Single-atom oxygen reduction reaction electrocatalysts of Fe, Si, and N co-doped carbon with 3D interconnected mesoporosity

The development of non Pt-based catalysts (non-PBCs) that show excellent oxygen reduction reaction (ORR) activity for high-performance Zn-air battery (ZAB) and anion exchange membrane fuel cell (AEMFC) is highly necessitated. Here, the unprecedented single-atom ORR activity of Fe, Si, and N co-doped carbon (FeSiNC) supported on 3D interconnected mesoporous carbons (25 and 50 nm) derived from silica templates is reported. Si moieties connected to a carbon surface were involved in the formation of an atomically distributed FeSi_xN_4−xsite through substitution of Si at the N position in the Fe-N₄site, which is the ORR active site of the conventional FeNC. FeSiNC with its larger mesopore (50 nm) exhibits outstanding ORR activity comparable to the most efficient non-Pt-based catalysts and enhanced single-cell performances due to its enhanced mass-transport property. According to theoretical calculations, the ORR activity is originated from not only FeSi_xN_4−xsites located at the basal plane and inter-edge sites, but also C sites adjacent to the Si dopant in both edge and basal regions. Therefore, this study provides a facile strategy toward the rational design of inexpensive and highly active ORR catalysts applicable to single-cell devices.