Chemical affinity-assisted H2 isotope separation using Ca-rich onion-peel-derived nanoporous carbon composite

Abstract

Stable isotopes of hydrogen are a prerequisite for many industrial and scientific applications and require their ready supply on a large scale. Herein, we explore the chemical affinity-assisted separation of D₂ from a hydrogen isotopic mixture using calcium-rich porous carbon derived from onion peel. A sustainable physical activation using CO₂ of onion-peel-derived carbon led to nanoporous carbon formation with a specific surface area of 433 m² g⁻¹ and a total pore volume of 0.27 cm³ g⁻¹ along with a calcium composition of 17 wt% without using any calcium precursor. Calcium increases the chemical affinity of synthesized materials towards D₂, evidenced by the observation of a higher uptake for D₂ than H₂ in gas sorption and thermal desorption spectroscopy studies. Additionally, a promising D₂/H₂ selectivity of 5.6 at 40 K and a desorption energy difference of 2.31 kJ mol⁻¹ further support the higher binding strength for D₂, which endows its separation from the isotopic mixture. Hence, the current approach of using biowaste provides an environmentally friendly alternative for biowaste management in addition to a promising isotope separation candidate.