Expansion of effective pore size on hydrogen physisorption of porous carbons at low temperatures with high pressures

Hydrogen (H-2) has been considered a promising alternative to fossil fuels as a future energy source. To achieve great H-2 uptakes through physisorption, an accurate understanding of the pore sizes should be involved. Related studies have reported that micropores (<2 nm) are the most effective pores for high H-2 uptakes at 77 K and 1 bar. For clarifying the pore size effects, the relationship between H-2 physisorption behavior and pore sizes was studied in this work. Silica elimination and KOH activation were used to prepare porous carbons with various pore sizes, especially up to narrow mesopores (<4 nm). The results indicated that micropores (<2 nm) are important for H-2 excess uptakes (Q(Excess)) at 77 K and 1 bar, however, pores with a diameter up to 4 nm are the most effective pores for high QExcess at 77 K and 60 bar, suggesting that the effective range of pore sizes that contribute to Q(Excess) would be widened at higher pressures. This is concluded that the optimum pore size ranges for better H-2 physisorption behavior was found to be closely associated with the storage pressures, providing guidance for the preparation of porous materials for efficient H-2 physisorption under different storage conditions. (C) 2019 Elsevier Ltd. All rights reserved.