In situ XRD and operando spectra-electrochemical investigation of tetragonal WO3-x nanowire networks for electrochromic supercapacitors

Shen Wang,Hongbo Xu,Jiupeng Zhao,Tingting Hao,Xiang Zhang,Hongming Zhang,Junying Xue,Peiyuan Wang,Yao Li

doi:10.1038/s41427-021-00319-7

Abstract

Electrochromic supercapacitors (ESCs) are appealing for smart electronic device applications due to their advantages of dual-function integration. Unfortunately, the synchronous dual-function evaluation and the essential reaction mechanism are ambiguous. Herein, we constructed a 3D WO3-x nanowire networks/fluorine-doped tin oxide (WO3-x NWNs/FTO) bifunctional electrode for ESCs by a solvothermal self-crystal seeding method. The synchronous correspondence relationship between the optical and electrochemical performances of the WO3-x NWNs/FTO electrode was explored using an operando spectra-electrochemical characterization method. It reveals an excellent areal capacity of 57.57 mF cm−2 with a high corresponding optical modulation (ΔT) of 85.05% and high optical-electrochemical cycling stability. Furthermore, the synergistic reaction mechanism between the Al3+ ion intercalation behavior and the surface pseudocapacitance reaction during electrochemical cycling is revealed utilizing in situ X-ray diffraction. Based on these results, an ESC device was constructed by pairing WO3-x/FTO as the cathode with V2O5 nanoflowers/FTO (V2O5 NFs/FTO) as the anode, which simultaneously deliver high capacity and large optical modulation. Moreover, the energy storage level of the ESC device could be visually monitored by rapid and reversible color transitions in real time. This work provides a promising pathway to developing multi-functional integrated smart supercapacitors.

Highlights

As smart power systems, electrochromic supercapacitor (ESC) devices have attracted increasing attention
The prepared WO3-x/FTO was heat-treated at 400 °C for 2 h, and thermal gravimetric analysis (TGA) was performed on the WO3-x precursor in an air atmosphere
Based on the results of an operando spectra-electrochemical synchronous test, the WO3-x NWNs/FTO cathode exhibits a high areal specific capacitance (57.57 mF cm−2) with a corresponding large ΔT (85.05%) and excellent cycling stability owing to the 3D crosslinked nanowire network structure, hierarchical porous channel, large specific area and strong adhesion with the FTO substrate

Summary

Introduction

Electrochromic supercapacitor (ESC) devices have attracted increasing attention. The higher specific surface area of the 3D WO3-x NWNs/FTO electrode allows for enough electroactive sites for the electrochemical reaction to occur, improving the energy storage and the corresponding optical performance.

Results

Conclusion