Main-Group Metal-Nonmetal Dynamic Proton Bridges Enhance Ammonia Electrosynthesis

The electrochemical nitrogen reduction reaction (eNRR) is a crucial process for the sustainable production of ammonia (NH₃) for energy and agriculture applications. However, the reaction's efficiency is highly dependent on the activation of the inert N≡N bond, which is hindered by the electron back-donation to the π* orbitals of the N≡N bond, resulting in low eNRR capacity. Herein, we report a main-group metal-nonmetal (O-In-S) eNRR catalyst featuring a dynamic proton bridge, with In-S serving as the polarization pair and O functioning as the dynamic electron pool. In situ spectroscopic analysis and theoretical calculations reveal that the In-S polarization pair acts as asymmetric dual-sites, polarizing the N≡N bond by concurrently back-donating electrons to both the π_x* and π_y* orbitals of N₂, thereby overcoming the significant band gap limitations, while inhibiting the competitive hydrogen evolution reaction. Meanwhile, the O dynamic electron pool acts as a "repository" for electron storage and donation to the In-S polarization pair. As a result, the O-In-S dynamic proton bridge exhibits exceptional NH₃ yield rates and Faradaic efficiencies (FEs) across a wide potential window of 0.3 V, with an optimal NH₃ yield rate of 80.07±4.25 μg h^-1 mg^-1 and an FE of 38.01±2.02 %, outperforming most previously reported catalysts.