Synthesis, characterization, and CO2 capture study of micro-nano carbonaceous composites

The micro-nano carbonaceous composite activated carbon fiber/carbon nanotube (ACF/CNTs) was obtained by chemical vapor deposition technology with CNTs growth on the substrate ACF, and the composite was further modified by branched polyethyleneimine (PEI). The morphological features of the as-grown ACF/CNTs and PEI-modified samples were analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermal gravimetric analysis respectively. Physical properties of the samples were recorded by conducting N2 adsorption/desorption at 77K. CO2 capture tests indicated that both the presence of CNTs and PEI increased the CO2 adsorption capacity, due to the unique hollow tubular structure of CNTs and poly amino groups of PEI. The CO2 adsorption capacities of ACF/CNTs and ACF/CNTs-PEI were tested to be 66.2 mg/g and 98.8 mg/g, respectively at 30°C, which were much higher than that of unmodified ACF (42.4 mg/g). Increasing adsorption temperature up to 60°C further promoted the CO2 adsorption capacity of ACF/CNTs-PEI (121.2 mg/g) due to the maximum equilibrium adsorption between the chemical and physical adsorption at this temperature. Cyclic CO2 adsorption tests via thermal desorption proved that ACF/CNTs-PEI had a good regenerability of 96.2%, suggesting this material is a promising CO2 adsorbent for practical applications.