Enhanced anion exchange membrane water electrolysis based on advanced PGM-free electrode formulations

Abstract Optimal electrode formulations were developed for anionic exchange membrane electrolysis cells. These included improved platinum-group metals (PGMs) free cathodic NiMo and anodic NiFe-oxide-hydroxide (Layered Double Hydroxide, LDH)-based electrocatalysts. The synthesis of the electrocatalysts was performed using simple and cost-effective co-precipitation methods. The characterization of the electrocatalysts included an analysis of their physico-chemical properties with regard to the crystallite size and active phase dispersion. The optimal ionomer dispersion casted for the catalytic ink was investigated. The assessment of the improved electrodes was carried out in single cell in the presence of an AEM hydrocarbon FumaTech® membrane. Despite the reduced crystallite size in supported NiMo alloy electrocatalysts, their performance was affected by lower catalytic activity and higher activation control with respect to unsupported NiMo electrocatalysts. Three different ionomers’ contents were investigated (33 wt. %, 20 wt. % and 10 wt. %) to individuate the most promising electrode formulations for the AEM electrolysis. A 10 wt. % of ionomer content in the electrode showed the best performance for unsupported anode and cathode electrocatalysts. This optimal ionomer concentration appeared related to the enhanced gas permeability of the catalytic layers while assuring appropriate binding characteristics. The achieved performance was comparable or better than the best results observed in the literature under similar operating conditions showing more than 2 A cm −2 at 2 V/cell after 100 h operation for a PGM-free AEM water electrolysis cell. The optimized configuration showed promising characteristics for further development and upscaling for large scale AEM water electrolysis applications.