Tailored Exfoliation of Polymeric Carbon Nitride for Photocatalytic H 2 O 2 Production and CH 4 Valorization Mediated by O 2 Activation

Abstract The exfoliation of bulk C 3 N 4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation‐decomposition (NID) strategy that is effective in peeling off BCN into few‐layer C 3 N 4 (fl‐CN) with tailored thickness down to bi‐layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO 3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl‐CN, which is conducive to O 2 adsorption and hence relevant chemical processes. In photocatalytic O 2 reduction under visible light irradiation, the H 2 O 2 production rate over the optimal fl‐CN‐530 catalyst is 952 μmol g −1 h −1 , which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH 4 can be photocatalytically oxidized by on‐site formed H 2 O 2 and active oxygen species to generate value‐added C1 oxygenates with high selectivity of 99.2 % and record‐high production rate of 1893 μmol g −1 h −1 among the metal‐free C 3 N 4 ‐based photocatalysts.