Understanding the acceleration effect of manganese and cerium doping on the hydration of CaO in CaO/Ca(OH)2 heat storage by density function theory

• Published in: Journal of energy storage Vol. 56; p. 105953
• Main Authors: Bian, Zhiguo, Li, Yingjie, Wang, Feifei, Fang, Yi, Zhao, Jianli, Qi, Jianhui
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2022
• Subjects: CaO/Ca(OH)2 heat storage; Ce-doped CaO; Density functional theory; Hydration; Mn-doped CaO; CaO/Ca(OH)2 heat storage; Density functional theory; Ce-doped CaO; Hydration; Mn-doped CaO
• ISSN: 2352-152X; 2352-1538
• DOI: 10.1016/j.est.2022.105953

CaO/Ca(OH)2 heat storage system is one of the most promising candidates for large-scale thermochemical heat storage at temperature of 300–600 °C. In this work, the CaO/Ca(OH)2 heat storage performances of the Ce- and Mn-doped CaO were investigated and the mechanisms of promoting hydration by Ce and Mn doping were determined via density functional theory (DFT) calculations. The Mn-doped CaO exhibits the higher hydration conversion than CaO and Ce-doped CaO. The structural parameters, partial density of states, electron differential densities and energy barriers during hydration stage on the CaO, Ce- and Mn-doped CaO surfaces were compared to clarify the effects of Ce and Mn on hydration of CaO. The results show the detailed hydration reaction pathways on the CaO, Ce- and Mn-doped CaO surfaces. During the H2O adsorption stage, H2O on the Ce-doped CaO surface approaches the Ca atom first, while H2O on the Mn-doped CaO surface approaches the Os atom first. The adsorption energy for Ce- and Mn-doped CaO are −1.612 and −0.896 eV, respectively, which are higher than that for CaO. The doping of Ce and Mn accelerates the H2O adsorption on the CaO surface. The Mn doping causes the 84.3 % reduction in the energy barrier for hydration of CaO and the reduction by Mn doping is larger than that by Ce doping. Thus, Mn-doped CaO exhibits the higher hydration reactivity and hydration conversion than CaO and Ce-doped CaO. The DFT calculations determined the promotion mechanism of Ce and Mn doping on the hydration of CaO in CaO/Ca(OH)2 heat storage. •Ce and Mn doping are used to promote hydration of CaO in CaO/Ca(OH)2 heat storage.•Detailed reaction pathways on the Ce-doped and Mn-doped CaO surfaces are revealed.•Both Ce and Mn doping increase adsorption energy to accelerate the H2O adsorption.•Lower energy barrier by Mn doping causes higher hydration conversion than Ce doping.•The hydration conversion of Mn-doped CaO after 10 heat storage cycles achieves 88.4 %.