Design principles for transition metal nitride stability and ammonia generation in acid

Transition metal nitrides have shown promise as electrocatalysts in proton exchange membrane fuel cells and electrolyzers, but the instability of these nitrides in acid has limited their function for such technologies. On the other hand, having fast, complete nitride dissolution and ammonia formation in acid can offer new opportunities for distributed, on-demand ammonia generation. Optimizing nitride chemistries for these clean energy applications requires design principles for nitride dissolution and ammonia formation in acid. Here, we report that lowering the nitrogen 2p band center of transition metal nitrides relative to the Fermi level weakens metal-nitrogen bonds and increases labile metallic character, reducing dissolution reaction barriers and boosting ammonia formation kinetics in acid. Increasing the solubility of dissolved metal cat-ions further facilitates the decomposition of nitrides in acid by prohibiting surface oxide passivation. These findings highlight essential future directions for preventing nitride dissolution or facilitating ammonia production for diverse acidic applications.

Automated summary

Transition metal nitrides have potential as electrocatalysts in fuel cells and electrolyzers, but their instability in acid limits their function. However, complete nitride dissolution and ammonia formation in acid can provide new opportunities for on-demand ammonia generation. This study finds that lowering the nitrogen 2p band center weakens metal-nitrogen bonds, increases labile metallic character, and enhances ammonia formation kinetics in acid.