53 / 2026-09-19 15:02:28

Porosity–Connectivity Engineering of TT-Nb2O5 Nanowire Films for Dual-Band Electrochromism and Energy Storage

TT-Nb2O5; dual-band electrochromism; polaron; Li⁺ intercalation; energy storage; smart windows

Decoupled visible (VIS) and near-infrared (NIR) regulation with charge-storage capability remains challenging for single-component electrochromic materials. Here, porous TT-Nb₂O₅ nanowire films were directly grown on FTO by regulating hydrothermal temperature and reaction time. The nanowire architecture evolves from a compact network to an interconnected porous network and finally aggregated structure. The optimized film obtained at 180 °C for 14 h exhibits a porosity of 47.1 ± 0.9% and enables three distinct optical states. At +1.2, −0.5, and −1.0 V, the integrated T_VIS/T_NIR values are 60.0/97.2%, 50.9/92.1%, and 1.2/1.9%, respectively, corresponding to bright-warm, dark-warm, and dark-cool modes and yielding integrated VIS and NIR modulations of 58.8% and 95.3%. The single-wavelength modulation reaches 74.0% at 700 nm and 98.5% at 1200 nm. Beyond optical regulation, the film delivers an areal discharge capacity of 281.9 mAh/m² at 1 A/m², and achieves a charge-recovery ratio η_Q of 64.7% and an energy-recovery efficiency η_E of 58.2%, respectively. State-dependent ICP-OES, optical, XRD, and Raman analyses reveal progressive Li⁺ insertion (x = 0.50 → 0.56 → 0.88), an apparent band-gap decrease, preservation of the TT framework within XRD resolution, and a broad NIR absorption band near 1100 nm consistent with polaron-related absorption. A sealed two-electrode device reproduces the three-mode optical regulation, while two charged devices connected in series power a 1.5 V LED for more than 20 min. These results establish porosity-controlled microstructure engineering of TT-Nb₂O₅ as an effective route to integrate spectrally selective electrochromism with recoverable charge storage in a simple single-component oxide platform.