Inverse nanocomposites of polyaniline/MnO2 nanorods for efficient production of hydrogen peroxide through electrocatalytic oxygen reduction in acidic solution

Abstract

The selective two-electron oxygen reduction reaction (2e⁻ ORR) producing H₂O₂ through an electrocatalytic approach is an attractive alternative to the industrial anthraquinone oxidation method, enabling decentralized H₂O₂ production. This study explored the potential use of an inverse nanocomposite comprising polyaniline (PAni)-embedded α-MnO₂ nanorods for a selective 2e⁻ ORR in acidic medium. α-MnO₂, PAni, and inverse composites of α-MnO₂/PAni with different compositions were synthesized using hydrothermal, chemical oxidative polymerization, and solution sonication methods, respectively. Transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were employed to clarify various aspects, such as morphology, functional groups, microphase, crystallinity, etc., of the prepared materials. The electrocatalytic activity of the prepared inverse nanocomposites containing minute amounts of PAni dispersed phase towards the ORR in an acidic solution was evaluated with voltammetry at a rotating ring disk electrode, while the rate of H₂O₂ production was determined through chronoamperometry and the iodometric titration method. The rod-like, inverse α-MnO₂/PAni nanocomposite catalyst performs commendably for the 2e⁻ ORR with, on average, 80% selectivity toward H₂O₂ at a production rate of 433 mmol g_cat⁻¹ h⁻¹. A plausible mechanism for the ORR on the α-MnO₂/PAni nanocomposite in an acidic medium is discussed. These findings highlight the promise of inverse α-MnO₂/PAni nanocomposites as affordable and efficient electrocatalysts for on-site production of H₂O₂ through the ORR.