P-Block Atomically Dispersed Antimony Catalyst for Highly Efficient Oxygen Reduction Reaction.

Main-group (s- and p-block) metals are generally regarded as catalytically inactive due to the delocalized s/p-band. Herein, we successfully synthesized a p-block antimony single-atom catalyst (Sb SAC) with the Sb-N4 configuration for efficient catalysis of the oxygen reduction reaction (ORR). The obtained Sb SAC exhibits superior ORR activity with a half-wave potential of 0.86 V and excellent stability, which outperforms most transition-metal (TM, d-block) based SACs and commercial Pt/C. In addition, it presents an excellent power density of 184.6 mW cm-2 and a high specific capacity (803.5 mAh g-1 ) in Zn-air battery. Both experiment and theoretical calculation manifest that the active catalytic sites are positively charged Sb-N4 single-metal sites, which have closed d shells. Density of states (DOS) results unveil the p orbital of the atomically dispersed Sb cation in Sb SAC can easily interact with O2 -p orbital to form hybrid states, facilitating the charge transfer and generating appropriate adsorption strength for oxygen intermediates, lowering the energy barrier and modulating the rate-determining step. This work sheds light on the atomic-level preparing p-block Sb metal catalyst for highly active ORR, and further provides valuable guidelines for the rational design of other main-group-metal SACs.