Design of molecular M-N-C dual-atom catalysts for nitrogen reduction starting from surface state analysis

Under electrocatalytic conditions, the state of a catalyst surface (e.g., adsorbate coverage) can be very dif-ferent from a pristine form due to the existing conversion equilibrium between water and H-and O-containing adsorbates. Dismissing the analysis of the catalyst surface state under operating conditions-may lead to misleading guidelines for experiments. Given that confirming the actual active site of the cat-alyst under operating conditions is indispensable to providing practical guidance for experiments, herein, we analyzed the relations between the Gibbs free energy and the potential of a new type of molecular metal-nitrogen-carbon (M-N-C) dual-atom catalysts (DACs) with a unique 5 N-coordination environ-ment, by spin-polarized density functional theory (DFT) and surface Pourbaix diagram calculations. Analyzing the derived surface Pourbaix diagrams, we screened out three catalysts, N3-Ni-Ni-N2, N3-Co-Ni-N2, and N3-Ni-Co-N2, to further study the activity of nitrogen reduction reaction (NRR). The results dis-play that N3-Co-Ni-N2 is a promising NRR catalyst with a relatively low DG of 0.49 eV and slow kinetics of the competing hydrogen evolution. This work proposes a new strategy to guide DAC experiments more precisely: the analysis of the surface occupancy state of the catalysts under electrochemical conditions should be performed before activity analysis. (c) 2023 Elsevier Inc. All rights reserved.