H₂O₂/steam activation as an eco-friendly and efficient top-down approach to enhancing porosity on carbonaceous materials: The effect of inevitable oxygen functionalities on CO₂ capture

Nanoporous materials have been developed as carbon dioxide (CO₂)-capturing materials. In carbonaceous materials, physical activation by steam or CO₂ is a common top-down method that is known to be effective for developing nanopores on carbon surfaces. However, it is less efficient at improving porosity compared to common chemical activation. Herein, we propose a simple and eco-friendly approach to improving the efficiency of physical activation in developing porosity on carbonaceous materials. Using hydrogen peroxide (H₂O₂) as an activating agent with pressure in the reactor resulted in significant enhancement compared with steam activation without pressure. However, a high number of oxygen functionalities were generated on the carbon surfaces, which interfered with CO₂ capture performance (e.g., uptake, selectivity, and the adsorption rate). We used thermal reduction to remove oxygen functionalities on the carbon surface, which overcame the CO₂ affinity and uptake loss caused by the oxygen functionalities. Therefore, the H₂O₂/steam activation approach may be used to improve the textural properties of carbonaceous materials. Furthermore, our work provides evidence that the oxygen functionalities of solid carbonaceous adsorbents influence CO₂ capture performance, including practical applications.