Novel Mn-/Co-N<i><sub>x</sub></i> Moieties Captured in N-Doped Carbon Nanotubes for Enhanced Oxygen Reduction Activity and Stability in Acidic and Alkaline Media
Syed Shoaib Ahmad Shah, Tayyaba Najam, Muhammad Sufyan Javed, Mohammed M. Rahman, Panagiotis Tsiakaras
Abstract
Fe–N–C-based electrocatalysts have been developed as an encouraging substitute compared to their expensive Pt-containing equivalents for the oxygen reduction reaction (ORR). However, they still face major durability challenges from the in- situ production of Fenton radicals. Therefore, the synthesis of Fe-free ORR catalysts is among the emerging concerns. Herein, we have precisely applied a multistep heating strategy to produce mesoporous N-doped carbon nanostructures with Mn-/Co-Nx dual moieties from mixed-metal zeolitic imidazolate frameworks (ZIFs). It is found that their unique structure, with dual-metallic active sites, not only offers a high electrochemical performance for the ORR (E1/2 = 0.83 V vs reversible hydrogen electrode (RHE) in acid media), but also enhances the operational durability of the catalyst after 20 000 cycles with 97% of retention and very low H2O2 production (<5%) in 0.1 M HClO4. In addition, the catalyst performs well toward the ORR also in alkaline solution (exhibiting E1/2 = 0.90 V and 30 000 cyclic stability).