Facile Synthesis of High-Porous Noble-Metal-Free Catalyst for Highly Efficient Oxygen Reduction Reaction

Abstract

High-porous noble-metal-free catalyst is great alternative for oxygen reduction reaction (ORR) in fuel cells. But, there are some challenges in further performance and stability and understanding of reaction mechanisms on electro-catalyst. Herein, we design a facile method to synthesis high-porous noble-metal-free material from metal-organic framework through only one pathway. After significant pyrolysis process of metal−metalloporphyrin framework (MMPF-6), resultant product could potentially play a very important role for highly efficient oxygen reduction reaction in both alkaline and acidic mediums. Carbonized MMPF-6 shows highest ORR activity with onset and half-wave potentials of 976 and 848 mV in 0.1 M KOH, respectively, which are similar activity to those of commercial Pt/C (half-wave potential 860 mV vs RHE). Moreover, carbonized MMPF-6 has much greater long-term stability under alkaline and acidic mediums than commercial Pt/C. We suggest that the carbonized MMPF-6 catalyst has an electrochemical active surface area due to ensemble effect between zirconium oxide cluster and iron as active site. Electrochemical analysis shows that the carbonized MMPF-6 catalyst in 0.1 M KOH and HClO4 follows the efficient four-electron-tranfer pathway.