Regulated iron corrosion towards fabricating large-area self-supporting electrodes for an efficient oxygen evolution reaction

Abstract

Exploring cost-effective electrodes operating at a high current density above 400 mA cm⁻² is still challenging for the industrial application of water splitting. Herein, the corrosion layers of iron foam are tailored towards preparing self-supporting electrodes for the oxygen evolution reaction (OER). Corrosion reactants (Ni²⁺, O₂ and H₂O) are adopted to regulate the structures and electrochemical performances of electrodes on account of the diverse iron corrosion behaviors. By further comparing the spontaneous iron corrosion in ZnCl₂, CoCl₂, NiCl₂ and FeCl₃ solutions, it is identified that the appropriate electrode potentials of Ni/Ni²⁺ and Co/Co²⁺ are favourable for achieving uniformly ordered corrosion layers owing to the simultaneously occurring oxygen corrosion and replacement reaction. The as-prepared electrode exhibits excellent OER performances of affording low overpotentials of 221 and 291 mV to reach 100 and 500 mA cm⁻², respectively, as well as steadily operating at 500 mA cm⁻² for 100 h. Integrating with a prominent hydrogen evolution reaction (HER) catalyst, an industrially required current density of 500 mA cm⁻² has been obtained at 1.81 V. Importantly, a large-area electrode (8 × 8 cm²) has been successfully prepared. This work establishes potential possibilities for designing inexpensive and efficient electrocatalysts through regulated metal corrosion.