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 (H₂ O₂ ) generation are researched but it is still challenging to obtain high H₂ O₂ yields. Herein, graphite carbon nitride (Fe_SA /CN) confined single Fe atoms with N/O coordination is prepared, and Fe_SA /CN shows high H₂ O₂ production via oxalic acid and O₂ activation. Under visible light illumination, the concentration of H₂ O₂ generated by Fe_SA /CN can achieve 40.19 mM g^-1 h^-1 , which is 10.44 times higher than that of g-C₃ N₄ . The enhanced H₂ O₂ 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 Fe_SA /CN is higher than that of g-C₃ N₄ , which facilitates the formation of H₂ O₂ . 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 H₂ O₂ generation.