Iron-nitrogen-carbon(Fe-N-C)materials with Fe-N_(4)structures have been considered as the most promising alternatives of scarce and precious platinum(Pt)for oxygen reduction reaction.Particularly,the hightemperature p...Iron-nitrogen-carbon(Fe-N-C)materials with Fe-N_(4)structures have been considered as the most promising alternatives of scarce and precious platinum(Pt)for oxygen reduction reaction.Particularly,the hightemperature pyrolysis of a precursor mixture of N-containing amine polymers,Fe salts,and carbon supports,has become a popular method for the synthesis of high-performance Fe-N-C catalysts.The oxidative polymerization of amine monomers can usually proceed under acidic conditions,however,the acidcaused protonation of N-groups is not conducive to their coordination with Fe ions for the formation of high-density Fe-N_(4)sites.Here,we propose a protonation elimination strategy of soaking the polymerization products in alkaline solutions to increase Fe-N_(4)active sites.Theoretical calculations display that the Gibbs free energy change values of binding reactions between Fe ions and N-groups are-3.70 and-26.99 kcal/mol at p H 0 and 7,respectively,suggesting that the deprotonation can facilitate the Fe-N coordination.There is a two-fold increase in the number of Fe-N_(4)active sites for final Fe-N-C catalyst which exhibits significantly enhanced ORR activity and excellent Zn-air battery performance.This deprotonation effect can be applied to different amine compounds and transition-metal ions as a universal strategy for the development of preeminent non-precious metal carbon catalysts.展开更多
基金sponsored by the National Natural Science Foundation of China(No.22272105)the Natural Science Foundation of Shanghai(No.23ZR1423900)。
文摘Iron-nitrogen-carbon(Fe-N-C)materials with Fe-N_(4)structures have been considered as the most promising alternatives of scarce and precious platinum(Pt)for oxygen reduction reaction.Particularly,the hightemperature pyrolysis of a precursor mixture of N-containing amine polymers,Fe salts,and carbon supports,has become a popular method for the synthesis of high-performance Fe-N-C catalysts.The oxidative polymerization of amine monomers can usually proceed under acidic conditions,however,the acidcaused protonation of N-groups is not conducive to their coordination with Fe ions for the formation of high-density Fe-N_(4)sites.Here,we propose a protonation elimination strategy of soaking the polymerization products in alkaline solutions to increase Fe-N_(4)active sites.Theoretical calculations display that the Gibbs free energy change values of binding reactions between Fe ions and N-groups are-3.70 and-26.99 kcal/mol at p H 0 and 7,respectively,suggesting that the deprotonation can facilitate the Fe-N coordination.There is a two-fold increase in the number of Fe-N_(4)active sites for final Fe-N-C catalyst which exhibits significantly enhanced ORR activity and excellent Zn-air battery performance.This deprotonation effect can be applied to different amine compounds and transition-metal ions as a universal strategy for the development of preeminent non-precious metal carbon catalysts.
