Residual ZnN_x moieties in ZIF-8 derived catalysts: Protective and synergistic effects for oxygen reduction

ZIF-8 derived carbons demonstrate admirable application prospects in electrocatalytic fields, while ZnN_x remaining in those materials are overlooked, crippling the validity of theoretic studies in researches. Herein, the residual Zn in ZIF-8 derived carbons are found could exceed 10 wt% even at carbonization temperatures over 900℃, and Zn-NCs with various Zn contents are adopted as supports to synthesize low-platinum ORR catalysts. Substantial characterizations manifest that ZnN_x in Zn-NC can not only provide Zn source for L1₀-PtZn intermetallic, but act as ‘spatial barriers’ to prevent the formation of inactive PtN_x, elevating the active Pt proportion in catalyst by ∼104%. The resultant Zn-NC-Ar-PtZn exhibits a mass activity of 0.557 mA/g_Pt and a peak density of 1.485 W/cm². DFT calculations show the strong thermodynamic tendency of forming PtN₄ without the protection of ZnN₄, and the superior durability and activity of Zn-NC-Ar-PtZn should be attributed to its Zn-derived ligand effects and the SMSI.