Pristine S,N-containing Mn-based metal organic framework nanorods enable efficient oxygen reduction electrocatalysis

Abstract

Owing to their unique physicochemical properties, metal–organic frameworks (MOFs) are a kind of promising material for electrocatalysis. However, many reports focus on the use of MOFs as precursors to produce efficient electrocatalysts by pyrolysis. The use of pristine MOFs with well-defined structures as efficient electrocatalysts directly is still a challenging problem. Herein, S,N-containing Mn^II[(Tdc)(4,4′-Bpy)]_n with different morphologies have been obtained by using Mn^II, thiophene-2,5-dicarboxylate (Tdc) and 4,4′-bipyridine (4,4′-Bpy) as raw materials via hydrothermal synthesis. Furthermore, the influences of different hydrothermal reaction times (0, 2 and 4 h) and anions (SO₄²⁻, Cl⁻, NO₃⁻ and CH₃COO⁻) on the morphologies, compositions and ORR activity of the resultant Mn-MOFs are also investigated at length. The results indicate that only the reaction of MnSO₄ with Tdc and 4,4′-Bpy for 4 h can form relatively uniform one-dimensional (1D) MOF nanorods. The 1D nanorods combine the favorable features towards the oxygen reduction reaction (ORR), such as a high surface area and efficient 1D electron/mass transport capability. Therefore, the Mn^II[(Tdc)(4,4′-Bpy)]_n nanorods display the highest ORR activity with an onset potential of 0.98 V and a half-wave potential of 0.78 V vs. RHE (reversible hydrogen electrode), which is even comparable to that of Pt/C. In addition, the Mn^II[(Tdc)(4,4′-Bpy)]_n nanorods exhibit higher stability, methanol resistance and ORR selectivity than Pt/C. The present study illustrates an efficient fabrication strategy for highly efficient 1D MOF nanorods for energy storage and conversion applications.