One-step annealing synthesis of Co core-PdZn intermetallic shell composite as a bifunctional oxygen electrocatalyst for zinc-air batteries

PdZn intermetallic has excellent electrocatalytic properties due to the strong synergistic effects caused by the ordered arrangement of atoms. It is often synthesized by annealing Pd/ZnO in a hydrogen atmosphere. However, the low conductivity of ZnO crystals limits electron conduction , which is not conducive to electrocatalytic reactions . To avoid conductivity degradation, we annealed Zn 2+ -doped ZIF-67 adsorbed with Pd precursors in a nitrogen atmosphere. The key component, “ghost ZnO,” produced by the decomposition of ZIF during pyrolysis , was used to form intermetallic with Pd by reactive metal-support interaction. The remaining ZnO crystals were converted to amorphous ZnO or removed by sublimation. A composite structure of metal core-intermetallic shell was formed with the surface energy as the driving force. Co@o-PdZn/NC (Pd weight  = 2.47 %) exhibited strong oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electrocatalytic activity (reversible oxygen overpotential of 0.771 V). Moreover, it provided great performance in rechargeable zinc-air batteries (ZABs). In this study, the reactive metal-support interaction (RMSI) between the key component “ghost ZnO” and Pd was used by a one-step annealing method, and the growth process of nanoparticles was precisely controlled using the difference in surface energy between the metals to properly design the catalyst surface structure. The synthesized metal core-PdZn intermetallic shell composite is a promising bifunctional oxygen electrocatalyst . These findings provide a new strategy for designing composites with a metal core-intermetallic shell structure.