Tubular MgO for anti-sintering CO2 capture

https://doi.org/10.1039/D2NA00213B

“Therefore, the MgO/CNT_Air with modified morphology exhibited enhanced cycling stability of CO₂ capture performance due to the delayed sintering. The modified morphology consists of elongated plate-like MgO structures separated by empty spaces. Sintering at the particle interfaces induces the agglomeration of particles and reduces active sites. The carbonation causes the volume expansion of particles, resulting in more interfaces. According to Bork et al.,²⁹ Gao et al.,³⁰ and Lee et al.,³¹ the surface volume expansion from MgO to MgCO₃ was reported to be within hundreds of nanometers. However, the empty spaces in the modified morphology had a thickness of 1–2 μm. The empty spaces and plate-like structure could effectively reduce the intersection and agglomeration of separated MgO particles (Fig. 8). The agglomeration inhibition delayed the sintering of MgO/CNT_Air, resulting in extended durability. On the other hand, the morphology of MgO_HT had no inhibitory effect on agglomeration, resulting in gradual performance decay.”

“Fig. 8 Simplified schemes of morphological evolution during carbonation–calcination reaction in MgO/CNT_Air and MgO.”

“Structural modification of MgO-based sorbents is often focused on modifying the nanoscale structure of MgO. For example, mesoporous MgO,¹⁸ nanosheet MgO,¹⁶ nanostructured microsphere MgO,³² and eggshell membrane template MgO³³ were proposed, achieving enhanced surface area and porosity. However, these MgO-based sorbents exhibited rapid performance decay in early cycles. Compared to other studies, the proposed MgO/CNT_Air has a unique decay pattern in which the CO₂ capture performance increased and was maintained in early cycles, allowing enhanced cycling stability. Therefore, the possibility of durability enhancement by micro-scale MgO structure modification is proposed for the first time.”