Plasma-assisted Ni catalysts: Toward highly-efficient dry reforming of methane at low temperature

Dry reforming of methane (DRM) reaction can convert primary greenhouse gases (CH₄ and CO₂) to value-added chemicals (H₂ and CO), but generally suffers from harsh reaction conditions (>700 °C) and inevitable deactivation of catalysts. In this work, we report supported Ni catalysts based on a topotactic transformation process from the layered double hydroxides (NiZnAl?LDHs) precursors. Structural characterizations (XRD, HRTEM, CO chemisorption) verify a uniform distribution of Ni nanoparticles (～7 nm) on the mixed metal oxides support with a high dispersion (denoted as Ni/MMO). With the assistance of non-thermal plasma (NTP), the optimal sample (Ni/MMO?S2) exhibits a good catalytic conversion of CH₄ (～69%) and CO₂ (～54%) at low temperatures (30–60 °C), which is comparable with the activity of thermocatalytic process at ～650 °C without NTP. The energy efficiency of NTP-assisted catalysis process is an order of magnitude higher than that of thermocatalytic process at ～650 °C and enhances by 80% relative to NTP-alone process at low temperatures. The Ni/MMO?S2 catalyst shows satisfactory stability after 600 min stability test, with a slight decrease in conversion (within ～1%). In addition, a combined study including catalytic evaluations, operando OES, XAFS and XPS verifies that metallic Ni species acts as active center, which can promote the dissociation of CH₄ and CO₂ into highly reactive intermediate species with the assistance of NTP. This synergistic effect between plasma and Ni catalyst remarkably decreases the apparent activation energy by ～50%, accounting for the high catalytic performance at low temperatures. This work demonstrates a promising synergistic catalysis strategy between plasma and catalysts at low temperatures, which can be extended to other reactions operated under harsh conditions.