MnO2 nanoparticles supported on graphitic carbon nitride as an electrocatalyst for oxygen reduction and evolution

The aim of this study is to present a straightforward methodology for the preparation of non-precious metal catalysts comprising MnO₂ and carbonaceous materials, namely graphite powder (C), graphitic carbon nitride (gCN), and graphitic carbon nitride/graphite powder (gCN/C) substrates. The morphology and composition of the prepared MnO₂/C, MnO₂–gCN, and MnO₂–gCN/C catalysts have been investigated using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrochemical performance of the prepared MnO₂/C, MnO₂–gCN, and MnO₂–gCN/C catalysts has been investigated for the oxygen reduction reaction (ORR) and oxygen evolution (OER) reaction using cyclic and linear voltammetry. All of the investigated catalysts exhibited enhanced electrocatalytic activity with regard to the ORR and OER processes when compared with the bare substrates. The MnO₂–gCN/C catalyst was found to be the most efficient catalyst for both investigated reactions when compared with MnO₂/C and MnO₂–gCN. The MnO₂–gCN/C catalyst demonstrated the most positive ORR onset potential of 0.9 V and the most negative OER onset potential of 1.53 V. Furthermore, it demonstrated remarkable stability, retaining approximately 85% of its initial signal after a continuous test of 24 hours in both long-term ORR and OER processes.