Sustainable and scalable production of nanoporous carbon derived casein nanoparticles with high surface area for promising hydrogen storage capacity and CO2/H2 separation

Herein, sustainable, economical, ultrahigh surface area, and scalable nanoporous carbon nanoparticles were developed for efficient hydrogen storage and gas separation. Spherical casein nanoparticles (CNPs) were greenly developed using a one-pot solvent- free solid-state ball-milling method. The ball-milling time was varied between 24 and 72 h, and in turn, the average size of casein nanoparticles developed varied, recording 41.2 and 35.4 nm for 24 and 72 h, respectively. Secondly, the developed nanoparticles were carbonized, followed by chemical activation, yielding nanoporous carbon nanoparticles with superior textural properties and inherently doped with oxygenated and nitrogenated functional groups. The developed nanoporous carbon nanoparticles exhibited outstanding microporosity with ultrahigh BET-SSA of 3035.9 m2 g 1 and total pore volume of 1.73 cm3 g 1 with ultramicropores of size 0.56–0.68 nm. This is associated with intrinsic doping levels of oxygenated and nitro genated surface groups. The developed nanoporous carbon adsorbent revealed high H2 storage capacities at 77 and 298 K, achieving 5.97 and 0.405 wt% at pressures of 70 and 80 bar, respectively. The isosteric heat of adsorption of H2 corroborated the synergistic role of microporosity and intrinsic doping of O and N species for boosting H2 interaction with the developed adsorbent, recording an average value of 8.68 kJ mol 1. On the other hand, the developed nanoporous carbon nanoparticles showed promising CO2 capture, achieving 22.35 mmol g 1 at 298 K and 30 bar, revealing its suitability for pre-combustion CO2 capture as well. Additionally, the CO2/ H2 separation selectivity was also studied using ideal adsorbed solution theory (IAST) at different binary gas mixtures of 50:50, 40:60, and 20:80 at RT and 30 bar. Remarkably, the sustainable nanoporous carbon nano particles achieving CO2/H2 separation selectivity of 18.9, 28.45 and 75.89 for gas mixtures of 50:50, 40:60, and 20:80, respectively, revealing their potential for H2 purification applications.