Synergistic Enhancement of CO₂ Conversion via Surface Microenvironment Engineering in a Nonthermal Plasma

The conversion of CO₂/H₂O into valuable chemicals with nonthermal plasma (NTP) under mild conditions represents a promising strategy, whereas the quenching effect and side reactions caused by H₂O seriously restrict its efficiency. Herein, we propose a surface microenvironment modulation strategy by confining phosphomolybdic acid (PMA) within UiO-66 to construct a highly hydrophilic PMA/UiO-66 catalyst for plasma-catalytic CO₂ conversion in a dielectric barrier discharge system. Theoretical calculations and experimental results confirm that the abundant exposed oxygen atoms in PMA/UiO-66 can form a hydrogen-bonding network with H₂O molecule, which effectively promotes the enrichment and activation of H₂O on the catalyst surface and suppresses the quenching effect of bulk H₂O molecules on the plasma-induced dissociation of CO₂. Meanwhile, the hydrogen-bonding network acts as an electron-trapping center and proton transport channel, lowering the free energy barrier for CO₂-to-*COOH step, thereby accelerating the reaction kinetics of CO₂ conversion. Under optimal energy efficiency conditions for NTP-catalyzed CO₂ conversion, the PMA/UiO-66 system achieves a CO₂ conversion of 17.78%, which is approximately 5 times greater than that of the plasma-only system. The study on the regulation of the catalyst surface microenvironment offers valuable insights for designing high-performance catalysts for plasma-catalytic CO₂ conversion.