• • Ag loading on MgO(100) enhances C2H4 adsorption to -1.46 eV, but O2 adsorption remains weak at -0.45 eV, limiting complete oxidation; Cu addition improves O2 adsorption to -0.76 eV, enabling synergistic co-activation.
• • Among 17 AgCu-MgO DAC configurations, those with Ag and Cu at Mg sites exhibit binding energies below -10 eV, ensuring thermodynamic stability under reaction conditions, critical for long-term catalyst durability.
• • Configuration 6 of AgCu-MgO shows the lowest rate-limiting energy barrier of 0.32 eV for C2H4 oxidation to *CH3 and CO2, outperforming other configurations and indicating superior catalytic activity at low temperatures.
• • C2H4 oxidation over AgCu-MgO preferentially proceeds via C=C bond cleavage to *CH3 and CO2, with energy barriers consistently lower than the *HCO and CH2O pathway, guiding catalyst design for selective total oxidation.