Mechanism of CO2 Adsorption on the Green Oxygen-Doped Hierarchical Biochar Activated by Dual Organic Salts.

Excessive carbon dioxide emissions have led to global climate change, resulting in significant environmental impacts. Efficient CO2 adsorbents are crucial for carbon dioxide capture. This study employs a green dual organic salt activation strategy to prepare a series of OPPCx (orange peel porous carbon) materials. Combining experimental results with DFT simulations, a reliable mechanism for CO2 adsorption was proposed. Compared to the activation with sole C6H5K3O7, the introduction of C12H10Mg3O14 modulated the porous structure of the carbon material and enhanced the oxygen content and biochar yield. Micropore volume and surface oxygen functional groups are important factors influencing CO2 adsorption. Oxygen functional groups exhibit strong electrostatic attraction to CO2. The introduction of ketones (C═O), which have the highest content in the OPPCx samples, increased the adsorption energy by 109.9% compared to the original carbon substrate. The OPPC31 sample exhibits the highest CO2 adsorption capacity, reaching 4.31 mmol/g at 298 K and 1 bar. In addition, the OPPC31 sample exhibits a moderate adsorption heat of 28.9 kJ/mmol, with an adsorption selectivity for CO2 over N2 of 17. The material also demonstrates good recyclability, as its adsorption capacity remains at 4.19 mmol/g (298 K, 1 bar) after five cycles, indicating that it is a promising CO2 adsorbent material.