Ultrahigh Performance H 2 O 2 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 (H 2 O 2 ) generation are researched but it is still challenging to obtain high H 2 O 2 yields. Herein, graphite carbon nitride (Fe SA /CN) confined single Fe atoms with N/O coordination is prepared, and Fe SA /CN shows high H 2 O 2 production via oxalic acid and O 2 activation. Under visible light illumination, the concentration of H 2 O 2 generated by Fe SA /CN can achieve 40.19 mM g -1 h -1 , which is 10.44 times higher than that of g-C 3 N 4 . The enhanced H 2 O 2 generation can be attributed to the formation of metal-organic complexes and rapid electron transfer. Moreover, the O 2 activation of photocatalysts is revealed by 3,3',5,5'-tetramethylbenzidine oxidation. The results display that the O 2 activation capacity of Fe SA /CN is higher than that of g-C 3 N 4 , which facilitates the formation of H 2 O 2 . Finally, density functional theory calculation demonstrates that O 2 is chemically adsorbed on Fe atomic sites. The adsorption energy of O 2 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 O 2 adsorption and activation. Finally, the photocatalytic mechanism is elaborated, which provides a deep understanding for SACs-catalyzed H 2 O 2 generation.