Controllable synthesis and electrochemical capacitor performance of MOF-derived MnOx/N-doped carbon/MnO2 composites

Abstract

A series of MnO_x/N-doped carbon/MnO₂ composites with high nitrogen amounts, namely MnO_x/NC/MnO₂, was successfully fabricated. These composites were synthesized by soaking the thermally decomposed products of Mn-MOF precursors in potassium permanganate solutions of different concentrations. The Mn-MOF precursors were constructed from the coordination of N-rich linker, 3-amino-1H-1,2,4-triazole-5-carboxylic acid (HATC) or pyrazine-2,3-dicarboxylic acid (H₂PDA) with Mn(II) ions. The as-synthesized composites, particularly the samples with moderate carbon/nitrogen ratios (6.76 and 1.84 for C1- and C2-based composites, respectively,) showed excellent rate capabilities, low series resistances and charge-transfer resistances as well as superior long-term cycling stabilities (more than 88% after 5000 unceasing cycles). This enhancement should be attributed to the inter-effect relationship among carbon, nitrogen and the MnO₂ layer, which gives rise to a superior synergistic-effect in minimizing ionic and electronic transmission distances, resulting in better performances.