One-Pot Synthesis of CoFe-Nanomesh for Oxygen Evolution Reaction

Abstract

Iron-doped cobalt-based nanomeshes have been synthesized in a one-pot methodology. 2-Methyl imidazole (2-HMIM) acted as an etchant, while high valent iron increased the acidity of the solution and helped to synthesize ultrathin (thickness 1.9−2.0 nm) two-dimensional (2D)-nanomeshes having small uniform mesopores (3.8−4.0 nm) on the basal plane with high surface area and high pore volume. 20% iron-doped nanomesh material (Co 0.8 Fe 0.2 (OH) x ) revealed the best water oxidation reactivity, having an overpotential of 314 ± 3 mV, a mass activity of 413 ± 19 A/g, a turnover frequency (TOF) of 1.41 ± 0.04 s −1 , and a TOF EIS of 4.15 ± 0.04 s −1 . Electrochemical results suggested that the Co 0.8 Fe 0.2 (OH) x -nanomesh had a double-layer capacitance of 12.2 mF/cm 2 , corresponding to a roughness factor of 452, i.e., ion accessibility inside the nanomaterial was improved 452 times compared to the geometrical surface area of the electrode. This remarkable reactivity was due to (a) improved active sites for water oxidation at protruding edge sites and narrow mesopores on the basal planes of nanomeshes, (b) narrow mesopores on the basal planes ensured vertical ion penetration, vacant sites for water oxidation, and easy O 2 release from the material, and (c) electrochemical impedance spectroscopy results suggested that nanomesh formation ensured fast charge propagation inside the nanomaterial during the oxygen evolution reaction (OER) and fast charge transfer at the electrode/electrolyte interface.