New catalyst builds proton highways to tackle a long-standing hurdle in green ammonia synthesis
Over a century ago, the Haber-Bosch process, a two-step reaction for the synthesis of ammonia (NH₃), an irreplaceable chemical for the fertilizer industry, prevented the world from going into a serious food crisis. Today, however, the same method consumes about 1% of global energy and contributes more than 1% of annual anthropogenic CO₂ emissions.
A new covalent organic framework catalyst has been developed to address a major challenge in green ammonia synthesis. This innovation could help mitigate the substantial energy consumption and carbon emissions associated with the traditional Haber-Bosch process for producing ammonia, a crucial component of the fertilizer industry.
The research team designed hydroxyl-functionalized copper phthalocyanine-based covalent organic frameworks as electrocatalysts for electrocatalytic nitrate reduction, an environmentally-friendly alternative that employs nitrate from agricultural runoff and industrial waste instead of nitrogen gas. The catalyst's performance was enhanced by incorporating hydroxyl groups around copper active centers, which reorganized water molecules on the catalyst surface into continuous hydrogen-bonded chains.
This restructuring formed high-speed proton expressways, directing nearly all electrical charge towards ammonia production rather than unwanted byproducts. The most effective version of the catalyst achieved a peak Faradaic efficiency of 98.95%, and produced 65.84 mg of ammonia per hour in a flow cell, demonstrating superior selectivity and efficiency compared to standard catalysts.
While the benefits of this new catalyst are promising, further testing in real-world wastewater is necessary to ensure its efficiency remains consistent.
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