Fig. 2: Effect of catalyst location m-SiO₂ on NTP-CM performance.

a TEM image and EDS spectra of spent catalysts In-m-SiO₂, Out-m-SiO₂, and Both-m-SiO₂ (after 60 min of reaction). b Schematic illustration of the role of m-SiO₂ and the effect of catalyst position on methane coupling. c Mn³⁺/(Mn³⁺+Mn²⁺) ratio for fresh and spent catalysts. d Yields of C₂H₂ and C₂H₄ (defined as the product of CH₄ conversion and the selectivity of C₂H₂ and C₂H₄) and equivalent carbon deposition rate (ECR, defined as the solid carbon selectivity on the catalyst divided by the methane conversion) (Conditions: 1 bar, SEI 5.1 kJ L⁻¹, total flow rate 200 mL min⁻¹, discharge power 17 W, experiment duration 60 min).