Rare earth insitu-doped ZIF-67 derived N doped C encapsulated Sm2O3/Co nanoparticles as excellent oxygen reduction reaction catalyst for Al-air batteries

A novel carbon coupled rare earth Sm doped zeolitic imidazolate framework-67 (ZIF-67) derived Sm2O3–Co/NEC300J electrocatalyst with an encapsulated structure was prepared via a composite synthetic strategy, which owns highly dispersed active sites and high conductivity. The introduction of Sm2O3 significantly improves the oxygen reduction reaction (ORR) electrocatalytic performance due to the strong synergistic effect between promoter Sm2O3 and guest Co species, in which the onset potential, half-wave potential and limiting current density are all improved compared to pristine ZIF-67 derived Co/NC. The introduction of Ketjen black EC300J (EC300J) brings high conductivity, so the precursor can be calcined under relative low temperature, and huge highly dispersed ORR active sites are created, meanwhile the EC300J offers a restricted pyrolysis environment to form carbon encapsulated structure. Therefore, Sm2O3–Co/NEC300J exhibits excellent activities and stability compared to Sm-doped ZIF-67 derived Sm2O3–Co/NC. For practical application, the designed Al-air battery with an air-cathode catalyst of Sm2O3–Co/NEC300J achieves the specific capacity of 1588 mAh·g-1Al at the discharge current density of 20 mA·cm−2, which almost equals to that of Pt/C. Furthermore, the peak power density and discharge voltage of Sm2O3–Co/NEC300J based Al-air battery are much higher than the Sm2O3–Co/NC, Co/NC and Pt/C counterparts.