Abstract
Conversion of naturally abundant nitrogen to ammonia is a key (bio)chemical process to sustain life and represents a major challenge in chemistry and biology. Electrochemical reduction is emerging as a sustainable strategy for artificial nitrogen fixation at ambient conditions by tackling the hydrogen- and energy-intensive operations of the Haber–Bosch process. However, it is severely challenged by nitrogen activation and requires efficient catalysts for the nitrogen reduction reaction. Here we report that a boron carbide nanosheet acts as a metal-free catalyst for high-performance electrochemical nitrogen-to-ammonia fixation at ambient conditions. The catalyst can achieve a high ammonia yield of 26.57 μg h–1 mg–1cat. and a fairly high Faradaic efficiency of 15.95% at –0.75 V versus reversible hydrogen electrode, placing it among the most active aqueous-based nitrogen reduction reaction electrocatalysts. Notably, it also shows high electrochemical stability and excellent selectivity. The catalytic mechanism is assessed using density functional theory calculations.
Highlights
Conversion of naturally abundant nitrogen to ammonia is a keychemical process to sustain life and represents a major challenge in chemistry and biology
Biological N2 fixation is catalyzed by nitrogenase at ambient conditions through multiple proton and electron transfer steps, requiring a significant energy input delivered by adenosine triphosphate (ATP)[11,19,20,21]
In 0.1 M hydrochloric acid (HCl), it is capable of achieving an average NH3 formation rate and a Faradaic efficiency (FE) as high as 26.57 μg h–1 mg–1cat. and 15.95% at –0.75 V, respectively, placing it among the most active aqueous-based N2 reduction reaction (NRR) electrocatalysts
Summary
Conversion of naturally abundant nitrogen to ammonia is a key (bio)chemical process to sustain life and represents a major challenge in chemistry and biology. Electrochemical reduction is emerging as a sustainable strategy for artificial nitrogen fixation at ambient conditions by tackling the hydrogen- and energy-intensive operations of the Haber–Bosch process It is severely challenged by nitrogen activation and requires efficient catalysts for the nitrogen reduction reaction. Electrochemical N2 reduction using protons and electrons can be powered by renewable energy from solar or wind sources, offering a promising environmentally benign process for sustainable artificial N2 fixation at room temperature and pressure[22,23] This process, is severely challenged by N2 activation and demands efficient catalysts for the N2 reduction reaction (NRR)[24,25,26]. Density functional theory (DFT) calculations suggest that the *NH2–*NH2→*NH2–*NH3 reaction is the rate-limiting step
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