Carbon materials as CO2 adsorbents: a review

Environmental pollution is a serious issue with the rapid development of urbanization, industrialization and vehicle traffic. In particular, fossil fuel pollution increases atmospheric CO2 levels. To alleviate this problem, various carbon capture and storage technologies have been developed, yet they are actually limited by cost and energy requirements. Alternatively, adsorption appears as a promising technique for carbon capture due to its low cost, low energy requirement and applicability over a wide range of temperature and pressure. Here, we review carbonaceous materials such as activated carbon, activated carbon nanofibers, hollow carbon spheres and biochar for CO2 capture, and we discuss factors controlling CO2 adsorption. CO2 adsorption primarily depends upon micropore volume and surface area which in turn are controlled by carbonization and activation temperature, activating agent and its impregnation ratio, activation time and presence of moisture. Additionally, introduction of basic functional groups such as N-containing functional groups into the adsorbent enhances the adsorption capacities. We discuss possible modifications for cost-effective and commercially viable carbon materials as CO2 adsorbents.