Iron doping of coordination polymer nanocubes and post-thermolysis for efficient oxygen reduction reaction single-atom catalysis

Abstract

Increasing the number of iron-nitrogen (Fe-Nx) active sites is essential for enhancing the electrocatalytic activity of iron-nitrogen-carbon (Fe_NC) catalysts toward the oxygen reduction reaction (ORR), as Fe-Nx sites facilitate the direct 4-electron reduction pathway. In this study, we develop a Fe_NC catalyst derived from Zn-based coordination polymer nanocube (Zn-CPN). Zn-CPN is synthesized by incorporating the [N3] ligand into a mixture of Zn2+ and 2-methylimidazole (2-MeIM), which is subsequently transformed into Fe_NC through Fe doping followed by pyrolysis. The tridentate Namide−Npyridine−Namide fragments within the [N3] ligand function as metal-binding sites for Fe ions during the doping process, ultimately yielding a substantial quantity of Fe-Nx active sites. Notably, structural analyses reveal that Fe atoms are atomically dispersed within the Fe_NC catalyst, forming single-atom Fe-Nx active sites that further boost catalytic efficiency. Consequently, the obtained Fe_NC demonstrates enhanced ORR activity, attaining an onset potential of 1.064 V and a half-wave potential of 0.872 V, outperforming those of Pt/C and the ZIF-8-derived counterpart. The superior ORR activity of Fe_NC can be attributed to the abundance of single-atom Fe-Nx active sites, along with its high surface area and plentiful porosity inherited from the Zn-CPN template. Our research presents an innovative strategy for developments in synthesizing single-atom catalysts. © Elsevier B.V.