Ammonia splitting with electrode alternating for durable hydrogen production

Abstract

Ammonia is a promising hydrogen carrier. However, its practical deployment hinges on cost-effective splitting approaches to release hydrogen. Ammonia electrolysis, combining the ammonia oxidation reaction (AOR) and the hydrogen evolution reaction, is a promising decentralized solution that operates under mild conditions. Nevertheless, the susceptibility of nearly all AOR catalysts to severe poisoning compromises activity and stability. Here we show an electrode-alternating approach to regenerate poisoned catalysts in AOR while maintaining high hydrogen productivity. A Pt/C catalyst is chosen for demonstration because it synergizes high intrinsic activity, high regeneration capability and excellent corrosion resistance in electrolytes. Key parameters in electrode alternating, including step time and voltage, are optimized to minimize the hydrogen loss while maximizing productivity. A prototype with electrode alternating (±0.8 V) demonstrates ammonia splitting at a sustained current density of ~2 A cm−2 over 1,000 h, corresponding to a cost of ammonia decomposition to produce H2 at $$\sim {\rm{US}}{\rm{\$}}1\,{{\rm{kg}}}_{{{\rm{H}}}_{2}}^{-1}$$ . Electrocatalysts for ammonia oxidation tend to be poisoned by nitrogen-based intermediates. Here the authors use an electrode-alternating strategy that uses pulsed potential reversal to continuously regenerate the deactivated surface, enabling Pt-based ammonia electrolysis for over 1,000 h.