Interlayer-confined dual sites in a doped graphene/MoS 2 bilayer: Synergistic effects and active site switching for boosted electrochemical nitrogen reduction

Abstract Single-atom catalysts (SACs) with a TM-N4-C structure, where a transition metal (TM) atom is embedded in nitrogen-doped graphene, have emerged as promising electrocatalysts for electrochemical nitrogen reduction reaction (eNRR). However, their performance is often limited by weak N2 adsorption and insufficient activation of the inert N≡N bond. In this work, we propose a novel bilayer catalyst architecture, Mn-N4-C/MoS2-TM, by vertically integrating the Mn-N4-C site with sulfur vacancies (Vs) on the MoS2 basal plane, where TM dopants are anchored at the Vs sites (denoted as MoS2-TM). Using first-principles simulations, we investigated the eNRR performance within the interlayer space of this hybrid system. Our results reveal that the confined interlayer region with the dual active site of Mn-N4-C and MoS2-TM acts as an efficient nano-reactor, working synergistically to enhance N2 adsorption and activation. Notably, during catalysis, the active site dynamically shifts between the Mn-N4-C and MoS2-TM sites for binding key reaction intermediates, significantly lowering the energy barrier of the potential-determining step, thereby promoting the conversion of N2 to NH3. Mechanistic analyses identify Mn-N4-C/MoS2-TM (TM = Mn, Tc, and Ag) as particularly promising eNRR catalysts, exhibiting a low limiting potential of −0.3 V and a maximum kinetic barrier of 0.75 eV. Furthermore, we developed a novel descriptor, φ=θd×XTM, based solely on intrinsic material properties (i.e., the number of d electrons ( θd) and the electronegativity ( XTM)) of the TM dopants, which accurately predict eNRR activity across the series. This work presents a unique strategy for rational design of dual site catalysts, opening a new avenue for efficient eNRR electrocatalysts.