Microstructure regulation of carbon nitrides for electrochemical nitrogen fixation

Abstract

The electrochemical synthesis ammonia from nitrogen fixation utilizing sustainable electric energy to realize ammonia (NH3) production under ambient conditions. Herein, we introduce a microstructure regulation strategy to improve the electrochemical nitrogen reduction reaction (eNRR) performance of carbon-nitrogen solid materials (CNs). The CN-Ami, CN-Urea and CN-Mel were obtained under high temperature solid state reaction with 3-amino-1,2,4-triazole, urea and melamine as organic molecular precursors, respectively. Three CNs show great differences in their morphologies and microstructures. Where the CN-Ami has numerous heptazine fragments and more terminal CN sites compared to CN-Urea and CN-Mel. And CN-Ami exhibits the best eNRR performance in both of activity and selectivity among three CNs, the maximum production rate of NH3 is 10.2 μg−1 mg−1cat and Faraday efficiency of NH3 is 20.3% under the potential of 0 V vs reversible hydrogen electrode (RHE). The ammonia production rate remained initial 85.9% during the 6 cycles eNRR tests. Finally, the edge defect of heptazine (C3) is proved as the catalytic active site of NRR by theoretical calculations.