A novel melt infiltration method promoting porosity development of low-rank coal derived activated carbon as supercapacitor electrode materials

Focusing on the bottlenecks of traditional physical or chemical activation methods for the preparation of activated carbons, we report a simple and scalable melt infiltration strategy assisted with CO₂ activation for the preparation of activated carbons from Chinese large-scale reserve Zhundong coal. The preparation is achieved by the melt infiltration of a small amount of anhydrous FeCl₃ (10–20 wt%) into the coal framework and subsequent CO₂-assisted physical activation during which the encapsulated iron species play the dual role of pore-forming templates and activating catalysts. The as-obtained MI-AC-2 possesses a partially hierarchical pore structure with a high specific surface area of 1872 m² g⁻¹ five times more than the activated carbon prepared by solely physical activation, which endows the constructed MI-AC-2 electrode with good supercapacitive performances. Relative to the large consumption of activation agents used in a traditional chemical activation process, such a new method with low-cost resource materials and the low-dose FeCl₃ additive paves a scalable way to loading metal precursor into coal/biomass for the preparation of high-porosity activated carbons. This work also provides a simple and efficient strategy to encapsulate active materials into external matrix or substrate.