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

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.