Ce-Doped Fe–N–C/Fe<sub>3</sub>C Nanosheets\nas an Efficient Oxygen Electrocatalyst under Alkaline and Acidic Media

Reasonable design of an economical and efficient versatile\noxygen\nelectrocatalyst for the oxygen reduction reaction (ORR) and oxygen\nevolution reaction (OER) is urgently needed in metal-air batteries\nand fuel cells. Herein, a Ce-doped Fe-NC/Fe<sub>3</sub>C (Ce/Fe-NC/Fe<sub>3</sub>C-P) porous nanosheet catalyst was prepared from the pyrolysis\nof a two-dimensional ZIF assisted with NaCl molten salt. Under alkaline\nmedia, the ORR half-wave potential (<i>E</i><sub>1/2</sub>) is 0.87 V, and the OER overpotential is 389 mV. The Zn-air batteries\n(ZABs) assembled with the Ce/Fe-NC/Fe<sub>3</sub>C-P catalyst demonstrate\na maximum power density (<i>P</i><sub>M</sub>) of 184 mW\ncm<sup>–2</sup>. Under acidic media, the <i>E</i><sub>1/2</sub> of the ORR is 0.78 V, and the <i>P</i><sub>M</sub> is 347 mW cm<sup>–2</sup> in the proton exchange membrane\nfuel cell (PEMFC) cathode. The enhanced catalytic activity and stability\nbenefit from the abundant catalytic active sites (Fe<sub>3</sub>C,\nFe–N<sub><i>X</i></sub>, Ce–N) by Fe and Ce\ndoping, hierarchical porous structure, and relatively higher graphitization\noriginating from the molten NaCl assisting pyrolysis.