Potassium and Zeolitic Structure Modified Ultra-microporous Adsorbent Materials from a Renewable Feedstock with Favorable Surface Chemistry for CO2 Capture

5 years ago

Potassium and Zeolitic Structure Modified Ultra-microporous Adsorbent Materials from a Renewable Feedstock with Favorable Surface Chemistry for CO2 Capture

Chenggong Sun, Xin Liu, Colin Snape, Jingjing Liu, Qian Xue, Emily Smith, Hao Liu, Yuan Sun

Novel hierarchically structured microporous biocarbons with exceptionally high capacities for CO₂ capture have been synthesized from the abundant agricultural waste of rice husk (RH), using a facile methodology that effectively integrated carbonization, activation, and potassium intercalation into a one-step process. Textural characterization demonstrates that the synthesized biocarbons exhibit exceedingly high ultra-microporosity accounting for up to 95% of total porosity mainly as a result of the naturally occurring silicon compounds within the RH molecular framework structures. With a modest surface area of up to 1035 m²/g and a total pore volume of 0.43 cm³/g, the best performing RH carbon has shown exceptionally high and fully reversible CO₂ uptake capacity of 2.0 mmol/g at 25 °C and a CO₂ partial pressure of 0.15 bar, which represents one of the highest uptakes ever reported for both carbon and MOF materials usually prepared from using cost-prohibitive precursor materials with cumbersome methodologies. It has been found that up to 50% of the total CO₂ uptake is attributable to the unique surface chemistry of the RH carbons, which appears to be dominated by the enhanced formation of extra-framework potassium cations owing to the exceedingly high levels of ultra-microporosity and the presence of zeolitic structures incorporated within the carbon matrices. Characterizations by EDX element mapping, XPS, and heat of adsorption measurements confirm the existence of a range of zeolitic structures, which essentially transforms the RH carbons into a kind of zeolite–carbon nanocomposite material with strong surface affinity for CO₂.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b06665

DOI: 10.1021/acsami.7b06665