Kim Kiwoong, Han Jeong Woo, Lee Kwang Soon, Lee Won Bo
Department of Chemical and Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 121-742, South Korea.
Phys Chem Chem Phys. 2014 Dec 7;16(45):24818-23. doi: 10.1039/c4cp03809f.
Developing next-generation solid sorbents to improve the economy of pre- and post-combustion carbon capture processes has been challenging for many researchers. Magnesium oxide (MgO) is a promising sorbent because of its moderate sorption-desorption temperature and low heat of sorption. However, its low sorption capacity and thermal instability need to be improved. Various metal-promoted MgO sorbents have been experimentally developed to enhance the CO2 sorption capacities. Nevertheless, rigorous computational studies to screen an optimal metal promoter have been limited to date. We conducted first-principles calculations to select metal promoters of MgO sorbents. Five alkali (Li-, Na-, K-, Rb-, and Cs-) and 4 alkaline earth metals (Be-, Ca-, Sr-, and Ba-) were chosen as a set of promoters. Compared with the CO2 adsorption energy on pure MgO, the adsorption energy on the metal-promoted MgO sorbents is higher, except for the Na-promoter, which indicates that metal promotion on MgO is an efficient approach to enhance the sorption capacities. Based on the stabilized binding of promoters on the MgO surface and the regenerability of sorbents, Li, Ca, and Sr were identified as adequate promoters among the 9 metals on the basis of PW91/GGA augmented with DFT+D2. The adsorption energies of CO2 on metal-promoted MgO sorbents for Li, Ca, and Sr atoms are -1.13, -1.68, and -1.48 eV, respectively.
开发下一代固体吸附剂以提高燃烧前和燃烧后碳捕获过程的经济性，对许多研究人员来说一直是一项具有挑战性的任务。氧化镁（MgO）是一种很有前景的吸附剂，因为它具有适中的吸附-解吸温度和较低的吸附热。然而，它的低吸附容量和热稳定性需要改进。为了提高二氧化碳吸附容量，人们通过实验开发了各种金属促进的MgO吸附剂。尽管如此，迄今为止，用于筛选最佳金属促进剂的严格计算研究仍然有限。我们进行了第一性原理计算，以选择MgO吸附剂的金属促进剂。选择了五种碱金属（Li、Na、K、Rb和Cs）和四种碱土金属（Be、Ca、Sr和Ba）作为一组促进剂。与纯MgO上的CO2吸附能相比，除了Na促进剂外，金属促进的MgO吸附剂上的吸附能更高，这表明在MgO上进行金属促进是提高吸附容量的有效方法。基于促进剂在MgO表面的稳定结合和吸附剂的可再生性，在PW91/GGA并结合DFT+D2的基础上，在这9种金属中，Li、Ca和Sr被确定为合适的促进剂。Li、Ca和Sr原子在金属促进的MgO吸附剂上的CO2吸附能分别为-1.13、-1.68和-1.48 eV。
