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 (FeSA /CN) confined single Fe atoms with N/O coordination is prepared, and FeSA /CN shows high H2 O2 production via oxalic acid and O2 activation. Under visible light illumination, the concentration of H2 O2 generated by FeSA /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 FeSA /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 OO 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.
Keywords: H 2O 2 generation; coordination interactions; oxalic acid activation; photocatalysis; single atom catalysts.
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