First-principles insights into NO electroreduction on Ti- and Co-doped Au(111) monolayers: Structural reconstruction, electronic synergy, and reaction mechanism

• Ti/Co doping embeds into Au(111), inducing lattice distortion and charge redistribution. • NO adsorption shows N–O bond elongation and significant charge transfer. • Dopant d –NO π* orbital hybridization promotes NO activation. • Free-energy analysis reveals moderate barriers (0.56–0.86 eV). In this work, we employed density functional theory (DFT) calculations to investigate the structural, electronic, and catalytic properties of Ti- and Co-doped Au(111) monolayers as electrocatalysts for NO electroreduction. Structural relaxations reveal that the transition-metal dopants become embedded into the Au(111) surface, inducing local lattice distortions and pronounced charge redistribution. Ab initio molecular dynamics simulations confirm the thermal stability of the doped surfaces up to 1500 K. Adsorption studies show that NO preferentially binds to atop Au sites adjacent to the dopants, with significant N–O bond elongation and charge transfer, indicating strong activation. Charge density difference and projected density of states (PDOS) analyses demonstrate synergistic interactions between dopant d states and NO π* orbitals, enhancing orbital hybridization and weakening the N–O bond. Crystal orbital Hamilton population (COHP) further confirms the strengthened surface–adsorbate bonding. Free-energy profiles constructed within the computational hydrogen electrode framework reveal that the rate-determining step is the first hydrogenation (*NO → *NHO) on Co–Au(1 1 1) (Δ G = 0.56 eV), while Ti–Au(1 1 1) exhibits two critical barriers: initial *NHO formation (0.66 eV) and final NH 3 release (0.86 eV). These results reveal structure–activity relationships and guide efficient NO-to-NH 3 electrocatalyst design.