Facile Ammonia Synthesis from Electrocatalytic N2 Reduction under Ambient Conditions on N-Doped Porous Carbon

Abstract

Ammonia has been used in important areas such as agriculture and clean energy. Its synthesis from the electrochemical reduction of N 2 is an attractive alternative to the industrial method that requires high temperature and pressure. Currently, electrochemical N 2 fixation has suffered from slow kinetics due to the difficulty of N 2 adsorption and N≡N cleavage. Here, N-doped porous carbon (NPC) is reported as a cost-effective electrocatalyst for ammonia synthesis from electrocatalytic N 2 reduction under ambient conditions, where its N content and species were tuned to enhance N 2 chemical adsorption and N≡N cleavage. The resulting NPC was effective for fixing N 2 to ammonia with a high ammonia production rate (1.40 mmol g –1 h –1 at −0.9 V vs RHE). Experiments combined with density functional theory calculations revealed pyridinic and pyrrolic N were active sites for ammonia synthesis and their contents were crucial for promoting ammonia production on NPC. The energy-favorable pathway for ammonia synthesis was *N≡N → *NH═NH → *NH 2 –NH 2 → 2NH 3 .