Due to the intensification of global energy crisis and the associated climate change, the search for sustainable, high-capacity energy storage materials has become urgent. Hydrogen (H2) is regarded as one of the attractive alternative clean energy carriers with high high-energy-density. This study investigates the porous carbon materials derived from two brands of Arabica and Robusta spent coffee ground and systematically compares their hydrogen storage capacity at 298K and high pressure conditions. Both Arabica and Robusta samples were carbonized at 350, 400, and 450 °C and KOH-activated at 800 °C under argon (1.7L/min), yielding markedly different textural properties. Scanning electron microscopy (SEM), nitrogen adsorption–desorption isotherms, thermogravimetric analysis (TGA), and most importantly their H2 storage capacity were used to analyze the samples. SEM images reveal that the samples are highly porous and this was confirmed with BET analysis. The Arabica spent coffee-derived activated carbon achieved a BET surface area of 2728 m²g-1, while Robusta activated carbon maximum BET surface area was 1983 m²g-1. The H₂ adsorption measurements of pelletized samples were conducted using a Rubotherm Magnetic Suspension Balance, which allows precise determination of gas adsorption under high-pressure conditions through gravimetric analysis The gravimetric H2 adsorption measurements at 298 K shows maximum uptakes of 2.616 mmolg-1 for H₂ at 35 bar. The adsorption data isotherm model fitting analysis indicates that the Langmuir model was found to best describe the H₂ adsorption properties, indicating monolayer adsorption process. This work represents the first comparative H2 adsorption study of Arabica and Robusta coffee waste-derived activated carbons in pellet form. This study demonstrates the potential of spent coffee waste as a scalable, sustainable porous material for clean energy storage applications.
