A low-temperature ammonia electrolyser for wastewater treatment and hydrogen production

Ammonia is a pollutant present in wastewater and is also a valuable, carbon-free hydrogen carrier. Stripping, recovery, and anodic oxidation of ammonia to produce hydrogen via electrolysis is gaining momentum as a technology, yet the development of an inexpensive, stable catalytic material is imperative to reduce cost. Here, we report on a new nickel-copper (NiCu) catalyst electrodeposited onto a high surface area nickel felt (NF) as an anode for ammonia electrolysis. Cyclic voltammetry demonstrated that the catalyst/substrate combination reached the highest current density (200 mA cm−2 at 20 °C) achieved for a non-noble metal catalyst. A NiCu/NF electrode was tested in an anion exchange membrane electrolyser for 50 h; it showed good stability and high Faradaic efficiency for ammonia oxidation (88%) and hydrogen production (99%). We demonstrate that this novel electrode catalyst/substrate material combination can oxidise ammonia in a scaled system, and hydrogen can be produced as a valuable by-product at industrial-level current densities and cell voltages lower than that for water electrolysis.