A silica-confined strategy for completely atomic level Fe(II)-N-C catalysts with a non-planar structure toward oxygen reduction reaction

Abstract

Constructing pure iron-nitrogen-carbon (Fe-N-C) catalysts without Fe-based particles for the oxygen reduction reaction (ORR) is extremely important to design efficiently next-generation non-platinum electrocatalysts for fuel c ells. Herein, we propose a silica-confined strategy for the pure Fe–N–C catalysts without Fe-based impurity phases, through post grafting iron and nitrogen atoms onto the surface of a carbon black. In an alkaline media, compared with the conventional Fe-N-C catalyst without silica, the silica-confined catalyst exhibits a remarkably improved catalytic activity and durability for the ORR, which are even higher than those obtained by a commercial Pt/C. The superior activity can be attributed to the inclusive Fe-N-C moieties with a non-planar Fe(II)-N4 structure, raised by an interaction between the disordered carbon black and pyrrolic N4-plane in this catalyst. The introducing of silica can not only contribute to the generation of the active Fe(II)-N4 moieties but also suppress the formation of Fe-based impurity phases. This work may open a door to the rational design and facile synthesis of highly active non-precious metal electrocatalysts towards the ORR.