Pyrolytic Metamorphosis of Zn-TAL MOF into Highly Active Nitrogen-Doped Carbon Catalyst for Oxygen Reduction Reaction

Abstract

Metal-organic frameworks (MOFs) are promising precursors for the synthesis of high-performance metal-nitrogen-carbon (M-N-C) electrocatalysts. However, during pyrolysis, MOF’s initial structure integrity often breaks down and yields catalytically inactive metal agglomerates. This study describes the pyrolytic conversion of a Zn-MOF to Zn-N-C electrocatalyst. The optimized pyrolysis of the Zn-TAL MOF precursor successfully preserved its hollow sphere morphology, while the relatively low boiling point of zinc prevented the formation of Zn agglomerates. The pyrolysis at 1000 °C yielded ZnMOF-1000 - a highly porous electrocatalyst (SBET = 615 m2 g -1) with excellent oxygen reduction reaction (ORR) performance, namely onset potential (Eonset) value of 0.98 V, and half-wafe potential (E1/2) value of 0.84 V vs. reversible hydrogen electrode (RHE), comparable to the commercial Pt/C electrocatalyst. physical characterisation was performed to assess the morphology of the carbon framework, the absence of zinc aggregates, and the composition of the catalyst. In an anion exchange membrane fuel cell (AEMFC), the ZnMOF-1000 reached a peak power density of 553 mW cm-2 at 60 °C. The results show that Zn-TAL MOF is a promising precursor for Zn-N-C catalysts, offering an efficient platinum-free electrocatalyst option for fuel cells.