Amorphous nanostructured Ni–Fe oxide as a notably active and low-cost oxygen evolution reaction electrocatalyst for anion exchange membrane water electrolysis†

Abstract

The oxygen evolution reaction (OER) is a critical bottleneck in the commercial evolution of anion exchange membrane water electrolyzers (AEMWEs). As a potential substitute for the scarce and expensive noble metal-based electrocatalysts typically used to improve the OER activity, here amorphous NiFe oxides with varying Ni/Fe ratios were synthesized using a simplistic and cost-effective sol–gel method. After carefully investigating the structural and morphological attributes of the derived electrocatalysts, their OER activities were analyzed by acquiring the half-cell measurements. First, the influence of the electrochemical ink formulation and additives on the activity of the electrocatalyst was studied, followed by elucidating the electrocatalyst loading to configure the working electrode on the rotating disk electrode (RDE). By comparing the activities of different synthesized NiFe oxides, it was observed that Ni_0.75Fe_0.25O delivers the peak performance with a minimum overpotential of ca. 290 mV. Therefore, the aforementioned sample was utilized to configure the anode electrode for a lab-scale AEMWE, achieving 3.7 A cm⁻² at 2 V and 80 °C while demonstrating promising stability trends.

Keywords: NiFe oxide; AEM-WE; Alkaline media; Inorganic oxides; OER; PGM-free electrocatalysts.