Carbon-Negative Ammonia Production from the Air.

Abstract

Ammonia holds paramount importance as a fundamental chemical commodity for large-scale production of fertilisers and hydrogen carriers. The conventional Haber-Bosch process relies heavily on fossil fuels, making ammonia synthesis a significant contributor to greenhouse gas emissions. Here, we show a carbon-negative ammonia synthesis process that not only produces ammonia from the air but also directly captures the atmospheric CO₂ (DAC). This process uses lithium as a mediator to cleave the nitrogen gas via a nitridation reaction at ambient pressure below 80 °C. Exposing the nitride to moisture naturally yields ammonia. The co-produced lithium hydroxide intermediate allows for spontaneous absorption of CO₂ with an exceptional capacity of 18.4 mmol CO₂/g. The resultant lithium carbonate is electrolysed at ambient conditions to recycle the metallic lithium and release high-purity gaseous CO₂. This proof-of-concept of ammonia production from air coupled with DAC paves a new way for the development of sustainable and negative-emission technologies.