Boosting the electrochemical performance of hematite nanorods via quenching-induced metal single atom functionalization

Abstract

Currently there is tremendous interest in supported metal single atom (MSA) materials owing to their remarkable performance in many fields. Typically MSA materials are prepared by co-precipitation or pyrolysis methods, and can be highly variable in terms of the spatial distribution of MSA sites created. Herein, we report a new method, quenching, as an effective synthetic strategy for loading MSA sites onto nanostructured supports. As a proof of concept, a hot α-Fe₂O₃@CNT fiber (CNT = carbon nanotube) was quenched rapidly by immersion in an aqueous solution of SnCl₄ at 4 °C, to yield a fiber uniformly decorated with Sn single atoms (Sn-Fe₂O₃@CNT fiber). The resulting Sn-Fe₂O₃@CNT fiber electrode exhibits outstanding performance, offering a capacitance of 391.32 mF cm⁻² at 0.24 mA cm⁻², which is more than 1.5 times that of the α-Fe₂O₃@CNT fiber. Moreover, an all-solid-state fiber-shaped supercapacitor consisting of a Sn-Fe₂O₃@CNT fiber negative electrode and a MnO₂@CNT fiber positive electrode affords a very high areal capacitance of 105.68 mF cm⁻² and an exceptional energy density of 6.09 mW h cm⁻³. The surface quenching strategy is expected to be widely applicable for the synthesis of MSA functionalized materials, thus opening up new avenues for energy and catalysis research.