Interfacial Design of Dichalcogenide–Graphene Hybrids for Enhanced Electrochemical NO-to-NH3 Conversion

Abstract

Carbon-engineered tungsten dichalcogenides were examined as sustainable electrocatalysts for the ambient-condition electrochemical synthesis of ammonia (NH3) from nitric oxide (NO) using density functional theory (DFT). Three catalyst systems, including carbon-substituted WS2 (C-WS2), carbon-substituted WSe2 (C-WSe2), as well as C-WS2 and graphene heterostructure (C-WS2||G), were systematically investigated to elucidate the roles of carbon substitution, chalcogen chemistry, and interfacial electronic coupling in governing NO activation, reaction energetics, and product selectivity. All three catalysts exhibit strong NO adsorption at the carbon active site, accompanied by significant charge transfer that weakens the N–O bond and facilitates subsequent proton-coupled electron transfer (PCET) reactions. Among the investigated reaction pathways, the N-first hydrogenation pathway emerged as the thermodynamically preferred minimum-energy pathway (MEP). The potential-determining step was identified as the *NHO → *NH2O transformation, corresponding to limiting potentials (UL) of –0.80, –0.68, and –0.48 V for C-WS2, C-WSe2, and C-WS2||G, respectively. The nonelectrochemical NH3 and H2O desorption processes incur modest thermodynamic penalties (ΔG = 0.10–0.15 eV and 0.13–0.47 eV, respectively) and low kinetic barriers (Ea = 0.22–0.25 eV and 0.28–0.54 eV, respectively), indicating that the catalyst regeneration is kinetically accessible for all three catalysts. Graphene acts as an electronic regulator that optimizes the local electronic environment through interfacial electronic coupling, preserving catalyst–intermediate bonding while minimizing structural reorganization during the potential-determining *NHO → *NH2O hydrogenation step. This synergistic electronic modulation lowers the thermodynamic barrier for the NO reduction reaction and establishes the catalytic activity trend C-WS2||G > C-WSe2 > C-WS2. These findings demonstrate that the synergistic combination of carbon substitution and graphene interfacial engineering provides an effective strategy for designing high-performance electrocatalysts for sustainable electrochemical NO-to-NH3 conversion.