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

Electrochromic smart windows have attracted great attention due to their dynamic regulation of the solar spectrum. NiO and MnO are typical anodic coloration materials and widely investigated as complementary electrodes with WO. However, NiO and MnO 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 Ni/Ni and Mn/Mn 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 NiMnO 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 at a current density of 0.1 mA cm. These results suggest that the as-prepared NiMn-LDH film electrode is a promising candidate for both electrochromic and energy storage applications.