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

Abstract

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.