S Mofarah Sajjad, Adabifiroozjaei Esmaeil, Yao Yin, Koshy Pramod, Lim Sean, Webster Richard, Liu Xinhong, Khayyam Nekouei Rasoul, Cazorla Claudio, Liu Zhao, Wang Yu, Lambropoulos Nicholas, Sorrell Charles C
School of Materials Science and Engineering, UNSW Sydney, Sydney, NSW, 2052, Australia.
Research Center for Functional Materials (RCFM), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, 305-0047, Japan.
Nat Commun. 2019 Jun 13;10(1):2594. doi: 10.1038/s41467-019-10621-2.
Two-dimensional metal oxide pseudocapacitors are promising candidates for size-sensitive applications. However, they exhibit limited energy densities and inferior power densities. Here, we present an electrodeposition technique by which ultrathin CeO films with controllable volumetric oxygen vacancy concentrations can be produced. This technique offers a layer-by-layer fabrication route for ultrathin CeO films that render Ce concentrations as high as ~60 at% and a volumetric capacitance of 1873 F cm, which is among the highest reported to the best of our knowledge. This exceptional behaviour originates from both volumetric oxygen vacancies, which enhance electron conduction, and intercrystallite water, which promotes proton conduction. Consequently, simultaneous charging on the surface and in the bulk occur, leading to the observation of redox pseudocapacitive behaviour in CeO. Thermodynamic investigations reveal that the energy required for oxygen vacancy formation can be reduced significantly by proton-assisted reactions. This cyclic deposition technique represents an efficient method to fabricate metal oxides of precisely controlled defect concentrations and thicknesses.
二维金属氧化物赝电容器是尺寸敏感型应用的理想候选材料。然而，它们的能量密度有限，功率密度也较差。在此，我们提出一种电沉积技术，通过该技术可以制备出具有可控体积氧空位浓度的超薄CeO薄膜。该技术为超薄CeO薄膜提供了一种逐层制造路线，使得Ce浓度高达约60原子百分比，体积电容为1873 F/cm³，据我们所知，这是报道的最高值之一。这种优异的性能源于体积氧空位（增强电子传导）和晶间水（促进质子传导）。因此，表面和体相同时发生充电，导致在CeO中观察到氧化还原赝电容行为。热力学研究表明，质子辅助反应可显著降低形成氧空位所需的能量。这种循环沉积技术是制备具有精确控制的缺陷浓度和厚度的金属氧化物的有效方法。
