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 FeSixN4−x site through substitution of Si at the N position in the Fe–N4 site, 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 FeSixN4−x sites 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.