Nitrogen-Defective Polymeric Carbon Nitride Nanolayer Enabled Efficient Electrocatalytic Nitrogen Reduction with High Faradaic Efficiency
Guiming Peng, Jiawen Wu, Mingzhan Wang, Jens Niklas, Hua Zhou, Chong Liu
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 mNH3-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 N2C vacancies achieved an NH3 production of 2.9 μg mgcat.–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.