Gao Rui, Shang Zhaoru, Zheng Lirong, Wang Junkai, Sun Limei, Hu Zhongbo, Liu Xiangfeng
Center of Materials Science and Optoelectronics Engineering, College of Materials Science and Opto-Electronic Technology , University of Chinese Academy of Sciences , Beijing 100049 , P. R. China.
Beijing Synchrotron Radiation Facility , Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049 , China.
Inorg Chem. 2019 Apr 15;58(8):4989-4996. doi: 10.1021/acs.inorgchem.9b00007. Epub 2019 Feb 21.
Li-O battery attracts great interest because of the high energy density. But the poor kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have blocked the practical application. Designing the efficient bifunctional cathode catalysts is of great importance for the Li-O battery. Tuning the electronic and surface structure of the catalysts plays an important role. Herein, we propose to enhance the catalytic performance of CoO nanosheets for rechargable Li-O batteries by hydrazine hydrate-induced oxygen vacancy formation. The hydrazine hydrate reduction not only introduces oxygen vacancies into CoO nanosheets and modulates the electronic structure but also roughens the surface, which all contribute to the enhancement of ORR and OER activity, especially the activity and stability for OER. Li-O cells catalyzed by the oxygen defects-enriched CoO ultrathin nanosheets exhibit much better electrochemical performances in terms of the high initial capacity (∼11 000 mAh g), the lower overpotential (∼1.1 V), and the longer cycle life (150 cycles@200 mA g). This can be largely attributed to the synergy of the enriched oxygen vacancies and the roughened surface of CoO nanosheets, which not only improves the electron and Li conductivity but also provides more active sites and reaction spots. The proposed facile strategy may also be applied to modify other oxides based catalysts for Li-O batteries or other fields.
锂-氧电池因其高能量密度而备受关注。然而，氧还原反应（ORR）和析氧反应（OER）缓慢的动力学阻碍了其实际应用。设计高效的双功能阴极催化剂对锂-氧电池至关重要。调节催化剂的电子和表面结构起着重要作用。在此，我们提出通过水合肼诱导形成氧空位来提高CoO纳米片对可充电锂-氧电池的催化性能。水合肼还原不仅将氧空位引入CoO纳米片中并调节其电子结构，还使表面粗糙化，所有这些都有助于提高ORR和OER活性，特别是OER的活性和稳定性。由富含氧缺陷的CoO超薄纳米片催化的锂-氧电池在高初始容量（约11000 mAh g）、较低过电位（约1.1 V）和较长循环寿命（200 mA g下150次循环）方面表现出更好的电化学性能。这在很大程度上归因于CoO纳米片富含的氧空位和粗糙表面的协同作用，这不仅提高了电子和锂的导电性，还提供了更多的活性位点和反应位点。所提出的简便策略也可应用于修饰锂-氧电池或其他领域的其他氧化物基催化剂。
