In situ simultaneous chemical activation and exfoliation of carbon quantum dots for atmospheric adsorption of H2S and CO2 at room temperature

Abstract

Herein, novel nitrogen-doped nanoporous carbons possessing 2.63 at.% N and high porosity were prepared using nitrogen-rich carbon quantum dots (N-CQDs) via a facile chemical activation. To this end, after performing the hydrothermal process on the raw materials, chemical activation was carried out by various KOH/N-CQDs ratios (2:1 to –4:1), resulting in unique micro-mesoporous structures (i.e., HNAC samples). In this approach, a large surface area (1477 m2g−1) and pore volume (1.05 cm3g−1) were obtained, where the micropore volume was increased by decreasing the KOH/N-CQDs ratio, activation time and augmenting the activation temperature, that caused considerable adsorption at 1 bar. It is worth mentioning that mesopores could be generated by condition optimization that led to higher adsorption at high pressure. Due to their large surface area and high nitrogen loading, the HNAC samples demonstrated excellent H2S and CO2 adsorption capacity at ambient conditions (9.28 mmolg−1 for H2S and 4.28 mmolg−1 for CO2 at 1 bar and 25 °C) and at higher pressures (18.0 mmolg−1 for H2S and 6.20 mmolg−1 for CO2 at 10 bar and 25 °C). According to the significant performance of the prepared nanosorbents along with stable cyclic adsorption-desorption performance, the HNACs are proposed as promising adsorbents with outstanding adsorption.