Two-Dimensional Mosaic Bismuth Nanosheets for Highly Selective Ambient Electrocatalytic Nitrogen Reduction

Electrochemical fixation of N₂ to ammonia is a promising strategy to store renewable energy and mitigate greenhouse gas emissions. However, it usually suffers from extremely low ammonia yield and Faradaic efficiency because of the lack of efficient electrocatalysts and the competing hydrogen evolution reaction. Herein, we report that the semiconducting bismuth can be a promising catalyst for ambient electrocatalytic N₂ reduction reaction (NRR). A two-dimensional mosaic bismuth nanosheet (Bi NS) was fabricated via an in situ electrochemical reduction process and exhibited favorable average ammonia yield and Faradaic efficiency as high as 2.54 ± 0.16 μgNH₃ cm⁻² h⁻¹ (∼13.23 μg mgcat.⁻¹ h⁻¹) and 10.46 ± 1.45% at −0.8 V versus reversible hydrogen electrode in 0.1 M Na₂SO₄. The high NRR electrocatalytic activity of the Bi NS could be attributed to the sufficient exposure of edge sites coupled with effective p-orbital electron delocalization in the mosaic bismuth nanosheets. In addition, the semiconducting feature, which limits surface electron accessibility, could effectively enhance the Faradaic efficiency. This work highlights the potential importance of less reactive main group elements with tunable p-electron density, semiconducting property, and ingenious nanostructure for further exploration of N₂ reduction reaction electrocatalysts.