Ultrahigh Performance H2O2 Generation by Single‐Atom Fe Catalysts with N/O Bidentate Ligand via Oxalic Acid and Oxygen Molecules Activation

Single‐atom catalysts (SACs) for photocatalytic hydrogen peroxide (H2O2) generation are researched but it is still challenging to obtain high H2O2 yields. Herein, graphite carbon nitride (FeSA/CN) confined single Fe atoms with N/O coordination is prepared, and FeSA/CN shows high H2O2 production via oxalic acid and O2 activation. Under visible light illumination, the concentration of H2O2 generated by FeSA/CN can achieve 40.19 mM g−1 h−1, which is 10.44 times higher than that of g‐C3N4. The enhanced H2O2 generation can be attributed to the formation of metal‐organic complexes and rapid electron transfer. Moreover, the O2 activation of photocatalysts is revealed by 3,3′,5,5′‐tetramethylbenzidine oxidation. The results display that the O2 activation capacity of FeSA/CN is higher than that of g‐C3N4, which facilitates the formation of H2O2. Finally, density functional theory calculation demonstrates that O2 is chemically adsorbed on Fe atomic sites. The adsorption energy of O2 is enhanced from −0.555 to −1.497 eV, and the bond length of OO is extended from 1.235 to 1.292 Å. These results exhibit that the confinement of single Fe atoms can promote O2 adsorption and activation. Finally, the photocatalytic mechanism is elaborated, which provides a deep understanding for SACs‐catalyzed H2O2 generation. Herein, graphite carbon nitride confined single Fe atoms with N/O coordination is prepared through a thermal polymerization process. The formation of metal–organic complexes, the rapid transfer of charge carrier, the broadened absorption of solar light, and the presence of Fe atomic sites can promote molecular oxygen and oxalic acid activation, thereby enhancing photocatalytic H2O2 production.