Electrocatalytic oxygen reduction reaction at FeS2-CNT/GCE surface in alkaline medium

Abstract

The oxygen reduction reaction (ORR) has attracted more attention in recent time due to its wide applications in electrochemical energy transformation such as fuel cells, metal-air batteries, electrolyzers, and wastewater treatment. However, the development of inexpensive and highly efficient ORR electrocatalysts is still a great challenge. Herein, FeS2-carbon nanotube (CNT) nanocomposite was fabricated and deposited on a glassy carbon electrode (GCE) surface to inspect the electrocatalytic ORR in an alkaline medium. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were utilized to characterize the FeS2-CNT/GCE surface. The EIS and open circuit potential (OCP) analysis showed that the FeS2-CNT/GCE has excellent catalytic effects compared to a bare GCE. Kinetic investigations revealed that the ORR occurred through a consecutive reaction pathway accompanied by a fast electron transfer step and controlled by a diffusion-limited process. Analysis of hydrodynamic voltammograms confirmed that the oxygen molecules undergo a 2e- transfer irreversible redox process and HO2- is generated as an intermediate before converting into hydroxide as the final product. The standard rate constant was calculated to be 2.5 × 10−7 cms−1 and the reaction followed first order kinetics.