Oxygen-Vacancy-Engineered Pd-WO_3-x for Enhanced Plasma-Catalyzed CO₂ Hydrogenation to CO

Plasma-catalytic CO₂ hydrogenation to CO offers a promising route for carbon-neutral chemical synthesis. However, its advancement is constrained by low energy efficiency and limited mechanistic insight. Here, we developed an oxygen vacancy-engineered Pd-WO_3-x catalyst supported on nickel foam (NF), which exhibits enhanced performance in ambient plasma-driven CO₂ conversion. The system leverages the conductive properties of NF to spatially divide the discharge zone into streamer and filamentary discharge zones, thereby enhancing plasma activation and interfacial charge transfer. Catalyst characterization reveals that Pd plays a critical role in stabilizing metastable oxygen vacancies (OVs) within WO_3-x , which function as electron reservoirs to promote CO₂ dissociation into CO. Density functional theory calculations and in situ spectroscopic studies confirm that Pd facilitates H₂ dissociation, while vibrationally excited CO₂ generated in the plasma gas phase preferentially adsorbs at OV sites. At a specific energy input of 33.6 kJ L^-1, the system demonstrates superior performance, achieving 54.9% CO₂ conversion with 99.8% selectivity toward CO, surpassing typical plasma-catalytic benchmarks. The catalyst exhibited good stability over 100 h of continuous operation, with a slight decrease in CO₂ conversion (<10%) and nearly unchanged CO selectivity (>99%) due to strong metal-support interactions and the conductive nature of NF. This work demonstrates that OV engineering provides a promising strategy for designing efficient plasma-catalytic systems for CO₂ conversion.