Atomically dispersed antimony on N-doped carbon for highly efficient oxygen reduction reaction

Abstract

Main-group metal based single-atom catalysts are attracting increasing research attention in electrochemical catalysis owing to their partially occupied valence p-orbitals. Herein, we report a series of atomically dispersed Sb-N-C catalysts (including Sb-N-CNP, Sb-N-CNL and Sb-N-CNT) synthesized by a facile adsorption-pyrolysis strategy for oxygen reduction reaction (ORR). Apart from generating atomically dispersed Sb-N5 sites as active centers, self-evaporation of Sb during pyrolysis process has created abundant micro/meso-pores in Sb-N-C catalysts. Benefitting from these advantageous features, Sb-N-C presents outstanding ORR activity (Sb-N5 sites) and efficient mass transport (micro/meso-pores). By rotating disk electrode (RDE) test in alkaline media, Sb-N-C exhibits a most positive half-wave potential of 0.90 V vs. RHE and a highest kinetic current density up to 43.8 mA cm−2 at 0.85 V vs. RHE. As gas diffusion electrode (GDE), Sb-N-CNP0.2 demonstrates fast O2 diffusion and transport that enables smaller mass transport overpotential at high current densities up to 800 mA cm−2. Finally, Zn-air battery that uses the Sb-N-CNP catalyst as air electrode achieves a maximum power density of 180 mW cm−2 and more than 1000 hs of continuous operation. This work further demonstrates the excellent performance of main-group Sb single-atom catalyst toward ORR and applications in practical energy conversion devices.