Bismuth stabilized by ZIF derivatives for electrochemical ammonia production: Proton donation effect of phosphorus dopants

N₂ electroreduction reaction (NRR) offers a feasible and promising alternative for NH₃ production by using clean energy sources. However, it is still obstructed by the pretty low NH₃ yield rate and Faradaic efficiency (FE) primarily due to the undesired competing hydrogen evolution reaction and the extremely stable N≡N bond. Herein, bismuth nanoparticles were successfully embedded in N and P co-doped carbon nanoflakes (Bi/NPC) by high-temperature pyrolyzation of Bi-zeolitic imidazole frameworks (ZIF) followed by phosphorization, and used as a high-efficiency catalyst toward N₂ electroreduction to NH₃. In 0.1 M KHCO₃ electrolyte, Bi/NPC exhibits excellent NRR performances, including a high NH₃ yield rate of 3.12 µg·h⁻¹·cm⁻² (−0.6 V vs. reversible hydrogen electrode (RHE)), an outstanding FE of 13.58% (−0.4 V vs. RHE), and a remarkable stability up to 36 h under ambient conditions. This outstanding NRR catalytic activity is mainly attributed to the intrinsic electrocatalytic NRR activity combined with the inert hydrogen evolution reaction (HER) activity of Bi, the adsorption and activation of N₂ facilitated by N dopants, as well as the superior conductivity and the large specific surface area of the two-dimensional layered carbon matrix. Notably, the hydrogen source provided by P dopant promotes the hydrogenation of the adsorbed N, which further boosts the NRR performance in alkaline electrolyte. The ultralong durability of Bi/NPC is attributed to the highly dispersed bismuth catalytic active centers confined in the skeleton of N and P co-doped carbon nanoflakes, which inhibits the agglomeration of bismuth centers. This work presents a novel avenue for designation and fabrication of high-performance Bi-based electrocatalysts for NRR.