Promoting N2 electroreduction into NH3 over porous carbon by introducing oxygen-containing groups

Abstract

The electroreduction of N2 into NH3 is regarded as an environmentally-benign and sustainable strategy for artificial N2 fixation at ambient conditions. Nevertheless, most of the catalysts suffer from low yield rate and Faradaic efficiency in this process. In this work, we developed a porous carbon with oxygen-containing groups (denoted as oxidized carbon) to promote N2 electroreduction into NH3. At −0.3 V versus reversible hydrogen electrode (vs RHE), oxidized carbon achieves a high Faradaic efficiency of 16.50% for NH3, which is 3.3 times as high as porous carbon (denoted as pristine carbon) (5.07%). Notably, the yield rate of oxidized carbon for NH3 reaches 32.20 μgNH3mg−1cat. h−1, higher than that (14.52 μgNH3 mg−1cat. h−1) of pristine carbon at −0.5 V vs RHE. Mechanistic studies revealed that the introduction of oxygen-containing groups into porous carbon effectively decreased the energy barrier of hydrogenation and suppressed the competing hydrogen evolution reaction, thereby promoting N2 electroreduction to NH3.