Straightforward Preparation of Fe-Based Electrocatalytic Films at Various Substrates for IrO2-like Water Oxidation Activity

Abstract

Here, we report a cost-effective and easily accessible nanotextured iron oxide electrocatalyst, which behaves much better than the benchmark noble metal catalysts, such as IrO2, for oxygen evolution reaction (OER) catalysis. In a typical procedure, a magnetite electrocatalytic layer (Fe3O4-ECs) is deposited over high surface area three-dimensional substrates, such as Fe foam (FeF), stainless steel mesh (SS), and Ni foam (NiF), following a simple chemical vapor deposition process. As-prepared catalysts are thoroughly analyzed by various analytical techniques. Field emission scanning electron microscopy (FESEM) analysis shows conformal coatings of catalysts over all of the substrates; however, a continuous sheath of spherical nanostructures is shown to grow over FeF surfaces only. OER activities of all electrocatalytic layers were comparatively evaluated under similar electrochemical conditions in alkaline (1.0 M KOH) media. All of the catalysts employed here presented satisfactory OER activity. Interestingly, the samples prepared over FeF (Fe3O4-ECs/FeF) exhibit a comparatively significant OER activity, initiating OER and achieving current decade at an overpotential of just 160 and 180 mV, respectively. It further presents a low Tafel slope of 41 mV/dec, high exchange current density, mass activity, electrochemically active surface area (ECSA), and specific activity of 4.9 mA/cm2, 8750 mA/mg, 376.25 cm2, and 2.79 mA/cm2, respectively. Notably, Fe3O4-ECs/FeF also demonstrates strong long-term durability for an extensive OER process with its activity being retained for continuous 20 h and a high turnover frequency of 4.6 s–1 at an overpotential of 0.32 V. Thus, Fe3O4-ECs/FeF outperforms benchmark OER catalysts, including IrO2, NiO, and CoO, when studied under identical conditions. This distinct behavior among other catalysts may be ascribed to nanoscale morphological features and synergistic effects of Fe-based catalysts with underlying Fe support. Thus, this study facilitates the time-effective development of 3D low-cost electrocatalysts for efficient OER that may have commercial applicability.