Tackling the Activity and Selectivity Challenges of Electrocatalysts toward the Nitrogen Reduction Reaction via Atomically Dispersed Biatom Catalysts

Abstract

Developing efficient catalysts for nitrogen fixation is becoming increasingly important, but is still challenging due to the lack of robust design criteria to tackling the activity and selectivity problems, especially for electrochemical nitrogen reduction reactions (NRR). Herein, by means of large-scale density functional theory (DFT) computations, we reported a descriptor-based design principle to explore the large composition space of two-dimensional (2D) bi-atom catalysts (BACs), namely metal dimers supported on 2D expanded phthalocyanine (M2-Pc or MM’-Pc), towards NRR. We sampled both homonuclear (M2-Pc) and heteronuclear (MM’-Pc) BACs, and constructed the activity map of BACs by using N2H* adsorption energy as the activity descriptor, which reduces the number of promising catalyst candidates from over 900 to less than 100. This strategy allowed us to readily identify three homonuclear and 28 heteronuclear BACs, which could break the metal-based activity benchmark towards efficient NRR. Particularly, using the free energy difference of H* and N2H* as selectivity descriptor, we screened out five systems, including Ti2-Pc, V2-Pc, TiV-Pc, VCr-Pc, and VTa-Pc, which exhibit a strong capability of suppressing the competitive hydrogen evolution reaction (HER) with favorable limiting potential of -0.75, -0.39, -0.74, -0.85 and -0.47 V, respectively. This work not only broadens the possibility of discovering more efficient BACs towards N2 fixation, but also provides a feasible strategy for rational design of NRR electrocatalysts, and help pave the way to fast screening and design of efficient BACs for NRR and other electrochemical reactions.