Abstract
The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction (ORR) at the cathode. Herein, we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube (FeSAC/PCMT) sponge. Benefiting from its unique structure that greatly facilitates the catalytic kinetics, mass transport, and electron transfer, our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at -3 mA cm(-2). When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries, high peak power densities of 183.1 and 58.0 mW cm(-2) were respectively achieved, better than its powdery counterpart and commercial Pt/C catalyst. Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N-5 species in FeSAC/PCMT. This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes, provides a significant new insight into the catalytic mechanisms, and helps to realize significant advances in energy devices.