Insights into Plasma-Catalytic Dry Reforming of Methane over Nickel Foam-Supported Transition-Metal Catalysts: Performance Optimization and Mechanism Exploration

Plasma-catalytic dry reforming of methane (DRM) enables the simultaneous mitigation of greenhouse gases and the production of value-added chemicals; however, achieving a high conversion efficiency alongside controlled product selectivity remains challenging. Here, a water-grounded dielectric barrier discharge (DBD) reactor integrated with nickel foam (NF)-supported transition-metal catalysts (NiAl/NF, CoAl/NF, CuAl/NF) was employed to investigate CO₂ and CH₄ conversion and elucidate reaction mechanisms. Combined in situ FTIR, physicochemical characterization, and plasma diagnostics revealed that the release of lattice oxygen and its reaction with CH_x intermediates are pivotal for catalytic enhancement. NiAl/NF delivered 33.8 and 30.1% higher CO₂ and CH₄ conversion, respectively, over plasma-only discharge, accompanied by a 91.3% increase in total liquid product selectivity. Selective methanol formation reached 4.0% (74.6% higher than plasma-only), while CoAl/NF achieved 10.4% acetic acid selectivity (96.7% higher). Mechanistic analysis indicated that excessive bidentate carbonate accumulation can suppress reaction pathways, underscoring the decisive role of the catalyst structure and active sites. This work demonstrates that tailoring active metal species enables targeted oxygenate synthesis in low-temperature plasma DRM, providing both mechanistic insight and a practical strategy to optimize the conversion efficiency and selectivity.