Effective Electrochemical Nitrogen Reduction through π Back-donation Process in Mn3+ of Mn-doped g-C3N4.

Ammonia (NH3) synthesis via nitrogen reduction reaction under mild conditions is challenging due to the difficulty of activating nitrogen. Herein, Mn-doped g-C3N4 (x-Mn-CN, x = 5, 10, and 15) catalysts with efficiency NRR performance were synthesized. The resulting 5-Mn-CN exhibits higher NRR performance (NH3 yield rate: 15.2 μg h−1 mgcat−1, Faradaic efficiency: 7.1%) at -0.4 V (vs. RHE) than others. It is found that the active sites of Mn3+ are generated by electron transfer from Mn2+ to the N of g-C3N4, and active N2 through the π back-donation process. This is evidenced by the experimental result that the NH3 yield rate of 5-Mn-CN significantly decreases from 15.2 μg h−1 mgcat−1 to 2.6 μg h−1 mgcat−1 after lowering the concentration of Mn3+. The concentration of Mn3+ is reduced by treating the catalyst in the ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) solution. This study enhances the understanding of N2 activation and provides insights into the transition metal-doped g-C3N4 as NRR catalysts. [ABSTRACT FROM AUTHOR]