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Design of Heterostructures of MXene/Two-Dimensional Organic Frameworks for Na–O2 Batteries with a New Mechanism and a New Descriptor

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posted on 15.03.2021, 16:36 by Yuxiang Min, Hao Yuan, Wugang Wang, Lai Xu
Na–O2 batteries are promising candidates to replace Li–O2 batteries for their excellent performance. However, the charge overpotential of Na–O2 batteries is usually too high. In this work, we designed combinations of MXene and a two-dimensional organic framework for Na–O2 batteries. The results show that the Ti2CO2/Cu-BHT has low OER and ORR overpotentials of 0.24 and 0.32 V, respectively. Besides this, the conductivity and the adsorption energy to Na+ (Eads(Na+)) are promoted due to the charge transfer between layers. We also found that the OER and ORR overpotentials are negatively and positively correlated with Eads(Na+), respectively, where Ti2CO2/Cu-BHT has a moderate Eads(Na+) (−2.20 eV) and, therefore, has good performance. Moreover, a new mechanism called the Na encapsulation mechanism was proposed on a two-dimensional organic framework surface. Through least absolute shrinkage and selection operator (LASSO) regression, we found a new descriptor that consists of inherent properties that could help us screen better heterostructures for Na–O2 batteries.