Promoting Oxygen Reduction Reaction by Inducing Out-of-Plane Polarization in a Metal Phthalocyanine Catalyst

Metal phthalocyanine (MPc) material with a well-defined MN₄ moiety offers a platform for catalyzing the oxygen reduction reaction (ORR), while the practical performance is often limited by the insufficient O₂ adsorption due to the planar MN₄ configuration. Here, a design (called Gr-M_G -O-M_P Pc) is proposed, where the metal of MPc (M_P ) is axially coordinated to a single metal atom in graphene (Gr-M_G ) through a bridge-bonded oxygen atom (O), introducing effective out-of-plane polarization to promote O₂ adsorption on MPc. Manipulating the out-of-plane polarization charge by varying types of M_P and M_G (M_P = Fe/Co/Ni, M_G = Ti/V/Cr/Mn/Fe/Co/Ni) in the axial coordination zone of -M_G -O-M_P - are examined by density functional theory simulations. Among them, the catalyst of Gr-V-O-FePc stands out with the highest calculated O₂ adsorption energy, which is synthesized successfully and verified by systemic X-ray absorption spectroscopy measurements. Importantly, it delivers a remarkable ORR performance with half-wave potential of 0.925 V (versus reversible hydrogen electrode) and kinetic current density of 26.7 mA cm^-2 . This thus demonstrates a new and simple way to pursue high catalytic performance by inducing out-of-plane polarization in catalysts.