Electrical and Structural Dual Function of Oxygen Vacancies for Promoting Electrochemical Capacitance in Tungsten Oxide

Abstract

Intrinsic defects, including oxygen vacancies, can efficiently modify the electrochemical performance of metal oxides. There is, however, a limited understanding of how vacancies influence charge storage properties. Here, using tungsten oxide as a model system, an extensive study of the effects of structure, electrical properties, and charge storage properties of oxygen vacancies is carried out using both experimental and computational techniques. The results provide direct evidence that oxygen vacancies increase the interlayer spacing in the oxide, which suppress the structural pulverization of the material during electrolyte ion insertion and removal in prolonged stability tests. Specifically, no capacitive decay is detected after 30 000 cycles. The medium states and charge storage mechanism of oxygen‐deficient tungsten oxide throughout electrochemical charging/discharging processes is studied. The enhanced rate capability of the oxygen‐deficient WO3−x is attributed to improved charge storage kinetics in the bulk material. The WO3−x electrode exhibits the highest capacitance in reported tungsten‐oxide based electrodes with comparable mass loadings. The capability to improve electrochemical capacitance performance of redox‐active materials is expected to open up new opportunities for ultrafast supercapacitive electrodes.

Reversible hydrogen spillover in Ru-WO3-x enhances hydrogen evolution activity in neutral pH water splitting

“…The W 4 f XPS spectrum of Ru-WO 3−x /CP displays two peaks at 35.58 eV and 37.68 eV, which correspond well to the W 4 f 2/7 and W 4 f 2/5 of W(VI), respectively (Fig. 2g ) 40 , 41 . Additionally, two more deconvoluted peaks at 34.53 eV and 36.63 eV can be assigned to W(V) 43 , 45 .…”

“…Oxygen-deficient tungsten oxide (WO 3−x ) displays the excellent capability of storing protons in water 39 – 41 . If the inserted protons in WO 3−x are mobile, WO 3−x may be used as a proton reservoir to supply H to increase θ H on Ru during HER, which thus shall promote the HER kinetics of Ru in neutral medium.…”

A carbon-coated spinel zinc cobaltate doped with manganese and nickel as a cathode material for aqueous zinc-ion batteries

“…35 Generally, b values equal to 0.5 and 1 represent the current being completely controlled by semi-infinite linear diffusion and a pure capacitive process, respectively. 36 Here by calculating the slope of the log (i) vs.log (v) plots shown in Fig. 4b, the b values of four redox peaks are 0.84, 0.85, 0.775, and 0.885, respectively, which indicates that the electrochemical reaction of the ZNMC@C electrode is mainly dictated by pseudo-capacitance behavior.…”

Synthesis of Oxygen‐Deficient WO3−x Nanoplates and Hollow Microspheres Decorated on a Carbon Cloth for Supercapacitors

“…[15] The existence of a large number of defects contributes to the increase of the carrier density of the electrode material, thus improving the charge transfer, accel-erating the reaction kinetics, and obtaining an excellent charge storage capacity. [16] Figure 3d signifies that the CCÀ WO 3À x are polycrystalline and inferior crystalline structure. The EDS elemental mapping images of CCÀ WO 3À x display the homogeneous distributions of O and W elements (Figure 3e), which demonstrate that the WO 3À x were successfully synthesized and attached to the surface of CC.…”