Two-dimensional WO3 nanosheets for high-performance electrochromic supercapacitors

In the present study, two-dimensional (2D) WO3 nanosheet arrays with (101) preferential orientation facets (WO3 NSHs) were successfully assembled on a fluorine-doped tin oxide (FTO) electrode through a simple solvothermal method. Physicochemical properties analysis affirmed the prepared WO3 was a single-crystal-like monoclinic nanosheet with an anomalous intense [101] dominant orientation. As an electrochromic supercapacitor (ESC) cathode electrode, the WO3 NSHs/FTO electrode delivered a high areal capacity of 59.55 mF cm(-2) and corresponding transmittance modulation (Delta T) of 85.05% (at 1000 nm) at 5 mV s(-1), and remarkable optical-electrochemical cycling stability in AlCl3 electrolyte. The superior optical-electrochemical bifunctional performance could be attributed to the synergistic effect of the WO3 nanosheet arrays structure and highly preferential (101) crystal facets. Furthermore, the internal mechanism affecting the optical-electrochemical performance, namely the synergistic reaction between the single-phase reaction for Al3+ ions insertion/extraction into monoclinic WO3 tunnels and the surface pseudocapacitance-controlled reaction, was confirmed by utilizing in situ X-ray diffraction. Similarly, the ESC device based on the WO3 NSHs/FTO electrode also displayed excellent optical-electrochemical performance in AlCl3 electrolyte, such as 26.11 mF cm(-2) areal capacitance, 42.39% Delta T (at 650 nm), and 94.87% capacitance retention after 5000 cycles. In addition, we could judge the capacity for the ESC device by the color changes.

Automated summary

In this study, 2D WO3 nanosheet arrays with unique structure were successfully prepared, showing excellent optical-electrochemical performance in AlCl3 electrolyte, with high areal capacity and good optical modulation effect.