Ultra-thin bismuth nanosheets on copper foam enabling high-efficiency electrocatalytic nitrogen reduction for ammonia synthesis

Electrocatalytic nitrogen reduction reaction (NRR) represents a promising technology poised to mitigate the high energy consumption and substantial CO₂ emissions inherent in conventional ammonia (NH₃) synthesis method. However, sluggish N ≡ N bond dissociation and competitive hydrogen evolution reaction severely impede the NRR. Therefore, it is crucial to rationally design electrocatalysts to achieve efficient NRR. In this work, bismuth (Bi) nanosheets grown on three-dimensional copper foam substrates are synthesized by a simple galvanic replacement reaction and subsequently employed as efficient NRR catalysts. The high catalytic activity of Bi nanosheets for NRR can be attributed to the ultra-thin thickness of 4–6 atomic layers, extensive specific surface area, abundant pore structure as well as enhanced charge transfer. It is shown that Bi nanosheets subjected to a 24-h galvanic replacement reaction exhibit optimal activity, achieving an NH₃yield of 1.99 μg cm⁻² h⁻¹ and a Faradaic efficiency of 4.68 %. In addition, the Bi nanosheets on copper foam demonstrate relatively excellent stability over 12 h of operation. This work introduces a novel approach for developing electrodes via galvanic displacement reactions to enhance the NRR performance.