Water splitting studies in alkaline medium using graphite electrodes modified with transition metal oxides and compositions containing them

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: Mn[O.sub.2] and [Fe.sub.3][O.sub.4]. 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 [O.sub.2] and [H.sub.2] evolution reactions (OER and HER) was studied in alkaline medium. Out of the Mn[O.sub.2]-based electrodes, the one modified with the suspension containing 2 mg Mn[O.sub.2], 1 mg Carbon Black and 10 [micro]L Nafion solution displayed an OER overpotential ([[eta].sub.O2]) value, at i = 10 mA/[cm.sup.2], of 0.53 V, while the one manufactured using the suspension with 4 mg Mn[O.sub.2] and 10 [micro]L Nafion solution showed a HER overpotential ([[eta].sub.H2]) of 0.427 V (at i = -10 mA/[cm.sup.2]). From the [Fe.sub.3][O.sub.4]-based electrodes, the one modified with the suspension containing 2 mg [Fe.sub.3][O.sub.4] and 2 mg Carbon Black evidenced the highest catalytic activity for both reactions ([[eta].sub.O2] = 0.51 V and [[eta].sub.H2] = 0.43 V). Keywords: water splitting, oxygen evolution reaction, hydrogen evolution reaction, metal oxide, electrocatalysis