Rapid and efficient PM_2.5 filtration and NO degradation enabled by pore-functionalized hierarchical SiC membrane with high gas permeance

SiC catalytic membranes with rapid and efficient multipollutant removal performance are highly desired for industrial emissions treatment. Nevertheless, achieving these dual objectives simultaneously poses significant challenges due to the ‘residence time’ paradox. While ‘rapid removal’ necessitates high gas permeance, it results in low residence time, which is detrimental to ‘efficient catalytic removal’. Drawing inspiration from the dynamic characteristics of nanofibers, we engineered a simulated nanofiber-stacked structure by first growing carbon nanotubes (CNTs) throughout the SiC substrate, followed by in-situ hydrothermal synthesis of MnO_x catalysts on CNTs (MnO_x@CNT/SiC). Characterization results reveal that an Fe(NO₃)₃ concentration of 0.5 mol/L is critical for efficient growth of CNTs, and that HNO₃ and a hydrothermal temperature of 120 °C are essential for the in-situ growth of MnO_x on CNTs. The MnO_x@CNTs on the surface shrink the pore diameter of the SiC substrate, forming a membrane layer that achieves both exceptional gas permeance of 405 m³ m^−2•h^−1•kPa⁻¹ and an initial PM_2.5 filtration efficiency of 99.95 %. Additionally, the MnO_x@CNTs embedded within the SiC substrate contribute to prolonging the contact time with reactant gases, working synergistically with the surficial MnO_x@CNTs to achieve complete NO degradation efficiency within the temperature range of 190–220 °C. This combination of high gas permeance and effective pollutant removal demonstrates the significant potential of MnO_x@CNT/SiC catalytic membranes for real-world emissions treatment applications.