanosheets by calcination via TEM analysis. g-C3N4/TiO2@C aerogel for photocatalytic activation of hydrogen peroxide (H2O2) had an excellent efficiency of 90.7% for NO removal at parts per million level. This efficiency was 4.9 times and 7.8 times that of g-C3N4/TiO2@C aerogel and H2O2 individually, due to the synergy between photocatalysis and H2O2 oxidation. Meantime, g-C3N4/TiO2@C aerogel exhibited an enhanced performance compared with g-C3N4 nanosheet (55.7%) and TiO2@C aerogel (38.5%). It was attributed to the large specific surface area (93.82 m2/g) with hierarchical mesoporous and macroporous structure and the 2D/OD/2D heterojunction of g-C3N4/TiO2@C aerogel, further enhancing electron-hole separation. The mechanism was hypothesized that g-C3N4/TiO2@C aerogel activated H2O2 to generate hydroxyl radicals (·OH) and superoxide radicals (·O2-) for oxidation of NO.