Ammonia Electrolysis Stack of Dual Layer Electrode with Pt-Ir Catalyst for Hydrogen Production

Abstract

Ammonia (NH3) electrolysis is an eco-friendly and economical hydrogen production technology. However, the slow kinetics of the ammonia oxidation reaction (AOR) limit the hydrogen production capacity and elevates the cell voltage with oxygen evolution reaction (OER) due to competitive OH adsorption at the anode. Herein, we fabricated the bulk top and dense bottom Pt-Ir catalyst dual layer electrode (Pt-Ir CDLE). The dense bottom catalyst layer (prepared by the doctor blade method) affects the AOR activity by improving ammonia mass transfer, and the bulk top catalyst layer (prepared by the spray method) prevents loss of the dense bottom catalyst layer to secure durability. We confirmed that the poisoning of the electrode surface elevates the cell voltage to the oxygen evolution reaction (OER) region. Ammonia electrolysis performance was evaluated with a single cell and then scaled up to an 8-cell stack with a total area of 200 cm2 for the first time in this study. Finally, an 8-cell stack of alkaline ammonia electrolysis produced 23~25 L hr-1 of hydrogen from ammonia with 45 % less power consumption than the water electrolysis stack. This study proposes a large-scale stack system for alkaline ammonia electrolysis and presents practical criteria for developing hydrogen production technology from ammonia with low power consumption.