Proton-assisted creation of controllable volumetric oxygen vacancies in ultrathin CeO2−x for pseudocapacitive energy storage applications

Abstract

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 2− x films with controllable volumetric oxygen vacancy concentrations can be produced. This technique offers a layer-by-layer fabrication route for ultrathin CeO 2− x films that render Ce 3+ concentrations as high as ~60 at% and a volumetric capacitance of 1873 F cm −3 , 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 2− x . 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.

Redox Tuning in Crystalline and Electronic Structure of Bimetal–Organic Frameworks Derived Cobalt/Nickel Boride/Sulfide for Boosted Faradaic Capacitance

“…With the redox treatment, the oxygen vacancies are formed and the S 2− is absorbed by the positive holes through the electrostatic attraction. All above will be responsible for the formation of defect structure, which is consistent with the HRTEM observation (Figure ) . The spectra of Co‐Ni‐S and Co‐Ni‐S‐B are also analyzed comparatively (Figure S8, Supporting Information).…”

Tailoring Oxygen Vacancies in CoMoO4 for Superior Lithium Storage

“…The reduction of bandgap leads to the enhancement of electronic conductivity, and further enhancing the electrochemical performance. [56] To probe the structural transformation of the as-synthesized CoMoO 4 -N 2 electrode material, the ex situ TEM characterization was carried out on the cell at 3.0 V, which is performed under 500 mA g À 1 for 100 cycles ( Figure S17). It is obvious that the nanorods are well preserved without serious breakdown, and a slight volume expansion can be seen on the surface of the electrode material ( Figure S17a).…”

Strain engineering of oxide thin films for photocatalytic applications

“…The results shown in Fig.3 indicate that this is indeed the case. Our simulations of non-stoichiometric ceria, CeO 2−δ , considering an arbitrary but representative δ of 0.125 [41] (Sec. II and Supplementary Methods), show that both positive and negative η's can be used to reduce substantially E g (by ∼ 10% of the value obtained at zero strain, which is 2.1 eV), with tensile strain being particularly effective (Fig.3a).…”

“…Band gaps of 1.7 and 1.4 eV are obtained respectively at the highest compressive and tensile strain values considered in this study. These sizable E g reductions result from the combined action of oxygen vacancies, which are known to reduce the neighbouring Ce 4+ ions and lower the CB edge due to the appearance of new unoccupied 4f states (Fig.3b) [41], and biaxial strain.…”