Generation of air discharge plasma in the cavities of porous catalysts: a modeling study

A study of the behaviors of air discharge plasma inside a catalyst's pores is important to understand the plasma catalysis mechanism; however, few articles have reported the generation characteristics of air plasma in the pores of catalysts. The production of air microdischarge in a pore was studied by a two-dimensional fluid model, mainly focusing on the effect of pore size and applied voltage. The results show that an increase in the pore size in the range of 20–100 μm facilitates the occurrence of microdischarge in the pore. In addition, at an applied voltage of 9 kV, the ionization of air mainly occurs near the topside of the pore when the pore diameter is less than 20 μm, leading to a low plasma density in the pore, but the time-averaged plasma density in the pore reaches a maximum value at a 70 μm pore diameter. Moreover, the applied voltage also has an important effect on the production of air microdischarge in the pore. The existence of a pore of 80 μm diameter on the dielectric has no obvious influence on the plasma density in the pore at 2 kV applied voltage, but the plasma density in the pore begins to sharply rise when the voltage exceeds 3 kV due to the enhanced air ionization at higher applied voltage. The study indicates that microdischarge can be generated in a pore with a size of tens of micrometers, and the microdischarge in porous catalysts will affect the catalytic degradation efficacy of gaseous pollutants.