Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal-organic framework(MOF)precur-sors,have attracted extensive attention owing to their promising oxygen reduction reaction(ORR)cat-alytic activity in fuel cells and/or metal-air batteries.However,post-treatments(acid washing,second pyrolysis,and so on)are unavoidable to improve ORR catalytic activity and stability.The method for introducing Fe3+sources(anhydrous FeCl3)into the MOF structure,in particular,is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-Nx active sites.Herein,three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance.Fe-NC(Zn2+),synthesized by one-step pyrolysis of Fe doped ZIF-8(Zn2+)precursor which was obtained by adding the anhydrous FeCl3 source into the Zn(NO3)2·6H2O/methanol solution before mixing,possessed the highest Fe-Nx active sites due to the high-efficiency substitution of Zn2+ions with Fe3+ions during ZIF-8 growth,the strong interaction between Fe3+ions and N atoms of 2-Methylimidazole(2-Mlm),and ZIF-8's micropore confinement effect.As a result,Fe-NC(Zn2+)presented high ORR activity in the entire pH range(pH=1,7,and 13).At pH=13,Fe-NC(Zn2+)exhibited a half-wave potential(E1/2)of 0.95 V(vs.reversible hydrogen electrode),which was 70 mV higher than that of commercial Pt/C.More importantly,Fe-NC(Zn2+)showed superior ORR sta-bility in neutral media without performance loss after 5,000 cycles.A record-high open-circuit voltage(1.9 V)was obtained when Fe-NC(Zn2+)was used as a cathodic catalyst in assembled Mg-air batteries in neutral media.The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn2+)has enormous potential for use in flexible and wearable Mg-air batteries.

Yang Liu;Suqiong He;Bing Huang;Ziyan Kong;Lunhui Guan

CAS Key Laboratory of Design and Assembly of Functional Nanostructures,Fujian Key Laboratory of Nanomaterials,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences,Fuzhou 350002,Fujian,China;University of Chinese Academy of Sciences,Beijing 100049,China

能源化学

[1]Yang Liu;Suqiong He;Bing Huang;Ziyan Kong;Lunhui Guan-.Influence of different Fe doping strategies on modulating active sites and oxygen reduction reaction performance of Fe,N-doped carbonaceous catalysts)[J].能源化学,2022(07):511-520

Fe3+sources,Methylimidazole,Mlm

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