Axial π─Bond Tuning of Anchored FeN₄ for Electrocatalytic Oxygen Reduction

The curvature change of the support can control the induced local stress strain and directly change the properties and performance of the layered materials. Herein, we successfully in situ grew graphdiyne (GDY) on the surface of carbon nanotubes (CNTs) to form a heterojunction material with curved structure and highly surface-active. Our results indicated that the surface-grown GDY can deform into a curved-GDY (cGDY) due to internal stress. Such structural rearrangement regulates the charge distribution on interface of graphdiyne/CNTs and increases the charge density of C_sp─C_sp bonds within bent diacetylene linkages (-C_sp≡C_sp-C_sp≡C_sp-). While loading iron phthalocyanine (FePc) to this bent surface, the interactions and the interfacial repulsive force in the system were greatly enhanced, resulting in the elevated energy level of Fe 3d_z2, which was beneficial to the adsorption of O₂, and the hybridization between Fe (3d_xz, 3d_yz, and 3d_z2) and *OO (2p_x, 2p_y, and 2p_z) orbitals, significantly enhancing activation of O₂. Therefore, compared with the FeN₄ moiety on pure CNTs or GDY, this heterojunction structure through axial π─bond tuning demonstrates superior performance with a half-wave potential of 0.905 V and a Tafel slope of 31.7 mV dec^-1.