One-step hydrothermal growth of porous nickel manganese layered double hydroxide nanosheet film towards efficient visible-light modulation

Abstract

Electrochromic smart windows have attracted great attention due to their dynamic regulation of the solar spectrum. NiO and MnO₂ are typical anodic coloration materials and widely investigated as complementary electrodes with WO₃. However, NiO and MnO₂ films often cannot be bleached to complete transparency, resulting in low transmittances and low optical modulations in the short-wavelength visible region. Herein, we report a porous nickel manganese layered double hydroxide (NiMn-LDH) nanosheet film directly grown on fluorine-doped tin oxide (FTO) glass using a one-step hydrothermal method, which demonstrates a high transmittance of 80.1% at 550 nm (without deduction of FTO glass). Induced by the double-redox couples of Ni²⁺/Ni³⁺ and Mn³⁺/Mn⁴⁺ associated synergistic electrochromic effect, the as-grown NiMn-LDH film electrode exhibits a large optical modulation of 68.5% at 550 nm, and a large solar irradiation modulation of 59.0% in the visible region of 400–800 nm. After annealing at 450 °C for 2 h, the NiMn-LDH film can be transformed into Ni₆MnO₈ film with a reduced optical modulation of 30.0% at 550 nm. Furthermore, the NiMn-LDH film electrode delivers an areal capacitance of 30.8 mF cm⁻² at a current density of 0.1 mA cm⁻². These results suggest that the as-prepared NiMn-LDH film electrode is a promising candidate for both electrochromic and energy storage applications.