Defect Engineering Metal‐Free Polymeric Carbon Nitride Electrocatalyst for Effective Nitrogen Fixation under Ambient Conditions

Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions provides an intriguing picture for the conversion of N 2 into NH 3 . However, electrocatalytic NRR mainly relies on metal‐based catalysts, and it remains a grand challenge in enabling effective N 2 activation on metal‐free catalysts. Here we report a defect engineering strategy to realize effective NRR performance (NH 3 yield: 8.09 μg h −1  mg −1 cat. , Faradaic efficiency: 11.59 %) on metal‐free polymeric carbon nitride (PCN) catalyst. Illustrated by density functional theory calculations, dinitrogen molecule can be chemisorbed on as‐engineered nitrogen vacancies of PCN through constructing a dinuclear end‐on bound structure for spatial electron transfer. Furthermore, the N−N bond length of adsorbed N 2 increases dramatically, which corresponds to “strong activation” system to reduce N 2 into NH 3 . This work also highlights the significance of defect engineering for improving electrocatalysts with weak N 2 adsorption and activation ability.