A study on pore formation of high surface area activated carbon prepared by microwave-induced plasma with KOH (MiWP-KOH) activation: Effect of temperature-elevation rate

The activation using microwave-induced plasma with KOH (MiWP-KOH activation) can realize extremely fast synthesis of activated carbon (AC), which needed only several minutes. The present work focusses the effect of temperature-elevation rate on pore formation. For the discussion, AC was prepared using a conventional heat conduction method with various temperature-elevation programs, and the structural analysis results from these experiments were compared with those observed in AC prepared by the MiWP-KOH activation. As a feature in the pore structure of AC induced by the MiWP-KOH activation, micropore volume highly dominates over mesopore volume with (micropore/mesopore) ratio = 4.3-4.9. This property can be explained by the experiments with the controlled temperature-elevation rate, suggesting that rapid temperature-elevation rate is the key factor for such micropore-dominating structure. Additionally, it was suggested that the temperature of the feed material in the MiWP-KOH activation can become about 800 degrees C within 75 s. MiWP-KOH activation can generate significantly higher surface area than the conventional heating with the similar temperature changing program, suggesting the effect of microwave irradiation to enhance the pore formation. Based on these investigations, a characteristic pore formation model in the MiWP-KOH activation is considered.