Rational design of bimetallic atoms supported on C₃N monolayer to break the linear relations for efficient electrochemical nitrogen reduction

Linear relations between the adsorption free energies of nitrogen reduction reaction (NRR) intermediates limit the catalytic activity of single atom catalysts (SACs) to reach the optimal region. Significant improvements in NRR activity require the balance of binding strength of reaction intermediates. Herein, we have investigated the C₃N-supported monometallic (M/C₃N) and bimetallic (M₁M₂/C₃N) atoms for the electrochemical NRR by using density functional theory (DFT) calculations. The results show that this linear relation does exist for SACs because all the intermediates bind to the same site on M/C₃N. But the synergistic effect of the two atoms in M₁M₂/C₃N can create a more flexible adsorption site for intermediates, which results in the decoupling of adsorption free energies of key intermediates. Subsequently, the fundamental limitation of scaling relations on limiting potentials is broken through. Most notably, the optimal limiting potential is increased from −0.63 V for M/C₃N to −0.20 V for M₁M₂/C₃N. In addition, the presence of bimetallic atoms can also effectively inhibit the hydrogen evolution reaction (HER) as well as improve the stability of the catalysts. This study proposes that the introduction of bimetallic atoms into C₃N is beneficial to break the linear relations and develop efficient NRR electrocatalysts.