Iron-Polypyrrole Electrocatalyst with Remarkable Activity and Stability for Oxygen Reduction Reaction

Abstract

Listen

Translate article

A new facile template-free method is presented to synthesize Fe-treated N-doped carbon (Fe/N-C) catalysts for oxygen reduction reaction (ORR) by employing a synthesis protocol of pyrolysis-leaching-stabilization (PLS) sequence of polypyrrole in the presence of ferric source, which serves dual purposes of an oxidant for pyrrole polymerization and an iron source. Each step in the PLS sequence is assessed in detail in terms of related structural properties of resulting carbon catalysts, and their effects on ORR activities are elaborated to confirm the validity of the current synthesis protocol. It is found that as-prepared carbon catalyst exhibits outstanding high catalytic activity in both alkaline and acidic conditions. The carbon catalyst prepared at pyrolysis temperature of 900 oC (FePPyC-900) shows remarkably high ORR activity with onset potential of 0.96 V (vs. RHE), which is similar to that of Pt/C, whereas the half-wave potential (E1/2) of FePPyC-900 is 0.877 V, which is more positive than that of Pt/C at the same catalyst loading amount in alkaline condition. Furthermore, the FePPyC-900 catalyst also illustrates exceptionally high activity in acidic condition with onset and half-wave potentials, which are almost comparable to those of the state-of-the-art Pt/C catalyst, which is rarely observed for non-Pt based carbon catalyst. In addition, the FePPyC-900 catalyst displays much better stability and methanol tolerance than the Pt/C and exhibits four electron transfer pathway in both alkaline and acidic conditions. Such extraordinary high ORR activity and stability the FePPyC samples can be attributed to the implementation of extra stabilization step in addition to conventional sample preparation steps of pyrolysis and subsequent leaching in current PLS synthesis protocol as well as to the use of highly conducting PPy as a single precursor of carbon and nitrogen in the presence of Fe.