Reactant‑Transporting Metal-Support Interaction for Lattice Carbonate‑to‑Methane Catalysis.

Area of Science:

• Heterogeneous catalysis
• Materials science
• Geochemistry
• Carbon cycle research

Background:

• Metal-support interactions (MSI) are crucial in heterogeneous catalysis, influencing activity, selectivity, and stability through electronic and geometric effects.
• Lattice carbon in carbonate minerals represents Earth's largest carbon reservoir, with potential for carbon cycle management.
• Existing catalytic approaches primarily focus on CO2 management related to the fast carbon cycle (FCC).

Purpose of the Study:

• To report a new form of metal-support interaction (MSI) that facilitates reactant transport.
• To demonstrate the direct hydrogenation of lattice carbonate to methane using this novel interaction.
• To explore the potential of low-temperature lattice-carbonate conversion for accelerating the slow carbon cycle (ACC).

Main Methods:

• Utilized operando techniques to investigate the catalytic process.
• Characterized the dynamic interfacial behavior between the metal catalyst and the carbonate support.
• Analyzed reaction kinetics to differentiate between low-temperature solid-state and high-temperature gas-phase pathways.

Main Results:

• A strong metal-reactive support interaction (SMRSI) was identified, enabling Pt/H2 to hydrogenate calcite lattice carbonate to methane with high selectivity (>98%) starting at ≤415°C.
• An amorphous, permeable interphase was observed to transport carbonate ions (CO3^2-) to active sites, forming a mobile triple-phase boundary.
• The process involves interfacial CO2 release, hydrogenation of a CO intermediate to methane, and subsequent re-carbonation of the solid product, regenerating the carbonate and maintaining selectivity over cycles.

Conclusions:

• SMRSI represents a reactant-transporting mechanism, extending the concept of MSI beyond electronic/geometric tuning.
• This catalytic approach offers a complementary strategy to FCC-based CO2 management by enabling low-temperature conversion of the ACC reservoir.
• The findings highlight the role of dynamic solid-solid@gas interfaces in mediating solid reactant transformations.