Dynamic Quantification of Nitrogen Species in Acidic Titanium-Catalyzed Nitrate Reduction toward Ammonia

The electrochemical reduction of NO 3 – to NH 3 offers a sustainable pathway for nitrogen recycling and can have significant implications for future chemical production. Key challenges in this domain include identifying the transient nature of reactive intermediates and the quantitative measurement of reaction products. These areas are critical for mechanistic insights that can inform future technological development. Here, we report an analysis of NO 3 – reduction on a metallic Ti surface, enabled by experimental methodologies with exceptional sensitivity and time resolution for the identification and quantification of NO 3 – reduction species. Combining gas chromatography, ion chromatography, and electrochemical mass spectrometry, we identified and quantified key reduction products (NH 4 +, H 2, NO 3 –, NO 2 –, N 2 O), including difficult-to-detect species NO. Ti electrodes achieved high NH 4 + Faradaic efficiency, averaging 82.3% at −1.0 V vs RHE, while for the first time, quantifying detectable NO and N 2 O. The appearance of NO supports its role as a reaction intermediate, while N 2 O formation points to an alternative N pathway that does not produce NH 3 . We also observed increased H 2 production, likely linked to Ti hydride formation, that coincides with decreases in NO and N 2 O production. These findings advance our understanding of NO 3 – reduction and offer new avenues for rationally designing catalysts that enhance NH 4 + selectivity and efficiency.