WATER SPLITTING STUDIES IN ALKALINE MEDIUM USING GRAPHITE ELECTRODES MODIFIED WITH TRANSITION METAL OXIDES AND COMPOSITIONS CONTAINING THEM

Abstract

Present day scientific research is focused on the identification of renewable and clean alternatives to fossil fuels, with hydrogen being a promising energy source that fulfills both requirements. Given this context, the current work investigates the water splitting electrocatalytic properties of two hydrothermally synthesized transition metal oxides: MnO₂ and Fe₃O₄. Electrodes were obtained by modifying graphite substrates with suspensions in ethanol containing the catalytic materials as such or in compositions, and their activity for the O₂ and H₂ evolution reactions (OER and HER) was studied in alkaline medium. Out of the MnO₂-based electrodes, the one modified with the suspension containing 2 mg MnO₂, 1 mg Carbon Black and 10 µL Nafion solution displayed an OER overpotential (η_O2) value, at i = 10 mA/cm², of 0.53 V, while the one manufactured using the suspension with 4 mg MnO₂ and 10 µL Nafion solution showed a HER overpotential (η_H2) of 0.427 V (at i = -10 mA/cm²). From the Fe₃O₄-based electrodes, the one modified with the suspension containing 2 mg Fe₃O₄ and 2 mg Carbon Black evidenced the highest catalytic activity for both reactions (η_O2 = 0.51 V and η_H2 = 0.43 V).