P-012

Virginija Kepenienė

virginija.kepeniene@ftmc.lt

Aušrinė Zabielaitė, Dijana Šimkūnaitė, Raminta Stagniūnaitė, Jūratė Vaičiūnienė, Loreta Tamašauskaitė-Tamašiūnaitė and Eugenijus Norkus

Center for Physical Sciences and Technology

Enhanced Electrocatalytic Activity of MnO2 Nanoparticles Supported on Graphitic Carbon Nitride for Oxygen Reduction and Evolution

This work presents the straightforward synthesis of non-precious catalysts, namely MnO2/C, MnO2-gCN, and MnOMnO2-gCN/C. 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). In comparison to the metal-free C, gCN, and gCN/C substrates that were used, the immobilization of MnO2 nanoparticles on the surface resulted in an enhancement of the electrocatalytic activity and the selectivity of the catalyst towards the four-electron reduction reaction of O2 to H2O The electrochemical performance of the prepared MnO2/C, MnO2-gCN, and MnO2-gCN/C catalysts has been investigated for oxygen reduction (ORR) and oxygen evolution (OER) reactions using cyclic and linear voltammetry. It has been demonstrated that the MnO2-gCN/C catalyst exhibits the most positive onset potential for the ORR, equal to 0.9 V vs. RHE, and a current density that is twofold that of the MnO2/C and MnO2$-gCN catalysts. Furthermore, the immobilization of MnO2 nanoparticles on carbonaceous substrates has been observed to increase the activity of OER, enhancing the onset potential to 0.15 V for all investigated catalysts. However, the most effective catalyst for the OER was the MnO2-gCN/C catalyst, which exhibited an onset potential of 1.53 V with an overpotential of 300 mV and a lowest overpotential of 390 mV at a current density of 10 mA·cm-2. Additionally, it displayed a Tafel slope of 85.2 mV dec-1. Furthermore, the MnO2-gCN/C catalyst exhibited noteworthy stability and catalytic activity, retaining approximately 85% of its initial signal in both long-term ORR and OER processes following continuous testing during chronoamperometric measurements for 3600 seconds. The results demonstrate that the MnO2/C, MnO2-gCN, and MnO2-gCN/C catalysts, which have been prepared in this study, have the potential to be employed as promising catalysts for low-cost and efficient non-precious metal electrocatalysts for ORR and OER.