Fe2O3/Fe/Fe-N multidimensional cross-linked composite enhancing oxygen reduction reaction of al-air batteries: Oxygen vacancies and bandgap engineering

Surface oxygen vacancy increases active site numbers, and multidimensional cross-linked structure improves the exposure of active sites. Thereby, they can enhance the oxygen reduction reaction (ORR) performance of Fe-N-C catalysts effectively. Herein, Fe(NO3)3·9H2O and carbon nanotubes (CNTs) were introduced into zeolitic imidazolate framework nano leaves (ZIF-L) to prepare multidimensional cross-linked Fe-N-CNTs with surface oxygen vacancies through co-pyrolysis at the high-temperature. As expected, the synthesized multidimensional cross-linked Fe-N-CNTs-900-0.2 composite rich in oxygen vacancies increased the conduction band potential and improved the reducing capacity. Thus, Fe-N-CNTs-900-0.2 possessed a better ORR electrochemical performance (half-wave potential = 0.892 V vs. RHE) that surpass the Pt/C catalysts. Moreover, the Al-air batteries containing Fe-N-CNTs-900-0.2 displayed a higher maximum power density than those of Pt/C catalysts. The electronic band structure shows that Fe-N-CNTs-900-0.2 rich in oxygen vacancy concentration has higher conduction band potential and effectively improves the activity of ORR catalysts. This work innovatively proposes that the joint work of multidimensional cross-linked structure and oxygen defects is an effective method to enhance the ORR performance and clarifies its internal reaction mechanism, which provides a new idea to design and preparer Fe-N-C catalysts.