• Adding N2 to CO2 hydrate formation retards nucleation and growth, leading to larger crystals and rougher morphology, which enhances mass transfer.
• N2 delays secondary nucleation on the hydrate film, preserving pore-throat structure and improving gas exchange efficiency.
• Hydrate film vertical growth rate is primarily controlled by supercooling and gas composition, not absolute temperature or pressure.
• Optimal CO2+N2 composition for maximum mass transfer coefficient is 60% CO2 + 40% N2, with a value of 3.98 × 10^-8 mol·cm^-2·s^-1·MPa^-1.