Pyrolysis-Free Synthesis of Bimetal Phthalocyanine Covalent Organic Polymers/Ordered Mesoporous Carbon Nanocomposites for an Efficient Oxygen Reduction Reaction

Abstract

The development of non-noble metal−nitrogen ring complex (M−N− C) catalysts with high activity and stability for the oxygen reduction reaction (ORR) is of great significance. However, M−N−C catalysts are generally prepared from precursors under high-temperature pyrolysis, which leads to complex product structures and makes it difficult to identify the catalytic active center. Herein, we have successfully structured a novel bimetal phthalocyanine covalent organic polymer/ordered mesoporous carbon (CoFe-COP/OMC) electrocatalyst through a pyrolysis-free approach. Due to the well-defined active sites (Fe/CoN 4 ), ordered COP structure, and highly conductive carrier materials, the CoFe-COP/OMC nanocomposite exhibits remarkable ORR electrocatalytic activity with a half-wave potential and initial potential of 0.908 and 0.932 V (vs reversible hydrogen electrode (RHE)), respectively, a limiting current density of 5.35 mA cm −2 , and a nearly four-electron reduction pathway. In addition, the acquired hybrid catalysts show excellent methanol resistance and electrochemical stability compared with Pt/C. The outstanding performance confirms that the CoFe-COP/OMC nanocomposite is a promising high-efficiency ORR catalyst for metal−air batteries and fuel cells.

Mono-, bi- and tri-metallic Fe-based platinum group metal-free electrocatalysts derived from phthalocyanine for oxygen reduction reaction in alkaline media

“…Overall, the ORR results for Fe 600 and Fe–Ni–Cu 600, with E on values of 0.96 V ( vs. RHE) and E 1/2 values of 0.9 V ( vs. RHE), exhibited intriguing performance compared to similar electrocatalysts reported in previous related articles (Table S6†). 38,56–58,63,93–96…”

Activity Origin and Catalytic Mechanism of the M–N–C Catalysts for the Oxygen Reduction Reaction

“…Among the different transition metal (Fe, Co, Mn, Ni, Cu, and Zn) active sites, atomically dispersed Fe–N–C and Co–N–C are most considered for ORR due to their higher activity. − The Co–N–C catalysts show alleviated “Fenton-like” process and is considered as an ideal substitute for Fe–N–C electrocatalysts . In many reports, ZIF-67, − cobalt ion-coordinated covalent–organic polymer (Co/COP), ,, cobalt phthalocyanine (CoPc), − etc., have been applied as precursors for the synthesis of Co–N–C catalysts. For instance, Freitas et al used ZIF-67 as single Co- and N-source to synthesize Co(10)–N–C, which possessed high 4e – ORR activity with an E 1/2 of 0.85 V versus RHE under alkaline conditions.…”