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 (Fe-SA/CN) confined single Fe atoms with N/O coordination is prepared, and Fe-SA/CN shows high H2O2 production via oxalic acid and O-2 activation. Under visible light illumination, the concentration of H2O2 generated by Fe-SA/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 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-C3N4, which facilitates the formation of H2O2. 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 angstrom. 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 H2O2 generation.

Automated summary

In this study, single Fe atoms were successfully immobilized on Fe-SA/CN, which exhibited high efficiency in generating hydrogen peroxide (H2O2) through oxalic acid and O2 activation. Under visible light, the H2O2 concentration generated by Fe-SA/CN reached 40.19 mM g(-1) h(-1), which was 10.44 times higher than that of g-C3N4. This enhancement can be attributed to the formation of metal-organic complexes and rapid electron transfer. Furthermore, the O2 activation capacity of Fe-SA/CN was found to be higher than that of g-C3N4, facilitating H2O2 formation. Density functional theory calculations revealed that O2 was chemically adsorbed on Fe atomic sites, promoting O2 adsorption and activation. The photocatalytic mechanism of SACs-catalyzed H2O2 generation was also elucidated, providing a deeper understanding of this process.