Electrical properties of carbon dioxide hydrate: Implications for monitoring CO2 in the gas hydrate stability zone

CO₂ and CH₄ clathrate hydrates are of keen interest for energy and carbon cycle considerations. While both typically form on Earth as cubic structure I (sI), we find that pure CO₂ hydrate exhibits over an order of magnitude higher electrical conductivity (σ) than pure CH₄ hydrate at geologically relevant temperatures. The conductivity was obtained from frequency-dependent impedance (Z) measurements made on polycrystalline CO₂ hydrate (CO₂·6.0 ± 0.2H₂O by methods here) with 25% gas-filled porosity, compared with CH₄ hydrate (CH₄·5.9H₂O) formed and measured in the same apparatus and exhibiting closely matching grain characteristics. The conductivity of CO₂ hydrate is 6.5 × 10⁻⁴ S/m at 273K with an activation energy (E_a) of 46.5 kJ/mol at 260–281 K, compared with ∼5 × 10⁻⁵ S/m and 34.8 kJ/m for CH₄ hydrate. Equivalent circuit modeling indicates that different pathways govern conduction in CO₂ versus CH₄ hydrate. Results show promise for use of electromagnetic methods in monitoring CO₂ hydrate formation in certain natural settings or in CO₂/CH₄ exchange efforts.