Effect of functional group type and concentration, and pore width of porous carbon on H2 storage using a grand canonical Monte Carlo simulation: temperature dependence and heat contributions

Adsorption of H-2 on functionalized graphite slit-pore at 77 and 298 K was investigated by using a grand canonical Monte Carlo simulation. The physical pore width in a range of micropores was studied. We plotted the adsorbed amount and heat contributions as a function of pore width and pressure. We found that the pore width, pore volume, and functional group play a key role in H-2 uptake in different conditions. Pore widths of 0.65 and 1.0 nm are the optimum widths and play an important role at low pressures while the total pore volume is the key at higher pressures in H-2 gravimetric capacity at a wide temperature range of 77-298 K. However, functional group properties do not play a significant role in H-2 adsorption capacity at 298 K. They play a significant role and become more pronounced at a lower temperature (< 298 K) during low pressures until the functional group becomes saturated by adsorbate. The results obtained with different force fields confirm that N-doped porous carbons are more effective than O-doped porous carbons for enhanced H-2 storage. The heat contribution between H-2 and functional group type is divided into three levels base on the values which is in the order of quaternary-N/pyridinic-N-oxide > pyrrolic-N/carboxyl > hydroxyl/carbonyl. Moreover, the adsorbed amount and all the heats of the higher concentration of functional group are higher than that of lower concentration of functional group. The saturation of the higher concentration of functional group occurs at a higher pressure, thereby indicating the wider pressure range of enhanced H-2 storage. This work provided a new strategy to develop the optimum pore width and suitable functional group type for enhancing H-2 storage in porous carbons.

Automated summary

Adsorption of H-2 on functionalized graphite slit-pore was studied using Monte Carlo simulation. The effects of pore width, pore volume, and functional group on H-2 uptake were investigated. N-doped porous carbons were found to be more effective than O-doped porous carbons for enhanced H-2 storage. The heat contribution between H-2 and functional group type played a crucial role in H-2 adsorption capacity.