Nitrogen-Defective Polymeric Carbon Nitride Nanolayer Enabled Efficient Electrocatalytic Nitrogen Reduction with High Faradaic Efficiency

Abstract

Identifying highly selective catalysts and accurately measuring NH₃ yield without false-positives from contaminations remain two challenges in electrochemical nitrogen reduction reaction (NRR). Here, we report N-defective carbon nitride grown on carbon paper (CN/C) as a highly selective electrocatalyst. The NH₃ yield was determined reliably by the slope of m_NH3-time plot rather than averaging the accumulated amount over time. Results showed the as-synthesized CN/C₆₀₀ (synthesized at 600 °C) with a higher density of C=N-C N_2C vacancies achieved an NH₃ production of 2.9 μg mg_cat.^-1 h^-1 at -0.3 V (versus RHE), ∼5.7-fold higher than CN/C₅₀₀. The Faradaic efficiency for CN/C₆₀₀ is among the highest of 62.1%, 33.9%, and 16.8% at -0.1 V, -0.2 V, and -0.3 V, respectively. The NH₃ production was verified by isotope ¹⁵N₂ experiments. Further increase of N-defects on CN/C₆₀₀ using plasma etching led to higher NH₃ yield than comparably larger current, pointing to N-defects sites for promoting NRR.