Exploring the Regulation Mechanism of Heat‐Treating Temperature on ZIF‐8 for Oxygen Reduction Reaction

Abstract Zeolitic imidazolate framework‐8 (ZIF‐8) exhibits broad application in oxygen reduction reaction (ORR). Herein, we heat treated ZIF‐8 nanoparticles under different temperature to investigate temperature regulation mechanism for ORR. Zn─N 4 coordination is maintained for all the catalysts. As the heat‐treatment temperature increases, the bond length of Zn─N decreases from 2.017 Å for ZIF‐8 to 1.978 Å for ZIF‐8–600. Shortened bond length increases electron cloud overlap and enhances charge transfer from N to Zn, leading to increased *OOH adsorption and enhanced O─OH bond cleavage. Thus, ORR selectivity is shifted from H 2 O 2 to H 2 O. ZIF‐8 exhibited optimal 2‐electron performance with 2.56 transferred electrons and 72% H 2 O 2 selectivity at 0.3 V. As the heating temperature increases, 4‐electron ORR selectivity is preferred. The H 2 O 2 selectivity dropped to 23.6% with nearly 4 transferred electrons. ZIF‐67, with Co as the metal center, exhibits high 4‐electron ORR activity with a H 2 O 2 selectivity of only 10.6% and a transferred electron number of 3.79. Therefore, the change of selectivity preference is closely related to the metal center and bond length of Zn─N. Namely, Zn center and longer Zn─N bond length promotes 2‐electron ORR selectivity. These findings provide a guideline to design efficient ORR catalysts with controlled selectivity.