The generation of high-density plasmas on the surface of porous catalysts is very important for plasma catalysis, as it determines the active surface of the catalyst that is available for the reaction. In this work, we investigate the mechanism of surface and volume plasma streamer formation and propagation near micro-sized pores in dielectric barrier discharges operating in air at atmospheric pressure. A two-dimensional particle-in-cell/Monte Carlo collision model is used to model the individual kinetic behavior of plasma species. Our calculations indicate that the surface discharge is enhanced on the surface of the catalyst pores compared with the microdischarge inside the catalyst pores. The reason is that the surface ionization wave induces surface charging along the catalyst pore sidewalls, leading to a strong electric field along the pore sidewalls, which in turn further enhances the surface discharge. Therefore, highly concentrated reactive species occur on the surfaces of the catalyst pores, indicating high-density plasmas on the surface of porous catalysts. Indeed, the maximum electron impact excitation and ionization rates occur on the pore surface, indicating the more pronounced production of excited state and electron-ion pairs on the pore surface than inside the pore, which may profoundly affect the plasma catalytic process.

The surface and volume discharge enhancement phenomena and streamer propagation direction control in catalytic pores are significant for the plasma catalytic degradation of pollutants. In this work, we use a two-dimensional particle-in-cell with Monte Carlo collisions model to explore the effect of lateral voltage on streamer enhancement and streamer propagation control for different driving voltages in pores of various shapes, sizes, and numbers. The driving voltage is applied to the top of the device, while the lateral voltages are applied at the left and right sides of the device. The surface and volume discharge enhancement phenomena become more significant and streamer propagation is more restricted within a narrow channel as the lateral voltage (with the same values on the left and right sides) increases from −5 kV to −30 kV for a fixed driving voltage of −20 kV. In this case, both the volume and surface discharges are intensive, leading to highly concentrated plasma species in a narrow channel. Moreover, the streamer propagates in a straight direction, from top to the bottom plate, with the lateral voltage added on both sides. The streamer propagation, however, deviates from the center and is directed to the right side when the lateral voltage is applied to the left. Our calculations also indicate that increasing the number or size of the pores enhances both the volume and surface discharges.