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

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