Facile and fast fabrication of iron-phosphate supported on nickel foam as a highly efficient and stable oxygen evolution catalyst

Abstract

Electrocatalytic water splitting is one of the most promising routes for large-scale hydrogen production. However, it is hindered by the complex oxygen evolution reaction (OER) with sluggish kinetics. NiFe-based catalysts, which are known for their high activity, durability, and low-cost, have been a “hot topic” in research on OER catalysts. Increasing numbers of reports have indicated that Fe sites provide active centers. Meanwhile, Fe is considered as the cheapest and one of the most abundant transition-metal elements. Herein, we report a facile and fast method to prepare iron–phosphate films supported on a nickel foam scaffold (Fe–Pi/NF), with exposed Fe sites at the surface. Fe–Pi/NF exhibited outstanding activity for the OER, requiring low overpotentials of 215 and 257 mV to drive current densities of 10 and 100 mA cm⁻², respectively, in 1 M KOH solution. The TOF was as high as 0.381 s⁻¹ at an overpotential of 270 mV. The Tafel slope was as low as 28 mV dec⁻¹ between current densities of around 30 to 125 mA cm⁻². It also exhibited excellent durability during a 90 h stability test, and the calculated faradaic efficiency was close to 96%. For comparison, Fe(OH)₃/NF electrodes were also prepared. The results showed the OER activity of Fe–Pi/NF to be superior to those of Fe(OH)₃/NF. The incorporation of electronegative phosphate groups results in the great hydrophilicity of Fe–Pi/NF and effectively adjusts the electronic structure of Fe³⁺ and facilitates the oxidation of Fe³⁺ to Fe⁴⁺.