Bimetallic synergistic catalysts based on two-dimensional carbon-rich conjugated frameworks for nitrate electrocatalytic reduction to ammonia: catalyst screening and mechanism insights

Abstract The discovery of the ‘two birds, one stone’ electrochemical nitrate reduction reaction (NO 3 RR) allows for the removal of harmful NO 3 − pollutants as well as the production of economically beneficial ammonia (NH 3 ). However, current understanding of the catalytic mechanism of NO 3 RR is not enough, and this research is still challenging. To determine the mechanism needed to create efficient electrocatalysts, we thoroughly examined the catalytic activity of molybdenum-based diatomic catalysts (DACs) anchored on two-dimensional carbon-rich conjugated frameworks (2D CCFs) for NO 3 RR. Among the 23 candidate materials, after a four-step screening method and detailed mechanism studies, we discovered that NO 3 RR can efficiently generate NH 3 by following the N-end pathway on the MoTi-Pc, MoMn-Pc, and MoNb-Pc, with limiting potential of −0.33 V, −0.13 V, and −0.38 V, respectively. The activity of NO 3 RR can be attributed to the synergistic effect of the TM 1 –TM 2 dimer d orbital coupling to the anti-bonding orbital of NO 3 − . Additionally, high hybridization between the Mo-4d, TM-3d(4d), and NO 3 − −2p orbitals on the MoTMs-Pc DACs can speed up the flow of electrons from the Mo-TM dual-site to NO 3 − . The research presented here paves the way for the reasonable design of effective NO 3 RR catalysts and offers a theoretical basis for experimental research.