Confinement Functionalization of Pd/UiO-66 for Steering Non-Thermal Plasma Catalysis toward CO2 Deep Hydrogenation to CH4

Abstract Nonthermal plasma (NTP) coupled with catalysts for the conversion of CO2/H2O into value-added chemicals presents an effective pathway for carbon resource recycling. However, when H2O is used as a sustainable hydrogen source, plasma-driven CO2 hydrogenation is largely limited by electron quenching and poor control over reaction depth, typically leading to CO as the dominant product. Herein, we report a confinement functionalization strategy for steering NTP-catalytic CO2/H2O conversion toward deep hydrogenation by dispersing Pd nanoparticles (Pd NPs) within the plasma-stable pores of UiO-66 and on its external surface. This material is applied for the first time in NTP catalytic CO2 hydrogenation using H2O as the hydrogen source. The optimized 2.5% Pd/UiO-66 catalyst delivers a CH4 selectivity of 52.45% and a CH4 formation rate of 2.82 mmol·g–1·h–1, which is 752.70 and 6.36 times higher than those of the plasma-only and pristine UiO-66 systems, respectively. Mechanistic studies reveal that confined Pd NPs not only promote the activation of CO2 and H2O-derived hydrogen species, but also enrich interfacial electrons and increase the surface collision probability of plasma-excited species, thereby facilitating *CO retention and subsequent hydrogenation toward CH4. This work provides a sustainable strategy for selective CO2 methanation using H2O as the hydrogen donor.