Plasma catalysis in fluidized-bed reactor for reverse water gas shift reaction

Plasma catalysis for valorization of gas, i.e., CO₂, is attracting increasing attention. High value-added chemicals, i.e., CO, CH₃OH, are possible to be formed under mild conditions. However, plasma-catalyst interaction is typically limited in conventional packed-bed DBD reactors. Herein, a fluidized-bed DBD reactor was newly proposed. Powdered catalyst was fluidized directly in plasma, yielding an enhanced plasma-catalyst coupling and heat transfer. Reverse water gas shift reaction over Pd₂Ga/SiO₂ was selected as a model, by which we confirmed plasma catalysis yielded more than doubled CO₂ conversion compared to thermal catalysis. Further promotion was achieved by increasing discharge frequency, where, interestingly, we found thermal equilibrium was well beyond. Meanwhile, linear Arrhenius behavior for plasma catalysis was experimentally obtained, by which a dramatic decrease of activation energy from 75 kJ/mol of thermal to 43 kJ/mol was observed. Lissajous plot analysis and electron collision kinetics further suggested increasing low-energy electron concentration is the key, where vibrational excitation contributed to a kinetically and thermodynamically favored CO₂ conversion. A green plasma technology assisted by catalysis for energy conversion was developed successfully.